LECTURE 19: ANATOMICAL & FUNCTIONAL ORGANIZATIONOF 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, alongwith concepts derived from this knowledge

Explicit (declarative) memory is recalled by conscious effort, and can involveassembly 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 forstaged 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 informationfrom more than one sensory modality.

POSTERIOR ASSOCIATION AREA: perception of place, construction of languageLIMBIC 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:

1. Semantic (factual) knowledge … objects, facts, concepts, word definition, spoken fluency

2. Episodic knowledge …. Events

Semantic knowledge is a rich and “upgradable” set of associationsthe 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,BUT taste 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 OPERANTBEHAVIOR DO NOT YIELD ANTICIPATED STIMULUS

CONDITIONED RESPONSE MEMORIES STORED IN SENSORY & MOTOR CIRCUITSWHICH 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 ResponseAuditory 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 ResponseAmygdala 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