KIN240 Principles of Biobehavioral Health PDF

Notes KIN240: Principles of Biobehavioral Health Cognition Trajectories of Cognitive Change How do we rectify the idea that experience/wisdom comes with age, amidst common steroetypes regarding declining cognitive function and poor memory that also comes with age? Some insight into this is provided...

Notes KIN240: Principles of Biobehavioral Health Cognition Trajectories of Cognitive Change How do we rectify the idea that experience/wisdom comes with age, amidst common steroetypes regarding declining cognitive function and poor memory that also comes with age? Some insight into this is provided by clarifying some common misconceptions regarding cognition and by taking into considering how and why specific aspects of cognition change over the course of development and age. While a compelling argument could be made that every aspect of cognition is fundamental for supporting health and wellbeing; there are a few aspects of cognition that have predominately been focused upon that warrant further discussion and clarification. Motor Speed — The time it takes to initiate and complete an intentional movement. Although tests of motor speed are typically viewed as having minimal cognitive demands, they provide essential information regarding the ability to understand and carryout instructions. Thus, if an individual is unable to complete or has difficulty completing tests of motor speed, it calls into question the validity of being able to assess more complex cognitive abilities. They key issue is that the predominate way of assessing more complex cognitive abilities is through the use of speeded responding and intentional decision making based upon directions. So if an individual is unable to complete the motor movement (such as in the case with populations with motor impairments such as Cerebral Palsy), unable to follow basic instructions, or even if the movement is just slowed then that could impact upon the measurement of more complex cognitive abilities. In some context — typically sports related, motor speed is viewed as critically important to support high level performance. Although there are well–established relationships between the complexity of the stimulus and reaction time such that reaction time slows as complexity increases, this is usually attributed to information processing demands rather than being related to motor speed. Tests of motor speed typically utilize very basic assessments such as finger tapping (how many times can you tap your dominant index finger during a 15 second period, repeat for non–dominant hand), simple reaction time tasks (push a button as soon as this light turns on), or ruler drop tests (how far does a ruler drop before it can be caught). Using such approaches, motor speed does show considerable variation across individuals but appears to have © Michigan State University Chapter 11 100 Notes KIN240: Principles of Biobehavioral Health a lower bound. In these simple tasks, in the absence of anticipation responses it appears to take at least 150 milliseconds to execute a response using the dominant/preferred hand, with nondominant hand responses occurring more slowly. Information Processing — The cognitive processes involved with perceiving a stimulus, interpreting its meaning and the corresponding action, and initiating a response. The focus on information processing ultimately reflects attempts to understand basic decision making processes — choosing a response from a set of alternatives to achieve a desired outcome. Although the nature of decision making in the context of an infinite or undefined set of alternatives (e.g., what should my major be?) is particularly expansive; in the case of information processing the focus is much more constrained. The basic situation is that in a given context, the individual is asked to take in environmental information that tells them what decision should be made. The individual must then process that information, assign meaning to it, obtain the action corresponding to the information, and then initiate the response. Although there are a number of hypothesized mechanisms that would enable such a process, it is generally thought that information processing is the result of multiple functional systems acting in parallel. The deliberative system (also sometimes referred to as Type 2 processing) reflects the traditional view of action–selection (choosing what to do) resulting from processing and analysis of the environmental information, consideration of alternative outcomes and potential risk–reward relationships until an action is decided upon. So if you are driving a vehicle in another country and pull up to a sign that you do not know the meaning of, you pull from various sources of information and decide on an action. But this deliberative system is slow, and grows progressively slower with decision complexity. In contrast, the habit system (also sometimes referred to as Type 1 processing) is particularly fast, and requires relatively minimal cognitive effort. The characteristic of this system is that through exposure we begin to learn associations between particular situations and their associated actions. So instead of actually having to processes information to determine the course of action (action–selection), an action can be released as soon as the situation is recognized (situation–recognition). So as you pull up to the sign, you recognize a pattern of behaviors that are consistent with other signs you are familiar with. Instead of having to wait until the deliberative system finishes processing, the habit system brings online the appropriate action based upon the recognized situation. Tests of information processing are amongst the most highly varied of all cognitive © Michigan State University Chapter 11 101 Notes KIN240: Principles of Biobehavioral Health assessments with virtually all cognitive assessments requiring some degree of information processing/decision making. A popular assessment of information processing utilized within intelligence test batteries is the digit symbol substitution test (given a set of digits and symbols, go through and put the symbol associated with each digit) or the trail making task (connect the dots, alternating between letters and numbers in the correct sequence). Attention — The cognitive operations involved with the allocation of resources towards the selection and processing of information. Attention is generally characterized into subdomains associated with how the control of attention is implement. Although necessarily reliant upon sensory information and associated with information processing, the concept of attention focuses on the idea of selecting out only the most relevant and important information from the sensory inputs so that it can be focused upon and utilized. At any given moment our sensory systems are taking in a great deal of information, it is therefore necessary to have some processes that help us focus on the things we are interested in while also retaining some degree of environmental awareness. Alerting (sometimes referred to more generally as arousal) reflects the basic attentional state that an organism exists within. This level of alertness describes the extent to which the organism is prepared to perceive and respond to a given situation. The general perspective is that the level of alertness follows a curvilinear path for optimal functioning. If alertness is too low, the organism has difficulty engaging attention and exhibits generally lethargic (sluggish, slow, lazy) responsivity to environmental cues. If alertness is too high, the