In this chapter we will consider the neurology of cognition. We all have the ability to think and remember, but how does this happen? What neurological structures are behind our thinking?
IN THIS CHAPTER
In this chapter, we will . . .
■ Define cognition
■ Describe the mental processes involved in cognition
■ Survey three components of our cognitive abilities: attention, memory, and executive functions
■ Review the neurology of attention, memory, and executive functions
■ Consider disorders in the area of attention, memory, and executive functions
1. The learner will define the term cognition and list various cognitive functions.
2. The learner will define the following: attention, memory, and executive function.
3. The learner will describe the neural basis of attention, memory, and executive functions.
4. The learner will list and describe select disorders of attention, memory, and executive functions.
• Types of Attention
• Neural Mechanisms of Attention
• Attention-Deficit/Hyperactivity Disorder
• Working Memory
• Short-Term Memory
• Long-Term Memory
■ Executive Functions
■ Cognitive-Communicative Disorders
• Right Hemisphere Disorder
• Traumatic Brain Injury
■ Summary of Learning Objectives
■ Key Terms
■ Draw It to Know It
■ Questions for Deeper Reflection
■ Case Study
■ Suggested Projects
If there is one experience that truly tests and shapes our cognition, it is (or should be) college. What is this thing called cognition? Cognition is the mental process of knowing in which we acquire and act upon knowledge. This mental process is made up of at least five general functions: perceiving, remembering, comprehending, judging, and reasoning. Perception refers to recognizing if information is present, whether it be auditory, visual, or other information. Remembering is storing the information. After it is stored, the information has to be understood (comprehension). At this point, judgment occurs as one determines the accuracy or correctness of the information. Finally, reasoning takes place, as evidenced through either drawing conclusions or making arguments.
There are numerous specific cognition functions worth mentioning. These include attention, orientation, memory, new learning, thought organization, reasoning, problem solving, and executive functions. These cognitive functions can be conceptualized through a pyramid (FIGURE 14-1). Attention forms the base of the cognitive functions on top of which orientation, memory, learning new information (i.e., new learning), thought organization, reasoning, and problem solving are built. Finally, executive functions reside at the top, ordering all of the other cognitive components for goal-directed behavior. In this chapter, one example will be surveyed from each level of this pyramid. More specifically, attention, memory, and executive functions will be explored, as well as some select disorders of cognition and communication.
Types of Attention
The neural system behind consciousness makes humans generally aware of themselves and their environment. Building upon consciousness is another cognitive ability—attention. Attention is a person’s focus on a stimulus in the environment. It involves engaging a stimulus over time as well as disengaging from other stimuli (Ward, 2008). It is a very useful cognitive process because it helps us detect important stimuli in our environment and helps us react quickly to them. Attention can be either bottom-up attention (nonvolitional), driven by some characteristic of the stimulus itself, or top-down attention (volitional), driven by a person’s will. For example, if there is a dog in the room (i.e., the stimulus), I can voluntarily choose to look at the dog (top-down). If the dog suddenly barks, then my attention might be involuntarily drawn to look at the dog (bottom-up).
Attention forms the foundation for our other cognitive and language abilities. For example, if one cannot attend to the professor’s lecture, how will one remember anything about it? Attention can be directed toward various types of stimuli, including auditory and/or visual stimuli (e.g., the professor talking and writing on the board). Before talking about the neural basis of attention, different types of attention will be surveyed using a clinical model developed by Sohlberg and Mateer (1989) (FIGURE 14-2).
■ Focused attention: Focused attention is the general ability to focus on a specific stimulus, whether it is auditory, visual, tactile, or the like.
■ Sustained attention: Sustained attention allows humans to focus on a specific stimulus over a certain amount of time. For example, visual sustained attention is crucial for reading this text and gathering all its wisdom.
■ Selective attention: Selective attention or vigilance is the ability to focus on a certain stimulus while ignoring competing stimuli. Using the example of reading this text, a student would be using selective attention if he or she maintains attention on reading while ignoring his or her roommate’s phone conversation.
FIGURE 14-1 Organization of cognitive functions.
FIGURE 14-2 Types of attention. (Note: Focused attention is involved in each of these.)
■ Alternating attention: Alternating attention is exhibited when a person shifts focus from one task to another task. A student might read his or her book, then shift attention to writing an essay, and then shift back to reading the book.
■ Divided attention: Divided attention is the ability to focus on two stimuli at the same time. For example, a person might drive and talk on a cell phone at the same time, though this example may be problematic because driving becomes an automatic task that draws less on our attentional resources. It is also problematic because doing both is illegal in many states. A better example comes from the study by Spelke, Hirst, and Neisser (1976), who studied divided attention by having subjects read stories while also writing down words dictated to them. They found that divided attention abilities could be improved through practice. Wang and Tchernev (2012) found the opposite regarding media multitasking—that this behavior degrades cognitive performance. Students might want to consider this when they are tempted to text or use social media in class.
Neural Mechanisms of Attention
Right Posterior Parietal Lobe
The posterior parietal cortex is known to disengage our attention from a stimulus (Wright & Ward, 2008) (FIGURE 14-3). Neglect syndrome is a condition of disengagement in which a patient ignores stimuli (e.g., objects or people) in one visual field or the other.
