A
Abduct To move structures apart.
Absolute refractory period The time after a neuron fires when it is unresponsive because sodium channels are inactivated.
Acetylcholine (ACh) A rapid-fire neurotransmitter of the peripheral nervous system’s neuromuscular junction that causes muscle tissue to contract. It has a restricted role in the central nervous system, being found only in the brainstem, the base of the forebrain, and the basal ganglia. It is thought to regulate central nervous system neuronal activity, especially in alertness, attention, memory, and learning. Achalasia A condition of the esophagus in which smooth esophageal muscle fails to relax, resulting in pain and regurgitation.
Action potential A rapid change in membrane polarity, which moves or propagates like a wave down the axon.
Activity barriers Difficulties in executing activities, especially skills of daily living like walking or eating.
Adduct To bring structures together.
Afferent communication Bottom-up or ascending (body to the brain) sensory communication.
Agraphia An acquired disorder of writing.
Agyria/lissencephaly A condition in which the brain lacks its characteristic sulci and gyri and looks rather smooth in appearance. The condition is associated with severe motor, intellectual, and psychological disability. Akinesia A loss of voluntary movement.
Akinetic mutism A condition in which patients are passive and do not move or talk.
Alexia An acquired disorder of reading.
All-or-none principle A principle stating that when a threshold is reached, a neuron will depolarize and fire at a fixed strength. If the threshold is not met, the neuron will not fire.
Allographic agraphia A reading problem caused by left parieto-occipital lesions resulting in errors in lowercase versus uppercase letters (e.g., mR. sMitH). It can also include confusion of print and cursive scripts.
Alpha motor neurons Neurons that innervate extrafusal muscle fibers, which leads to muscle contraction.
Alzheimer disease A progressive neurological disease that results in a general intellectual decline.
Amygdala Paired almond-shaped nuclei situated in the medial temporal lobe that are involved in fear and aggression.
Amyotrophic lateral sclerosis (ALS) The most well- known type of motor neuron disease. It is characterized by progressive weakness that often begins in the hands, feet, or mouth, but then involves the rest of the body. Also known as Lou Gehrig disease.
Anarthria Having no speech at all. Compare to dysarthria. Anatomical position The starting position to describe anatomical features and positions.
Anatomy The structure of the body.
Anencephaly A severe neural tube defect in which neurological development ceases at the brainstem, leaving the infant without cerebral hemispheres and thus without higher cortical functions.
Anesthesia A lack of sensation (numbness).
Aneurysm An abnormal ballooning of a weakened artery wall that can rupture.
Angiography An invasive neuroimaging technique that uses iodine and x-rays to produce pictures of the blood vessels.
Anomia Impairment in the ability to name objects. It is a symptom of aphasia.
Anosmia An inability to smell.
Anosognosia A disorder of executive function in which a person lacks insight into his or her deficits.
Anterior Toward the belly.
Anterior (ventral) corticospinal tract A nerve tract that originates in the motor and premotor areas of the frontal lobe and then courses ipsilateral down the spinal cord, inputting at the ventral horn. It controls the trunk muscles. Anterior reading system A neural system involving Broca’s area as well as the ventral and dorsal premotor areas that plays an important role in word analysis in terms of spoken language and articulation; it also plays a role in silent reading. Anton syndrome A rare condition in which patients have visual loss and visual anosognosia (i.e., denial of visual deficits) due to damage to the visual cortex. Also known as cortical blindness.
Aphasia An acquired multimodality language disorder.
Apraxia of speech (AOS) A motor speech disorder involving difficulty planning or programming the articulators for speech in the absence of muscle weakness.
Apraxic agraphia A problem in writing due to damage to the superior parietal lobe, premotor cortex, and supplementary motor area that results in people not being able to call up the motor plans for writing.
Aprosody A lack of melodic contour (or prosody) in speech; monotone.
Arachnoid mater The middle layer of the meninges that is made up of a thin, delicate connective tissue.
Arachnoid space An actual space below the arachnoid mater and above the pia mater.
Aspiration Penetration of food or liquid below the vocal cords, providing a clear path to the lungs.
Astereognosis Difficulty recognizing three-dimensional forms via touch, often due to damage to the primary sensory cortex.
Astrocyte A star-shaped nervous system cell that nourishes neurons and helps to maintain the neuronal environment. Astrocytoma An abnormal mass of astrocyte cells.
Ataxic dysarthria A form of dysarthria caused by cerebellar damage and characterized by harsh voice, monopitch, loud voice, imprecise consonants, and irregular breakdown in articulation. People with this form of dysarthria often sound drunk in their speech.
Athetosis Slow, twisting movements of the hands and feet. Attention A person’s focus on a stimulus in the environment. Attentional alexia A condition in which the person can read single words, but when there are multiple words on a page the person becomes distracted and unable to read. Usually caused by damage to the prefrontal cortex, which helps mediate attention.
Audition The process of hearing whereby acoustic or sound energy waves are changed into neural impulses.
Auditory association cortex An area in the superior temporal lobe involved in auditory processing and attaching meaning to spoken words. Also known as Wernicke’s area.
Auditory brainstem response (ABR) A test that evaluates the integrity of cranial nerve VIII and the central auditory pathway without depending on a voluntary response from the patient.
Auditory processing disorder (APD) A condition that can be thought of as dyslexia of the ears in that there is difficulty processing and interpreting auditory symbols, similar to how people with dyslexia have difficulty interpreting written symbols.
Autism A neurological developmental disorder that occurs in 1 in 68 children in the United States and is characterized by problems in social interaction, communication problems, and stereotyped behaviors, all of which are diagnosed before a child is 3 years of age.
Autonomic nervous system That part of the motor nervous system involved in body functions that happen automatically and without conscious control. Contrast with the somatic nervous system.
Axoaxonic synapse A synapse that involves the axon of one neuron connecting and sending a chemical signal to the axon of another neuron. These are usually regulatory in nature.
Axodendritic synapse A synapse that involves the axon of one neuron connecting and sending a chemical signal to the dendrite of another neuron. These are usually excitatory in nature.
Axons Neurites that send signals away from the neuron’s cell body.
Axosomatic synapse A synapse that involves the axon of one neuron connecting and sending a chemical signal to the soma of another neuron. These are usually inhibitory in nature.
B
Babinski sign A sign elicited when scratching the bottom of the foot. In a healthy adult, a normal (negative) Babinski sign occurs when the toes curl and withdraw from the scratching. An abnormal (positive) Babinski occurs when the big toe extends and the other toes flare out, indicating upper motor neuron damage.
Ballism A quick flinging of a limb or limbs.
Basal ganglia A group of subcortical gray matter structures including the caudate nucleus, globus pallidus, and putamen. It is a key component of the motor system. Damage results in dyskinesias.
Benedikt syndrome A condition caused by damage to the midbrain, resulting in contralateral hemiparesis and ataxic tremor.
Binaural hearing Hearing with two ears that allows us to determine the location of a sound.
Blood-brain barrier (BBB) A barrier located in the walls of the central nervous system’s blood vessels that protects the brain from foreign invaders, hormones, antibodies, and other substances that might adversely affect it.
Bolus A food or liquid ball that is swallowed by a person.
Bottom-up attention A type of attention that is nonvoli- tional and driven by some characteristic of the stimulus itself.
Bradykinesia A dyskinesia involving slowed movements. Brain death A state in which a person has no purposeful responses to stimuli, no brainstem reflexes, and no sleepwake cycle, and there are flat electroencephalographic patterns.
Brainstem Three-part structure that is continuous with the spinal cord and lies inferior to the cerebral hemispheres. It consists of the medulla, pons, and midbrain, which together control many basic life functions and reflexes.
Broca's aphasia A type of aphasia in which people have limited verbal output that is agrammatic in nature.
Broca's area An area named after Paul Broca located in the inferior frontal gyrus of the frontal lobe (areas 44 and 45) that is involved in language processing and speech production.