organism has difficulty keeping attention focused and exhibits hyperactive/hypersensitive responsivity to environmental cues. While this is biologically helpful in situations where perceiving threat is advantageous, it is generally less useful than having more moderate levels of alertness that allow for both sustained attentional engagement and shifting attention. Orienting enables brief shifts in attention to occur in order to direct attention to items of interest and determine if they warrant further attention. This orienting response can occur in response to environmentally driven sensory input (footsteps or a door slamming) or in response to conscious/voluntary control. Shifts in attention therefore occur when the orienting response causes attention to disengage from what it was previously focused upon, shift to the new stimuli, and then re–engage; potentially repeating this process to return to the original thing attention was focused upon. Executive attention works to sustain attentional engagement despite potential distractions and reflects © Michigan State University Chapter 11 102 Notes KIN240: Principles of Biobehavioral Health aspects of attention popularly known as 'concentration'. The concept of attention is sometimes described as a resource limited 'spotlight'. So long as the attentional needs are low it is possible to extend that spotlight over a larger area, but if greater attentional processing is required then that spotlight must necessarily narrow. A common example of this is the situation of driving your car while listening to music. When the weather is nice you have no issue driving and singing along. However, when the weather gets bad, it is dark, and heavily raining what is the first thing you do? Typically turn down the music. This reflects the resource limited nature of attention, by reducing the volume of the music you enable your system to focus more attention on the primary task of driving. Thus, performance in 'dual task' situations or context in which attention is divided across multiple things is generally explained by the level of attentional/cognitive demand. So long as the total demands do not exceed capacity, it is possible to retain performance despite the dual–task situation. But if the demands exceed capacity (regardless of the reason), then performance would be expected to deteriorate. This concept underlies recommendations for avoiding distracted driving. Cognitive Control — A set of goal–directed, self–regulatory cognitive operations that allow for the optimization of behavioral interactions with the environment. The concept of cognitive control (also referred to as executive control, executive function, and sometimes self–regulation) refers to a set of processes that enable for the selection, scheduling, and coordination of processes underlying perception, memory, and action. Therefore novel tasks, tasks which require planning, problem solving, or intentional choices among alternatives all require aspects of cognitive control. Essentially, this aspect of cognition controls the way other cognitive processes are utilized and enables the shifting of approaches/cognitive strategies to enable us to achieve our goals. The high–level nature of these cognitive operations make it such that they require conscious awareness, are resource limited, and do not become automatic over time (you cannot eventually do it without thinking). Although the concept of cognitive control and its underlying core processes have undergone considerable revisions since it was first proposed, the core cognitive processes which collectively comprise cognitive control are generally believed to include inhibition, working memory, and cognitive flexibility. Inhibition relates to the ability to gate out task irrelevant information that may cause conflict with the desired goals (interference control), inhibit a dominant response to allow for the selection of © Michigan State University Chapter 11 103 Notes KIN240: Principles of Biobehavioral Health the appropriate response (response inhibition), as well as to inhibit a response that has already been initiated (response suppression). Working memory is sometimes also discussed in the context of short term memory; however, the key distinction is that working memory operations specifically enable the holding of multiple items of information within memory and the manipulation of those items to facilitate decision making and behavioral regulation. The term Cognitive flexibility refers to the capacity to alter behavioral goals, shift focus of attention, and strategically alter response behaviors. Although these core processes are functionally distinct in adulthood, they are highly integrated and in some context may not be fully dissociable. Nevertheless, cognitive control operations are vital for maintaining control over the organisms actions despite ever–changing multifaceted environments and varied goal behaviors. During early child development these core processes are not fully differentiated/distinct; which is why research focusing on earlier developmental periods (typically under the age of eight years old) tends to use measures that treat cognitive control as a singular concept. While after this point these core processes become more distinct, they can take another decade or so to reach full maturation. This helps explain the common occurrence during development where a young adult will engage in problematic behaviors. When confronted about those behaviors, they fully recognize that the behavior was problematic but for some reason they were unable to prevent themself from doing it. Thus, either as a result of a failure in inhibition (to stop the problematic behavior) or working memory (to keep the idea of the behavior being problematic forefront in their mind) they still engaged in the problematic behavior. Neuroimaging investigations have revealed a number of anatomical structures that are consistently activated in response to tasks requiring aspects of cognitive control. Thus, convergent evidence suggests that three neural structures are particularly important to support cognitive control operations: the dorsolateral prefrontal cortex (DLPFC) which is responsible for implementing control, the anterior cingulate cortex (ACC) which is responsible for monitoring cognitive operations to reinforce behaviors and signal when adjustments in control are necessary, and the basal ganglia (BG) which is responsible for the selection of motor outputs to execute intended actions. From a neural perspective, the dorsolateral prefrontal cortex (DLPFC) is ideally suited for the active maintenance of task–relevant goals as it routinely exhibits sustained neuronal activity over delays, suggesting the capacity to actively maintain information. The implementation of cognitive control is thought to occur through a cascade of regions in the dorsolateral prefrontal cortex (DLPFC). When exposed to a particular situation, information regarding previous experiences and © Michigan State University Chapter 11 104 Notes KIN240: Principles of Biobehavioral Health previously implemented goal–sets are sent to the rostral (front) portions of the dorsolateral prefrontal cortex (DLPFC). The DLPFC integrates this information and uses this goal/strategy related information to bias decisional processes towards approaches that fit the current goal representations. The caudal (back) portions of the dorsolateral prefrontal cortex (DLPFC) uses this action–schema information along with information regarding specific environmental stimuli to make a decision to act/not act. Information regarding this decision