ALIEN HAND SYNDROME
A clinical disorder in which the hand of the patient performs actions that are beyond the patient's control. The actions appear purposeful, but the patient claims the actions are involuntary. Alien hand syndrome is also known as the “Dr. Strangelove effect.”
AMNESIA
Loss of memory due to any cause.
ANEURYSM
An abnormal dilatation of a blood vessel. When a brain aneurysm bursts it causes bleeding into the brain and the destruction of brain tissue.
ANOSOGNOSIA
A term first used by Joseph Babinski in 1914, anosognosia literally means “lack of knowledge of the existence of disease.”The patient with anosognosia is unaware of a neurological disability. A patient may be anosognosic for any neurological condition, but the most common form of anosognosia is unawareness of paralysis.
ANTEROGRADE AMNESIA
A variety of amnesia (memory loss) in which the person cannot form new memories. Anterograde amnesia is a common occurrence in patients who demonstrate the syndrome of confabulation.
ANTON'S SYNDROME
This syndrome was named after Gabriel Anton, one of the first investigators to describe the condition. Anton's syndrome is a form of anosognosia in which the patient is unaware of blindness. The blindness may be caused by disease anywhere in the visual system, but most commonly is due to bilateral strokes in the visual cortices of the brain.
APHASIA
A disturbance of language that is caused by brain damage.
ASOMATOGNOSIA
A term that literally means “lack of recognition of the body.” A patient with asomatognosia denies that a part of the body
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belongs to him or her. The most common form of asomatognosia is denial of ownership of a paralyzed left arm.
AUTOBIOGRAPHICAL MEMORY
A general term for memories about the self. Autobiographical memory may include the recall of facts about the self as well as the memories of specific events in one's life.
AUTOSCOPY
A clinical condition also known as heutoscopy. Autoscopy refers to the visual hallucination of one's self. Autoscopy may be due to a variety of neurological and psychiatric conditions, and may also occur under conditions of psychological stress.
BEHAVIORAL NEUROLOGY
A subspecialty of neurology that is primarily concerned with brain-behavior relationships. The behavioral neurologist specializes in the treatment of patients with neurological disorders that cause intellectual and emotional problems.
BILATERAL
Pertaining to both sides of the brain or body
BINDING
The mechanism by which the brain integrates multiple perceptual features into a single object. In the visual system, binding is the process the brain uses to integrate multiple visual features, such as color and shape, into a single object. The“binding problem” describes the question of how the brain can unify in consciousness multiple features of an object if different specialized brain regions code for different features of a stimulus.
BINOCULAR
A term that refers to vision with both eyes.
BRAINSTEM
A neurological term that refers to three structures—the medulla, pons, and midbrain—that connect the spinal cord with the higher brain structures.
BROCA'S APHASIA
A variety of aphasia characterized by slow, hesitant, and effortful speech. The speech pattern of the Broca's aphasic is agrammatic and often characterized as “telegraphic” because it resembles the fragmented pattern of a telegram.
CAPGRAS SYNDROME
A delusional misidentification syndrome in which the patient denies the identity of a person or persons. The patient with Capgras syndrome often claims that the misidentified person is an imposter or double of the “real” person and that there are two versions of the misidentified person. There may also be misidentification of places and objects. Capgras syndrome may be due to a variety of neurological and psychiatric conditions.
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CARTESIANISM
Another word for dualism, the belief that brain and mind are composed of different substances. See DUALISM.
CARTESIAN THEATER
A term introduced by philosopher Daniel Dennett to describe an imaginary place in the brain where all the output of the brain that is destined for consciousness can “come together” for simultaneous viewing.
CAT SCAN
The abbreviation for computerized axial tomography scan. A noninvasive imaging technique that is capable of producing pictures of the inside of the body or brain.
CENTRAL NERVOUS SYSTEM
The nervous system is composed of the central nervous system that includes the brain and spinal cord as well as the peripheral nervous system that is composed of the nerves outside the spinal cord.