Brodmann map A map of the human brain in which the cerebral cortex is divided into 52 areas based on differences in gross anatomy and cellular structure with the thought that each of these areas is responsible for certain functions.
C
Cannon-Bard theory A theory of emotion that states that an external stimulus simultaneously triggers a physiological response and an emotional experience, both occurring independently of each other.
Carotid arteries The main arteries that run up the anterolateral part of the neck and feed the brain blood.
Caudal Latin for “tail”; it means inferior.
Caudate nucleus One of the three structures that make up the basal ganglia. It has a functional relationship with the putamen, together forming the striatum.
Cell doctrine The belief that the brain’s ventricles (i.e., cells) have psychic gases (or humors) in them responsible for mental functions.
Cell theory A theory that states that all organic beings (humans, animals, and plants) are composed of individual cells.
Cells The fundamental units of an organism.
Central Toward the center.
Central agraphia A reading problem involving impairment in the underlying linguistic reading system.
Central alexia A linguistic problem that affects the underlying reading system.
Central auditory system The auditory system that involves hearing structures found centrally in the head, including areas in the brainstem, the thalamus, and the cerebral cortex.
Central fissure A deep groove in the brain that separates the frontal lobe from the parietal lobe.
Central nervous system (CNS) The part of the nervous system made up of the brain and spinal cord.
Centrosome A cell structure that directs the growth of the cell through cell division.
Cerebellar circuit A neural circuit involving the cerebellum, premotor cortex, and precentral gyrus that integrates proprioceptive and kinesthetic information into motor activity so that motor movements are smooth and precise.
Cerebellar hemispheral syndrome A condition of the cerebellum that can be caused by stroke, tumor, and multiple sclerosis that primarily affects the ipsilateral limbs, causing tremor, dysmetria, and dysdiadochokinesia.
Cerebellar peduncles Nerve tracts that make communication between the cerebellum and other nervous system structures possible.
Cerebellum A structure that lies just posterior to the pons and is involved in the coordination and precision of fine motor movement.
Cerebral hemispheres The areas of the brain, divided into left and right cerebral hemispheres, that control higher cortical functions such as cognition and language as well as planning motor function and interpreting sensory experiences.
Cerebral palsy (CP) A nonprogressive neurological brain disorder that develops before birth (prenatal), during birth (perinatal), or shortly after birth (postnatal) and that affects movement, posture, balance, and sometimes speech and swallowing. Cerebral refers to the brain and palsy refers to paralysis or uncontrolled movements. CP can be caused by a lack of oxygen, premature birth, infections, brain hemorrhages, jaundice, and head injury.
Cerebral peduncles Portion of the midbrain that includes everything except the tectum.
Cerebral spinal rhinorrhea A condition caused by trauma to the nose resulting in cerebral spinal fluid leaking through the nose.
Cerebral vascular accident (CVA) An event that involves some kind of interruption to the brain’s blood supply, whether a blockage or a hemorrhage. Popularly known as a stroke.
Cerebrospinal fluid (CSF) A clear, colorless fluid found in the brain’s ventricles and the arachnoid space of the meninges. It cushions brain tissue, reduces the brain’s weight through buoyancy, removes waste, and transports nutrients and hormones to the brain.
Chorea Means “like a dance”; quick movements of the hands or feet that have a dance-like quality.
Choroid plexus A structure located in each ventricle that produces cerebrospinal fluid.
Cingulate cortex An area located in the medial surface of the brain between the corpus callosum and the cingulate sulcus. It is a part of the limbic system, our emotional processing center.
Circle of Willis A circular array of blood vessels at the base of the brain that helps to equalize blood flow and pressure. The carotid and vertebral arteries feed this system.
Circumventricular organs (CVOs) Highly vascular brain structures that lack a normal blood-brain barrier and, thus, are routes around the blood-brain barrier.
Claustrum A sheet-like membrane of neurons under the cortex that appears to provide some level of cortical control of swallowing.
Clonus Involuntary muscle contractions, which can have a rhythmic quality; one common example is hiccups.
Closed head injury A type of traumatic brain injury that involves forces that cause damage to the brain, but without penetrating the skull; compare to open head injury.
Cochlear nucleus (CN) A collection of specialized auditory cells located at the cerebellopontine area where cranial nerve VIII inputs.
Cognition The mental process of knowing in which we acquire and act upon knowledge.
Coma A state in which a person does not respond purposefully to stimuli or have a sleep-wake cycle but does demonstrate brainstem reflexes and electroencephalographic (EEG) patterns, though the EEG is severely depressed.
Commissurotomy A surgical procedure in which the corpus callosum is severed. This procedure is usually performed to help people with severe epilepsy.
Comprehension The understanding of information acquired through perception and remembered.
Computed tomography (CT) A neuroimaging technique that passes x-rays through the human body that reflect off different densities of tissue, bone, and fluid in different ways, producing an image.
Conduction aphasia A type of aphasia in which people have difficulty repeating words said to them but have preserved speech fluency as well as auditory comprehension.
Connectionism The belief that there are centers in the brain responsible for certain functions, but that these areas are connected together and work cooperatively.
Consciousness The ability to be aware of self and surroundings.
Constitution view A belief regarding human constitution that humans are material only but are different from animals because people have a first-person perspective (i.e., extended consciousness).
Content The meaning of words. Also known as semantics.
Contralateral Opposite side.
Contralateral innervation The fact that, due to decussation of motor tracts, the right side of the brain controls the left side of the body and the left side of the brain controls the right side of the body.
Contrecoup damage A brain injury caused by the rebounding of the brain to the opposite site of the skull, causing a second area of damage.
Core consciousness From a neuroscience perspective, a type of consciousness involving our sense of ourselves in the here and now (i.e., at this very moment), objects in the world, and our relationship to those objects.
Corona radiata Means “radiating crown”; a fan-shaped sheet of axons between the thalamus and cortical surface.
Coronal A body section that splits a structure into front and back portions.
Corpus callosum A band of axonal fibers that connects the two cerebral hemispheres, allowing them to communicate with each other.
Coup damage The initial brain injury caused by the brain banging up against the inside of the skull; compare to contrecoup damage.
Cranial nerve A nerve that arises directly from the brain or brainstem that helps in information exchange between the brain and head and neck structures. Humans have 12 pairs of cranial nerves.
Creature consciousness From a philosophical perspective, the consciousness of whole organisms involving both wakefulness and core consciousness.
Cricopharyngeus A muscle at the top of the esophagus that relaxes, allowing the bolus to enter the esophagus.
Crus cerebri The anterior portion of the midbrain’s cerebral peduncles.
Cytoskeleton A cell structure made up of microtubules that transport molecules around the cell.
D
Declarative memory The conscious, willful recall of memories. Memory for facts (semantic memory) and space-time events (episodic memory). Also known as explicit memory.
Decussation The point where a contralateral tract crosses from left to right (or right to left).
Deep agraphia A writing disorder characterized by semantic paraphasias (i.e., substituting one word for another) and spelling errors, especially homophones (e.g., night versus knight). Also known as semantic agraphia.
Deep alexia A condition in which people recognize words as other words (e.g., scale is perceived as skate). Also known as semantic alexia.
Deep cerebral veins Veins in the brain that collect blood from subcortical gray matter structures, like the thalamus and hippocampus.
Deglutition The act of swallowing.
Dementia A group of progressive neurological disorders (e.g., Alzheimer disease) that lead to cognitive decline.
Dendrite A neurite that receives signals and sends them to the neuron’s cell body.
Depolarization The balancing of charge and concentration gradients in an axon resulting in an action potential.
Dermatome A specific skin region associated with a specific spinal nerve.
Diadochokinesia The ability to make rapid, alternating motor movements (e.g., saying “pa-ta-ka” quickly).
Diadochokinetic rates Rapid, alternating motor movements, such as saying “pa-ta-ka” as fast as possible.
Diencephalon A neurodevelopmental term for a set of brain structures found superior to the midbrain. Includes the thalamus, subthalamus, hypothalamus, and epithalamus.