The patient has not lost visual abilities in one visual field, which would be a condition called hemianopsia, but rather simply does not pay attention to either the right or left side of space. Studies have shown that neglect is caused, at least in part, by damage to the posterior right hemisphere (Heilman & Van Den Abell, 1980; Katz, Hartman-Maeir, Ring, & Soroker, 1999; Vallar & Perani, 1986). The right hemisphere processes visual-spatial information, and this particular part of the right hemisphere analyzes the where of vision (i.e., objects’ positions in space), which is the dorsal stream of vision. If this ability were damaged, then a patient would not attend to objects in one side of space.
The superior colliculi are located in the midbrain and play an important role in vision. Specifically, they contain a topographic map of the world we see and help direct the head and eyes to new stimuli found in the peripheral vision. In other words, the superior colliculi assist our eyes in shifting attention to a new stimulus (Wright & Ward, 2008). For example, as the author sits at his computer typing, the office door is in the right visual field. As one of the author’s children walks down the hallway by the door, the author’s visual attention is stimulated and he looks over and attends to his child (most of the time!).
The pulvinar nucleus is located in the thalamus and is a prime candidate in attention because of its numerous reciprocal connections to the frontal, temporal, parietal, and occipital lobes as well as subcortical structures, like the superior colliculus. Specifically, it helps to engage and maintain attention to a new stimulus while also suppressing information from stimuli that are not needed, a process called filtering (Ward, 2008). Damage to the pulvinar nucleus can result in both temporal and spatial attention problems, though usually not as severe as damage to the cortical area.
FIGURE 14-3 Attention and the brain. (Note: this is a lateral view of the right hemisphere.)
Frontal Eye Fields
The frontal eye fields are located in the prefrontal cortex in Brodmann area (BA) 8. They are important in visual attention and eye movements. When damaged, the eyes deviate toward the side of injury and/ or display rapid, irregular movement during focusing activities, which is called saccadic eye movements. As Ramat, Leigh, Zee, and Optican (2007) explain, “Saccades are rapid eye movements that redirect the fovea from one object to another” (p. 10). The fovea of the eye is that part of the retina packed with cones that is responsible for high-acuity central vision.
Attention-deficit/hyperactivity disorder (ADHD) is a chronic, genetic condition characterized by inattention, hyperactivity, and impulsivity. It affects approximately 6% to 7% of children. Symptoms include distractibility, trouble staying on task, boredom, daydreaming, trouble following directions, fidgeting, nonstop talking, and impatience. Several genes related to dopamine are affected, and many patients with ADHD take medications like Ritalin, which increase the effect of dopamine and reduce inattention, hyperactivity, and impulsivity. The use of stimulant medications like Ritalin is controversial, with some patients complaining that the drug dulls their senses. Others believe ADHD medications are overprescribed and that some children are simply more active than others are.
Two stories of extraordinary memory are a fitting way to begin a discussion on the topic of memory. S. (1886-1958), a Russian man, remembered everything. His doctor, A. R. Luria, tested his remarkable memory over a 30-year period. The good doctor would give S. lists of words that were sometimes 70 words long, and S. could not only immediately remember all the words but also recall them some 15 years later. S.’s memory was so good that he quit his job and became a mnemonist—a professional stage performer who did memory tricks for a living. As a university student reading about S. one is probably envious, but there was a dark side to remembering everything. He had trouble following stories and integrating new information into older information. In addition, there are many things that we would like to forget in our lives, but S. remembered it all.
Compare the story of S. with the story of H. M. (1926-2008). At around age 10 years, H. M. began experiencing serious epileptic seizures, perhaps due to a bicycle accident he suffered a few years earlier. Even with anticonvulsant drugs, H. M.’s seizures grew more serious over the years to the point where he could not work anymore. It was the early 1950s and the only option left for him was surgery. At 27 years old, H. M.’s medial temporal cortex was bilaterally removed. This removal included the temporal lobe’s parahippocampal gyrus and hippocampal complex. After surgery, he appeared to be the same in personality and intelligence, but a serious memory problem resulted from his surgery. H. M. could not remember some events preceding his surgery (retrograde amnesia), but, more dramatically, could not remember anything that occurred after the surgery (anterograde amnesia). He was frozen in 1953 where Eisenhower was always president, the Cold War was in its early throes, and his mother was always alive. Even though H. M. had these terrible memory deficits, there was an aspect of memory that was still a strength—procedural memory.
The cases of S. and especially H. M. have taught the world much about memory, challenging some long-held false beliefs. What is long-term memory? How long is short-term memory? In patients with dementia, is all memory impaired or only certain types? Can one learn new things and not be aware of learning these things? In this section, new paradigms for memory will be reviewed.
When speaking of memory, almost everyone thinks in terms of long- and short-term memory. Today, neuroscientists conceive of memory in three categories: working memory, short-term memory, and long-term memory. The terms short term and working memory are sometimes used synonymously, but some experts, such as Baddeley (2012), believe there is a distinction between the two. He believes shortterm memory is about temporary storage, whereas working memory (WM) is more about manipulation. In other words, WM can be thought of as a system in the mind that allows for the manipulation of information. Think of it as a scratch pad where verbal and nonverbal problems are worked out. WM involves the use of executive functions, attention, and short-term memory storage. The neuroanatomical structures involved in WM consist of a network that includes the prefrontal cortex, cingulate cortex, and parietal lobe.
