Neurology of Intelligence and Memory PDF

Neurology of Intelligence and Memory Shafiq Dexter Abou Zaki Internist-Neurologist Intelligence Intelligence Intelligence, or intelligent behavior, has been variously defined as a “general mental efficiency,” as “innate cognitive ability,” or as “the aggregate or global capacity o...

Neurology of Intelligence and Memory Shafiq Dexter Abou Zaki Internist-Neurologist Intelligence Intelligence Intelligence, or intelligent behavior, has been variously defined as a “general mental efficiency,” as “innate cognitive ability,” or as “the aggregate or global capacity of an individual to act purposefully, to think rationally, and to deal effectively with his environment” (Wechsler) → the capacity to have ideas and reason about them Global - individual’s behavior as a whole Aggregate - composed of a number of independent and qualitatively distinguishable cognitive abilities Intelligence The level of intelligence differs from one person to another If properly motivated, intelligent children excel in school and score high on intelligence tests The first intelligence tests, devised by Binet and Simon in 1905, were for the purpose of predicting scholastic success Intelligence Quotient (IQ) The term intelligence quotient was introduced by the German psychologist Stern and used by Terman in 1916 for the development of intelligence testing. The loosely IQ correlates with achievement in school and to a lesser extent with eventual success in professional work. An individual’s IQ increases with age up to the 14th to 16th years and then remains stable, at least until late adult life. Nature vs Nurture Strong suggestion that genetic endowment is the more important factor and that life experience alters intelligence, but in a modest way. However, there is equally valid evidence that early learning modifies the level of ability that is finally attained. Intelligence may be looked upon not as the sum of genetic and environmental factors but as the product of the two. It is generally appreciated that non-scholastic achievement or success is governed by factors other than intellectual ones, such as curiosity, a readiness to learn, interest, persistence, sociability, and ambition or motivation Genetic Inheritance a limited amount is known excess of males with “developmental delay,” and there are several well-characterized syndromes in which the inheritance of mental retardation is X-linked different patterns of performance between males and females on subtests of the various intelligence tests (males perform better in spatial ability and certain mathematical tasks). Genetic Inheritance Males are more likely to be affected by advantageous or by aberrant genes on their single X chromosome, whereas females benefit from the mosaic provided by two X chromosomes. In some families, high intelligence segregates to certain individuals through an X-linked pattern Neuroanatomic Correlation Intelligence and brain volumes are positively related; both gray and white matter volumes are positively related to intelligence Morphometric features of the regions of the cortex that are presumed to underlie IQ and verbal skills, such as the frontal and language areas, show a heritable component when measured on high-resolution MRI scans Studies measuring the volume of regions of interest showed moderately significant correlations in frontal, parietal, and temporal brain regions, along with the hippocampus and the cerebellum vs other areas of the brain Distributed Brain Network for Human Intelligence Distributed Brain Network for Human Intelligence Occipital and temporal areas process sensory information in the first processing stage: - Extrastriate cortex (BA 18 and 19) and Fusiform gyrus (BA 37): involved with recognition, imagery and elaboration of visual inputs - Wernicke's area (BA 22): analysis and elaboration of syntax of auditory information Distributed Brain Network for Human Intelligence Integration and abstraction of the sensory information by parietal association areas - BA 39 (angular gyrus) - BA 40 (supramarginal gyrus) - BA 7 (superior parietal lobule) Distributed Brain Network for Human Intelligence The parietal areas interact with the frontal lobes: Involves problem solving, evaluation, and hypothesis testing BA 6 - Premotor and supplementary motor cortex BA 9 - Dorsolateral/anterior prefrontal cortex (motor planning, and organization) BA 10 - Anterior prefrontal cortex (memory retrieval) BA 45 - Broca’s area (expressive speech) BA 46 - dorsolateral prefrontal cortex (cognitive functions = attention, working memory; and executive functions = willed action and regulating self-control) BA 47 - pars orbitalis (language processing) Distributed Brain Network for Human Intelligence The anterior cingulate (BA 32) is implicated for response selection and inhibition of alternative responses, once the best solution is determined Distributed Brain Network for Human Intelligence Discrete brain regions of the dorsolateral prefrontal cortex (BAs 9, 45, 46, and 47) and the parietal cortex (BAs 7 and 40) could be considered most important for human intelligence. Grey matter and White matter both contribute to