Cognition, Learning, and Memory III

learning

process of acquiring new information

memory

ability to store and retrieve information

specific information stored in brain

memory has temporal stages:

short, intermediate, and long

iconic memory

briefest memories and store sensory impressions that only last a few seconds

short-term memory (working memory)

usually last only for up to 30 seconds or throughout activity, retained with rehearsal

subdivided into three components, all supervised by an executive control module: phonological loop, visuospatial sketch pad, episodic buffer

short-term memory components

phonological loop, visuospatial sketch pad, episodic buffer

phonological loop

contains auditory information (e.g. speech to rehearse that phone number)

visuospatial sketch pad

holds visual impressions (e.g. imagine the route back to your car in a parking building)

episodic buffer

contains more integrated sensory info (like movie clips)

intermediate-term memory

outlasts working memory, but is not permanent (fades quickly without rehearsal), limited capacity (e.g. you may recall today’s weather forecast but not that of a few days ago)

long-term memory

last for days to years, large capacity, stimulated with a cue/hint (e.g. address of your childhood home, how to ride a bike)

a substantial body of evidence indicates that STM and LTM in particular rely on

different processes to store information

drugs and memory formation

have been used extensively to study this, this approach has led to many interesting discoveries and to new concepts

can produce relatively brief, accurately timed effects, and subjects can be tested in their normal state both before and after treatment

different agents appear to affect different stages of memory formation, this result has given rise to the concept of sequential neurochemical processes in this formation

agents that caused memory failure by about 5 minutes after training blocked

STM

e.g. KCl

agents thay caused memory failure by about 15 minutes after training blocked

ITM

e.g. ouabain

agents that caused memory failure by about 60 minutes after training blocked

LTM

e.g. anisomycin

because different amnestic agents are thought to impair different stages of memory,

they provide a means of observing the duration of each stage

experiments to test the hypothesis that the formation of LTM requires protein synthesis have employed both

behavioural intervention (in the form of training) and somatic intervention (in the form of agents that inhibit protein synthesis)

LTM experiment and behavioural intervention

training enriched experience, increases the branching of dendrites and number of synaptic contacts

LTM experiments and somatic intervention

antibiotic anisomycin very effective at inhibiting protein synthesis without causing toxic side effects

prevents LTM storage in mice without affecting STM

the stronger the training was, the longer the inhibition has to be maintained to cause amnesia

protein synthesis involved in the formation of LTM

appears to occur in two successive waves: the first about 1 hour after training, the second about 5-8 hours after training

inhibitors of protein synthesis so that they were effective at either of these periods prevented the formation of this by preventing the structural changes in neurons that would normally encode the memory trace

primacy effect

higher performance for items at the beginning of a list (words 1-3, LTM)

recency effect

shows better performance for the items at the end of a list (words 7-10, STM)

immediate list recall test

recency effect but no primacy effect

list recall test after short delay

both recency and primacy effects

list recall tests after longer delay

primacy effect but no recency effect

a functional memory system incorporates three aspects:

encoding, consolidation, retrieval/recall

encoding

sensory information passed into short term memory

consolidation

short/intermediate term memory formation transferred into long term storage

retrieval/recall

stored information is used

process of reconstruction/reactivation of various elements of past experiences from all parts of the brain

the brain has a left and right hemisphere covered by

a layer of nerve tissue called cerebrum (cerebral cortex)

each half of cerebrum has four different lobes

underneath the cerebrum are other brain structures, including

amygdala, thalamus, corpus callosum, hippocampus, all of which play important roles in human behaviour, memory, and emotions

brain structures in recalling pictures

right prefrontal cortex and para-hippocampal cortex in both hemispheres activated

brain structures and recalling words

left prefrontal cortex and left para-hippocampal cortex activated

which brain structures are important for consolidation?

prefrontal cortex and para-hippocampal cortex

hemispheric specializations

left- for language

right- for spatial ability

engram

also called memory tract

physical changes (several different synapses within a neural circuit) in the brain that underlie a LTM

each time activated and recalled, it is subject to changes- process of retrieving information from LTM can cause memories to become unstable and susceptible to disruption or alteration

the hippocampal system does not store

long-term memory

LTM storage

occurs in the cortex, near where the memory was first processed and held in short term memory

post-traumatic stress disorder

characterized as reliving and being preoccupied by traumatic events

memories produce stress hormones that further reinforce the memory

which substances can enhance memory formation in animal models?