Different types of WM have been proposed (FIGURE 14-4). Executive attention control is a type of WM that controls our attention to select a stimulus and suppress other stimuli that might compete with it, which allows us the cognitive space to manipulate or work out the information from the selected stimulus. For example, if someone were to give you a math problem, you would use this form of WM to focus on the problem while suppressing other stimuli (e.g., the TV, the dog barking). Another type of WM is our visuospatial sketchpad, which we use to temporally store visual features of objects, like color, shape, location, and orientation. You might practically use this WM in describing an object (e.g., a flower) to a friend. In the realm of speech-language pathology and audiology, the phonological loop (sometimes called the phonological buffer) is an important type of WM focused on assembling phonemes and keeping them in WM long enough that we can turn them into speech sounds. It also is important for temporarily holding auditory information long enough that we can process and attach meaning to it. Executive attention control WM is the boss of these two types of WM (visuospatial sketchpad and phonological loop) in that it allocates space for them as needed.
Short-term memory is storage for small amounts of information needed for a short time (seconds).
FIGURE 14-4 Types of working memory.
In terms of elements, it is usually described as holding seven elements total plus or minus two. For example, an acquaintance might give you her phone number and you store it long enough to type it in your phone or write it down on a piece of paper. The information in this temporary storehouse will quickly decay unless rehearsed using a memory strategy, like rehearsal. One theory to how it works is called the synaptic theory, which states that short-term memory works through neurotransmitter release (acetylcholine) but decays as neurotransmitter uptake occurs. As mentioned earlier, WM and short-term memory are sometimes lumped together; however, neuroscientists view them as distinct types of memory, associating short-term primarily with holding information, and WM with actively manipulating information.
Many times short-term memories undergo memory consolidation (often during sleep), which means they are converted into long-term storage. Longterm memory involves memories that last for days, weeks, months, and even years. An example might be the trip to the Grand Canyon you took with your family when you were 10 years old. Long-term memory can be broken down into two major categories, declarative memory and nondeclarative memory (FIGURE 14-5).
Declarative memory (or explicit memory) is the conscious, willful recall of memories. The name “declarative” is descriptive of the type of memory; you consciously declare facts or events to others. It involves two subtypes, episodic memory and semantic memory. Episodic memory is memory for space-time episodes in life, like the trip to the Grand Canyon. It often integrates autobiographical memory by placing you as an actor in your memories. Semantic memory is recall of facts and general knowledge. For example, recalling that George Washington was the first president of the United States is a semantic memory feat. Episodic memory is personal, whereas semantic memory is impersonal. Both of these memory types depend on the medial temporal lobe, which contains the hippocampal structures (FIGURE 14-6).
Nondeclarative memory (or implicit memory) is a type of memory that cannot be consciously brought
FIGURE 14-5 Types of long-term memory.
Data from Henke, K. (2010). A model for memory systems based on processing modes rather than consciousness. Nature Reviews Neuroscience, 11 (7), 523-532.
FIGURE 14-6 A transverse section of the brain illustrating important brain structures in memory.
Data from Eichenbaum, H. (2008). Memory. Scholarpedia, 3(3), 1747.
into awareness. It involves learning, but being unaware of that learning. One type of nondeclarative memory is procedural memory, which is memory for skills and habits, like riding a bike (a motor skill) or doing an algebra problem (a cognitive skill). Somewhere one learns how to do these activities, and once learned, one does not need to consciously recall memories to do them. Although H. M. could not make new declarative memories, his procedural memory was intact because his basal ganglia (specifically, the striatum) was neurologically intact. This type of memory is also a strength in patients with dementia and can be harnessed through techniques like spaced retrieval training to teach these kind of patients new skills (BOX 14-1).
Another type of nondeclarative memory is priming memory. This type of memory takes advantage of unconscious associations between objects. For example, showing a person the word “red” might enable the person to more quickly recognize the word “apple” because red and apple are linked together. A baseball analogy would be that red serves to bring apple up “on deck” while other less-related words stay in the dugout. Priming memory appears dependent neuro- logically on the neocortex (i.e., the six layers of the cerebral cortex) (Henke, 2010).
Neural Basis for Long-Term Memory
The medial temporal lobe is a key area in declarative memory. This area includes the parahippocampal gyrus, hippocampus, and rhinal cortices. The rhinal cortices occupy BAs 28 and 34-36 and include the entorhinal and perirhinal cortices. These structures in the medial temporal lobe are crucial for explicit memory consolidation (i.e., making long-term declarative memories); the case of H. M. illustrates the devastation that can occur if these structures are removed or damaged. The flow of information through the medial temporal lobe occurs like this:
Damage to the rhinal cortex causes severe damage to the ability to recognize objects (a semantic memory task), but damage to the hippocampus does not have this effect. Thus, it appears that the rhinal cortices are crucial for semantic memory and the hippocampus is central for episodic memory.