is then sent separately to the the anterior cingulate cortex (ACC) and the basal ganglia (BG). The anterior cingulate cortex (ACC) has been found to be consistently activated in response to tasks or events which are cognitively challenging, novel, or create conflict. Accordingly, the dorsal anterior cingulate cortex (ACC) is thought to integrate information from multiple areas (including the dorsolateral prefrontal cortex (DLPFC) which provides information regarding the current goal-set) in order to detect potential problems (such as conflicting action-schemas or the occurrence of errors) and signal for adaptations in behavior. In such an instance, the anterior cingulate cortex (ACC) then sends information regarding the need for greater control to the dorsolateral prefrontal cortex (DLPFC) so that the decision related process can be revised or supervised to a greater extent, and the basal ganglia (BG) which can better monitor what action was ultimately performed and delay actions if necessary. As the basal ganglia (BG) is a vital structure in the initiation of movements, the extensive connections with both the dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex (ACC) allow for modulations in the motor system to implement flexible shifts in behavior. The basal ganglia (BG) therefore takes in the information from the dorsolateral prefrontal cortex (DLPFC) about the decided upon action, in addition to information from the anterior cingulate cortex (ACC) about potential conflict or need for additional control (restraint) prior to initiating or delaying the desired action. When an action is signaled for, information is sent back separately to the anterior cingulate cortex (ACC) and the dorsolateral prefrontal cortex (DLPFC) to indicate what behavioral response was activated and what response actually occurred (as these could be different). Although the basal ganglia (BG) is most prominently involved in motor commands, it also plays a role in providing a means of interrupting working memory. One of the core tenants of working memory is that it can rapidly update and maintain information; however, in a resource limited system these functions are ideologically at odds with each other in that if you are continuously updating information then it is not possible to maintain information within © Michigan State University Chapter 11 105 Notes KIN240: Principles of Biobehavioral Health the same system. Accordingly, the the dorsolateral prefrontal cortex (DLPFC) intrinsically assumes a maintenance state (holding information within active memory), with the basal ganglia serving as a interrupt signal that enables rapid updating mechanisms to alter that information within the DLPFC when necessary (Frank et al., 2001). Interaction between these three structures therefore enable the three very different cognitive control processes to maintain control of actions despite the potential presence of conflicting, difficult, or unfamiliar situations. Declarative Memory — The cognitive processes involved with the the ability to encode and recall specific facts, events, and details. The process of memory must take meaningless sensory information and translate it into meaningful patterns, store/consolidate those patterns, and then retrieve that information at a later time. Declarative memory reflects a specific subtype of long–term memory (the ability to permanently hold information in your mind). However, unlike what is commonly represented in popular culture, this information is not stored as a perfect ‘snapshot’ or ‘recording’. Prominent theories of memory suggest that it is largely stored relationally, encoding small bits of information that link with multiple context. The nature of declarative memory, however, makes it such that it largely requires conscious effort to encode and retain information. The concept of declarative memory is commonly differentiated into aspects related to Episodic memory which encompasses information regarding personal events and Semantic memory which encompasses information about vocabulary, everyday items, and general information (such as what you are learning in class). The encoding and retrieval of information from declarative memory is thought to be primarily supported by the hippocampus and other structures within the medial temporal lobes. Clarifying Some Cognitive Concepts The concept of intelligence tries to explain why some individuals exhibit a greater ability to be successful; to judge, comprehend, and adapt to the environment; to think rationally and act purposefully. The general popularity of the concept of intelligence reflects its emergence as a solution to two issues that were particularly prominent in the early 1900's, who should be admitted to schools and who should be placed within leadership positions within the military. During this period in history there was widespread educational reform resulting in a greater number of children attaining access to school, and multiple global conflicts requiring escalation of military service. © Michigan State University Chapter 11 106 Notes KIN240: Principles of Biobehavioral Health The earliest forms of intelligence tests assessed the ability to use language, follow instructions, and remember items; characteristic abilities that generally improve over the course of childhood development. The concept of intelligence (IQ) was thus expressed as the ratio between the individual's mental abilities and their current age (multiplied by 100). So in this sense, an IQ of 70 would indicate that the individuals mental abilities are at 70% of the level expected for their current age; whereas an IQ of 130 would indicate that the individuals mental abilities are at 130% of the level expected for their current age. In this way intelligence is not about being 'smart' but rather about having general cognitive abilities (use language, follow instructions, and remember items) consistent with or exceeding your age. Armed with this perspective, schools and the military used and promoted this concept of intelligence as a way to justify the exclusion of individuals who exhibited lower abilities to use language, follow instructions, and remember items. Over the course of the next century, substantial research in this area began to conceptualize intelligence not as a unitary concept, but rather as a reflection of a combination of cognitive abilities. A particularly prominent perspective viewed intelligence as primarily segmented into crystallized and fluid components. Crystallized intelligence consists of those knowledge and abilities that an individual has already acquired. So tests of crystallized intelligence will have individuals name pictured objects and answer vocabulary related questions to assess the things that the person knows. Fluid intelligence consists of the individuals ability to solve novel problems through the use of reasoning. So rather than testing what the individual already knows, tests of fluid intelligence will have individuals solve pattern related puzzles to get at their problem solving ability. Cattell–Horn–Carroll (CHC) Theory of Intelligence — Conceptualization of the structure of human cognitive abilities into narrow factors associated with specific cognitive abilities that generally cluster together into related broad categories of cognition. The Cattell–Horn–Carroll (CHC) theory of intelligence is named in recognition of these scholars early work and contributions in understanding aspects of cognition. This theory considers over 80 different specific cognitive abilities (such as the ability to remember auditory patterns for a short period, the ability