11- Learning, Memory, and Amnesia

Learning and memory

Both are neuroplastic processes; they deal

with the ability of the brain to change its functioning in response

to experience

Learning

deals with how experience changes the brain

Memory

deals with how these

changes are stored and subsequently reactivated

Amnesia

any pathological loss of memory

Henry Molaison

man who in 1953, at the age of 27, had

the medial portions of his temporal lobes removed

for the treatment of a severe case of

epilepsy

Bilateral medial temporal lobectomy

removal of the medial portions

of both temporal lobes, including most of the hippocampus,

amygdala, and adjacent cortex

Lobectomy

operation in which a lobe, or a major part

of one, is removed from the brain

Lobotomy

operation

in which a lobe, or a major part of one, is separated

from the rest of the brain by a large cut but is not removed

Retrograde amnesia

Backward-acting,Unable to remember the past

Anterograde amnesia

Forward-acting,Unable to form new memories

Short term memory

storage of new information for brief periods of

time while a person attends to it

Long-term memory

storage of new information once the person stops attending to it

Digit span + 1 test

H.M.’s inability to form certain

long-term memories was objectively illustrated by his

performance on the -

Block-tapping memory-span test

H.M.’s amnesia was not restricted to verbal material

by assessing his performance on the + 1 version of the -`

Global amnesia

amnesia for information presented in

all sensory modalities

Mirror-drawing test

The first indication that

H.M.’s anterograde amnesia did not involve all long-term

memories came from the results of a -

Incomplete-pictures test

nonsensorimotor test of memory that employs five sets of fragmented

drawings.

Pavlovian conditioning

A tone was sounded just before a puff

of air was administered to his eye; these trials were repeated

until the tone alone elicited an eye blink.

mnemonic

H.M.’s case renewed efforts to relate individual brain

structures to specific - (memory-related) processes;

Remote memory

memory for experiences in the distant past

Memory consolidation

the translation of short-term memories into long-term

memories

1. Explicit/declarative memories

2. Implicit memories

distinct categories of long-term memories:

Explicit/declarative memory

Conscious

long-term memories became known as -

Implicit memory

longterm

memories demonstrated by improved test performance

without conscious awareness became known as

Medial temporal lobe amnesia

Neuropsychological patients with a profile of mnemonic

deficits similar to those of H.M., with preserved intellectual

functioning, and with evidence of medial temporal

lobe damage are said to suffer from

Repetition priming tests

Tests that assess implicit memory

Semantic memories

explicit memories for general facts or information

Episodic memories

explicit memories for the

particular events (i.e., episodes) of one’s life

episodic memories

People with medial temporal lobe amnesia

have particular difficulty with - (episodic or semantic memories?)

Endel Tulving

been a major force in research

on the semantic-episodic dichotomy

The Case of K.C., the Man Who Can’t Time Travel

had a motorcycle accident in 1981. He suffered diffuse

brain damage, including damage to the medial temporal lobes.

Global cerebral ischemia

Patients who have experienced ___—

that is, have experienced an interruption of blood supply to

their entire brains—often suffer from medial

temporal lobe amnesia.

CA1 subfield

In R.B’s postmortem examination, obvious

brain damage was restricted largely to the pyramidal cell

layer of just one part of the hippocampus, the -

Transient global amnesia

the strongest evidence that selective hippocampal

damage can cause medial temporal lobe amnesia

comes from cases of -

Transient global amnesia

its sudden onset in the absence

of any obvious cause in otherwise normal adults

Transient global amnesia

the amnesia is transient, typically

lasting only 4 to 6 hours.

Korsakoff’s syndrome

disorder is largely attributable

to the brain damage associated with the thiamine deficiency

that often accompanies heavy alcohol consumption

Korsakoff’s syndrome

it is characterized by a variety of sensory

and motor problems, extreme confusion, personality

changes, and a risk of death from liver, gastrointestinal,

or heart disorders.

Medial diencephalon

Postmortem

examination of Korsa typically reveals lesions to the

mammillary bodies

The

first hypothesis, which was based on several small postmortem

studies, was that damage to the -

of the hypothalamus was responsible for the memory

deficits of Korsakoff patients

Medial diencephalic amnesia

N.A. is a particularly well-known patient with - (amnesia, such as Korsakoff amnesia,

associated with damage to the medial diencephalon

Alzheimer’s disease

another major cause of amnesia, wherein The first sign is often a mild deterioration

of memory.

Alzheimer’s disease

Eventually, dementia develops and becomes

so severe that the patient is incapable of even

simple activities

predementia Alzheimer’s patients

Alzheimer’s patients who have yet to develop dementia

Acetylcholine

The level of - is greatly reduced in the

brains of Alzheimer’s patients

basal forebrain

This reduction of acetylcholine results

from the degeneration of the - (a midline

area located just above the hypothalamu), which is the brain’s main source of acetylcholine.

Concussion

a temporary disturbance

of consciousness produced by a nonpenetrating

head injury

Posttraumatic amnesia (PTA)

Amnesia following a nonpenetrating

blow to the head is called -

Coma

pathological state of unconsciousness

anterograde amnesia

Period of - suggests a temporary failure of memory consolidation

Islands of memory

surviving memories

for isolated events that occurred during periods for which

other memories have been wiped out.