Diffuse damage Traumatic brain injury that tends to be widespread in nature.
Diplopia Double vision, or seeing two images simultaneously.
Disfluency Any interruption in the smoothness with which sound, words, and sentences flow during oral language.
Distal The part of the limb farthest from its attachment.
Dopamine A neurotransmitter that plays a role in motor control as well as our reward system.
Dorsal Toward the back.
Dorsal column medial lemniscal pathway A sensory pathway that involves fine touch (as is found in the hands and mouth), vibratory sense, and proprioception.
Dorsal columns Nerve tracts that reside in the dorsal area of the spinal cord but have their origin at the dorsal root ganglion. The dorsal columns relay fine and discriminative touch, pressure, and proprioceptive sensory information to the brainstem, then the thalamus, and finally the sensory cortex for final processing.
Dorsal induction A neurodevelopmental period (3—7 weeks’ gestation) in which the neural tube is formed.
Dualist A person who believes that humans are two substances, a material body (with a brain) and an immaterial soul (with a mind).
Dura mater The outermost layer of the meninges that adheres to the inner surface of the skull.
Dynamic polarization of neurons A theory that information flows only one way through a neuron, beginning with dendrites, then through the cell body, and finally through the axon.
Dysarthria Speech that is slurred and/or uncoordinated due to central or peripheral nervous system problems that affect one or more of the following: respiration, phonation, resonance, or articulation. Involves weakness in the speech muscles.
Dyskinesia A movement disorder involving involuntary movements (e.g., tremor).
Dyslexia A term for developmental problems in acquiring reading skills.
Dysphagia A condition in which a person has difficulty swallowing. It can involve any of the swallowing stages (oral preparatory, oral, pharyngeal, and/or esophageal).
Dystonia A dyskinesia in which sustained muscle contractions result in distorted body postures.
E
Ectoderm An embryonic layer that later turns into the skin and nervous system.
Efferent communication Top-down or descending (i.e., brain to the body) motor communication.
Electroencephalography (EEG) A temporal resolution neuroimaging technique that measures the neuronal electrical activity through electrodes placed on the scalp.
Embolus A type of ischemic clot that originates somewhere else in the body and then lodges in a cerebral blood vessel; compare to a thrombus.
Emergent dualism A belief regarding human constitution that the human mind emerges or arises from a combination of many brain activities.
Emotion Defined objectively, a certain set of physiological responses to certain stimuli. Defined subjectively, a conscious internal experience of feelings.
Emotional intelligence (EI) Our ability to understand our own emotions as well as those of others that guides us in our personal relationships.
Emotional lability An involuntary display of emotion that can sometimes be the result of a neuropathology.
Empathy The action of understanding, being aware of, being sensitive to, and vicariously experiencing the feelings, thoughts, and experiences of another of either the past or present without having the feelings, thoughts, and experience fully communicated in an objectively explicit manner
Encephalocele A rare malformation of the skull in which a malformed portion of the brain, usually the occipital lobe, protrudes from the skull in a sac.
Endoplasmic reticulum A cell structure that acts as a production plant for proteins needed by the cell.
Enteric nervous system A part of the autonomic nervous system that manages the gastrointestinal system.
Entorhinal cortex A major input/output relay between the cerebral cortex and the hippocampus.
Epidural hematoma A hemorrhage that occurs between the skull and the outer layer of the meninges (dura mater). Epidural space A potential space between the skull and the dura mater.
Epinephrine A neurotransmitter involved in regulating heart rate, blood pressure, and breathing and in the fight- or-flight response.
Episodic memory A type of declarative memory for space-time episodes in life, like a family trip.
Epithalamus A part of the diencephalon that regulates genital development, the sleep-wake cycle, and optic reflexes.
Equilibrium A person’s sense of coordination and balance. Esophageal stage A stage of the normal swallow that is involuntary and variable in length (8-20 seconds), depending on the substance eaten. After the bolus enters the esophagus, peristaltic waves move the bolus to the stomach in conjunction with gravity.
Executive functions The human capacity to order and manage all other cognitive functions (e.g., attention, memory) for the purpose of setting and attaining goals.
Expressive aphasia An acquired language loss in speaking and/or writing.
Extended consciousness From a neuroscience perspective, a type of consciousness involving our sense of self in the flow of time. We think of ourselves in the past and anticipate ourselves living in a future (i.e., autobiographical self). Extension The act of straightening a joint.
Extra-axial hemorrhage A type of hemorrhagic stroke that involves bleeding in or around the meninges; compare to an intra-axial hemorrhage.
Extrapyramidal system An indirect motor system that controls involuntary movements involved in posture, muscle tone, and reflexes as well as the coordination or modulation of movements.
F
Fasciculation Involuntary muscle fiber twitches.
Fissures Deep grooves in the brain.
Flaccid dysarthria A type of dysarthria caused by lower motor neuron damage in the pyramidal system, resulting in speech that is breathy in voice, monopitch, and hypernasal and that uses short phrases and imprecise consonants.
Flexion The act of bending a joint.
Fluency The smoothness with which sound, words, and sentences flow during oral language.
Fluency shaping A type of stuttering therapy that focuses on fluency itself and strategies that promote more fluent speech; compare to stuttering modification.
Focal damage Brain damage due to cerebral vascular accidents that tends to be focused to a particular area of the brain.
Form The structure of language. Also known as grammar. Friedreich ataxia An inherited, progressive neurological disorder caused by an autosomal recessive inheritance pattern resulting in cerebellar dysfunction. Symptoms include progressive muscle weakness in the limbs, loss of coordination, dysmetria, dysarthria, curvature of the spine, and vision and hearing issues.
Frontal lobe An area of the cerebral cortex that lies at the front of the brain, just above the eyes, with the posterior border being the central fissure. Overall, its main functions include reasoning, planning, and voluntary motor movement.
Functional imaging A class of neuroimaging techniques that reveal the physiology of the brain.
Functional magnetic resonance imaging (fMRI) A neuroimaging technique that combines the advantages of magnetic resonance imaging with the advantages of positron emission tomography, showing both the anatomy and physiology of the brain by measuring blood oxygenation. Function barriers Problems in body function or alterations in body structure, such as paralysis and blindness.
G
Gait A person’s walking ability/characteristics.
Gait ataxia A condition in which the person walks with a wide base or the feet wide apart, giving the person more stability.
Gamma-aminobutyric acid (GABA) The main inhibitory neurotransmitter of the central nervous system. In addition to controlling information flow in the nervous system, GABA plays a role in the sleep-wake cycle.
Gamma motor neurons Neurons that innervate intrafusal muscle spindles, which is important for proprioception and reflexes.
General somatic afferent (GSA) fibers A type of spinal nerve fiber that carries sensory information from the skin.
General somatic efferent (GSE) fibers A type of spinal nerve fiber that carries motor information to skeletal muscles.
General visceral afferent (GVA) fibers A type of spinal nerve fiber that carries sensory information from the lungs and digestive tract.
General visceral efferent (GVE) fibers A type of spinal nerve fiber that carries motor information to smooth muscle, the heart, and glands.
Geniculocalcarine tract A visual neural tract that runs from the lateral geniculate nucleus of the thalamus and projects to the occipital lobe where visual information is processed.
Genu A bend where the internal capsule passes between the thalamus and the basal ganglia.
Glasgow Coma Scale (GCS) A 15-point scale that attempts to measure a patient’s level of consciousness in three areas: eyes, motor, and verbal.
Glial cell A nervous system cell that anchors, nourishes, insulates, and protects neurons. Some may also play a role in neural transmission.
Global aphasia A form of nonfluent aphasia in which a person has little to no verbal output, poor auditory comprehension, and poor repeating skills.
Globus pallidus One of the three structures that make up the basal ganglia. It has an anatomical relationship with the putamen, together forming the lenticular nucleus.
Glutamate The major excitatory chemical of synaptic activity in the central nervous system. It plays a role in synaptic plasticity, learning, and memory, which is the same role acetylcholine plays in the peripheral nervous system.