to hear words despite background noise, the ability to remember complex patterns) which are viewed as as the lowest (narrow) level of cognition. To clarify, however, this theory does not contend that these are the only aspects of cognition or that these aspects of cognition are unimportant. Rather © Michigan State University Chapter 11 107 Notes KIN240: Principles of Biobehavioral Health these cognitive abilities are those that are classically assessed by many existing test batteries generally because they have been shown to elicit deviant performance in response to particular issues. By considering how strongly these various cognitive abilities relate to each other, broad cognitive abilities are then constructed representing the combined performance on the specific cognitive abilities within the broader ability. So the broad cognitive ability of visual processing is made up of performance across a variety of tests which relate together such as spatial scanning (quickly and accurately scanning a visual field), visual memory (remembering complex visual images), and visualization (perception and rotation of visual images). Performance on each specific cognitive ability is standardized against others of a similar age who completed the test and then combined to create a metric of their broad cognitive ability within a domain. By combining performance across broad cognitive abilities, a 'global' score of general intelligence (g) can then be obtained. The benefit and popularity of this model is that it enables a wide variety of traditional psychological assessment tools to be brought together despite utilizing assessments of different cognitive abilities. As long as these different psychological assessment tools ultimately characterize the same broad cognitive abilities, the fact that they test different specific cognitive abilities is irrelevant. Although the assessment of intelligence is critically important given state and federal mandates that have integrated these assessments into processes for securing additional funds for student services, equal rights provisions, and even mental–health diagnosis; it is important to also understand that the very nature of such a concept is debated; as is the way it is assessed. Amongst one of the many criticism of typical intelligence based views on cognition, is that to assess this concept you have to utilize broad based cognitive batteries which attempt to assess cognition across too many cognitive abilities. This is not unique to just intelligence tests, but also applies to popular 'neuropsychological assessment batteries' which assess multiple aspects of cognition and then attempt to combine performance to create a singular usable metric, as well as tests of academic achievement. Such batteries must navigate multiple competing issues. First, is the issue of psychometric stability. In order to provide a usable measure of a cognitive domain, it is necessary to have multiple questions, attempts, or trials. Although there is no set 'minimum', having very few questions increases the relative influence of performance on that question. If you were to take an exam with only two questions on it (each question worth 50 points), your performance on each question would be weighted more heavily than on an exam with 50 questions (each question worth 2 points). So an error on a single question would © Michigan State University Chapter 11 108 Notes KIN240: Principles of Biobehavioral Health have drastically different implications. Similarly, if we were interested in assessing your visual search abilities, having a greater number of trials on a given test increases the stability of the assessment. You might be particularly fast on one trial, very slow on another, but with multiple trials we could obtain an assessment of your general abilities. A general rule–of–thumb — which is based upon motor based assessments — is that you should obtain at least 30 samples of something to reduce the potential for any one individual sample to skew the result. However, there are a variety of arguments for why that should or should not apply outside of motor responding. However, more trials means that the assessment will take longer. The issue of assessment duration is not just of practical importance — it is more difficult to schedule very long duration testing sessions, but also relates to issues such as cognitive engagement and fatigue. A comprehensive intelligence battery can take over 4 hours. Although traditional cognitive views treated these concepts as highly stable with very little day to day variation; those views have gradually been replaced in recognition that cognitive function can change over a period of only a few minutes. Consider how your cognitive function changes following consuming a cup of coffee or caffeine. Classic research from radar operators indicates that sustained cognitive engagement rapidly declines following a period of only 20 to 40 minutes. So assessments that last longer than this would have to manage if reduce performance was the result of lower cognitive abilities or the long assessment duration. The more cognitively demanding, the sooner assessment duration would likely have an effect. Finally, it is also important to consider the sensitivity of the given assessment — what is ultimately being assessed? Consider a test of mathematical ability. Is the test trying to determine differences in performance associated with age/grade, if so then there can be relatively large jumps in question difficulty (addition, subtraction, algebraic expression, matrix multiplication, calculus). Or is the test trying to determine understanding of a specific type of mathematical ability such as calculus, if so then the questions would be more specific to limits, derivatives, and integrals. But if the test is too sensitive, you increase the risk of saturation. If you give a calculus-focused test to 3rd graders, it is very likely that you will run into floor effects where performance is all at the level of chance (or even below). If you give a test of addition–subtraction to college–students, it is very likely that you will run into ceiling effects. In either case there is very little meaningful variation in performance to look at, as the measurements become saturated and unable to differentiate what you are interested in assessing. So there must be a © Michigan State University Chapter 11 109 Notes KIN240: Principles of Biobehavioral Health balance of the sensitivity of the instrument: very insensitive instruments tend to be applicable to a wide variety of populations but may miss important differences, very sensitive instruments tend to be able to detect even small differences but only if properly tailored to the group of interest. Since we would need to have a sufficient number of questions on each mathematical concept being assessed to obtain a stable measure, but not so many that the individual would fatigue or that it would take too long to administer; we have to be intentional about the sensitivity of the assessment. When put into practice, assessments of cognition make intentional choices reflecting a balance of these issues. Take for instance the Immediate Postconcussion Assessment and Cognitive Testing (ImPACT) program that is widely used to assess cognitive functioning of athletes before and after a concussion. This test is designed to be completed in under 20 minutes, and uses 8 cognitive assessments; meaning each aspect of cognition is allocated less than 3 minutes for assessment. The test is further designed to be completed by those age 12 to 80, which represents a substantial broad range