lecture 9

Question 1

what is declarative memory

Answer 1

Long term explicit memory and encompasses episodic and semantic memory .
It is theorised that the medial temporal lobe declarative memory system.

Question 2

perceptual learning in hippocampal patients (Graham et al., 2006)

Answer 2

Repeated exposure → better discrimination
Phase 1: Face scene dsicrimination task - baseline
Phase 2: Perceptual learning phase - face and scene categorization trials (exposure)
Phase 3: re test face and scene discrimination - comparison
Patients with hippocampal damage showed intact perceptual learning for faces but disrupted perceptual learning for scenes
consistent with domain-specific processing in medial temporal lobe structures.
Subdivision of medial temporal lobe for processing of different content (distinct and dissociable functions?)

note: the use of face and scene stimuli also extends this to a study of obect and spatial memory

Question 3

what is habit learning

Answer 3

gradual acquisition of associations between stimuli and responses, such as learning to make one choice rather than another

Question 4

what is the test for recognition memory

Answer 4

Sample; delay; choice (non/match) repeat with novel stimuli
stimuli are never used more than once
Required perception, discrimination, familiarity?, recollection
Not associative memory but is traditionally promoted as a memory task dependent upon the integrity of MTL

Question 5

what is the concurrent discrimination learning task

Answer 5

presented with two stimuli at a time, one of which will have been arbitrarily assigned a reward
phase 1: guess, and learn outcomes
repeated until should reasonably score 100%
requires associative learning
each stimulus presented the same number of times so cannot rely on familiarity judgements

traditionally thought to be a habit learning task
BUT HM impaired - therefore cannot be a nondeclarative memory task

impaired after MTL lesions in monkeys

Question 6

what are the theorised relationships between episodic and semantic memory

Answer 6

Tulving: animals must have a certain amount of semantic information before episodic memories can be formed

Squire: semantic memory is information that we have exprienced repeatedly - actual learning expereinces become blurred and only the facts remain such that semantic memory develops out of episodic memory

evidence for the dissociation of the two comes from early hippocampal pathology and semantic dementia

Question 7

what is the MTL declarative memory system theory

Answer 7

MTL comprises a homogenous system (that is not subdivided) specialised exclusively for declarative memory

Question 8

what and where is the MTL

Answer 8

excludes the fornix which bridges the hippocampus in the MTL to subcortical structures

it is comprised of the hippocampus, amygdala, temporopolar cortex, perirhinal cortex, entorhinal cortex, and can be located via parahippocampal gyrus, lateral occipitotemporal gyrus, collateral sulcus, medial occiopotemporal gyrus, occipotemporal sulcus,

Question 9

what are the prominent connections into the MTL

Answer 9

dorsal stream from V5 to PPC (where/how pathway)

ventral stream V4 to TE (what pathway)
converge in MTL at the entorhinal cortex where spatial and object knowledge are configured

Question 10

what are the cortical inputs to the perirhinal cortex (Suzuki, 1996)

Answer 10

visual (TE, TEO)
auditory (superior temporal gyrus) 
somatosensory (insular cortex)
polymodal (dorsal STS, parahippocampal cortex, orbitofrontal cortex, cingulate cortex) 
not exclusively visual information
representation of objects at every level

Question 11

what were the findings of Henson’s (2005) neuroimaging studies of object recognition

Answer 11

reviewed the literature associated with recognition memory and concluded that there is no clear patterns to the findings

Question 12

what are the effects of MTL lesions on object recognition in macaques (Mishkin, 1978)

Answer 12

trained macaques on an object recognition task
manipulated the delay period and list length
combined lesion monkeys are very impaired
however monkeys with lesions to just the hippocampus or amygdala are at the 95% level

suggestion that there is damage to underlying cortical areas in combined lesion

bilateral neurotoxic lesions to the rhinal cortex
within the macaque MTL the perirhinal cortex is the most important strucurre contributing to object recognition memory

Question 13

what is the difference between memory and habit learning explanations for concurrent discrimination learning

Answer 13

initally MTL lesions were not thought to impair concurrent discrimination learning
however the addition of a set such that discrimination cannot be done on the basis of single-feature reveals that concurrent discrimination learning is impaired after perirhinal cortex lesions
large sets force configuration of a number of features, like an object,

Question 14

what evidence is there for the set size effect in delayed matching to sample

Answer 14

Recognition memory unimpaired with rhinal lesion in small set
Same task with large set highlights deficit
Defining parameter is set size rather than task