overall intelligence: Gray matter supports information processing capacity, while white matter supports the efficient flow of information in the brain Psychological Theories of Intelligence Psychologic Theories of Intelligence Faculty Theory Oldest theory (18-19th century) Mind is composed of different faculties like reasoning, memory, discrimination, imagination among others These faculties are independent of each other and can be developed through training Psychologic Theories of Intelligence Unifactor Theory Reduces all abilities to a single capacity of general intelligence or “common sense” Impies that all forms of intelligence are correlated and would make no allowance for the uniqueness of a person Psychologic Theories of Intelligence Two-factor theory (Spearman) noted that all the separate tests of cognitive abilities correlated with each other, suggesting that a general factor (g factor) enters into all performance (universal inborn ability) Because none of the correlations between subtests approached unity, he postulated that each test measures not only this general ability (commonly identified with intelligence) but also a subsidiary factors specific to the individual tests, which he designated the s factors. (Abilities acquired from the environment) Psychologic Theories of Intelligence Multifactorial theory (Thorndike) Distinguished Four Attributes of Intelligence: Level – level of difficulty of a task that can be solved Range – number of tasks at any given difficulty Area – total number of situations at each level to which the individual is able to respond Speed – rapidity at which one can respond to the items Psychologic Theories of Intelligence Group Factory Theory (Thurstone) proposed that intelligence consists of a number of entirely separable primary mental abilities, such as memory, verbal facility, numerical ability, visuospatial perception, and capacity for problem solving, all of them more or less equivalent. these primary abilities, although correlated, are not subordinate to a more general ability Psychologic Theories of Intelligence Six Primary Factors: Number Factor – ability to do calculations Verbal Factor – ability to comprehend verbally Space Factor – ability to manipulate an imaginary object in space Memory Factor – ability to memorize quickly Word Fluency Factor – ability to think of specific words rapidly Reasoning Factor – ability to discover a rule or principle involved in a series or group of letters Psychologic Theories of Intelligence Structure of Intellect (Guildford) Every task can be classified according to its: Content (visual, auditory, symbolic, semantic and behavioral) Mental operation (cognition, memory retention, memory recording, divergent production, convergent production and evaluation) Resulting product (units, classes, relations, systems, transformations and implications) Psychologic Theories of Intelligence Multiple Intelligence Theory (Gardner) All are born with the potential to develop multiple intelligences 1. Linguistic (encompassing all language functions) 2. Musical (including composition and performance) 3. Logical–mathematical (the ideas and works of mathematicians) 4. Spatial (including artistic talent and the creation of visual impressions) 5. Bodily–kinesthetic (including dance and athletic performance) 6. Personal (consciousness of self and others in social interactions) 1. Interpersonal – understanding others 2. Intrapersonal – understanding self 7. Naturalistic – ability to manipulate elements of the enviroment Psychologic Theories of Intelligence Triarchic Theory (Sternberg) Three types of intelligence Analytical – ability to solve problems and gain knowledge Creative – ability to cope with novel situations and gain from experience Practical – “street smart” - ability to adapt to the environment Genius There are only limited data regarding the highest levels of intelligence, identified as genius. Terman and Ogden’s longitudinal study of 1,500 California schoolchildren who were initially tested in 1921 supported the idea that an extremely high IQ predicted future scholastic accomplishments (though not occupational or life success). On the other hand, most individuals recognized as geniuses have been especially skilled in one domain—such as painting, linguistics, music, chess, or mathematics—and such “domain genius” is not necessarily predicated on high IQ scores, although certain individuals display cross-modal superiorities— particularly in mathematics and music. Developmental Aspects of Intelligence One of the leading theories had been that of Piaget, who proposed that the emergence of intelligence is accomplished in discrete stages related to age: Sensorimotor, from 0 to 2 years; Preconceptual thought, from 2 to 4 years; Intuitive thought, from 4 to 7 years; Concrete operations (conceptualization), from 7 to 11 years; The period of “formal operations” (logical or abstract thought), from 11 years on. Developmental Aspects of Intelligence This scheme implies that the capacity for logical thought, developing as it does according to an orderly timetable, is coded in the genes. Flaw → does not take into account an individual’s special abilities, which