BOX 14-1 Spaced Retrieval Training
Spaced retrieval training (SRT) is a compensatory memory technique that helps people with memory problems learn new information through implicit memory, specifically procedural memory. In this method, the therapist helps the client learn important information (e.g., when to take a pill) through progressively increasing the time between learning trials. For example, if the therapist's goal is for the patient to learn the location of his or her room (e.g., room 121) to decrease wandering around the facility, the prompt would be, "What is your room number?" and the expected response would be "121." The prompt would be offered with progressively longer delays, and if the client were to fail at a level, the therapist would go back to the previous successful time interval and move on from that point. An example of the process might look this this:
Trial 1 (0 seconds)
Therapist: "What is your room number?" Client: "121." (correct)
Trial 2 (after 10 seconds)
Therapist: "What is your room number?" Client: "121." (correct)
Trial 3 (after 30 seconds)
Therapist: "What is your room number?" Client: "121." (correct)
Trial 4 (after 60 seconds)
Therapist: "What is your room number?" Client: "100." (incorrect)
Trial 5 (after 30 seconds)
Therapist: "What is your room number?" Client: "121." (correct)
SRT is an appropriate compensatory treatment method for people with declarative memory problems due to conditions like Alzheimer disease, who need to learn information through intact implicit memory routes. It has been found to be an effective memory strategy for these kinds of patients (see Brush & Camp, 1998; Han et al., 2017; Hopkins, Lyle, Hieb, & Ralston, 2016; Karpicke & Roediger, 2007; McKitrick & Camp, 1993; Oren, Willerton, & Small, 2014; Schacter, Rich, & Stampp, 1985). Try SRT the next time you need to memorize important facts for class, and see if it works for you.
So far, declarative memory has been discussed, but what about nondeclarative memory such as procedural memory? Does it operate on the same medial temporal lobe circuit, or does it utilize other brain structures? The answer is the latter. Nondeclarative memory depends on the basal ganglia, specifically the striatum of the basal ganglia, which includes the caudate nucleus and the putamen. The striatum is located in an important motor loop between the cortex and the thalamus; thus, motor repetition can lead to the establishment of new motor patterns without a person being conscious of this kind of learning. H. M.’s medial temporal cortices were removed and he suffered from profound amnesia, but his basal ganglia were not disturbed and he could still learn through his procedural memory.
► Executive Functions
The word executive features prominently in the familiar term chief executive officer. This term conjures up images of the boss who is in control of the various aspects of a business. In a neurological sense, executive functions are the boss of human cognition. Executive functions order and manage all other cognitive functions (e.g., attention, memory) for the purpose of setting and attaining goals.
The prefrontal cortex is an important neuroana- tomical structure for executive functions. Restraint, initiative, and order are important functions of the prefrontal cortex and, thus, of executive function (TABLE 14-1). Blumenfeld (2010) defines restraint as the “inhibition of inappropriate behaviors” (p. 908), which includes the following areas:
■ Judgment: making reasonable decisions (discernment, wisdom)
■ Foresight: seeing or knowing beforehand (anticipate, envision)
■ Perseverance: holding to a course of action without giving up (steadfastness)
■ Delaying gratification: holding off on things you want
■ Inhibiting socially inappropriate responses: for example, pinching someone
■ Self-governance: governing or ruling oneself and one’s life
■ Concentration: focusing on a stimulus
Initiative involves “the motivation to pursue positive or productive activities” (Blumenfeld, 2010, p. 908) and involves the following:
■ Curiosity: desiring to know and learn, especially about new, strange things
■ Spontaneity: engaging in unpremeditated actions
■ Motivation: having incentive to act
■ Drive: pressing or pushing toward action and goals
Inhibiting socially inappropriate responses
Shifting cognitive set
Data from Blumenfeld, H. (2010). Neuroanatomy through clinical cases. Sunderland, MA: Sinauer Associates.
■ Creativity: having the imagination and ability to create things
■ Shifting cognitive set: shifting thinking from one set of rules to another
■ Mental flexibility: handling different situations in different ways, especially to respond effectively to new, complex, and problematic situations (e.g., adapting to change, taking risks, solving problems in new ways)
■ Personality: having distinctive qualities, character, or traits
Lastly, Blumenfeld (2010) defines order as “the capacity to correctly perform sequencing tasks and a variety of other cognitive operations” (p. 908). Order involves the following:
■ Abstract reasoning: thinking about and cognitively manipulating events, things, or concepts that are not in one’s immediate presence or environment
■ WM: immediately storing information needed for ongoing cognitive operations
■ Perspective taking: stepping into another’s shoes and seeing his or her perspective
■ Planning: working out a program for action beforehand
■ Insight: discerning the true nature of a situation
■ Organization: pulling together items into an orderly whole
■ Sequencing: logically ordering one thing after another (e.g., washing a car)
■ Temporal order: Logically ordering space-time events (e.g., telling a story)
In thinking about how the executive functions control goal-directed behavior, many of the listed functions are crucial to this task. For example, under restraint, one would need foresight to see potential obstacles in attaining a goal as well as perseverance and concentration. Initiative might contribute drive and mental flexibility if obstacles are encountered. Lastly, order would add planning, organization, and sequencing in setting and attaining goals.
There are many disorders that can disrupt executive functions, including ADHD, depression, learning disabilities, dementia, cerebroventricular accidents, and traumatic brain injury. Signs of executive function problems are evident in the three categories presented earlier—restraint, initiative, and order. More specifically, those with executive function problems will have trouble planning projects and projecting the time needed to complete them, organizing thoughts logically in verbal and/or written tasks, and finding the motivation necessary to complete projects. These people will also sometimes struggle with being socially appropriate, which can lead to social isolation.