of assessment for aspects of attention and memory. Thus, while this assessment is good at identifying major deviations in cognitive abilities following a concussive injury, the sensitivity of the measure is quite poor for detecting smaller persistent deficits that may remain. Again this is not unique to this one tool, and there are a variety of reasons to explain why organizations might mandate the use of tools that lack sufficient sensitivity — it may be to reduce the occurrence of false positives (where the individual may be prevented from participating), it may be to focus efforts on only those with the most severe issues (because there is often not enough money to help everyone), or it may be intentional to enable claiming that there is no issue to be worried about (such as what is alleged to have occurred in the NFL). As most popular 'neuropsychological assessment batteries' and intelligence tests were designed to pick up large scale differences that might represent grade level or clinically significant impairment, it is important to understand that they may lack the nuance to capture smaller changes in cognition which might be observed in response to several weeks or months of a given treatment. It is also important to acknowledge that many popular tasks used in neuropsychological assessments came into fashion prior to the emergence of more modern definitions of particular aspects of cognition. Thus, rather than designing a new cognitive assessment to very carefully get at the aspect of cognition of interest; these tasks may actually require cognitive operations that pull from multiple cognitive domains. The argument is that these tools have been used for decades and have substantial bodies of research behind them. If we were to change the tool being used, how might that impact upon how they are © Michigan State University Chapter 11 110 Notes KIN240: Principles of Biobehavioral Health used? The issue, however, is that if the modern perspective on how a cognitive process might operate is no longer aligned with the nature of the task; how do we explain what causes a change in performance on the task. While it is certainly possible that changes in performance on the task could be explained by changes in the aspect of cognition of interest, they could just as easily be the result of changes in one or many other aspects of cognition. Relatedly, if a task engages multiple different aspects of cognition it also increases the potential for compensatory action of other aspects of cognition to potentially confound our understanding of what changes may be occurring — although one aspect of cognition may be impaired, performance on the cognitive task is sustained by relying upon different cognitive strategies or by bringing online different cognitive processes which may not have been previously involved. Thus, there is considerable debate over the use of some popular assessments and how their findings should be interpreted. One of the critical concepts to keep in mind with the study of cognition is that cognitive function is ultimately an artificial construct — an idea containing a composite of various conceptual components. As a result, there is no singular method of assessing cognitive health that encompasses all of these various conceptual components. Further complicating the matter, the underlying components that make up cognitive function are not uniformly defined. What that means is that there is no singular framework that is commonly accepted for differentiating types of cognitive function. Separating cognitive function into cognitive skills (thinking, problem solving), affective skills (emotional reactivity, interpersonal interactions), and psychomotor skills (manual motor skills) is equally valid as approaches that separate cognitive function into domains associated with attention, memory, and language. So although the Cattell–Horn–Carroll (CHC) theory of intelligence framework of cognitive abilities is popular within neuropsychological specialties, other specialties bringing expertise on neuroanatomical connections and/or neural—network based approaches to artificial intelligence generally view these cognitive abilities differently. Brain — The primary organ of the central nervous system. A physical structure. Mind — The psychological phenomena experienced during mental states. An abstract concept. The reason that there is no singularly accepted framework for differentiating types of cognitive function is that cognition is a manifestation of the psychological phenomena known as the mind. © Michigan State University Chapter 11 111 Notes KIN240: Principles of Biobehavioral Health In some ways it can be appealing to consider these concepts in terms of hardware and software. The physical structures and biochemicals that make up the brain can be characterized as the biological hardware, whereas psychological phenomena form a mental operating system enabling us to interact with the external environment. Cognitive functions thus reflect our interpretations of how that mental software could be laid out, organized, or described. But in considering the brain–mind in this manner, it is often easy to get caught in the trap of assigning psychological phenomena to particular structures within the brain. Certainly we can point to evidence regarding how the absence, loss, or damage to particular structures within the brain impacts upon the psychological processes of the mind; but as our conceptualization of psychological phenomena evolves, the particular brain structures that may support a given psychological phenomena would necessarily change as well. So it is relatively common to see both the description of psychological phenomena and the brain tissue associated with the phenomena change and differ across historical and modern perspectives — this is exceptionally common for the concepts of attention and cognitive control. The key is that cognitive processes do not necessarily have to have a biological basis, and the brain issues involved in supporting cognitive processes can change in response to a variety of context. Another factor that contributes to difficulty in understanding the link between the brain and mind results from our level of robustness — the ability to maintain function despite perturbations (disturbances) and uncertainty. Consider that the across a wide–range of potential issues (infection, disease, accidents, intoxication), aspects of our mental skills remain relatively intact and allow us to continue to function. This robustness is achieved through strategies such as modularity, redundancy, and degeneracy. The organization of neural networks and cellular architecture within the brain exhibit a great deal of modularity, being structured into a system of core segments that are spatially or structurally isolated. The benefit of this approach is that even if there is damage to some of these structures, the remaining elements are usually sufficient to continue to enable the organism to function. The idea of redundancy is that multiple modules or elements can perform the same essential process. Therefore, even if there is damage within a particular module (such as to a subset of cells), a core process can still be completed by other identical elements. Degeneracy in neuroscience refers to the capacity of many different unrelated modules to create the same outcome. So if a particular module becomes damaged or performs suboptimally, other neural regions can compensate to create the same process. Therefore, while a psychological processes of the mind may be primarily supported by a particular region of brain tissue; © Michigan