do not usually develop and reach their maximum at the same time as the more general intellectual capacities. Intelligence in Disease Presumably, Spearman’s g factor of intelligence would be impaired, by diffuse lesions, in proportion to the mass of brain involved, an idea expressed by Lashley as the “mass-action principle.” According to Chapman and Wolff, there is a correlation between the volume of brain tissue lost and a general deficit of cerebral function. Others disagree, claiming that no universal psychologic deficit can be linked to lesions affecting particular parts of the brain Probably the truth lies between these two divergent points of view. Intelligence in Disease Tomlinson et.al, who studied the effects of vascular lesions in the aging brain, lesions that involved more than 50 mL of tissue caused a moderate general reduction in performance, especially in speed and capacity to solve problems. Piercy, found correlations only between specific intellectual deficits and lesions of particular parts of the left and right hemispheres. It is important to acknowledge, that lesions of the frontal lobes, and particularly the prefrontal regions, do not measurably affect overall IQ but do, of course, slow mental processing and degrade subtests specific to these skills. Intelligence as Viewed Today Intelligence consists of a combination of multiple primary abilities, each of which may be inherited and each of which has a separate but poorly delineated anatomical representation. Neurologic data, while unable to locate the sources of a general factor for intelligence certainly does not exclude its possibility— one that is unavoidably measured in many different tests of cerebral functions. It is expressed if the connections between the frontal lobes and other parts of the brain are intact as attention, drive, and motivation are noncognitive psychologic attributes of fundamental importance to performance reside in this lobe. Intelligence as Viewed Today It is also possible, if not likely, that the parietal lobe associative areas of the cerebrum are engaged in the processing of sensory experiences and their manipulation in symbolic form. This applies equally to the ability to relate thoughts to each other and to stored concepts, but here, memory, symbols, and names, requiring the full function of the temporal lobes, play a central role. Creativity An equivalently complex problem arises in the neurologic analysis of the highest human achievement and the method of human advancement, namely creativity. Creativity is tied to special skills along the lines of Gardner’s modality-based intelligence, particularly as it relates to artistic work, but the brain structures involved in aesthetics and abstraction are obscure Traits such as creativity almost certainly do not reside in a particular lobe or structure of the brain and may depend on the overdevelopment of certain associative areas, as well as on frontal lobe drive and, are fully manifest only by exposure and encouragement. Memory Memory Process by which that knowledge is encoded, stored, and later retrieved Current understanding suggests that no single hippocampal neuron, for example, embodies a memory but that perhaps the connections between an ensemble of neurons in the medial temporal lobes and modality-specific neurons in the associative cortices are, in fact, the source of memory. Strengthening synaptic connections among this network serves to establish the memory. Neurologic Laws of Memory As memory fails, it first loses its hold on recent events. (Ribot’s Law) The extent in time of retrograde amnesia is generally proportionate to the magnitude of the underlying neurologic disorder In transitory amnesias (e.g., concussive head injury), memories are recovered in reverse order: first the remote and then the more recent. Kinds of Memory Kinds of Long-Term Memory Kinds of Memory Short-Term Memory exemplified by the common daily acts of hearing a phone number and retaining it to be able to walk across a room and dial the phone; or, performing a series of mental calculations that require holding an intermediate sum briefly in mind; all the numbers are soon forgotten. Long-Term Memory Explicit Memory - the individual’s awareness of the learning of new material Implicit Memory - not being conscious of the event of acquiring memory Long-Term Explicit Memory Episodic memory subsumes what most persons consider to be memory and learning, that is, the ability to retain and recount events that were consciously experienced by the person, including the time and general circumstances of the acquisition (autobiographical memory). [Contextual] Semantic memory, the learning of the nature of the environment and factual knowledge (such as the shape and color of a lion) is also a type of explicit memory but the event of acquiring the memory cannot be recalled. [Generic] Long-Term Implicit Memory Functions such the acquisition of physical skills (such as driving a car or playing tennis) are implicit memories that are termed procedural memory. Classic conditioning is considered another type of implicit memory whereby a conditioned stimulus (CS) becomes associated with an