Golgi apparatus The cell’s mail office that packages and sends sugars and proteins out of the cell.
Gradient A sloping or imbalance of some sort.
Graphemic agraphia A reading problem due to lesions to the left prefrontal cortex and left parietal lobe resulting in patients omitting, substituting, adding, or transposing letters.
Graphemic buffer agraphia A type of agraphia in which a person cannot hold written forms in the linguistic working memory long enough to write the word. Shorter words are easier to write than are longer words because shorter words require less graphemic buffer space.
Guillain-Barre syndrome (GBS) A rapid, progressive demyelinating disease of the peripheral nervous system from which most patients will recover.
Gyri Hills or raised-up portions of the cerebral cortex. Singular term is gyrus.
H
Hematoma A collection of blood in a tissue (e.g., subdural hematoma).
Hemianopsia One-sided visual loss.
Hemiballismus The flinging of a limb, occurring on only one side of the body.
Hemiplegia Weakness of one side of the body.
Hemispheric specialization The fact that, in terms of function, each hemisphere is not a mirror image of the other; rather, the two hemispheres function uniquely (e.g., language is a left hemisphere function in most people).
Hemorrhagic CVA A type of stroke that involves a blood vessel bursting and spilling blood into brain tissue or into the meningeal layers.
Hippocampus An S-shaped structure important for declarative memory, which is our memory for facts (semantic memory) and space-time events (episodic memory).
Holism The belief that the whole brain is involved in a mental function, not just a discrete part of the brain.
Holistic dualism A belief regarding human constitution that human persons are integrated wholes. In other words, bodily existence is what it is to be human, and there is no separation between material and immaterial because they are intertwined.
Holmes rebound phenomenon A reflex can be elicited by the patient holding out one of his or her arms while the examiner tries to push down on it. The rebound phenomenon occurs when the examiner lets go of the patient’s arm, which then bounces up significantly.
Holoprosencephaly A failure in brain cleavage resulting in impaired cerebral hemisphere development.
HOME An acronym for the functions of the limbic system: Homeostasis, Olfaction, Memory, and Emotion.
Homeostasis The body’s maintenance of the status quo (stability and constancy).
Hydrocephalus A condition in which cerebrospinal fluid accumulates in the brain ventricles, causing brain tissue to be compressed against the skull.
Hyperkinetic dysarthria A type of dysarthria due to extrapyramidal damage in the basal ganglia. Speech is characterized by a harsh voice, monopitch, loud voice level, imprecise consonants, and distorted vowels.
Hypersomnia Excessive daytime sleepiness that can sometimes be a result of thalamic damage.
Hypertonia Too much tone in muscles, resulting in spastic muscles.
Hypokinetic dysarthria A type of dysarthria due to extra- pyramidal damage in the midbrain’s substantia nigra, which affects dopamine production. Speech includes breathy voice, monopitch, reduced syllable stress, variable speech rate, and imprecise consonants.
Hypomyelination A recessive genetic disorder in which children have a reduced ability to produce myelin, resulting in slowed development and paresis, muscle atrophy, neuropathy, cataracts, dysarthria, and mild to moderate intellectual disability.
Hypothalamus A part of the diencephalon that regulates various body functions (e.g., body temperature).
Hypotonia Too little tone in muscles, resulting in flaccid muscles.
I
Idealism A belief regarding human constitution that the immaterial is all there is and that things in the material world (if there is a material world) are created from the immaterial. Priority is given to the mind.
Incidence The number of new cases per year in a given population.
Infarct A region of dead brain tissue after a neurological event like a stroke.
Inferior From a low position.
Inferior colliculus The auditory center of the midbrain that regulates the acoustic startle reflex, which is when we suddenly move in response to an unanticipated sound.
Initiative The motivation to pursue positive or productive activities.
Inner ear That part of the ear involved in mechanical energy being changed or transduced into hydraulic energy at the oval window and then electrochemical energy at the organ of Corti.
Insular cortex A structure that is folded up and located deep within the lateral sulcus. It contains a posteriordorsal portion involved in sensorimotor functions and an anterior part specializing in orofacial programs and emotions.
Intellectual disability A condition formerly known as mental retardation in which a person demonstrates subaverage intelligence during development that leads to difficulties functioning in his or her environment (e.g., home, school).
Internal capsule A narrow space between the caudate nucleus and the lenticular nucleus.
Interneurons Neurons that connect neurons together.
Intra-axial hemorrhage A type of hemorrhagic stroke that involves bleeding from a ruptured blood vessel inside the brain; compare to an extra-axial hemorrhage.
Ionotrophic receptor A type of postsynaptic receptor that directly opens or closes ion channels.
Ipsilateral Same sided.
Ischemic CVA A type of stroke that involves a loss of blood flow to the brain due to a blockage of some sort.
J
James-Lange theory A theory of emotion that proposes that physiological responses (e.g., trembling) to external stimuli lead to emotional experience.
Judgment A determination of the correctness of information perceived, remembered, and comprehended.
K
Kinesthesia The brain’s awareness of the position and movement of the articulators through sense organs embedded in muscles called proprioceptors.
Kluver-Bucy syndrome A condition caused by bilateral damage to the amygdala and that results in diminished fears, overeating, oral fixation, heightened sex drive, and visual agnosia.
L
Language A generative and dynamic code containing universal characteristics whereby ideas about the world are expressed through a conventional system of arbitrary symbols for communication.
Lateral Away from the body’s midline.
Lateral corticospinal/corticobulbar tract A nerve tract that originates in the motor cortex of the frontal lobe, decussates at the lower medulla-spinal cord juncture, and then inputs along the spinal cord at the ventral horns. Functionally, it is responsible for contralateral movement of the body. Lateral fissure A deep groove in the brain that separates the frontal lobe from the parietal and temporal lobes.
Lateral geniculate body (LGB) An important thalamic visual center that relays visual information from the optic tracts to the primary visual cortex of the occipital lobe.
Lateral lemniscus A tract of six auditory pathways/axons that travels from the cochlear nuclear complex and superior olivary complex to the inferior colliculus in the midbrain.
Lateral superior olivary complex (LSOC) The peripheral part of the olivary complex that specializes in higher frequency hearing.
Lateral vestibulospinal tract An ipsilateral neural tract that descends from the vestibular nuclear complex and terminates in the thoracic and lumbar levels of the spinal cord. The tract stimulates extensor leg muscles in order to maintain a balanced posture, especially when bending over (vestibulospinal reflex).
Law of specific nerve energies A statement that the origin of the sensation (e.g., visual or tactile) does not determine our sensory experience, but rather the pathway it is carried on determines it.
Lenticular nucleus A collection of similar cells involving the globus pallidus and the putamen.
Limbic lobe An arc-shaped brain region on the medial surface of the cerebral hemispheres that involves the cingulate gyrus and other brain structures.
Lissencephaly A condition caused by a lack of reelin, resulting in the brain having a smooth appearance with no characteristic hills and valleys.
Locked-in syndrome (LIS) A condition caused by damage to the ventral pons resulting in quadriplegia and cranial nerve paralysis. Fully aware, conscious people are locked inside bodies that do not work and cannot respond to stimuli. Some patients can communicate through eye blinking.
Long-term memory A type of memory that involves memories that last for days, weeks, months, and even years. Longitudinal fissure A deep groove that separates the left and right cerebral hemispheres.
Lower motor neurons (LMNs) That part of the pyramidal tract that runs from the brainstem through the cranial (or spinal) nerves, thus being housed entirely within the peripheral nervous system.
Lysosomes The garbage collectors of the cell, which use enzymes to break down and recycle used molecules.
M
Macropsia A condition due to dorsal stream of vision damage where things look abnormally large.
Magnetic resonance imaging (MRI) A neuroimaging technique that uses a magnetic current to flip protons within the body’s water molecules. The signal that is produced through this process is picked up by the MRI’s receiver coils and the data are formed into three-dimensional images. Medial Toward the body’s midline.