State University Chapter 11 112 Notes KIN240: Principles of Biobehavioral Health it is not uncommon (and in many cases is expected) that other regions of brain tissue and neural networks can create the same psychological processes of the mind. The same is true for cognitive operations. Even when the brain tissue is intact, changes in neural resource availability or strategy may require degeneracy such that compensatory action of other aspects of cognition can make up for the loss of or deficiency of another. Fixed Capacity Perspective — The idea that each individual has a particular limit to their cognitive abilities. While it is possible to improve cognitive abilities, the ability to improve diminishes as the individual nears this limit. Dynamic Capacity Perspective — The idea that cognitive abilities reflect their utilization. Improvement in cognitive abilities therefore reflects the way those abilities are consistently used and stressed. The analogy of hardware–software also sometimes contributes to fixed perspectives regarding systems of the brain and mind. Although the fixed capacity perspective actually predates the emergence of computers, this perspective exerted a particularly prominent influence in views that guided early concepts related to intelligence. When combined with sociocultural biases it then enabled problematic social behaviors to be justified. A child growing up in a poor farming family would have less opportunity to gain exposure to certain vocabulary, ways of speaking, and general access to early childhood education. As a result they would tend to perform more poorly on tests of intelligence. When viewed through the lens of the fixed capacity perspective, this was interpreted as suggesting that the child would likely have a lower educational ceiling and formed the basis for excluding them from educational opportunities. Yet unlike conventional computer hardware that limits what is possible for the computer software (or operating system) to do, psychological phenomena of the mind can induce alterations in the physical structures of the brain to better support those phenomena — a concept referred to as neural plasticity. Thus, although some remnants of the fixed capacity perspective still exist; more modern approaches generally follow the dynamic capacity perspective. The reason a child growing up with more highly educated parents tends to have greater 'intelligence' is generally explained by having a greater opportunity to gain exposure to certain vocabulary, ways of speaking, and greater general access to early childhood education. Early exposure and stressing of those abilities results in changes in cognitive processes and the physical structures of the brain; which then enable higher © Michigan State University Chapter 11 113 Notes KIN240: Principles of Biobehavioral Health educational attainment. Critically, evidence indicates that this is not dependent upon age. Take for instance evidence showing that relational memory (a subtype of declarative memory) is enhanced through experience as a taxi driver. Relational memory describes a critical cognitive ability regarding remembering how things are linked together and is supported by the hippocampus (a structure of the brain located in the medial temporal lobe). In a fixed perspective, an individual would be limited in their relational memory abilities. Thus, either in terms of their mental relational memory capacity or by the size and functioning of this neural structure, an individual would have some maximum ceiling at which the mind–brain become limited. Thus, relational memory could only improve up to this point. However, research has found that the volume of the hippocampus expands in response to experience as a Taxi driver (who has to remember how to navigate across complex urban environments) in association with increases in relational memory. Thus, as a cognitive ability is utilized, the brain tissue/networks supporting that process also undergo changes to allow the enhanced function. Given such abilities both the brain and mind are considered as dynamic, rather than fixed, systems prone to alterations reflecting their use/disuse. In this context, an increasingly common view is to consider cognitive operations much like a muscle; with consistent progressive overload these processes will enhance their capacity, but with disuse/neglect these processes will atrophy. Age Related Changes in Cognition One of the difficulties with studying how human cognition changes across the lifespan is our relatively long lifespan. As a result, much of our understanding of this area of research comes from cross–sectional comparisons of individuals at different stages of life and longitudinal studies that follow individuals across a smaller window of time. Nevertheless, such research generally aligns to indicate that although aging is associated with general declines in cognition, it is not universal for all aspects of cognition. Throughout development, semantic memory (crystallized intelligence, what you already know) tends to increase in a relatively linear trajectory from infancy throughout late adulthood (around 65 years of age). But interestingly, longitudinal studies of older adults have observed that semantic memory can still continue to improve even after this point. From a dynamic capacity perspective this would seem to make a great deal of sense. As an individual goes through their life, they accumulate greater exposure to new information, facts, and details. Although encoding (storing) this information into memory takes effort, that information which is stored then accumulates to enable © Michigan State University Chapter 11 114 Notes KIN240: Principles of Biobehavioral Health semantic memory to increase over the course of the lifespan. Episodic memory (what you experienced) tends to similarly increase throughout late adulthood (around 65 years of age), but then tends to stabilize (no longer continue to increase, but does not necessarily decrease) during older adulthood. Research in this area has taken a number of different views on this stability, but the general argument is that stabilization necessarily reflects loss of function (if we assume that episodic memory should increase similar to semantic memory). In the context of visiting your grandparents, this view becomes more readily apparent by their ability to easily retell a story about the neighbors/friends that happened 50 years ago — even in regards to something as mundane as that they took a fence down. Yet despite this your grandparents might have trouble remembering new information — such as asking your parents about their 'new' car even though they got the car a decade ago. Although episodic memory tends to remain relatively intact during older adulthood; this is only for memories that were formed earlier in life. Unfortunately, fluid intelligence and virtually every other cognitive process begins to decline after the age of 20. For aspects of cognition relating to motor speed, information processing, and attention these declines are relatively linear in nature, with each decade of life after age 20 contributing to gradually reductions (about a quarter of a standard deviation each decade) in performance on measures of these domains. Developmentally, these aspects of cognition also appear to reach optimal levels relatively early. Although their remains debate as to exactly how early this may be, the general consensus is that these reach peak levels between the ages of 12 and 15 years of age. This generally aligns with evidence from e–sports indicating peak performance generally occurs