► Cognitive-Communicative Disorders
Right Hemisphere Disorder
Historically, researchers in neuroscience have been more interested in left hemisphere function than right hemisphere function. In the 1870s, John Hughlings Jackson (1835-1911) was one of the early pioneers in exploring right hemisphere function, but he was followed by a great period of silence until the mid-20th century. Why this silence? It was thought that the right hemisphere was of little importance to communication and, thus, was not important overall.
In the 20th century, interest in this neglected half of the brain increased. Visual spatial deficits related to the right hemisphere were reported in the 1940s followed by an interest in communication problems in the 1960s and 1970s. Profiles of right hemisphere damage began to appear in the 1980s. Public awareness of right hemisphere damage also increased in the 1970s and 1980s through two famous cases. One of these involved the Supreme Court judge William O. Douglas (1898-1980), who suffered a right hemisphere stroke with left hemiparesis in 1974 but appeared to recover well, as he could still talk and write. He returned to the bench after his stroke, but observers of the Supreme Court noticed his communication rambled on and he often asked irrelevant questions; moreover, he denied having deficits, even his left hemiparesis. The other case involved James Brady (1940-2014), an aide to President Ronald Reagan, who was shot in the 1981 assassination attempt on the president. Damage was done to the right hemisphere, but Brady was not like Douglas in his symptomology. His conversations were relevant, coherent, and full of humor. Brady is remembered for the federal gun control legislation that bore his name—the Brady Handgun Violence Prevention Act—enacted in 1993 that mandated federal background checks and a 5-day waiting period for gun purchases.
Right hemisphere disorder (RHD) leads to deficits in two main areas—communication and cognition. Communication problems can be divided into linguistic and extralinguistic deficits. Linguistic deficits include rambling speech, poor coherence in producing and comprehending conversation and narratives, poor comprehension of abstract language and humor, and poor pragmatic skills. Extralinguistic deficits include aprosody and a lack of producing and interpreting emotion. In terms of cognition, we will consider the three cognitive areas we have discussed in this chapter—attention, memory, and executive functions—and look at how they are affected in RHD.
All forms of attention discussed in this chapter may be affected in RHD. This includes sustained, selective, alternating, and divided attention. This impaired attention may affect communication. For example, a person with RHD might not be able to sustain attention in a conversational situation and miss important information from the speaker. In addition, patients with RHD may also suffer neglect, which can impair reading and writing.
Gillespie, Bowen, and Foster (2006) performed a review of the literature on RHD and memory deficits. They found that RHD patients demonstrated deficits in episodic memory, most likely due to attentional problems. Logic would dictate that improvements in attention would result in improvements in episodic memory in this population.
People with RHD often suffer deficits in restraint, initiative, and order. Under restraint, they may demonstrate poor judgment and lack foresight in how their actions affect others. In terms of order, the case of William O. Douglas illustrated his denial of his deficits. This denial is called anosognosia, and this lack of insight (a subcomponent of order) is a major executive function issue in some people with RHD. (Note: Remember that James Brady did not suffer from this symptom.) This denial can be of cognitive- communicative deficits, but also physical problems, like hemiparesis.
Synthesis and inference are also executive function areas of struggle in RHD. These deficits are classified under order, specifically involving organization, sequencing, and temporal order. The Cookie Theft picture from the Boston Diagnostic Aphasia Examination is shown in FIGURE 14-7. Normally, if prompted to tell a story about this picture, a person without RHD would incorporate all the elements in the picture and produce something like the following:
FIGURE 14-7 The Cookie Theft picture.
Goodglass, H., & Kaplan, E. (2001). The assessment of aphasia and related disorders (3rd ed.). Austin, TX: Pro-Ed.
One day a woman was doing dishes in the kitchen. She began daydreaming about being outside in the nice weather. Because of her daydreaming, she did not realize that the water was overflowing from the sink onto the floor. Also, she did not notice her son, Mikey, stealing cookies from the cookie jar. His sister, Cindy, wants Mikey to give her a cookie too. As Mikey begins to take a cookie, he loses his balance on the stool and is about to fall onto the floor. The mom is going to be really upset when she sees the chaos in the kitchen. Mikey will have to apologize to his mom and be disciplined, but then all will be forgiven. The end.
Now compare a narrative from a patient with RHD:
Well, this is a scene in a house. It looks like a fine spring day. The window is open. I guess it’s not Minnesota, or the flies and mosquitos would be flying in. Outside I see a tree and another window. Looks like the neighbors have their windows closed. There’s a woman near the window wearing what appears to be an inexpensive pair of shoes. She’s holding something that looks like a plate. On the counter there, there’s a hat and two caps that look like they would fit on a child’s head.
There is no synthesis of the picture elements into an organized, cohesive narrative in the RHD example. Instead, the focus is on the details (e.g., “inexpensive shoes”), not the whole. There are even times the patient misperceives elements in the picture, like seeing a hat instead of a plate. This focus on the details at the expense of the whole picture can be a significant problem in telling stories to others or in having coherent and cohesive conversations.
Traumatic Brain Injury
Traumatic brain injury (TBI) results when extreme forces injure the brain after a motor vehicle accident, fall, assault, bomb blast, or collision in sports (see BOXES 14-2 and 14-3). The injury sustained can involve penetration of the skull (open head injury) or the brain coming in contact with the inside of the skull (closed head injury). Symptoms of TBI can include headache and nausea as well as cognitive, speech, and/ or language problems.