unrelated unconditioned stimulus (US) in order to produce a behavioral response Development of Explicit Memory Four Distinct Operations Encoding is the process by which new information is attended and linked to existing information in memory “Deep” Encoding - For a memory to persist and be well remembered, the incoming information must be encoded thoroughly This is accomplished by attending to the information and associating it with knowledge that is already well established in memory. Memory encoding also is stronger when one is well motivated to remember. Development of Explicit Memory Four Distinct Operations Storage refers to the neural mechanisms and sites by which memory is retained over time One of the remarkable features about long-term storage is that it seems to have an almost unlimited capacity; there is no known limit to the amount of information in long term storage. In contrast, working memory storage is very limited Development of Explicit Memory Four Distinct Operations Consolidation is the process that makes the temporarily stored and still labile information more stable consolidation involves expression of genes and protein synthesis that give rise to structural changes at synapses. 2 Processes: synaptic consolidation, which is thought to correspond to late-phase long-term potentiation (hours to days) systems consolidation, rendering hippocampus-dependent memories independent of the hippocampus → neocortex (weeks to years) Reconsolidation - previously consolidated memories can be made labile again through reactivation of the memory trace Long Term Potentiation persistent strengthening of synapses based on recent patterns of activity one of several phenomena underlying synaptic plasticity widely considered one of the major cellular mechanisms that underlies learning and memory Development of Explicit Memory Four Distinct Operations Retrieval is the process by which stored information is recalled. It involves bringing back to mind different kinds of information that are stored in different sites. Retrieval of memory is much like perception; it is a constructive process and therefore subject to distortion much as perception is subject to illusions Retrieval, particularly of explicit memories, also is partially dependent on working memory. Episodic Knowledge and the Medial Temporal Lobe Functional MRI scans show that activity in the medial temporal lobe is greater when subjects engage in deep encoding (e.g., attending to the meaning of information by judging whether a word is concrete or abstract) than when they engage in shallow encoding (e.g., judging whether a word is presented in upper- or lower-case letters). Activity in parts of the left prefrontal cortex is also enhanced during deep encoding suggesting that frontal lobe and medial temporal lobe processing contribute to encoding episodic memory Episodic Knowledge and the Medial Temporal Lobe At the time of encoding, activity in several regions of the left prefrontal cortex was enhanced when subjects were studying words that they were later able to recall In a similar study, researchers found greater activity in the right prefrontal cortex during encoding of pictures that were later recalled compared to pictures that could not be recalled. Episodic Knowledge and the Medial Temporal Lobe Interaction between the medial temporal lobe and distributed cortical regions is also central in current thinking about memory consolidation. the medial temporal region may play a temporary role in the consolidation of memories, but after a sufficiently long period it is no longer needed as memories can be retrieved directly from cortical regions. Episodic Knowledge and the Medial Temporal Lobe Reactions to visual cues (retrieval of episodic knowledge) – works in a top-down pattern from the primary visual cortex to the prefrontal cortex then to the inferior temporal cortex The retrieval of contextual or event details associated with episodic memory also involves activity in the medial temporal lobe, particularly in the hippocampus Prior to retrieval of information from the neocortex, visual and auditory association areas, the medial temporal lobe is activated Semantic Knowledge Semantic knowledge is distinguished from episodic knowledge in that it is typically not associated with the context in which the information was acquired. It is stored in a distributed manner in the neocortex, including the lateral and ventral temporal lobes. There is no single storage site for all of the semantic knowledge that we have acquired over our lifetime. Rather, the semantic components of a concept are distributed among many brain regions. Semantic Knowledge Neuroimaging studies using PET and fMRI provide more evidence about how different categories of knowledge are represented in the intact human brain. When people name pictures of animals there is greater activity in left inferior temporal regions, which represent information about the form of objects, than when they name pictures of tools. Semantic Knowledge In contrast, tool naming is associated with activity in left premotor regions, which represent information about the patterns of motor movements associated with