when the individual is between 12 and 20 years of age, with retirement from professional e–sports generally occurring after the age of 25. Although aspects of cognitive control and memory also begin to decline after the age of 20, there appear to be two critical windows when changes occur most dramatically. An initial small reduction (about a quarter of a standard deviation) in cognitive control and memory abilities tends to occur as individuals transition between the 20th and 30th decade of life. Cognitive control and memory then tend to stabilize from the 30th to 60th decade of life before exhibiting a large reduction (nearly half a standard deviation) each decade after. However, it is important to note that such findings are only present when the cognitive task is sufficiently difficult. So long as the level of cognitive control necessary to complete a task or the level of effortful memory search is low there are minimal or nonexistent age © Michigan State University Chapter 11 115 Notes KIN240: Principles of Biobehavioral Health differences. Mechanisms of Cognitive Aging Although there is no singular common perspective on cognitive aging, the various views generally center around the issue that with aging comes declines in the ability to utilize mental resources quickly. These views ultimately differ in the way in which they view the mechanism contributing to this decline. Critically, it is important to acknowledge that these perspectives are not mutually exclusive to each other, as there may be multiple factors that ultimately contribute to such dysfunction. Sensory Function Theory of Cognitive Aging — Age–related effects in performance are the result of impaired sensory function. The central tenant of the sensory function theory of cognitive aging is that nearly all tests of cognition rely upon intact sensory processing, particularly within visual and auditory domains. Therefore, if sensory function is diminished, then it takes a longer period of time for sufficient information to accumulate before decisions can be made. Thus, the assertion is that the core processes of cognition remain intact, it is just a matter of getting sensory information to them. The problem is that nearly every sensory system shows diminished responsivity in association with age. In particular, both vision and hearing function gradually show sensory impairments the progressively increase with each decade of life. This theory, thus, explains why an older adult would tend to exhibit a greater tendency to sit for a long period at a stoplight after it turns green as it simply takes longer for such visual information to be perceived. It also explains why aspects of cognition relating to motor speed and information processing tend to manifest with aging–related impairments earlier as methods of assessing them tend to be the most relient upon obtaining sensory information quickly. Processing Speed Theory of Cognitive Aging — Age–related effects in performance are the result of a generalized decrease speed of performing mental operations. Most cognitive tasks and real–world decision making behaviors occur within context where the appropriate response is time–limited. The processing speed theory of cognitive aging argues that deteriorations in performance associated with aging are the result of two related issues. The first issue is that the general speed of processing © Michigan State University Chapter 11 116 Notes KIN240: Principles of Biobehavioral Health information is impaired over the course of aging. Although processing is ultimately dependent upon obtaining sufficient information, evidence indicates that older adults tend to exhibit prolonged time in processing stages prior to making a decision. Even when relying upon situation–recognition, it simply takes a longer period of time to sift through the various situations that have accumulated over the course of their lifetime. Problematically, this delayed processing time has a cascade effect as decisional processes are multi–step processes where information flows from one system to another. So the second major issue is that the the within the time–limited context of these behaviors, decisions must be made before enabling processing to be complete. When given task–related context or social situations where decision making is not bounded by time constraints, older adults appear to be able to perform tasks at similar levels as younger adults. However, task situations which require more rapid or more complex processing in time–limited context manifest with the largest impairments for older adults, relative to younger adults. Resource Pool Theory of Cognitive Aging — Age–related effects in performance are the result of having a decreased pool of resources that could be brought online at any given moment. The resource pool theory of cognitive aging is conceptually similar to the processing speed theory of cognitive aging, but argues that with aging there becomes insufficient resources to support rapid processing. The core concept is that cognitive operations are effortfull and require energetic/metabolic resources to be completed, the more rapid or more complex the cognitive operations are the greater resources that are necessary. As processes associated with aging result in the pool of resources diminishing, it becomes more difficult to be able to allocate sufficient resources to support more rapid or more complex cognitive operations. As a result, cognitive systems adopt less resource intensive approaches such as slower processing time, skipping processing steps, and bringing online compensatory cognitive operations to try to make up for deficiencies in the resources that they have available. Interestingly, when environmental supports minimize the number of concurrent (happening at the same time) cognitive processes that are required to complete a task, older adults exhibit performance much more similar to that of younger adults. © Michigan State University Chapter 11 117 Notes KIN240: Principles of Biobehavioral Health Attention Inhibition Theory of Cognitive Aging — Age–related effects in performance are the result of difficulty sustaining attentional engagement and gaiting out irrelevant information, as well as suppressing responses. The attention inhibition theory of cognitive aging attributes age–related declines in cognition to reductions in the capacity to sustain attention on task relevant details. Older adults appear to take in and maintain a considerable amount of unnecessary/irrelevant information during the completion of cognitive tasks. As a result, cognitive operations must work harder to process the additional information contributing to reductions in available resources and delays in processing and evaluation. Thus, as older adult exhibit difficulties in narrowing attention to reduce irrelevant information and suppress potentially distracting or conflicting details; there is a cascade effect that contributes to impairments across a wide range of cognitive processes. Reductions in the ability to sustain attentional focus provides some justification for why older adults exhibit greater levels of distractibility and wandering attention. Similarly, as they take in additional unnecessary information, it can be more difficult to discern the relevant information from the irrelevant making them more prone to becoming confused. Dynamic Capacity Theory of Cognitive Aging — Age–related effects in performance are the result of societal tendencies that minimize the need for some aspects of cognition after retirement. The dynamic capacity theory of cognitive aging is generally more commonly