One of the main cognitive symptoms of TBI is attention problems, which can involve focused, sustained, selective, alternating, and divided attention. Related, TBI patients have poor ability to tune out distractions. In addition, overall cognitive processing speed is slowed by TBI (Ben-David, Nguyen, & van Lieshout, 2011). These problems can lead to vocational and educational issues, because a lack of attention impairs both memory and executive functions, and slowed thinking makes these pursuits frustrating.
The majority of patients (75%) with TBI report problems with memory (Thomsen, 1984). Because of the diffuse nature of TBI, these memory problems can occur in both declarative and nondeclarative memory. A deficit in memory is called amnesia (Greek for “forgetfulness”). There are two main types of amnesia, anterograde and retrograde (FIGURE 14-8). Retrograde amnesia is a loss of some or all memory before the brain injury, while anterograde amnesia is a loss of some or all memory between the brain injury and the present. Anterograde amnesia is the loss of the ability to make new memories post-accident, like in the case of H. M.
In addition to attention and memory, patients with TBI struggle with executive functions. These struggles can impair all three main areas of executive function (restraint, initiative, and order). In terms of restraint, patients will sometimes have difficulty inhibiting socially inappropriate behaviors. For example, they may make sexually explicit statements or inordinately use foul language. Initiative and order deficits can especially impair their ability to set, attain, and evaluate progress on goals. Goal-directed behavior is a part of everyday life. For example, when a college student wakes up in the morning, one of the first things he or she will do is think about what needs to be accomplished during the day and how it will get done. At the end of the day, most will think back and assess how well these goals were achieved and what is left to be done. This skill is often seriously impaired in TBI due to difficulty formulating and initiating goals as well as behavior that might interfere with these goals.
BOX 14-2 Traumatic Brain Injury in the Military due to Blast Injuries
In modern warfare, most head injuries to soldiers are the result of explosions rather than gunshot wounds. During the second Gulf War, many soldiers died or were injured by improvised explosive devices. When soldiers are exposed to bomb blasts, a series of tissue injuries will result due to the primary, secondary, tertiary, and quaternary levels of blast damage (FIGURE 14-9). The primary level of the blast involves the bomb's shock wave, which compresses and releases tissue in the body, including brain tissue. This can lead to concussions. The secondary level of damage results from flying shrapnel, causing open head injuries. The tertiary level of damage occurs when soldiers are knocked off their feet by the explosion. They may suffer a closed head injury due to hitting their head on the group or on an object. Lastly, quaternary levels of damage involve anything not covered under the categories of primary through tertiary levels of damage. This damage might include smoke inhalation or burns from the blast.
FIGURE 14-9 Levels of injury due to explosions.
We experience significant changes to our bodies as we age. Not only do we lose hair, teeth, and bone mass, but our brains change as well. Most people experience a decline in cognitive abilities as they age. More specifically, they experience increasing problems with WM, long-term memory, and verbal fluency. These problems are the result of structural changes in the brain. The brain shrinks with age, and the size of the ventricles increases. Some of this shrinkage is due to neuronal death, but most of it is due to myelin breaking down, the thinning of dendrites, and the loss of synapses.
Some people experience a faster than normal decline in their cognitive abilities. This is usually due to some kind of neurological pathology, such as mild cognitive impairment (MCI). People with MCI have mild cognitive issues that concern them but do not interfere with their daily life. Unfortunately, about 65% of people with MCI develop Alzheimer disease (AD), which as it progresses, seriously disrupts daily life (Sanes & Jessell, 2013).
BOX 14-3 Football and Chronic Traumatic Encephalopathy
In 2002, Dr. Bennet Omalu, a neuropathologist, performed an autopsy on a 50-year-old former National Football League (NFL) player named Mike Webster, who had died of a heart attack. Because of Webster's young age, but poor physical appearance, Dr. Omalu decided to remove and examine Webster's brain. Using a microscope, Dr. Omalu found clumps of tau proteins throughout Webster's brain, a finding similar to what is found in the brains of Alzheimer patients (FIGURE 14-10). Webster had suffered from amnesia, depression, and executive function issues for years, and Dr. Omalu's findings helped explain Webster's deteriorating condition. He named the condition chronic traumatic encephalopathy (CTE), a condition caused by the thousands of subconcussive hits football players suffer, especially linemen like Mike Webster. Dr. Omalu examined four more former NFL players who had suffered from similar symptoms and found the condition in them also. Since 2002, the brains of 111 former NFL players have been examined, and CTE has been found in 110 of them (Mez et al., 2017). A book about CTE in NFL players has been written called League of Denial. The PBS program Frontline produced a documentary film based on this book, also called League of Denial. There has even been a big-budget movie starring Will Smith called Concussion that dramatizes Dr. Omalu's discovery of CTE and the subsequent pushback by the NFL.
FIGURE 14-10 Chronic traumatic encephalopathy shown in immunostained sections of the medial temporal lobe; dark brown color indicates tau protein. A. Top: Whole brain section from a 65-year-old control subject showing no abnormal tau protein deposition. Bottom: Microscopic section showing no abnormal tau protein deposition. B. Top: Whole brain section from John Grimsley (former NFL player) showing abundant tau protein deposition in the brain. Bottom: Microscopic section showing numerous tau-containing neurofibrillary tangles in the brain. C. Top: Whole brain section from a 73-year-old world champion boxer with end-state CTE and dementia showing very severe tau protein deposition. Bottom: Microscopic section showing abundant tau-containing neurofibrillary tangles.
