chapter 14 relational learning and amnesia. human anterograde amnesia anterograde amnesia -...

Chapter 14Chapter 14

Relational Learning and Relational Learning and AmnesiaAmnesia

Human Anterograde Human Anterograde AmnesiaAmnesia

Anterograde amnesiaAnterograde amnesia - difficulty in learning new - difficulty in learning new information, due to head injury or certain degenerative information, due to head injury or certain degenerative brain diseases; pure form is rarebrain diseases; pure form is rare

Retrograde amnesiaRetrograde amnesia – inability to remember events that – inability to remember events that occurred prior to brain damage occurred prior to brain damage

Korsakoff’s syndromeKorsakoff’s syndrome – permanent anterograde amnesia – permanent anterograde amnesia caused by brain damage resulting from chronic alcoholism caused by brain damage resulting from chronic alcoholism or malnutrition (due to thiamine deficiency); also have or malnutrition (due to thiamine deficiency); also have confabulationsconfabulations (reporting of memories that did not occur, (reporting of memories that did not occur, without the intention to deceive)without the intention to deceive)

Anterograde amnesia can be caused by damage to Anterograde amnesia can be caused by damage to temporal lobestemporal lobes– e.g. patient H.M. – bilateral removal of medial temporal lobe to e.g. patient H.M. – bilateral removal of medial temporal lobe to

alleviate epilepsy; resulted in severe anterograde amnesiaalleviate epilepsy; resulted in severe anterograde amnesia


Basic descriptionBasic description– Results from study with H.M.Results from study with H.M.

1.1. The hippocampus is not the location of long-term memory (LTM); The hippocampus is not the location of long-term memory (LTM); nor is it necessary for the retrieval of LTMnor is it necessary for the retrieval of LTM

2.2. The hippocampus is not the location for short-term memory The hippocampus is not the location for short-term memory (STM)(STM)

3.3. The hippocampus is involved in converting STM into LTMThe hippocampus is involved in converting STM into LTM These results are too simple; anterograde amnesia is actually These results are too simple; anterograde amnesia is actually

much more complexmuch more complex Learning consists of at least 2 stages:Learning consists of at least 2 stages:

STMSTM – immediate memory for events, which may or may not be – immediate memory for events, which may or may not be consolidated into LTM; can only hold a limited amount of infoconsolidated into LTM; can only hold a limited amount of info

LTMLTM – relatively stable memory of events that occurred in the – relatively stable memory of events that occurred in the more distant past, as opposed to STM; no limit on amount of infomore distant past, as opposed to STM; no limit on amount of info

ConsolidationConsolidation – the process by which STM are converted into – the process by which STM are converted into LTMLTM

Simple model of memory Simple model of memory processprocess

Sensory info enters STMSensory info enters STM Rehearsal keeps that info in STMRehearsal keeps that info in STM Eventually, info will move into LTM via consolidationEventually, info will move into LTM via consolidation


Spared learning abilitiesSpared learning abilities– Still capable of: Still capable of:

Perceptual learningPerceptual learning– e.g. recognize broken drawings; also e.g. recognize broken drawings; also

faces and melodiesfaces and melodies Stimulus-response learningStimulus-response learning

– Can acquire a classical conditioned Can acquire a classical conditioned eyeblink responseeyeblink response

Motor learningMotor learning– Mirror drawing task – subjects required to Mirror drawing task – subjects required to

trace the outline of a figure while looking trace the outline of a figure while looking at the figure in a mirrorat the figure in a mirror


Declarative and nondeclarative memoriesDeclarative and nondeclarative memories– Although patients can learn other tasks, they cannot recall Although patients can learn other tasks, they cannot recall

ever learning themever learning them– Learning and memory involve different processesLearning and memory involve different processes– 2 major categories of memories2 major categories of memories

Declarative memoriesDeclarative memories – memory that can be verbally expressed, – memory that can be verbally expressed, such as memory for events, facts, or specific stimuli; this is such as memory for events, facts, or specific stimuli; this is impaired with anterograde amnesiaimpaired with anterograde amnesia

Nondeclarative memoriesNondeclarative memories – memory whose formation does not – memory whose formation does not depend on the hippocampal formation; a collective term for depend on the hippocampal formation; a collective term for perceptual, stimulus-response, and motor memory; not affected by perceptual, stimulus-response, and motor memory; not affected by anterograde amnesia; these control behavior; cannot always be anterograde amnesia; these control behavior; cannot always be described in wordsdescribed in words