Medial geniculate body (MGB) An important thalamic auditory center that relays auditory information from subcortical midbrain structures (i.e., inferior colliculus) to the primary auditory cortex of the temporal lobe.
Medial superior olivary complex (MSOC) The center part of the olivary complex that specializes in low-frequency hearing, specifically integrating low-frequency hearing from the right and left ears to create binaural hearing.
Medial vestibulospinal tract Neural tracts that input in the lower motor neuron portions of the cervical spinal cord, resulting in our ability to rotate our head in one direction and our body in the other direction.
Medulla The most inferior part of the brainstem. About 80% of motor fibers cross, or decussate, at this level, and various life function centers are located in it, including cardiac, vasoconstrictor, respiratory, and swallowing centers.
Membrane In human and animal cells, a double-walled structure (bilipid membrane) made up of lipids and proteins that when bonded together are called lipoproteins.
Meniere disease An ear disorder caused by a buildup of inner ear fluid leading to sensorineural hearing loss.
Meninges A three-layer membrane that surrounds and protects the cerebral hemispheres and the spinal cord.
Meningitis An inflammation of the meninges.
Mental-state consciousness From a philosophical perspective, consciousness as it relates to particular mental states and processes; essentially the same as extended consciousness.
Mental status The degree of cognitive competence a person has (e.g., orientation).
Mesencephalon A neurodevelopmental term for those embryonic structures that will develop into the midbrain.
Metabotrophic receptors A type of postsynaptic receptor that uses a secondary messenger (a molecule called a G-protein) to open or close ion channels.
Metastatic brain tumor A tumor that originates somewhere else in the body and migrates to the brain.
Metencephalon A neurodevelopmental term for those embryonic structures that will develop into the pons and cerebellum.
Microcephaly Abnormally small brain mass due to faulty proliferation of nervous system cells during the neural proliferation stage of development (3-4 months’ gestation).
Microglia A central nervous system cell thought to defend nervous system structures by warding off foreign invaders. Micropsia A condition due to dorsal stream of vision damage where objects look abnormally small.
Microtubules Components of a cell’s cytoskeleton that facilitate intracellular transport of molecules within the cell. Midbrain A brainstem structure that lies inferior to the diencephalon and superior to the pons and that contains the cerebral peduncles, tectum, and substantia nigra.
Middle ear That part of the ear involved in acoustic energy being changed or transduced into mechanical energy by the tympanic membrane. This mechanical energy is then transmitted through the ossicular chain (malleus, incus, and stapes) to the cochlea.
Midsagittal A body plane or section that cuts an organ in equal right and left portions.
Mind-brain debate The debate about whether humans have a mind and a brain or just a brain that is either the same thing as the mind or that gives rise to a mind.
Minimally conscious state (MCS) A state in which a person responds purposefully, but inconsistently, to stimuli and does demonstrate brainstem reflexes, a sleep-wake cycle, and electroencephalographic patterns. The condition is thought to be a state between persistent vegetative state and normal consciousness.
Mirror neuron A specialized neuron in the premotor cortex that fires when we watch someone else carry out a motor command, which is important in our ability to watch others and learn new skills.
Mitochondria The cell’s energy factory where oxygen and sugars are metabolized by enzymes and their energy powers the cell.
Mixed dysarthria A mixture of two or more of the pure dysarthrias due to damage to multiple motor systems.
Molecules Substances that consist of two or more atoms held together by a chemical bond.
Monist A person who believes that humans are one substance, a material body (with a brain/mind).
Morphology The study of a language’s word structure; a component of language form.
Motor neurons Multipolar neurons that connect to body structures (e.g., muscles) involved with movement.
Motor speech disorder (MSD) Disorders of the speech system, including the different types of dysarthria and apraxia of speech.
Motor units The motor neuron and the fibers (extrafusal versus intrafusal) it innervates.
Multiple sclerosis (MS) A condition in which the myelin sheath around the axon is damaged by an autoimmune response, impairing the ability of neurons to communicate with other neurons and muscles.
Myasthenia gravis (MG) A progressive autoimmune disease of the neuromuscular junction that affects women in their 30s and men in their 50s. The body’s antibodies block postsynaptic acetylcholine receptors at the neuromuscular junction, resulting in muscle weakness and fatigue.
Myelencephalon A neurodevelopmental term for those embryonic structures that will develop into the medulla.
Myelin/myelination A fatty, white coating that covers axons and aids neural transmission.
Myelitis A general term for inflammation of the spinal cord. Myoclonus Sudden involuntary muscle jerks.
N
Neglect alexia A condition that occurs usually because of damage to the right hemisphere. Sufferers will fail to identify the initial portions of a word or sentence as they try to read.
Neglect syndrome A condition of disengagement in which a patient ignores stimuli (e.g., objects or people) in one visual field or the other, but retains an intact visual system.
Neoplasms An abnormal massing of cells.
Nervous system A series of organs that make communication between the brain and body possible in order for humans to interact with the world around them.
Neural plate An embryonic structure formed around the third week of development when the dorsal ectoderm thickens.
Neural tube A tube from which the brain and spinal cord will develop. It forms around the fourth week of development when the neural plate bends and wraps around itself.
Neural tube defects (NTDs) Conditions in which the neural tube’s neuropores fail to close properly, resulting in a defect of the neural tube.
Neurites Projections (i.e., axons and dendrites) from a neuron’s cell body.
Neuroanatomy The study of the nervous system’s structure.
Neurogenesis A process at the heart of the neural proliferation stage involving the birth of new neurons.
Neurological disorder A disease of the nervous system that impairs a person’s health, resulting in some level of disability.
Neurological exam Systematic examination of the nervous system.
Neurologist A doctor with specialized training in nervous system anatomy, physiology, and pathology.
Neurology The study of the anatomy, physiology, and pathology of the nervous system.
Neuroma An abnormal mass of nerve tissue.
Neuron A nervous system cell with specialized projections that transfers information throughout the body via an electrochemical process.
Neuron doctrine The belief that each neuron is a separate cell and the fundamental building block of the nervous system.
Neuropathology The study of diseases of the nervous system.
Neurophysiology The study of how neurons function.
Neuroplasticity The adaptive capacity of the human brain, meaning that the brain is always changing, rewiring itself in response to internal and external influencers. Neuropores Openings at the ends of the neural tube.
Neurotransmitter A chemical messenger that transmits messages through the synaptic cleft from the presynaptic membrane to the postsynaptic membrane.
Neurulation The process of forming the neural tube.
Noise-induced hearing loss Hearing loss in the inner ear induced by loud noise, usually due to damage in the hair cells located in the organ of Corti.
Nondeclarative memory A type of memory that cannot be consciously brought into awareness. It involves learning, but being unaware of that learning. Also known as implicit memory.
Nonreductive materialism A belief regarding human constitution that experiences (e.g., beauty) cannot be reduced to mere neurological processes, but rather, other processes (psychological, philosophical, and theological) are needed to explain these complex, nonreducible experiences.
Nonsemantic reading A form of alexia in which the person can read real and nonwords, and regular and irregular words without difficulty; however, they do not comprehend what they are reading. Also known as reading without meaning.
Norepinephrine A neurotransmitter that modulates attention, the sleep-wake cycle, and mood.
Nucleolus A component of the nucleus that directs the creation of proteins using the RNA needed to build and repair the cell.
Nucleus That part of the cell that contains DNA, which is the genetic code that regulates the maintenance of the cell and production of new cells.
Nucleus ambiguus (NA) A set of specialized cells located in the medulla that acts as a motor swallowing center that innervates the swallowing muscles via cranial nerves in the peripheral swallowing system.
Nucleus tractus solitarius (NTS) A set of specialized cells located in the medulla that acts as a swallowing sensory center by receiving afferent information, such as touch and taste, from cranial nerves V, VII, IX, and X as well as sensory input from the respiratory and cardiovascular brainstem nuclei and then transferring this information to the nucleus ambiguus.
Nystagmus Involuntary eye movements; sometimes called dancing eyes.
