Transcript Document

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:
1.
Semantic (factual) knowledge … objects, facts, concepts, word definition, spoken fluency
2.
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,
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 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