Failure of relational learningFailure of relational learning– Verbal learning is disrupted in anterograde amnesiaVerbal learning is disrupted in anterograde amnesia

e.g. H.M. did not learn any new words after his surgery e.g. H.M. did not learn any new words after his surgery (biodegradable = “two grades”)(biodegradable = “two grades”)

– Episodic memoriesEpisodic memories – most complex form of declarative – most complex form of declarative memory; memory of a collection of perceptions of events memory; memory of a collection of perceptions of events organized in time and identified by a particular contextorganized in time and identified by a particular context

e.g. explain what you did this morning after waking upe.g. explain what you did this morning after waking up

– The hippocampal formation enables us to learn the relationship The hippocampal formation enables us to learn the relationship b/t the stimuli that were present at the time of an event (i.e. b/t the stimuli that were present at the time of an event (i.e. context) and then events themselvescontext) and then events themselves


Anatomy of anterograde amnesiaAnatomy of anterograde amnesia– Damage to the hippocampus or to regions that supply its Damage to the hippocampus or to regions that supply its

inputs and receive its outputs causes anterograde amnesiainputs and receive its outputs causes anterograde amnesia– The most important input to the hippocampal formation is the The most important input to the hippocampal formation is the

entorhinal cortex, which receives inputs from the limbic cortex entorhinal cortex, which receives inputs from the limbic cortex either directly or via the either directly or via the perirhinal cortexperirhinal cortex or the or the parahippocampal cortexparahippocampal cortex

– How does the hippocampus form new declarative memories?How does the hippocampus form new declarative memories? Hippocampus receives info about what is going on from sensory Hippocampus receives info about what is going on from sensory

and motor assc. cortex and from some subcortical regionsand motor assc. cortex and from some subcortical regions It processes this info and then modifies the memories being It processes this info and then modifies the memories being

consolidated by efferent connections back to these regionsconsolidated by efferent connections back to these regions Experiences that lead to declarative memories activate the Experiences that lead to declarative memories activate the

hippocampal formationhippocampal formation

– Patient R.B., suffered brain damage that lead to anterograde Patient R.B., suffered brain damage that lead to anterograde amnesia; after autopsy, found that field CA1 of the amnesia; after autopsy, found that field CA1 of the hippocampal formation was completely destroyedhippocampal formation was completely destroyed

Limbic cortexLimbic cortex


Anatomy of anterograde amnesiaAnatomy of anterograde amnesia– Damage to other subcortical regions that connect with the Damage to other subcortical regions that connect with the

hippocampus can cause memory impairmentshippocampus can cause memory impairments Limbic cortex of the medial temporal lobeLimbic cortex of the medial temporal lobe

– Semantic memoriesSemantic memories – a memory of facts and general info; different – a memory of facts and general info; different from episodic memoryfrom episodic memory

– Destruction of hippocampus alone disrupts episodic memory only; must Destruction of hippocampus alone disrupts episodic memory only; must have damage to limbic cortex of medial temporal lobe to also impair have damage to limbic cortex of medial temporal lobe to also impair semantic memory (and thus all declarative memory)semantic memory (and thus all declarative memory)

Fornix and mammillary bodiesFornix and mammillary bodies– Patients with Korsakoff’s syndrome suffer degeneration of the Patients with Korsakoff’s syndrome suffer degeneration of the

mammillary bodiesmammillary bodies– Most of the efferent axons of the fornix terminate in the mammillary Most of the efferent axons of the fornix terminate in the mammillary

bodiesbodies– Damage to any part of the neural circuit that includes the Damage to any part of the neural circuit that includes the

hippocampus, fornix, mammillary bodies and anterior thalamus cause hippocampus, fornix, mammillary bodies and anterior thalamus cause memory impairmentsmemory impairments


Role of the medial temporal lobe in spatial memoryRole of the medial temporal lobe in spatial memory– Individuals with anterograde amnesia are unable to Individuals with anterograde amnesia are unable to

consolidate info about the location of rooms, corridors, consolidate info about the location of rooms, corridors, buildings, roads, and other important items in their env’tbuildings, roads, and other important items in their env’t

– Bilateral medial temporal lobe lesions produce the most Bilateral medial temporal lobe lesions produce the most profound impairment on spatial memory, but enough damage profound impairment on spatial memory, but enough damage to only the R hemisphere is sufficientto only the R hemisphere is sufficient