O
Occipital lobe An area of the cerebral cortex that lies posterior to the parietal and temporal lobes and makes up the very back part of the brain. Its main function is visual processing.
Occipitotemporal reading system A posterior neural reading system involving the left inferior occipital area, left inferior-posterior temporal area, and fusiform gyrus that is concerned with visual word form recognition (i.e., sight-reading), rapid access to whole words, and integration of printed letters with their corresponding sounds (i.e., grapheme-to-phoneme conversion).
Ocular apraxia A disorder due to damage to the dorsal stream of vision involving difficulty voluntarily directing one’s gaze to a certain object.
Olfaction The sense of smell.
Oligodendroglia A central nervous system cell that produces and coats axons with myelin.
Open head injury A type of traumatic brain injury in which some object (e.g., bullet, shell fragment, rock) penetrates the skull and causes damage to the brain; compare to a closed head injury.
Optic ataxia A disorder due to damage to the dorsal stream of vision involving difficulty visually guiding the hand to touch an object.
Optic chiasm A structure between the optic nerves and the optic tracts where optic nerve fibers from the nasal retinas cross.
Oral preparatory stage A stage in the normal swallow that is voluntary and variable in length depending on the substance being eaten. In this stage, food is placed in the mouth and is prepared for swallowing through chewing.
Oral stage A stage in the normal swallow that is voluntary, lasting approximately 1 second. It begins once mastication ceases and ends once the bolus reaches the oropharynx. Order The capacity to correctly perform sequencing tasks. Organ A group of tissues that together carry out certain functions (e.g., heart, brain).
Outer ear The portion of the ear that includes the pinna (or auricle) and the external auditory meatus. It is involved in the hearing process that involves the pinna locating, collecting, and funneling acoustic energy (i.e., sound) to the middle ear via the external auditory meatus.
P
Palinopsia A recurring ghost image due to damage to the dorsal stream of vision.
Palsy A condition that involves paralysis, weakness, or even uncontrolled movements (e.g., shaking).
Papez circuit A set of structures (i.e., the sensory cortex, cingulate cortex, hippocampus, hypothalamus, and anterior thalamic nuclei) that make up the human emotional system. Parasagittal A body plane or section that cuts an organ into uneven left and right portions (i.e., not right in the middle of the organ).
Paresthesias Sensations that include such experiences as tingling, prickling, or burning.
Parasympathetic nervous system A part of the autonomic nervous system that calms and relaxes the body through slowing the heart and lowering blood pressure. It is sometimes referred to as the “rest and digest” system.
Paresis Weakness in a muscle or limb.
Parietal lobe An area of the cerebral cortex that lies posterior to the central fissure and superior to the lateral fissure. Its main functions include sensory perception and interpretation. Parietotemporal reading system A posterior neural reading system involving the angular gyrus (Brodmann area 39), the supramarginal gyrus (Brodmann area 40), and the posterior part of the superior temporal lobe that focuses on word analysis and the comprehension of written and spoken language.
Parkinson disease A degenerative disorder of the central nervous system characterized by tremors.
Participation barriers Problems with involvement in any area of life, such as participating in education and employment.
Pathology The study of disease processes that affect both anatomy and physiology.
Perception Recognizing whether information is present, whether it be auditory, visual, or other information.
Peripheral Toward the outer surface.
Peripheral agraphia Writing problems due to visuospa- tial processing and attention problems.
Peripheral alexia Reading problems due to visuospatial processing and attention problems.
Peripheral auditory system An auditory system that involves hearing structures found on the periphery of the head, including the outer, middle, and inner ear as well as cranial nerve VIII.
Peripheral nervous system (PNS) The part of the nervous system made up of the cranial and spinal nerves.
Peripheral neuropathy An inflammation of the peripheral nervous system that results in degeneration of the spinal nerves, usually in the hands and feet.
Peristalsis Involuntary, sequential, wavelike contractions of smooth muscle.
Persistent vegetative state (PVS) A state in which a person does not respond purposefully to stimuli, but does demonstrate brainstem reflexes, a sleep-wake cycle, and electroencephalographic patterns.
Pharyngeal stage A stage in the normal swallow that is essentially involuntary and lasts approximately 1 second. The bolus is moved from the oral cavity, through the pharynx, to the esophagus by pharyngeal squeezing action.
Phineas Gage A 19th-century railroad worker who suffered severe brain injury, yet survived. His case taught neuroscientists much about the functioning of the prefrontal cortex because Gage experienced significant personality changes after his accident.
Phonological agraphia A relatively mild form of agraphia in which patients can write regular and irregular words but have difficulty with nonwords or nonconcrete words (e.g., the word pride).
Phonological alexia A relatively mild form of dyslexia that usually does not affect the reading of real words, but rather the real difficulty comes in reading/sounding out new or nonwords (i.e., pseudowords).
Phonological dyslexia A type of central dyslexia that is a relatively mild form of dyslexia involving reading/sounding out new or nonwords (i.e., pseudowords).
Phonology The study of a language’s sound structure; a component of language form.
Phrenic nerve A nerve that originates mainly from the fourth cervical spinal nerve but receives some help from the third and fifth cervical spinal nerves. It innervates the diaphragm, which, along with other muscles, is crucial for supplying the air power for speech.
Phrenology A study based on the belief that bumps on the skull correspond to certain brain areas (and only those areas) that perform certain mental functions.
Physiology The study of the body’s function.
Pia mater The innermost layer of the meninges that adheres closely to the gyri and sulci of the cerebral cortex. Pineal gland An endocrine gland located in the epithalamus. Pituitary gland An endocrine gland associated with the hypothalamus that regulates growth, stress, reproduction, and lactation.
Planum temporale A triangular auditory area that lies posterior to the auditory cortex and makes up the heart of Wernicke’s area (Brodmann area 22). It is involved in the processing of auditory information.
Plegia Paralysis of a muscle or limb.
Plexus A branching network of sensory and motor nerve fibers that arise from the ventral rami of the spinal cord.
Polymicrogyria A condition associated with errors in cortical organization in which children have too many folds (gyri) in the cerebral hemispheres.
Pons A brainstem structure that lies superior to the medulla and inferior to the midbrain. It acts as a bridge, relaying neural fibers between the cerebrum, cerebellum, and lower structures like the medulla and spinal cord. It contains cranial nerve nuclei and other nuclei that help regulate respiration, swallowing, hearing, eye movements, and facial expression and sensation.
Positron emission tomography (PET) A spatial resolution neuroimaging technology that shows brain activity based on the brain’s glucose metabolism.
Posterior Toward the back.
Pragmatics The practical use of language in everyday life (e.g., conversation).
Prefrontal cortex An area in the anterior frontal lobe that plays an important role in cognition, personality, and emotion. Prefrontal lobotomy A surgical procedure done to help psychiatric patients that disconnects the prefrontal cortex from the rest of the brain, resulting in passivity and a lack of rational decision-making abilities and action based more on impulse.
Prevalence The total number of current cases in a given population at a point in time.
Primary brain tumor A brain tumor that originates in the brain.
Primary cerebellar agenesis A rare condition in which a person is born without a cerebellum.
Priming memory A form of nondeclarative memory that takes advantage of unconscious associations between objects for learning.
Procedural memory A type of nondeclarative memory for skills and habits, like driving a car or riding a bike.
Pronate When the face/ventral surface is down.
Proprioception The body’s eyes for itself or the brain’s ability to know where the different parts of the body (arms, legs) are in space at a given time.
Prosencephalon A neurodevelopmental term for the forebrain, which will develop into the diencephalon (i.e., thalamic structures) and telencephalon (i.e., cerebral hemispheres).
Prosopagnosia A disorder due to damage to the ventral stream of vision involving an inability to recognize familiar faces.
Proximal The point nearest a limb’s attachment.
Ptosis Drooping of the eyelids.
Pupillary light reflex A reflex in which the pupils change in size as light is introduced or removed.
Pure alexia A condition in which the person has difficulty reading, but writing ability is left intact. Also known as alexia without agraphia, verbal alexia, or letter-by-letter reading.