the use of an object, and in left middle temporal regions, which represent information about how objects move in space Implicit Memory and Priming Priming is a type of implicit memory that operates by activating an association or representation in memory just before another stimulus or task is introduced exposure to one stimulus influences a response to a subsequent stimulus, without conscious guidance or intention. Two types of priming have been proposed Conceptual priming – priming to items of a similar meaning Perceptual priming – priming to items of a similar form Implicit Memory and Priming Damage to unimodal sensory regions of cortex (areas related to the 5 senses) impairs modality-specific perceptual priming Initial exposure to a visual stimulus activates the higher-order visual areas of cortex but subsequent exposures do not trigger such a reaction (Perceptual Priming) These findings parallel the finding that activity in the left prefrontal cortex is reduced during Conceptual priming Implicit Memory and Priming Other forms of nondeclarative memory subserve the learning of habits, the learning of motor, perceptual, and cognitive skills, and the formation and expression of conditioned responses These forms of implicit memory are characterized by incremental learning, which proceeds gradually with repetition, and are independent of the medial temporal lobe system responsible for explicit memory Implicit Memory and Priming New perceptual, motor, or cognitive abilities are also learned through repetition. With practice, performance becomes more accurate and faster, and these improvements generalize to learning novel information. Skill learning moves from a cognitive stage, where knowledge is represented explicitly and the learner must pay a great deal of attention to performance, to an autonomous stage, where the skill can be executed without much conscious attention Implicit Memory and Priming The learning of sensorimotor skills depends in part on the basal ganglia, cerebellum, and neocortex. Functional imaging of healthy individuals during sensorimotor learning shows changes in the activity of the basal ganglia and cerebellum. Skilled behavior can depend on structural changes in motor neocortex, as seen by the expansion of the cortical representation of the fingers in musicians Implicit Memory Can Be Associative or Non-associative With non-associative learning an animal learns about the properties of a single stimulus. With associative learning the animal learns about the relationship between two stimuli or between a stimulus and a behavior. Two forms of non-associative learning: habituation & sensitization Two forms of associative learning Classical conditioning & operant conditioning Habituation vs Sensitization Habituation, a decrease in a response, occurs when a benign stimulus is presented repeatedly Sensitization (or pseudoconditioning) is an enhanced response to a wide variety of stimuli after the presentation of an intense or noxious stimulus Classical vs Operant Conditioning Classical conditioning involves learning a relationship between two stimuli Operant conditioning involves learning a relationship between the organism’s behavior and the consequences of that behavior. Classical Conditioning The essence of classical conditioning is the pairing of two stimuli. The conditioned stimulus (CS), produces either no overt response or a weak response usually unrelated to the response that eventually will be learned. The reinforcement, or unconditioned stimulus (US), produces a strong and consistent response (the unconditioned response) Unconditioned responses are innate; they are produced without learning. Repeated presentation of a CS followed by a US gradually elicits a new or different response called the conditioned response. Operant Conditioning operant conditioning can be considered as the formation of a predictive relationship between an action and an outcome operant conditioning tests behavior that occurs either spontaneously or without an identifiable stimulus Law of Effect - actions that are rewarded tend to be repeated, whereas actions followed by aversive, although not necessarily painful, consequences tend not to be repeated Extinction The probability of occurrence of a conditioned response decreases if the CS is repeatedly presented without the US. Extinction is an important adaptive mechanism; it would be maladaptive for an animal to continue to respond to cues that are no longer meaningful to it. The available evidence indicates that extinction is not the same as forgetting, but that something new is learned––the CS now signals that the US will not occur Forgetting Memories dissipate over time if not used frequently The brain actively removes useless information to prevent saturation of synapses Protein Phosphatase 1 (PP1) breaks down synapses leads to forgetting Inhibiting PP1 after learning allows memories to be retained longer Distributed > Massed Practice – Distributed practice allows distribution of the PP1 effect vs massed practice when PP1 effect acts on the whole memory at once Drac1 gene produced Rac Protein which causes memory decay – this is overcome by repeated practice.