CEREBRAL CORTEX
The most highly evolved portion of the brain, the cerebral cortex is the part of the brain responsible for our most advanced intellectual abilities. The cerebral cortex is the uppermost part of the nervous system. It is divided into two large and extensively folded hemispheres. Each hemisphere of the cerebral cortex is made up of millions of neural cells (grey matter) and nerve tracts (white matter).
CEREBRAL HEMISPHERE
The brain is divided into two hemispheres, a left hemisphere and a right hemisphere. The single designation hemisphere applies to either one. Each cerebral hemisphere is composed of the cerebral cortex and three deep structures, the hippocampus, the amygdaloid nucleus, and the basal ganglia.
CEREBROSPINAL FLUID
The fluid that circulates around the brain and within the brain's ventricles.
COMPLETION
A filling-in of missing aspects of a stimulus, especially in vision.
COMPLEX CORTICAL CELLS
A term that refers to a class of cells in the visual system. Complex cells receive converging input from multiple simple cortical cells. Complex cortical cells have more specific properties and larger receptive fields than simple cortical cells.
CONFABULATION
An erroneous yet unintentional false statement. The patient who confabulates is not trying to deceive the examiner. Confabulations vary from long and dramatic narratives to short
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errors of simple facts. Confabulations are traditionally associated with disorders of memory, but many neurological conditions are associated with the tendency to confabulate.
CONFABULATORY COMPLETION
A variety of completion in which the filled-in material is completely a product of the imagination, especially with reference to the completion that is present in split-brain patients.
CONSTRAINT
The control a higher level of a hierarchy exerts over a lower level of a hierarchy.
CONTRALATERAL
A term that refers to the opposite side of the body (e.g., the right hand is contralateral to the left hemisphere).
CONVERGENCE See TOPICAL CONVERGENCE. CORPUS CALLOSOTOMY
A term that refers to an operation on the brain in which part or all of the corpus callosum is cut. This operation creates what is known as the split brain. After a corpus callosotomy, the two halves of the brain are not in complete communication, and one hemisphere may possess information or perform actions out of the awareness of the other hemisphere.
CORPUS CALLOSUM
The massive bundle of nerve fibers that connects the two hemispheres of the brain.
CORTEX
See CEREBRAL CORTEX.
CORTICAL
Pertaining to the cortex of the brain. See CEREBRAL CORTEX.
CYCLOPEAN EYE
Named for the mythical monster “Cyclops,” who had a single eye in the middle of his forehead, cyclopean vision is the normal result of vision that utilizes two eyes. The integration of the two images makes it seem as if we have a visual point of view that originates from a point somewhere between and behind the actual eyes.
DELIRIUM
A mental disturbance characterized by confusion and agitation that is caused by a generalized disorder of brain function.
DELUSIONAL MISIDENTIFICATION SYNDROME
A clinical condition in which a person mistakes the identity of a person, place, or thing. The misidentification cannot be attributed to a simple cognitive disorder.
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The misidentification is delusional because the patient persists in the misidentification even if the error is corrected.
DOMINANT
A term that applies to a hemisphere of the brain when it plays a leading role in a certain function. In right-handed persons the left hemisphere is the language dominant hemisphere and the right hemisphere is dominant for directing attention.
DOWNWARD CAUSATION
Another term for constraint. In a hierarchy, the control a higher level exerts over a lower level.
DUALISM
The philosophical theory that holds that the brain is material and the mind is nonphysical, or at least not composed of the same substance as the brain.
EMERGENCE
A property of a hierarchical system that is in a fundamental way “more than the sum of its parts.” A property that is emergent cannot bereduced to its parts. Some writers claim that the mind is an emergent feature of the brain.
ENCEPHALOMALACIA
A term that refers to an area of softened and dead brain tissue.
ENVIRONMENTAL REDUPLICATION
Also known as reduplicative paramnesia, environmental reduplication refers to the mistaken belief that there are two nearly identical versions of a particular place.
EPISODIC MEMORY
The form of memory that is tied to specific moments in one's life. Episodic memory refers to the memory of things personally experienced as opposed to the knowledge of facts one has learned.
FRÉGOLI SYNDROME
A delusional misidentification syndrome in which the patient claims a person is in disguise or has taken on the appearance of someone else. The Fregoli delusion often takes the form of the belief that someone who is actually a stranger is “really”someone well known to the patient.