Pure word deafness A rare type of auditory agnosia resulting from damage to Brodmann areas 41 and 42. Sufferers have a pure deficit whereby they cannot understand speech; however, they do not have difficulties with speaking, reading, or writing. Patients report that they can hear the person talking but cannot understand what is being said.
Putamen One of the three structures that make up the basal ganglia. It has a functional relationship with the caudate nucleus, forming the striatum, and an anatomical relationship with the globus pallidus, forming the lenticular nucleus.
Pyramidal neurons The primary neurons found in the pyramidal tract, which are pyramid shaped.
Pyramidal system A direct, voluntary motor system that controls gross motor movement.
R
Radical dualism A belief regarding human constitution that is similar to substance dualism, but the emphasis is on the soul; the soul is the human person and the body is just a mechanism the soul inhabits for a time. This is the “ghost in the machine” view.
Rancho Levels of Cognitive Functioning (RLCF) An eight-level scale that describes the process of recovery from brain injury.
Reasoning The process of acting on information perceived, remembered, comprehended, and judged by drawing conclusions or by making arguments.
Receptive aphasia An acquired language loss in listening and understanding and/or reading.
Red nucleus A paired structure located in the tegmentum of the midbrain next to the substantia nigra. It receives connections from the cerebral cortex, and its axons give rise to the rubrospinal tract that descends from the brainstem and inputs into the spinal cord’s ventral horn cells. This tract modulates flexor tone in the upper extremities and probably participates in activities such as babies’ ability to crawl and arm swinging in walking.
Reductive materialism A belief regarding human constitution that all of life is reduced to the material and to naturalistic explanations. In this view, the mind is reduced to the brain.
Reflex A lightning-quick, unconscious response our body makes to environmental stimuli.
Reflex arc A neural pathway that controls reflexes. When a stimulus occurs, a sensory signal is sent to the spinal cord, which in turn responds and sends a motor signal back to the muscle to move.
Relative refractory period The time when a neuron will respond to another stimulus, but that stimulus must be stronger than normal due to sodium channels still being in recovery mode.
Remembering The storing of perceived information.
Restraint The inhibition of inappropriate behaviors.
Reticular activating system A system that begins in the midbrain’s reticular formation and radiates out to the cerebral cortex through the thalamus; activates and coordinates the cerebral cortex for conscious experience.
Reticular formation A series of nuclei in the center of the brainstem important in cortical wakefulness.
Reticulospinal tract A nerve tract that is involved in muscle tone in the trunk muscles as well as the proximal limbs and overall helps to control a person’s posture and facilitate gait.
Rhombencephalon A neurodevelopmental term for those embryonic structures that will develop into pons, medulla, and cerebellum (i.e., the myelencephalon and metencephalon). Also known as the hindbrain.
Ribosomes Cell structures found in the endoplasmic reticulum that are the primary place for protein synthesis.
Rigidity Stiff muscles that resist passive movement of a limb. Rubrospinal tract A nerve tract that begins in the midbrain, where it decussates and courses down the brainstem and spinal cord until inputting into the ventral horn of the spinal cord. In terms of function, it modulates flexor tone in the upper extremities.
S
Sagittal A body section that divides the body or a specific anatomical structure into left and right portions.
Satellite cells A peripheral nervous system cell that surrounds and nourishes neurons.
Schizencephaly A rare condition characterized by abnormal openings or clefts in the cerebral hemispheres.
Schwann cells Peripheral nervous system cells that produce and coat axons with myelin.
Seizures Electrical storms in the brain.
Semantic agraphia A disorder of writing in which a person has difficulty spelling homophones.
Semantic memory A type of declarative memory involving the recall of facts and general knowledge.
Sensorineural hearing loss A hearing loss caused by problems with either the inner ear, the vestibulocochlear nerve (cranial nerve VIII), or the central processing areas of the cerebral cortex.
Sensory neurons Unipolar or bipolar neurons that connect to sensory structures in the body.
Serotonin A neurotransmitter with both excitatory and inhibitory effects on the nervous system. It plays a role in arousal in the sleep-wake cycle.
Short-term memory A type of memory that involves storage for small amounts of information needed for a short time, such as seconds.
Sign An observation made by an observer sometimes involving equipment, such as a thermometer or blood pressure reader.
Simultanagnosia A disorder due to damage to the dorsal stream of vision in which a patient cannot put the parts of a visual scene together into a comprehensive whole.
Soma A neuron’s cell body.
Somatic nervous system A part of the nervous system that voluntarily and consciously coordinates the body’s skeletal muscles for movement. Contrast with the autonomic nervous system.
Somatosensory system The body sensory system that mediates our experiences of touch, pain, temperature, vibration, and proprioception.
Spastic dysarthria A type of dysarthria due to upper motor neuron damage in the pyramidal system, resulting in stiff, rigid muscles. Speech is characterized by a harsh/ strained voice, monopitch intonation, hypernasality, slow speech rate, and imprecise consonants.
Spatial agraphia A reading problem due to right hemisphere damage in which people have difficulty writing on a straight line and/or may write on one side of the paper or the other and/or will make extra marks on a letter.
Spatial resolution A class of neuroimaging techniques that show the location of brain activity.
Special somatic afferent (SSA) fibers Nerve fibers that conduct visual and auditory information from the eyes and inner ear to the appropriate cerebral cortex area
Special visceral afferent (SVA) fibers Nerve fibers that relay special sense information like smell and taste.
Special visceral efferent (SVE) fibers Nerve fibers that control glands in the head and neck.
Spina bifida (SB) A condition in which a neural tube defect affects the posterior neuropore, resulting in the development of a cyst on the lower back that may or may not affect the spinal cord.
Spinal cord A structure consisting of neural tracts housed in the vertebral column that connects the brain to the body, acting as the information superhighway of the body.
Spinal cord injury (SCI) Traumatic injury to the spinal cord that can result in either paresis or paralysis.
Spinocerebellar tracts Two nerve tracts (dorsal and ventral) that lie on the lateral edge of the spinal cord. They have their origin in the dorsal root ganglions and ascend to input into the cerebellum. They convey proprioceptive information about the body to the cerebellum.
Spinothalamic tract A nerve tract that lies in the lateral ventral portion of the spinal cord. It originates in the dorsal horns and then ascends through the spinal cord and brainstem to the thalamus. The thalamus then relays this tract to the sensory cortex. Functionally, this tract sends the following sensory information: pain, temperature, and crude touch. Strabismus Crossed vision due to poor eye teaming.
Striatum A functional unit of the caudate nucleus and putamen involved in motor activity.
Structural imaging A class of neuroimaging techniques that reveal the anatomy of the brain.
Stuttering A type of fluency disorder in which the smoothness of speech is interrupted beyond the normal disfluencies all people experience. The interruptions often occur within words, though there may be whole-word or between-word disfluencies as well.
Stuttering modification A type of stuttering treatment that focuses on the moment of stuttering and training patients to stutter more easily and with less tension; compare to fluency shaping.
Subarachnoid hematoma A type of hemorrhage that occurs in the arachnoid space, the space below the arachnoid mater.
Subarachnoid space A space below the arachnoid mater that is occupied by blood vessels, spider-web-like support structures, and cerebrospinal fluid.
Subdural hematoma A type of hemorrhage that occurs between the dura mater and the middle layer of the meninges (arachnoid mater).
Subdural space A potential space between the dura mater and the arachnoid mater.
Substance dualism A belief regarding human constitution that humans are both material and immaterial and that the immaterial can exist apart from the material for a time. In this view, the brain is material and the mind is immaterial. Substance P A type of neurotransmitter that sensitizes mammals to pain. It causes inflammation at an injury site, which leads to healing.
Substantia nigra A dopamine-producing area located in the midbrain.
Subthalamus A part of the diencephalon that regulates and coordinates motor function.
Sulci Grooves or valleys in the brain that are not as deep as fissures. Singular term is sulcus.