Dementia is a group of progressive neurological disorders that lead to cognitive decline. AD is the most well-known and common form of dementia (BOX 14-4). AD is a neurological condition in which patients experience a relentless decline in their cognitive abilities that results in difficulty completing activities of daily living. It is characterized by three changes to the brain. First, the brain atrophies at a greater rate than what is seen in normal aging (FIGURE 14-12). Second, brain tissue is characterized by amyloid plaques that surround and choke nervous system cells (FIGURE 14-13). These plaques are toxic to neural cells, causing inflammation and impairing their function. Third, neuron cell bodies develop neurofibrillary tangles in them. These tangles also interfere with normal neuronal function. These three signs of AD do not occur throughout the whole brain evenly, but rather occur in specific areas. The area most affected is the hippocampus and entorhinal area, critical structures for declarative memory. This explains why the first signs of AD are these types of memory issues.
BOX 14-4 Types of Dementia
Dementia is a term that describes several conditions of progressive, irreversible cognitive decline. The most well- known form of dementia is Alzheimer disease (AD), named after the German psychiatrist Alois Alzheimer, who first published on the condition. AD accounts for approximately 70% of dementia cases. Vascular dementia is another type of dementia that is caused by small strokes. It accounts for 17% of dementia cases. The remaining 13% of cases are other types of dementia, such as frontotemporal dementia (FTD) (Plassman et al., 2007). FTD involves deterioration of the frontal and temporal lobes, whereas AD affects the hippocampus and more posterior parts of the brain and then progresses forward over time. FTD affects people younger than 65 years of age, while AD's onset occurs after age 65 years.
Primary progressive aphasia (PPA) is associated with FTD, as one of the first signs of FTD is language issues. In comparison, in AD the initial signs are impaired cognition and memory. There are at least three subtypes of PPA (FIGURE 14-11). The first is fluent semantic dementia (SD), which is characterized by fluent language and semantic paraphasias. The second type is progressive nonfluent aphasia (PNFA), which involves labored speech, agrammatism, and phonological paraphasias. The final form is logopenic variant of PPA (LV-PPA). It includes anomia, impaired repetition, and phonological paraphasias. Patients with this logopenic variant can be both fluent when not having word retrieval problems and nonfluent when experiencing anomia. Recently, a possible fourth form of PPA has been described called mixed PPA; it combines features from SD, PNFA, and LV-PPA.
FIGURE 14-11 Types of primary progressive aphasia.
LV-PPA, logopenic variant of PPA; PPA, primary progressive aphasia; PNFA, progressive nonfluent aphasia; SD, semantic dementia.
Data from Mesulam, M. M. (2016). Primary progressive aphasia and the left hemisphere language network. Dementia and Neurocognitive Disorders, 15(4), 93—102.
Alertness and sustained attention are relatively intact in AD until the later stages of the disease (McGuinness, Barrett, Craig, Lawson, & Passmore, 2010). Both selective and divided attention have been shown to be impaired in most forms of dementia, including AD (Baddeley, Baddeley, Bucks, & Wilcock, 2001). This impairment can show up practically in the inability to resist distraction from competing stimuli.
In terms of memory, AD affects WM (Baddeley, Baddeley, Bucks, & Wilcock, 2001) and declarative memory abilities (Bayles, 1991; Salmon & Bondi, 2009). Previously we had seen that WM is dependent on the prefrontal cortex, cingulate cortex, and parietal lobe. As these areas are affected by AD, WM becomes impaired. Also, the hippocampus is one of the first brain structures to be damaged in AD, leading to episodic memory problems followed later by semantic memory issues. Compare AD to another progressive neurological disease, Huntington disease (HD).
FIGURE 14-12 Atrophy of the brain in Alzheimer disease compared to a normal, healthy brain.
FIGURE 14-13 An example of a healthy neuron compared to a neuron in a brain with Alzheimer disease that has neurofibrillary tangles and amyloid plaques.
This condition is genetic, following an autosomal- dominant inheritance pattern in which children of those affected have a 50% chance of inheriting the disease. Like patients with AD, patients with HD develop dementia and memory problems, but their issues are with nondeclarative procedural memory. HD attacks the basal ganglia’s striatum, which is preserved in AD. Procedural memory is a strength in dementia until the late stages of the disease.
Executive dysfunction is a common feature of AD, especially later in the disease (Perry & Hodges, 1999). Restraint, initiative, and order all become progressively impaired. In terms of restraint, AD patients struggle with self-governance and judgment, making them safety risks if left unattended. Initiative to communicate can wain as the disease becomes worse, and when they do speak, their thoughts can lack order and be confusing to the listener.
As a university student, your cognitive abilities should be working at a high level. The different forms of attention mentioned in this chapter are important for class lectures, reading, and other activities. Memory is critical for learning new information (declarative memory) and in learning new skills (nondeclarative memory). Executive functions are also essential for the many exams, quizzes, papers, and projects. In many ways, setting and achieving realistic goals is as important as acquiring knowledge and skills.