– R hippocampal formation is activated when a person is R hippocampal formation is activated when a person is remembering or performing a navigational taskremembering or performing a navigational task

– Damage to this area also impairs ability to learn spatial Damage to this area also impairs ability to learn spatial arrangement of objectsarrangement of objects


Role of the medial temporal lobe in memory retrievalRole of the medial temporal lobe in memory retrieval– The hippocampal formation and its related structures also play The hippocampal formation and its related structures also play

a role in memory retrievala role in memory retrieval– Anterograde amnesia is usually accompanied by retrograde Anterograde amnesia is usually accompanied by retrograde

amnesia; brain damage can either cause loss of memories or amnesia; brain damage can either cause loss of memories or loss of access to memoriesloss of access to memories

– However, if damage is only limited to field CA1, patients do not However, if damage is only limited to field CA1, patients do not show additional retrograde amnesiashow additional retrograde amnesia

– Semantic dementiaSemantic dementia – loss of semantic memories caused by – loss of semantic memories caused by progressive degeneration of the neocortex of the lateral progressive degeneration of the neocortex of the lateral temporal lobestemporal lobes

Impairment for meaning of words, and functions of common Impairment for meaning of words, and functions of common objectsobjects


ConfabulationConfabulation– May be a result of disruption of the normal functions of the May be a result of disruption of the normal functions of the

prefrontal cortexprefrontal cortex– Frontal lobes may be involved in distinguishing b/t real and Frontal lobes may be involved in distinguishing b/t real and

imaginary memories; may do this by helping us to distinguish imaginary memories; may do this by helping us to distinguish items with general familiarity from specific items we have items with general familiarity from specific items we have encountered beforeencountered before

Relational learning in lab Relational learning in lab animalsanimals

Lab animals with hippocampal Lab animals with hippocampal formation lesions do not sow formation lesions do not sow impairment in stimulus-impairment in stimulus-response learning, but with response learning, but with relational learning tasksrelational learning tasks

Remembering places visitedRemembering places visited– Radial maze task – food placed Radial maze task – food placed

at end of each arm, rats did at end of each arm, rats did not go down arm that they not go down arm that they had already collected food had already collected food from; lesions to hippocampus, from; lesions to hippocampus, fornix, or entorhinal cortex fornix, or entorhinal cortex impaired this task; animals impaired this task; animals must remember which arm must remember which arm they have collected from that they have collected from that exact day (as opposed to exact day (as opposed to another testing day)another testing day)


Spatial perception and learningSpatial perception and learning– Lab animals with hippocampal Lab animals with hippocampal

lesions show problems with lesions show problems with navigational tasks just as humans navigational tasks just as humans dodo

– Morris water maze task – requires Morris water maze task – requires rat to find a particular location in rat to find a particular location in the water drum, by means of the water drum, by means of visual cues external to the visual cues external to the apparatus; if rats wit hippocampal apparatus; if rats wit hippocampal lesions are released from same lesions are released from same position every testing time, they position every testing time, they perform fine (e.g. S-R learning), perform fine (e.g. S-R learning), but if they are started from a but if they are started from a different place, they cannot different place, they cannot complete the task correctly (e.g. complete the task correctly (e.g. relational learning)relational learning)


Spatial perception and learningSpatial perception and learning– Hippocampal lesions disrupt performance of homing pigeonsHippocampal lesions disrupt performance of homing pigeons– Hippocampal formation of animals that normally store seeds or Hippocampal formation of animals that normally store seeds or

food in hidden caches and later retrieve them is larger than food in hidden caches and later retrieve them is larger than that in animals without this abilitythat in animals without this ability

Role of hippocampal formation in memory consolidationRole of hippocampal formation in memory consolidation– Brain activity in the hippocampus is increased in mice learning Brain activity in the hippocampus is increased in mice learning

a spatial task; however, after 25 days of testing, the activity a spatial task; however, after 25 days of testing, the activity there decreases, suggesting that the hippocampus is involved there decreases, suggesting that the hippocampus is involved in consolidating spatial memories for only a limited timein consolidating spatial memories for only a limited time