Memory consolidation

Gradients of retrograde amnesia after concussion seem to

provide evidence for -

Hebb’s theory

memories are stored in the short term by neural activity

Electroconvulsive shock (ECS)

an intense, brief, diffuse,

seizure- inducing current that is administered to the brain

through large electrodes attached to the scalp

Standard consolidation theory or dual-trace theory

memories

are temporarily stored in the hippocampus until they

can be transferred to a more stable cortical storage system

Reconsolidation

Each time a memory is retrieved from LTM, it is temporarily held in STM

Reconsolidated

Memory in STM is susceptible to post-traumatic amnesia until it is -

Anisomycin

a protein synthesis inhibitor, prevents reconsolidation of conditioned fear in rats if applied directly to the amygdalae

Monkey version of the delayed nonmatching-to-sample test

It was hailed as a major

breakthrough because it opened up the neuroanatomy

of medial temporal lobe amnesia

to experimental investigation.

Monkey version of the delayed nonmatching-to-sample test

provided a means of testing

the assumption that the amnesia resulting from medial

temporal lobe damage is entirely the consequence of hippocampal

damage

1. Hippocampus

2. Amygdala

3. Medial temporal cortex

the locations

in the monkey brain of three major temporal lobe structures:

Rat version of the delayed nonmatching-to-sample test

The validity of the - has been established by studies of

the effects of medial temporal lobe lesions.

Aspiration

- used to lesion the hippocampus in monkeys –resulting in additional cortical damage

Mumby box

The version of the delayed nonmatching-

to-sample test for rats that most closely

resembles that for monkeys was developed

by David Mumby using an apparatus

that has become known as the -

rhinal cortex

Bilateral removal of the - consistently results in object-recognition deficits

hippocampus

Bilateral removal of the - produces no or moderate effects on object recognition

amygdala

Bilateral removal of the - has no effect on object recognition

CA1 pyramidal cells

Ischemia-induced hyperactivity of - damages neurons outside of the hippocampus

Extrahippocampal damage

- is not readily detectable

Morris water maze test

intact rats placed at various locations in a circular

pool of murky water rapidly learn to swim to a stationary

platform hidden just below the surface.

Radial arm maze

several (e.g., eight) arms radiate out from a central starting

chamber, and the same few arms are baited with food each

day.

reference memory

The ability to visit only the baited arms of the radial

arm maze is a measure of -

Reference memory

memory

for the general principles and skills that are required to

perform a task

Working memory

the ability to refrain from visiting an

arm more than once in a given day is a measure of -

Working memory

temporary memory that is necessary for the

successful performance of a task on which one is currently

working

Rhinal cortex

plays an important role in object recognition

Hippocampus

plays a key role in memory for spatial location

Place cells

neurons that respond

only when a subject is in specific locations

Entorhinal cortex

an area of the medial

temporal cortex that is a major source of neural signals to

the hippocampus

Grid cells

are entorhinal

neurons that each have an extensive array of evenly

spaced place fields, producing a pattern reminiscent of

graph paper

Head-direction cells

neurons of the entorhinal cells that are tuned to the direction of head orientation

Border cells

neurons of the entorhinal cells that fire when the subject is near the borders

of its immediate environment

Food-caching birds

must have remarkable spatial memories because, in order

to survive, they must remember the locations of hundreds

of food caches scattered around their territories.

time cells

certain cells in the hippocampus have recently been

shown to code for the temporal aspects of an experience—

so-called -

Jennifer Aniston neurons

Other medial temporal lobe neurons were discovered

that responded to other individuals known to the

patients (e.g., relatives, friends, or celebrities) or to known

objects, but because the first neuron responded to Jennifer

Aniston, they have all been termed -

concept cells

they respond to ideas or concepts rather than to particulars

Optogenetics

neuroscientists insert an opsin gene into

particular neurons, after which they can then use light to

either hyperpolarize or depolarize those neurons.

Engram cells

neurons that maintain an engram

1. Tagging stage

2. Manipulate stage

identification of an engram cell via optogenetics is

typically a two-stage process

Tagging stage

the neurons that are active during the learning task

are induced to express opsins while an animal engages in a

particular learning taskM

Manipulate stage

the previously active neurons are now either inhibited

or excited by using light to influence the activity of the

opsin-tagged neurons

Karl Lashley

wrote a famous review paper, In Search of the Engram

Cognitive map theory

hippocampus

constructs and stores allocentric maps

of the world

Medial temporal cortex

have roles in episodic memory

Inferotemporal cortex

Naya and colleagues concluded that

this reversed pattern of activity reflected the retrieval of

visual memories from -

Amygdala

thought to play a special

role in memory for the emotional significance of experiences

Prefrontal cortex

patients with - damage

often have difficulty performing tasks that involve a series of

responses

Cerebellum

thought to participate in the storage

of memories of learned sensorimotor skills through its

various neuroplastic mechanisms

Striatum

thought to store memories for consistent

relationships between stimuli and responses

Habit formation

the

type of memories that develop incrementally over many

trials. Sometimes this striatum-

based form of learning is referred to as -