LECTURE 19: ANATOMICAL & FUNCTIONAL ORGANIZATION OF LEARNING & MEMORY

LECTURE 19: ANATOMICAL & FUNCTIONAL ORGANIZATION OF LEARNING & MEMORY REQUIRED READING: Kandel text, Chapter 62 LEARNING: The process through which an organism acquires knowledge of the world MEMORY: The process through which knowledge is encoded, stored, and retrieved Two Types of Memory EXPLICIT MEMORY: Factual knowledge of people, places, things, and events, along with concepts derived from this knowledge Explicit (declarative) memory is recalled by conscious effort, and can involve assembly and association of many pieces of information in different modalities IMPLICIT MEMORY: Acquired information on how to perform skills and on associations between stimuli and responses Implicit (nondeclarative) memory is recalled unconsciously. Different regions of the brain are responsible for staged acquisition and storage of different types of memory

ANATOMY OF CEREBRAL BRAIN

ANATOMY OF HIPPOCAMPAL FORMATION

ANATOMY OF PRIMARY SENSORY AND ASSOCIATIVE CORTICES Each primary sensory cortex (visual, somatic, auditory) first projects to unimodal association areas, which extract more complex information from the sense. Unimodal association areas project to multimodal association areas, that integrate information from more than one sensory modality. POSTERIOR ASSOCIATION AREA: perception of place, construction of language LIMBIC ASSOCIATION AREA: memory storage, emotions ANTERIOR ASSOCIATION AREA: long-term planning, judgment, “heart of our identity?”

HIPPOCAMPAL FORMATION CRITICAL FOR ACQUISITION OF EXPLICIT MEMORY Damage to or surgical removal of hippocampal formation has severe and very specific consequences Memories established before lesion ---------> NORMAL New short-term (up to a few minutes) memories -------------> NORMAL Creation of new long-term explicit memories ---------------> IMPAIRED Development of new long-lasting implicit memory ----------------> NORMAL

HIPPOCAMPAL FORMATION DAMAGE DOES NOT IMPAIR FORMING NEW IMPLICIT MEMORY

INDIVIDUAL SIDES OF HIPPOCAMPUS ARE HIGHLY ACTIVE DURING LEARNING OR RECALLING DIRECTIONS OR WORDS

EXPLICIT MEMORY IS STORED IN ASSOCIATION CORTICES Explicit memories can be subdivided into two categories: Semantic (factual) knowledge … objects, facts, concepts, word definition, spoken fluency Episodic knowledge …. Events Semantic knowledge is a rich and “upgradable” set of associations the word or picture of an elephant invokes a repertoire of stored information (size, sound it makes, where it’s from, it’s appearance in circuses) Different types of memory and different components of the same memory are stored in various associative cortex areas that are linked together to allow their combined retrieval Certain focal lesions in associative cortex regions fragment a memory, destroying specific components

SELECTIVE VISUAL AGNOSIAS AFFECT MEMORY OF OBJECT FORM OR OBJECT NAME Lesion to posterior parietal cortex ASSOCIATIVE AGNOSIA Lesion to occipital associative cortex APPERCEPTIVE AGNOSIA

MEMORIES OF ANIMALS AND OBJECTS ARE STORED IN DISTINCT CORTICAL DOMAINS

EPISODIC MEMORY STORED IN FRONTAL ASSOCIATION CORTICAL REGIONS

MULTIPLE CATEGORIES OF IMPLICIT MEMORY Sensitization and habituation are forms of non-associative implicit memory EXAMPLES Startle response to a sudden loud noise upon repetition (habituation) Withdrawl from tactile stimulus is stronger following pinch to same area (sensitization) THESE IMPLICIT MEMORIES ARE STORED IN SPINAL REFLEX PATHWAYS

MULTIPLE CATEGORIES OF IMPLICIT MEMORY Classical and operant conditioning are forms of associative implicit memory CLASSICAL CONDITIONING Mild conditioning stimulus (CS) is followed after fixed interval by a strong favorable or unfavorable unconditioned stimulus (US). Repetition elicits learned behavior, where CS elicits a conditioned response (CR) in the absence of US. CS causes anticipation of US. Not all types of pairing between a CS and US lead to a CR. A taste CS paired with poison nausea US leads to food aversion CR, BUTtaste CS paired with electric shock US DOES NOT induce a CR. OPERANT CONDITIONING When a seemingly random behavior is followied by a favorable stimulus, organism learns to repeat the behavior in order to obtain repeat of favorable stimulus. Although operant behavior and stimulus do have an underlying purposeful relationship, operant conditioning is a more automatic learning that doesn’t require understanding. Therefore, operant conditioning much less applicable to high intelligence animals. BOTH TYPES OF CONDITIONING EXTINGUISH IF SEVERAL REPETITIONS OF CS OR OPERANT BEHAVIOR DO NOT YIELD ANTICIPATED STIMULUS

CONDITIONED RESPONSE MEMORIES STORED IN SENSORY & MOTOR CIRCUITS WHICH INCLUDE CEREBELLUM OR AMYGDALA When an unconditioned response is motor and non-emotional, a specific region of the cerebellum is used for learning/storing the conditioned response Conditioned Eyeblink Response Auditory CS pairing to air-puff-(US)-induced eyeblink leads to eyeblink CR following CS. The region of cerebellum controlling CR is DIFFERENT from region controlling US-induced blink. When an unconditioned response has a strong emotional component, the amygdala is used for learning/storing the conditioned response Freezing Fear Response Amygdala is required to learn association between CS and electric shock US, which produces the freezing fear response.

NEXT LECTURE: LEARNING & MEMORY, Part II READING: Kandel text, Chapter 63

LECTURE 19: ANATOMICAL & FUNCTIONAL ORGANIZATION OF LEARNING & MEMORY