FRONTAL LOBES
The most anterior lobes of the brain, the frontal lobes are highly developed in humans and make up a disproportionately large part of the human brain. The frontal lobes have extensive connections with other parts of the brain and they play a particular role in personality, self-regulation, and mental flexibility.
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FRONTAL LOBOTOMY
The operation in which the frontal lobes are surgically removed.
FRONTOCALLOSAL
A region of the brain that involves both a portion of the frontal lobe as well as part of the corpus callosum.
GRANDMOTHER CELL
A hypothetical cell so specialized that it responds only to the face of one's own grandmother. Although no one has ever found such specialized cells, in the visual system there are highly specific cells that respond preferentially to faces or hands. These cells are sometimes referred to as “grandmother cells” or “pontifical neurons.”
HEMIFIELD
One half, either left or right, of the visual field. Due to the crossing of the visual pathways in the brain, the left visual hemifield goes to the right hemisphere and the right visual hemifield goes to the left hemisphere.
HEMIRETINA
A term that refers to one half of the retina of either eye. The information from the right hemiretinas of both eyes is sent to the right hemisphere and the information from the left hemiretinas of both eyes travels the left hemisphere.
HEMISPACE
One half, either left or right, of the space around an organism.
HEMISPATIAL NEGLECT
This term is also referred to as “neglect.” A person with hemispatial neglect ignores stimuli on the side of the body or area of space opposite to a brain lesion. The most severe and longest lasting cases of neglect occur as a result of damage to the right hemisphere.
HEMISPHERE
See CEREBRAL HEMISPHERE.
HEMORRHAGE
A term that refers to any form of bleeding. In this book hemorrhage refers to bleeding into the brain that is often the result of ruptured cerebral aneurysms.
HIERARCHY
An organized system composed of parts that are arranged in some sort of graded series of levels.
HIGHER ORDER
A term that means more abstract, complex, or specific. In the visual neural hierarchy discussed in this book, a higher order cell is further along in the visual pathway and has more complex properties than a lower order neuron.
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HOMUNCULUS
This term literally means “manikin” or “little man.” It describes an imaginary man who is inside the brain and available to view the output of the brain. At one time the homunculus was invoked as an explanation for the unity of consciousness.
HYDROCEPHALUS
A ballooning of the fluid-filled ventricles of the brain due to the accumulation of cerebrospinal fluid.
HYPERCOMPLEX CORTICAL CELLS
Cells located far along in the visual processing stream that receive their input from multiple complex cells. Hypercomplex cells have very specific properties and may respond preferentially to visual stimuli such as the side view of a face or the image of a hand.
INFARCTION
An area of dead brain tissue that occurs as the result of the loss of blood supply to the affected region.
INFEROTEMPORAL CORTEX
An area of the brain in the lower part of the temporal lobe that responds to very complex visual stimuli.
INTENTIONALITY
Derived from the Latin verb intendo, which means to “point at” or “extend toward,” intentional phenomena are about or directed at something. It is supposed by some philosophers to be the mark of mental phenomena.
IPSILATERAL
A term that refers to the same side of the body as the side of the brain (e.g., the left arm is ipsilateral to the left hemisphere of the brain).
LIMBIC SYSTEM
Also known as the emotional brain. A term that refers to a relatively ancient part of the brain that is responsible for emotion and motivation. The limbic system also plays a key role in memory function.
LOWER ORDER
As opposed to higher order, a term that refers to cells with simple response properties.
MATERIALISM
Refers to the philosophical theory that the mind has a physical basis like the brain.
MENINGIOMA
A variety of brain tumor that is usually slow growing and benign.
MITOCHONDRIA
The microscopic organelles contained within the cells of all aerobic (oxygen-requiring) organisms. The mitochondria are responsible for carrying on cellular respiration.
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MODULE
An area of the brain that is supposed to perform a particular discrete cognitive or emotional function. A modular approach to understanding of brain function claims autonomous brain regions perform relatively independent functions. The modularity approach is opposed to the holistic argument that posits the brain performs operations as a whole.
