Memory Has Temporal Stages - PowerPoint Presentation

Slide1

Memory Has Temporal Stages

Sensory buffers “Iconic memories”

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

Short-term memories

(

STM

s) usually last only for up to 30 seconds or throughout rehearsal.

Short-term memory is also known as

working memory

.

An

intermediate-term memory

(

ITM

) outlasts a STM, but is not permanent.

Long-term memories

(

LTM

s) last for days to years.

Long-term memory has a large capacity.

Information can also be forgotten or recalled inaccurately.

Temporal Stages of Memory Formation

For visual “Iconic”

overlaps with “Short Term”

Memory Has Temporal Stages

Working memory

can be subdivided into three components, all supervised by an

executive control

module:1. Phonological loop—contains auditory information2. Visuospatial sketch pad—holds visual impressions3. Episodic buffer—contains more integrated, sensory informationExecutive control of information flowA functional memory system incorporates three aspects:

Encoding

—sensory information is passed into short-term memory.

Consolidation

—short-term memory information is transferred into long-term storage (

The Engram

).

Retrieval

—stored information is used.

Hypothesized Memory Processes: Encoding, Consolidation, and Retrieval

LTM is not forgotten

f

ailure

of retrieval

Reconsolidation

Successive Processes Capture, Store, and Retrieve Information in the Brain

The process of retrieving information from LTM can cause memories to become unstable and susceptible to disruption or alteration.

Reconsolidation

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

Reconsolidation can distort memories.Successive activations can deviate from original information.New information during recall can also influence the memory trace.Leading questions can lead to ‘remembering’ events that never happened.‘Recovered memories’ and ‘guided imagery’ can have false information implanted into the recollection.

Successive Processes Capture, Store, and Retrieve Information in the Brain

Multiple brain regions are involved in encoding, consolidation and retrieval

For recalling

pictures

, the right prefrontal cortex and parahippocampal cortex in both hemispheres are activated.For recalling words, the left prefrontal cortex and the left parahippocampal cortex are activated. These mechanisms reflect hemispheric specializations(left hemisphere for language and right hemisphere for spatial ability).Different brain circuits for consolidation and retrieval of declarativeHippocampal

damage impairs

consolidation

of declarative (see H.M. below)

LTM storage is in the cortex not the hippocampus

Consolidation requires processing in

Medial Temporal Lobe

circuitsPerirhinal, Entorhinal, Parahippocampal and hippocampusAfter consolidation retrieval can occur without MTL circuits

Encoding, Consolidation, and Retrieval of Declarative Memories

Amnesia “Without Memory”

Deficit in memory ability with two broad categories:

Retrograde

: loss of memories for events prior to damage

Anterograde

: loss of ability to store new memories

Both can occur within a patient at one time

Neurological Examination of Amnesia Patients

Based on amnesic patient Henry Molaison (H.M.)

Surgical damage to

Medial temporal lobes

and underlying structuresParahippocampal cortex, Hippocampus,play a critical role in our ability to form new memories “consolidation”Has functioning short-term memory so encoding is normalAnterograde Amnesia can not form new declarative memory but can form new nondeclarative memoryNote: also has some Retrograde Episodic amnesiaDemonstrated that not all forms of memory are equally affected by damage to the medial temporal lobes. Declarative (facts that can be declared) is disruptedNondeclarative “procedural” is largely intact forperceptual skills - read mirror-reversed text

motor skills - mirror-tracing task

conditioned responses – fear conditioning

demonstrate repetition priming - with word list and then word stems

Henry’s Performance on a Mirror-Tracing Task

There Are Several Kinds of Memory and Learning

Patient

N.A.

Accidental (sword up the nose) damage to the left dorsal thalamus, bilateral damage to the mammillary bodies and probable damage to the mammillothalamic tractLike H M, he has short-term memory but cannot form declarative long-term memories. (anterograde declarative amnesia)Korsakoff’s syndrome is a memory deficiency caused by lack of thiamine—seen in chronic alcoholism.Brain damage occurs in mammillary bodies and dorsomedial thalamus, similar to N.A., and to the basal frontal cortex.

anterograde declarative amnesia

Graded retrograde amnesia

Patients often

confabulate

—fill in a gap in memory with a falsification which they accept as true.

There Are Several Kinds of Memory and Learning

Patient K.C.

(Kent Cochrane, 1951 – March 27, 2014)

Accidental (motorcycle wreck) damage to the cortex and severe shrinkage of the hippocampus and parahippocampal cortex

Graded Retrograde Episodic amnesiacannot retrieve personal (episodic) memory his semantic memory (from before the accident) is goodAnterograde amnesiacannot form new personal (episodic) memory can form new semantic with difficultyTwo subtypes of declarative memory:

Semantic memory

—generalized memory, “word meaning”

Episodic memory

—detailed autobiographical memory,

“who-where-when”

Subtypes of Declarative and Nondeclarative Memory

Subtypes of Nondeclarative Memory

Three subtypes of nondeclarative memory

Skill learning

—learning to perform a task requiring motor coordination

Priming—repetition priming—a change in stimulus processing due to prior exposure to the stimulusAssociative learning—the association of two stimuli or of a stimulus and a responseOperant conditioningBehavior rewarded with foodClassical conditioningFear conditioning tone ---- shock

Experimental Research with Non-Human Animals

Testing declarative memory in monkeys:

Delayed non-matching-to-sample task

a test of

object recognition memorythe subject must choose the object that was not seen previously.Medial temporal lobe damage causes impairment on the delayed nonmatching-to-sample task.The amygdala is not necessary for declarative memory tasks.The hippocampus in conjunction with the entorhinal, parahippocampal and perirhinal cortices, is important for these tasks.

The Delayed Non-Matching-to-Sample Task

Memory Performance after Medial Temporal Lobe Lesions

Experiments on specific attributes of memory in rats(fig 17.18)

To test

spatial memory

, an eight-arm radial maze is used—must remember in which arm it previously found food.

Animals with hippocampal lesions were impaired on the spatial memory task.Memory test of motor behavior: the animal must remember whether it made a left or right turn previously.If it turns the same way as before, it receives a reward.Only animals with lesions to the caudate nucleus showed deficits.Sensory perception can be measured by the object recognition task.

Rats must identify which stimulus in a pair is novel.

This task depends on the

extrastriate

cortex

.

Experimental Research with Non-Human Animals

Tests of Specific Attributes of Memory

Brain Regions Involved in Different Kinds of Learning and Memory

Anatomical Details not on the exam