Superficial cerebral veins Veins in the brain that collect blood from the cerebral cortex and subcortical white matter. Superior From a high position.
Superior colliculi The visual center of the midbrain that receives input from the retinas and the primary visual cortex.
Superior olivary complex (SOC) An area in the pons that is important in integrating auditory information.
Supine When the face/ventral surface is up.
Surface agraphia A writing disorder caused by damage to extrasylvian temporoparietal regions of the left hemisphere. It involves impairments in spelling irregular words (e.g., island), but spelling of regular words is preserved.
Surface alexia Difficulty reading words with irregular print-to-sound correspondences (e.g., island).
Sympathetic nervous system A part of the autonomic nervous system that excites the body for action by increasing heart rate, blood pressure, and adrenaline. It triggers what is known as our “fight-or-flight” response.
Symptom A patient’s subjective report of what he or she is experiencing during an illness (e.g., “my stomach hurts”). Synapse A connection between a neuron and another neuron, muscle, or gland.
Synaptic pruning A process in which extra synaptic connections are eliminated during the cortical organization and synapse formation stage of neural development age (5 months to teen years).
Synaptic theory A theory of short-term memory that states that short-term memory works through neurotransmitter release (acetylcholine) but decays as neurotransmitter uptake occurs.
Synaptogenesis The formation of synapses between neurons during the cortical organization and synapse formation stage of neural development age (5 months to years postnatal). Syncope An episode of fainting in which a person loses consciousness.
и The study of a language’s phrase and sentence structure; a component of language form.
System A group of organs that together carry out certain functions (e.g., circulatory, digestive, reproductive).
T
Tectospinal tract A nerve tract that coordinates the movement of the head and neck with the eyes.
Tectum The roof of the midbrain that is responsible for auditory and visual reflexes.
Tegmentum The posterior portion of the midbrain’s cerebral peduncles, which contains several cranial nerve nuclei. Telencephalon A neurodevelopmental term for the cerebral hemispheres.
Temporal lobe An area of the cerebral cortex that lies inferior to the parietal lobe and posterior to the frontal lobe. Its main functions include the processing of auditory information (including speech) and some memory functions.
Temporal resolution A class of neuroimaging techniques that deal with the time between when a stimulus is introduced and the brain’s response to it.
Thalamic aphasia A type of aphasia with fluent verbal output and semantic paraphasias, auditory comprehension that is less severe than one would expect for the severity of verbal output, and minimally impaired or even intact repetition.
Thalamic pain syndrome A condition caused by damage to the thalamus resulting in burning or tingling sensations and possibly hypersensitivity to things that would not normally be painful, such as light touch or temperature change.
Thalamus A part of the diencephalon that acts as a relay station for sensory fibers.
Theory of mind (ToM) The human ability to understand that I have a mind, you have a mind, and that our minds are different from one another. In short, the capacity to be other-minded.
Thrombus A type of ischemic clot in which the blockage originates within a cerebral blood vessel itself; compare to an embolus.
Tics Repetitive involuntary motor and/or vocal behaviors associated with conditions like Tourette syndrome.
Tinnitus The sensation of ringing in the ears.
Tissue A group of similar cells that come together to carry out certain functions (e.g., muscle tissue, nervous tissue).
Tonotopic organization The basilar membrane’s and auditory cortex’s arrangement or organization by tones (i.e., different areas being sensitive to different sound frequencies).
Top-down attention A type of attention that is volitional and driven by a person’s will.
Transcortical sensory aphasia (TSA) A fluent form of aphasia similar to Wernicke’s aphasia but with paraphasias and echolalia, or repeating what other people say. Unlike people with Wernicke’s, patients with TSA can repeat words said to them. Auditory comprehension is poor, as is reading and writing.
Transducer A device that changes energy from one form to another (e.g., the ear).
Transient ischemic attack (TIA) A type of ischemic stroke involving a temporary loss of blood flow to the brain but with stroke symptoms resolving in a matter of minutes or within 24 hours.
Transport The moving of a substance from point A to point B. May be passive (i.e., no energy expended) or active (i.e., energy expended) in nature.
Transverse A body section that splits a structure into top and bottom portions.
Traumatic brain injury (TBI) Some type of traumatic blow to the brain that impairs the functioning of the brain. Tremor Involuntary, rhythmic shaking in which the shaking oscillates at a certain frequency.
Trephination The process of creating a hole in the skull through cutting, scraping, and/or drilling in order to relieve neurological problems.
Trephine Trephination instruments, usually sharp stones, used to create holes in skulls.
Two-factor theory This theory states that emotion is based on two factors—a physiological state and the interpretation of that state. Also known as the cognitive- appraisal theory.
U
Unilateral upper motor neuron (UMN) dysarthria A milder form of dysarthria caused by unilateral UMN damage that affects only one side of the face and mouth. It usually has minimal impact on speech because the person still has one functional side of the face and mouth.
Upper motor neurons (UMNs) That part of the pyramidal tract that runs from the cortex to the brainstem, thus being entirely housed within the central nervous system.
V
Venous system A waste disposal system in the brain that moves deoxygenated blood away from the brain as well as used cerebrospinal fluid from the ventricular system.
Ventral Toward the stomach.
Ventral induction A neurodevelopmental period in which the face and brain develop out of the superior end of the neural tube.
Ventricles Spaces in the brain that contain cerebrospinal fluid.
Vermal syndrome A condition caused by damage to the cerebellum’s vermis, resulting in trunk muscle unsteadiness, tremor, postural issues, and gait ataxia.
Vertebral arteries Arteries that run up the cervical vertebral column and supply the brainstem, cerebellum, and temporal lobe with blood.
Vertebral column A bony cylinder of 32 to 34 segments that surrounds and protects the spinal cord.
Vertigo The sensation of dizziness.
Vestibular nucleus (VN) A structure consisting of four nuclei (superior, inferior, medial, and lateral [Deiter] nuclei) on each side of the brainstem whose axons make connections with various nervous system structures.
Vestibulocollic reflex A reflex that allows people to rotate their head in one direction and their body in the other direction.
Vestibulo-ocular reflex A reflex mediated by various brainstem auditory nuclei that allows a person to keep his or her eyes fixed on a target while moving the head.
Vestibulospinal reflex A reflex that occurs when the leg extends in response to bending over, helping to maintain a balanced posture.
Vestibulospinal tract An ipsilateral neural tract that originates in the medulla and courses down the spinal cord until inputting into the ventral horn of the spinal cord. Function ally, this tract controls extensor tone, which is the amount of tension present in muscles when a joint is extended. It also mediates the vestibulospinal reflex.
Visceral sensory system The part of the sensory nervous system that mediates general sensory information like stretch, pain, temperature, and irritation in the internal organs as well as sensations like nausea and hunger, for the brain.
Visual alexia An impairment in the way written words are perceived and analyzed during reading. It manifests as letter or syllable substitutions, additions, or omissions.
Visual anosognosia A denial of visual deficits.
W
Wallenberg syndrome A disorder of the medulla involving contralateral loss of pain and temperature in the body, ipsilateral loss of pain and temperature in the face, vertigo, ataxia, paralysis of the ipsilateral palate and vocal cord, and dysphagia.
Wallerian degeneration A degenerative process that occurs after an axon is crushed or cut.
Weber syndrome A condition caused by damage to the midbrain resulting in contralateral hemiplegia and ipsilateral oculomotor paralysis with ptosis.
Wernicke's aphasia A form of fluent aphasia due to damage to Wernicke’s area that results in severe auditory comprehension deficits, verbal jargon, and poor repetition abilities.
Wernicke's area Named after Karl Wernicke, Brodmann area 22, which is involved in attaching meaning to auditory information, especially speech and language.
Wernicke-Geschwind model A model of language function that uses a connectionist framework, connecting the following structures in language tasks: Broca’s area, the arcuate fasciculus, Wernicke’s area, the angular gyrus, and the supramarginal gyrus.
Working memory (WM) A system in the mind that allows temporary memory space for the manipulation of information, like a scratch pad.