MOMENTARY CONFABULATION
Also known as “provoked confabulation” or the “confabulation of embarrassment,” momentary confabulations are short in duration and are often produced in response to questions that probe the patient's defective memory. Momentary confabulations often serve a “gap-filling” function.
MONOSYNAPTIC REFLEX
A reflex that consists of two neurons, one sensory and one motor, connected by a single synapse. A synapse is the point at which two neurons make contact. The knee jerk is considered monosynaptic because the reflex involves one neuron carrying information from the knee to the spinal cord and a second neuron that runs from the spinal cord to the muscles that move the leg.
MOTOR NEURON
The cell that runs from the spinal cord to the muscle fibers.
MOTOR UNIT
A term that refers to a single motor neuron and all the muscle fibers to which it is connected.
MRI
The abbreviation for magnetic resonance imaging scan. A method of obtaining pictures of the inside of the body. In neurology, an MRI scan of the brain produces a high-resolution picture of the brain's anatomical structure.
NEOCORTICAL
The phylogenetically most recent areas of the brain. The neocortical regions are responsible for all higher thought processes.
NESTED HIERARCHY
A term that describes a certain type of hierarchy. In a nested hierarchy, all higher levels of the hierarchy are physically composed of the elements at lower levels. An example of a nested hierarchy is a person who is composed of organs that are in turn composed of tissues that are composed of cells, and so on.
NEUROLOGY
The medical specialty that focuses on disorders of the nervous system.
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NEURON
A single nerve cell.
NEUROPSYCHOLOGICAL TESTING
A battery of tests that asseses a wide range of cognitive functions such as language, memory, attention, concentration, mental flexibility, and intelligence.
NON-NESTED HIERARCHY
A hierarchy in which all levels of the hierarchy are physically independent.
ONTOLOGY
A philosophical term that refers to what something really is when it is reduced to its essence. The ontology or ontological status of a thing is its true nature.
PAIN ASYMBOLIA
An unusual clinical condition that is caused by damage to the brain. The patient with pain asymbolia is able to discriminate various painful stimuli, but these stimuli do not create the appropriate emotional response. Persons with this condition do not realize that painful stimuli, such as a sharp pin or a match flame, are hurtful and might be harmful.
PARIETAL LOBE
One of the four lobes of the brain, the left parietal lobe plays a significant role in a variety of functions including language abilities, and the ability to calculate, read, and perform skilled movements. The right parietal lobe plays a prominent role in attentional, spatial, and emotional behaviors.
PERSONAL CONFABULATION
A term that describes a variety of confabulation in which the patient tells a specifically autobiographical fictional narrative. The personal confabulation is often a metaphorical representation of the patient's problems.
PINEAL GLAND
A small unpaired gland that is located deep in the middle of the brain. The fact that the pineal is unpaired was a chief reason Descartes chose it as the liaison between the brain, which is composed of two hemispheres, and the unified mind.
PROJECTION
Also known as projicience. The process whereby stimuli on the body surface are experienced as in the world. Since all stimuli that come from the world are received on the body, these stimuli are all projected when they are experienced in the world. An example of projection is light stimuli that when received on the retina are experienced by the receiver as originating from a point away from the eye.
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PROSOPOGNOSIA
A clinical condition caused by brain damage in which the patient cannot visually recognize faces. The patient with prosopognosia can recognize persons by nonfacial visual cues such as clothes or by nonvisual cues such as the sound of a person's voice.
PSEUDOBULBAR PALSY
A condition that is often caused by bilateral cortical strokes that disconnect the higher cortical motor regions from lower centers that control the musculature of the face, tongue, and throat. The patient with pseudobulbar palsy may experience pathological laughing or crying.
PSYCHIATRY
The medical specialty that focuses on mental disorders. There is increasing overlap between psychiatry and neurology.
QUALIA
A philosophical term to denote the way things feel. The subjective feeling of pain and the smell of a rose are examples of qualia.
RECEPTIVE FIELD
The area of space around an organism or on the surface of the body that influences a cell's firing. It is the area of space that a particular cell monitors.