GABA, ACh, opioid transmission

treatments that can block chemicals acting on the basolateral amygdala

may alter effect of emotion on memories

treatments that can block chemicals acting on the basolateral amygdala exmaples

bicuculline, picrotoxin, naloxone, propanolol, atropine

treatments that activate chemicals acting on basolateral amygdala examples

baclofen, muscimol, epinephrine, clenbuterol, oxotremorine

reconsolidation

return of a memory trace to stable long term storage after it’s temporarily volatile during recall

can distort memories

successive activations can deviate from original information

new information during recall can also influence memory trace

leading questions can lead to remembering events that never happened

recovered memories and guided imagery can have false information implanted into recollection

hypnosis or guided imagery

patient is encouraged to imagine hypothetical abuse scenarios, can inadvertently plant false details during reconsolidation

Phineas Gage

pointed rod shot through left cheek bone and through top of head

personality, reasoning, capacity to understand and follow social norms had been diminished or destroyed

little interest in anything

two major functions of the prefrontal cortex

emotion and cognition

frontal lobe

responsible for regulating temperament and expressing personality

primary motor cortex

controls voluntary body movements, including actions such as kicking your leg

prefrontal cortex

can be divided into lateral (side), medial (midline), ventral (bottom), and dorsal (top) regions

lateral division divides into dorsal and ventral halves separated by a major horizontal fold, inferior lateral sulcus

phylogeny and ontogeny of prefrontal cortex

has expanded over mammalian and primate evolution

a greatly enlarged one is a distinctive human and primate feature

accounts for 29% of total cortex in humans

more specific functions of prefrontal cortex

plays a central role in forming goals and objectives and then in devising a plan of action required to attain those goals

selects the cognitive skills needed to implement the plans, coordinates those skills, and applies them in a correct order

responsible for evaluating our actions as success or failure relative to our intentions

Gage’s injury inspired the development of the frontal lobotomy to

diminish aggression and rage in patients

generally results in drastic personality changes and an inability to relate socially

delayed response task

a working memory task, administered with the Wisconsin General Test Apparatus

in sample/cue phase, monkey observes while one of the food wells is baited with a food reward

during delay phase, an opaque screen is lowered and both food wells are covered by identical objects

response phase initiated by lifting the screen, upon which the monkey selects one of the food wells by displacing the cover in order to retrieve reward

working memory required in first task because at the time the animal responds, there are no external cues indicating the location of the food

prefrontal cortex is critical for

short term retention of information

mnemonic scotoma

spatially circumscribed region of working memory impairment

monkeys with prefrontal lesions demonstrate

selective impairment on the working memory delayed response task

delayed non-matching to sample task steps

monkey originally presented with sample object, when he displaces it he finds a pellet of food underneath

after a variable delay (seconds to minutes) the monkey is presented with the original object and another object

over a series of trials with different pairs of objects, monkey learns that food is present under object that differs from sample

monkeys are attracted to novelty, so choose

non-matching stimulus to the sample at the beginning of trial

oculomotor spatial delayed response task

used to study cells in the dorsal lateral prefrontal cortex

oculomotor spatial delayed response task steps

each trial starts with the monkey fixating the central fixation point indicated in central diagram

then a cue light was flashed briefly on in one of the eight locations indicated in the central diagram

after a delay, the monkey was allowed to respond by moving its eyes to the remembered location of the cue

neural activity from cuing each location is shown by the corresponding histogram

this neuron exhibited delay period activity when the cue to be remembered was presented in the lower middle quadrant of the visual field

Wisconsin Card Sorting Task

patients with damage in the lateral prefrontal cortex have difficulty with this

on each trial, subjects place top card on the deck under one of the four target cards

experimenter indicates whether the response is correct or incorrect, allowing subject to learn the sorting rule by trial and error

the sorting rule changes whenever the subject makes ten consecutive correct responses

temporal order of event impaired in

patients with prefrontal lesions