How about the patient population? Cognitive skills are necessary not only for college but also for life in general. All occupations require some degree of restraint, initiative, and order. Healthy human relationships require these too. Many patients, after a stroke or TBI, will struggle with these very processes, and it falls to many speech-language pathologists to help patients learn ways to compensate for cognitive impairment, especially in how it affects communication.
SUMMARY OF LEARNING OBJECTIVES
The following were the main learning objectives of this chapter. The information that should have been learned is listed below each learning objective.
1. The learner will define the term cognition and list various cognitive functions.
• Cognition: the mental process of knowing, in which we acquire and act upon knowledge
• Perceiving: recognizing if information is present, whether it be auditory, visual, or other information
• Remembering: storing the information perceived
• Comprehending: understanding the information that has been stored
• Judging: assessing the accuracy or correctness of the information
• Reasoning: either drawing conclusions or making arguments
2. The learner will define the following: attention, memory, and executive function.
• Attention: a person’s focus on a stimulus in the environment. The types of attention include focused, sustained, selective, alternating, and divided.
• Memory: storing information. The types of memory include working memory (WM), short-term memory, and long-term memory. Long-term memory includes declarative or explicit memory (includes episodic and semantic) and nondeclarative or implicit memory (includes procedural memory).
• Executive function: functions that order and manage all other cognitive functions (e.g., attention, memory) for the purpose of setting and attaining goals.
3. The learner will describe the neural basis of attention, memory, and executive functions.
• Attention: right posterior parietal lobe (disengage attention), superior colliculus (assist in shifting attention), pulvinar nucleus (engage and maintain attention), and frontal eye fields (visual attention)
• Memory: WM (prefrontal cortex, cingulate cortex, and parietal lobe), short-term memory (acetylcholine), long-term declarative memory (medial temporal lobe, parahippocampal gyrus, hippocampus, rhinal cortices, and diencephalon), and long-term nondeclarative memory (striatum of the basal ganglia)
• Executive functions: prefrontal cortex
4. The learner will list and describe select disorders of attention, memory, and executive functions.
• Attention-deficit/hyperactivity disorder: chronic, genetic condition characterized by inattention, hyperactivity, and impulsivity.
• Right hemisphere disorder: Caused by damage to the right hemisphere, which results in both cognitive (attention, memory, and executive functions) and communicative (linguistic and extralinguistic) deficits.
• Traumatic brain injury: a condition where patients can have deficits in attention, memory, and executive functions due to a traumatic blow to the head. Speech and language may also be affected, depending on the injury.
• Dementia: the title for a category of irreversible, progressive neurocognitive disorders, the most famous of which is Alzheimer disease (AD). In AD, the hippocampus is one of the first brain structures to be damaged, leading to episodic memory problems followed later by semantic memory issues. Procedural memory is a strength. By comparison, in Huntington disease the basal ganglia degenerate, resulting in nondeclarative memory issues (i.e., procedural memory).
Anosognosia Aprosody Attention Bottom-up attention
Cognition Comprehension Declarative memory Dementia Episodic memory
Executive functions Initiative
Long-term memory Neglect syndrome Nondeclarative memory Order
Procedural memory Reasoning Remembering Restraint
Semantic memory Short-term memory Synaptic theory Top-down attention Working memory (WM)
DRAW IT TO KNOW IT
1. Draw an illustration that would explain the dif- 3.
ferent types of attention discussed in this chapter.
2. Draw a rough sketch of the right hemisphere and label the parts important in attention (see Figure 14-3).
Look at Figure 14-6 and sketch this transverse view of the brain. Highlight and label important memory areas.
QUESTIONS FOR DEEPER REFLECTION
1. List the different types of attention and give illustrations of how you use these in everyday life.
2. What are the cognitive functions, and how do you use them in everyday life?
3. List the neurological structures associated with attention, memory, and executive functions.
4. Define and provide examples of the following: restraint, initiative, and order.
Barry is a 61-year-old male who suffered a (R) cerebrovascular accident (CVA). He spent 3 days in acute care, but then was released home by his physician due to “the patient having no significant residual effects from the CVA” Once home, Barry’s wife began to notice that he was different. Though he could talk fluently and understand what people said to him, he now appeared to ramble on in conversation. Once a gripping storyteller, he now verbally wandered in telling stories, perseverating on details and not telling the overall story arc. In conversation, he is pragmatically awkward as shown by dominating conversations,
1. Read Chapter 8 of Oliver Sacks’s book The Man Who Mistook His Wife for a Hat. Write a one- to two-page summary of this story of neglect.
2. Think about the following cognitive processes: perceiving, remembering, comprehending, judging, and reasoning. Think about your life as a student and give concrete examples of how you use these processes on a daily basis.
3. Think about executive functions and describe how you engage in goal-directed behavior on ignoring hints and request from others for repairs, and lacking an ability to effectively use facial expression and emotion with others. In addition to all this, his wife reports he denies having any problems at all after his stroke.
1. Based on the limited information above, what cognitive-communicative diagnosis do you think is most likely in Barry’s case? What factors lead you to this conclusion?
2. What is the medical term for denial of deficits?
3. What would your counseling look like to Barry’s wife?
a daily basis. Write up your thoughts and share in class.
4. Test your divided attention by attempting to read and talk to a friend at the same time. Write a paragraph describing how successful/unsuc- cessful you were in doing this.
5. Write a case of someone who has suffered a traumatic brain injury who now has executive function and memory problems.
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