Place cells in the hippocampal formationPlace cells in the hippocampal formation– When recording the activity of individual neurons in the When recording the activity of individual neurons in the

hippocampus of an animals moving around its env’t, some neurons hippocampus of an animals moving around its env’t, some neurons fired at a high rate only when the rat was in a particular locationfired at a high rate only when the rat was in a particular location

– The suggests evidence that different neurons have different spatial The suggests evidence that different neurons have different spatial receptive fields (i.e. they responded when the animals were in receptive fields (i.e. they responded when the animals were in different locations) – these neurons were named different locations) – these neurons were named place cellsplace cells

– When placed on a circular platform that is rotated slowly within a When placed on a circular platform that is rotated slowly within a larger chamber, rats will ignore local cues and orient themselves to larger chamber, rats will ignore local cues and orient themselves to face a cue card; the place cells however, oriented themselves to face a cue card; the place cells however, oriented themselves to the local cuesthe local cues

– When animals encounter new env’ts, they learn the layout and When animals encounter new env’ts, they learn the layout and “maps” become established in their hippocampus; an animal’s “maps” become established in their hippocampus; an animal’s location within each env’t is encoded by the pattern of firing of location within each env’t is encoded by the pattern of firing of these neuronsthese neurons

– Place cells are guided by both visual stimuli and internal stimuli Place cells are guided by both visual stimuli and internal stimuli (e.g. proprioceptive feedback) (e.g. proprioceptive feedback)

– Hippocampus receives spatial info via the entorhinal cortexHippocampus receives spatial info via the entorhinal cortex


Role of LTP in relational learningRole of LTP in relational learning– When place cells become active when an animal is present in a When place cells become active when an animal is present in a

particular location, this causes changes in the excitability of particular location, this causes changes in the excitability of neurons in the hippocampal formationneurons in the hippocampal formation

– Knockout mice for NMDA receptors specific for the field CA1: no Knockout mice for NMDA receptors specific for the field CA1: no establishment of LTP in field CA1, smaller and less focused establishment of LTP in field CA1, smaller and less focused spatial receptive fields, and learn Morris water maze task much spatial receptive fields, and learn Morris water maze task much slowerslower

– NMDA mediated LTP appears to be required for the NMDA mediated LTP appears to be required for the consolidation of spatial receptive fields in field CA1 pyramidal consolidation of spatial receptive fields in field CA1 pyramidal cells but not their short-term establishmentcells but not their short-term establishment

Modulation of hippocampal functionsModulation of hippocampal functions– Hippocampal formation receives input from ACh, NE, DA, and 5-Hippocampal formation receives input from ACh, NE, DA, and 5-

HT neuronsHT neurons– They appear to control the information-processing functions of They appear to control the information-processing functions of

the hippocampal formationthe hippocampal formation– 5-HT has suppressive effect on establishment of LTP in hipp. 5-HT has suppressive effect on establishment of LTP in hipp.

form.form.


Modulation of hippocampal functions (con’t)Modulation of hippocampal functions (con’t)– NE has a facilitator effect, particularly on synapses of terminals of NE has a facilitator effect, particularly on synapses of terminals of

entorhinal neurons of the dentate gyrusentorhinal neurons of the dentate gyrus– DA had excitatory effects on LTP and memory-related functions of DA had excitatory effects on LTP and memory-related functions of

the hippocampal formationthe hippocampal formation Synaptic plasticity is induced by simultaneous depolarization of Synaptic plasticity is induced by simultaneous depolarization of

hippocampal neurons and activation of DA receptors on these neuronshippocampal neurons and activation of DA receptors on these neurons

– ACh neurons from medial septum project to hippocampus via ACh neurons from medial septum project to hippocampus via fornix; activity of these neurons is responsible for hippocampal fornix; activity of these neurons is responsible for hippocampal theta rhythmstheta rhythms (medium amplitude, medium frequency waves) that (medium amplitude, medium frequency waves) that influence the establishment of LTP in the hippocampusinfluence the establishment of LTP in the hippocampus

If theta activity is disrupted, animals show deficits in learning tasks If theta activity is disrupted, animals show deficits in learning tasks that are affected by hippocampal lesionsthat are affected by hippocampal lesions

Theta behaviors – exploration or investigationTheta behaviors – exploration or investigation Nontheta behaviors – alert immobility, drinking, self-directed behaviorsNontheta behaviors – alert immobility, drinking, self-directed behaviors

chapter 14 relational learning and amnesia. human anterograde amnesia anterograde amnesia -...

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