REDUCTIONISM
The scientific program that attempts to explain all higher order structures or events by the analysis of lower order parts and processes.
REFLEX
An involuntary nervous reaction. The operation of a reflex does not require consciousness. An example of a reflex is the knee jerk, where a tap in the knee produces an involuntary jerk of the leg. This reflex will occur even if the person is asleep or in coma.
RETROGRADE AMNESIA
This term refers to a variety of amnesia (memory loss) in which the patient loses memories of experiences that occurred prior to the onset of the amnesia.
SIMPLE CORTICAL CELLS
The cells that are located in area V1 of the brain that respond to simple lines in specific orientations.
SPLIT BRAIN
A patient or animal that has undergone a corpus callosotomy. See CORPUS CALLOSOTOMY.
SPONTANEOUS CONFABULATION
A variety of confabulation that occurs without provocation from the examiner. Spontaneous confabulations are often long in duration and may contain bizarre or fantastical content.
STEREOGNOSIS
The capacity to identify objects by touch alone.
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STROKE
A term that refers to an injury to the brain caused by lack of blood supply to that region.
SYNAPSE
The site of the connection between two neurons.
SYNCHRONIZED OSCILLATIONS
A possible solution to the binding problem, the theory of synchronized oscillations posits that neurons from different brain regions are “bound” together in consciousness by the temporal correlation to their firing. In this way separate brain regions responsible for different features of a single object can be unified in consciousness.
TELEOLOGY
A doctrine that attempts to explain the end result of a process as its cause. In biological theory, it is the school of thought that invokes purpose and predetermined goals to explain the mechanism of natural processes.
TELEONOMY
According to Mayr, a teleonomic process is one that owes its goal directedness to the operation of a program. A teleonomic system does not necessarily foresee the endpoint of its operation. Rather, the achievement of an end result is built into the operation of a teleonomic process. Evolutionary processes produce biological systems that are teleonomic. Teleonomic processes are prominent in development, physiology, and behavior.
TEMPORAL LOBE
One of the four lobes of the cerebral cortex. In addition to visual and auditory functions, the temporal lobes play a particular role in memory and emotional functions.
THALAMUS
A deep brain structure, the thalamus plays a major role in sensory processing. The thalamus receives most of the sensory information that comes into the nervous system and relays this information to the cortex for further processing.
TOPICAL CONVERGENCE
The neural pattern in which several presynaptic neurons simultaneously make connections with a common single postsynaptic neuron. The convergence of multiple lower order neurons onto a single higher order neuron plays a role in the creation of complex perceptual features. The convergence of complex cells that respond to simple lines onto hypercomplex cells that code for a complex stimulus such as a face is an example of topical convergence.
UNILATERAL
Pertaining to one side of the brain or body.
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VENTRICLE
A term that refers to any one of the brain cavities within which the cerebrospinal fluid flows.
V1
This designation refers to cortical area V1. V1 is the primary visual area of the brain and it is the first cortical area to receive visual information. V1 contains simple cortical cells that code for elementary shapes such as single lines.
V5
This designation refers to cortical area V5. V5 is a visual area of the brain that contains cells that are selectively responsive to visual information about an object's movement.
VISUAL AGNOSIA
A clinical condition caused by brain disease in which the patient cannot recognize objects by visual means but may be able to do so by other means such as by feeling the object. The patient is not blind, however, and elementary visual functions are preserved.
WERNICKE'S APHASIA
A variety of aphasia. The patient with Wernicke's aphasia has difficulty with the comprehension of language. The speech output in this condition is fluent but may be meaningless or have frequent word substitutions.
describe another disorder related to the Capgras syndrome.
Frégoli Syndrome
While some patients lose their sense of personal relatedness, others seem to gain the same quality. Four years after the publication of Capgras and Reboul-Lachaux's report, two other French physicians, Courbon and Fail, published a paper entitled“Syndrome d'illusion de Frégoli et schizophrénie.”14 In this report, they described a case of “delusion of doubles.” But while patients with Capgras syndrome found imaginary differences between people, their patient found imaginary likenesses in the people around her—the opposite of Capgras syndrome.
Courbon and Fail described a twenty-seven-yea