focused upon age–related declines in cognitive control and declarative memory. The argument is that when looking at the trajectories of how cognition changes with age, there is considerable overlap between the two major time points when cognitive control and memory show dramatic reductions and major life events. The first drop off aligns when students leave college and enter into their careers, while the second drop off aligns with when adults enter into retirement. In each case, these transitions represent shifts in the way high level cognitive operations and memory are needed. Thus, in the context of the dynamic capacity perspective, as individuals are no longer being cognitively challenged then it is to be expected that cognitive abilities would then begin to diminish. Compellingly, evidence has demonstrated that cognitive control and memory tend to be sustained when students continue with graduate and post–graduate studies and by adults who continue to stress these cognitive abilities after retirement (such as by © Michigan State University Chapter 11 118 Notes KIN240: Principles of Biobehavioral Health working for non–for–profit organizations and community groups; or interacting with children to a greater extent). Dementia While aging is associated with gradual reductions in most cognitive abilities, a key characteristic of both healthy and normal aging is that reductions in cognitive abilities should not interfere with daily function or independence. However, popular culture generally clusters typical reductions in cognition associated with aging alongside terms such as mild cognitive impairment, dementia, and Alzheimer’s Disease without realizing that these terms reflect different things. Mild Cognitive Impairment — Age–related changes in cognition where one or more aspect of cognition is significantly impaired, but does not interfere with daily activities. The classification of mild cognitive impairment represents the initial stage at which declines in cognition reach clinically significant levels. Accordingly, individuals in this stage exhibit clear evidence of diminished cognitive abilities in at least one of the following aspects of cognition: motor speed, attention, cognitive control, learning/memory, or language. However, despite exhibiting a clear diminishment of cognition, an individual with mild cognitive impairment is able to maintain their independence while going about their daily life. Although some tasks may take additional time or may be performed less efficiently than before; they can still do these tasks with minimal aid or assistance. This clinical state represents approximately 15% of individuals over the age of 70, with diminished cognitive abilities more commonly occurring within declarative memory and cognitive control. The most common presentation is the need to re–ask questions; either as a result of not being able to remember the prior answer, not sustaining attention long enough to listen to the answer, or failures in inhibiting repeating the question. Beyond such a characteristic behavior, other common presentations include frequent impairments in finding/using the right words and impaired orientation (unaware of date, location, has difficulty navigating previously familiar routes). The more domains of cognition that exhibit significant declines, the more likely the individual is to progress into dementia. © Michigan State University Chapter 11 119 Notes KIN240: Principles of Biobehavioral Health Dementia — Age–related changes in cognition where more than one aspect of cognition is significantly impaired to the point of interfering with daily function or independence. The classification of dementia reflects the decline of multiple aspects of cognition (motor speed, attention, cognitive control, learning/memory, or language) to such an extent that the individual is no longer able to engage in activities of daily living without substantial interference. An individual in this stage may still be able to maintain some basic activities (bathing, dressing, personal hygiene activities), but other more intensive or complex activities such as paying bills, preparing a meal, or shopping may no longer be possible. When individuals reach this stage, brain imaging and blood tests are also typically used to ensure that brain tumors or brain lesions (wounds, damage) are not causing the cognitive impairment. Brain imaging and blood tests are not actually used for the diagnosis of dementia itself — because dementia is a disease of the mind. Although no treatments have been found effective at resolving either mild cognitive impairment or dementia, they may help to slow the progression of these disease states to reduce further deterioration. However, despite dementia being a disease of the mind; efforts in the late 1990's and early 2000's pushed medical specialties to adopt a very brain based view. As a result, specific subtypes of dementia are usually differentiated based upon the common symptom presentation (reflecting the issue in the mind) as well as the issue in the brain that is thought to cause the symptom presentation. Around 10% of cases of dementia reflect Fronto–Temporal dementia which is characterized by dramatic changes in personality, relationships, and conduct (swearing, stealing, impulsive/repetitive/inappropriate behaviors) and is usually attributed to progressive loss of brain tissue in the frontal and temporal lobes (essentially deterioration of structures involved with cognitive control). In some individuals this also relates to progressive lost in the ability to speak and even understand language. Another 10% of cases of dementia reflect Lewy Body dementia which is characterized by visual hallucinations, highly variable levels of confusion, muscle rigidity/stiffness, and loss of coordination. Lewy Body dementia is a progressive disease attributed to the accumulation of lewy bodies proteins, with most individuals surviving around eight years after symptoms begin to present. Around 30% of cases of dementia reflect Vascular dementia which occurs when blood vessels flowing to the brain become obstructed (essentially the brain version of coronary heart disease). The nature of the cognitive impairment depends upon the location of the reduced blood flow. © Michigan State University Chapter 11 120 Notes KIN240: Principles of Biobehavioral Health Finally, around 40% of cases of dementia reflect Alzheimer’s Disease which is characterized by cognitive impairments specific to language and memory and the abnormal accumulation of beta–amyloid (plaques) and tau proteins (tangles) on the brain. However, despite the wide—spread cultural awareness of Alzheimer’s Disease, there is considerable variability in how this disease is viewed. As a result, by some definitions Alzheimer’s Disease is alleged to be the underlying cause of 80% of cases of dementia as they attribute this disease to any cases of dementia that include at least one symptom that overlaps with Alzheimer’s Disease. Although we would generally reject such claims for any other disease state, this approach is quite prevalent for dementia. Additional Resources: Park, D. (2012). The basic mechanisms accounting for age–related decline in cognitive function. In D. Park & N. Schwar (Eds.), Cognitive aging: A primer. United Kingdom: Taylor & Francis. https://www.google.com/books/edition/Cognitive_Aging/S2SvjSoPikAC Knopman, D. S., & Petersen, R. C. (2014). Mild cognitive impairment and mild dementia: A clinical perspective. Mayo Clinic Proceedings, 89, 1452–1459. http://dx.doi.org/10.1016/j.mayocp.2014.06.019 © Michigan State University Chapter 11 121