Question 15

does the perirhinal cortex have a role in perception

Answer 15

traditionally it has been argued that the perirhinal cortex does not have a role in percpetion because this would violate MTL theory where MTL is exclusively involved in memory

Question 16

what is the odditiy task

Answer 16

Odd one out
Same view object oddity and different view object oddity (in both there is one different object but in different view the same object is presented at different perception which requires an understanding of the configuration of features)
One requires uni feature discrimination the other configuratin of features (object)
Same view unimpaired after peripheral lesions / different view impaired
Further discrimination tasks show that visual discriminations that can be solved on the basis of a single feature is unimpaired after periirhinal cortex lesions regardless of task difficulty
All tasks requiring feature configuration (object level) impaired
Impaired: rotated objects and faces; scenes
Unimpaired: same view objects and faces; colour; shape; size
Macaque perirhinal cortex is required for perceptual discriminatin between objects .’. Important for perception.

Question 17

does this role in perception carry to human models

Answer 17

Test patients with (likely) hippocampal lesions
Age match controls
Test patients with perirhinal cortex lesions as well
Three tasks animal model show no impairment: odd colour, size, shape
Two tasks animals show impairment: odd face and odd object task
Results replicate data from animal model where MTL group are impaired on face and novel object tasks

Question 18

what is semantic dementia

Answer 18

a temporal lobe variant of frontal-temporal dementia
atrophy in MTL heavily focused on the perirhinal cortex
progressive loss of semantic memory but preserved episodic memory and other cognitive domains
contrast scene and face oddity task with same and different view version
semantic dementia patients have no impairment on scenes relative to controls but are impaired on the face task
role in perception

Neuroimaging subtraction in odd face/scene discrimiantion
Demonstrates perirhinal activity

Question 19

how has conceptual understanding of objects been localised in the brain (Tyler et al., 2004)

Answer 19

basic level object naming vs domain level naming
only get activity in the perirhinal cortex when conceptualising at the basic level
sstimuli are processed conceptually at an object/basic level i the perirhinal cortex in the human brain
patients with damage to the perirhinal cortex show similar impairments as macques with selective lesions
and human perirhinal cortex is activated when discirminating between similar objects

Question 20

how is the human perirhinal cortex involved in familiarity judgements

Answer 20

Familiarity: sense of knowing seen something before
Recollection: vividly remember episode of an encounter
Proposed dissociation in MTL for these functions
Recognition memory task was originally thought to be a good test of declarative memory according to squire et al. BUT you could solve each problem based on familiarity rather than recollecting the actual experience
This is the distinction between remembering and knowing
The perirhinal cortex may be important for familiarity based recognition
BUT Squire et al. argue that the MTL cannot be subdivided into different regions mediating different aspects of declarative memory
This is the domain-general vs domain-specific distinction
Process-specific theory:
Perirhinal cortex: familiarity
Hippocampus: recollection

Question 21

what is the doors and people paradigm

Answer 21

Visual recognition:
participants attempt to memorise a series of colour photographs of doors
Memory is tested by recognition of each target door from a set of four doors varying in similarity, and hence difficulty
Visual recall:
Participant copies four patterns
Attempts to draw these patterns from memory
Three learning trial are allowed followed by a delayed recall
Verbal recognition
Participant reads out a series of names
Participant must recognise each from sets of four items
Verbal recall
Participant is required to learn the names of four people, a doctor, a postman, a minister and a newspaper boy.
Three learning trials are allowed, followed by a delayed recall to measure forgetting.

Some studies show impairments in both recall and recognition in amnesic patients (Manns & Squire, 1999)
Others show spared recognition when the brain regions affected are more restricted the hippocampus or fornix (not involving the perirhinal cortex) (Aggleton & Brown, 2006)

Question 22

how can scene familiarity be tested

Answer 22

Montaldi et al (2006)
subjects pressed a key depending on whether they thought it was a new scene (N), whether it felt weakly (F1), moderately (F2), or strongly familiar (F3), or whether they effortlessly recollected something about its presentation (R)
linear decreases in BOLD signal as strength of familiarity increased were seen in the left and right perirhinal cortex
Supports perirhinal cortex activation with familiarity

Question 23

what have single unit recordings from animal studies revealed about the perirhinal cortex

Answer 23

Animal models (Brown, 1996)
First presentation: large response in PR
Lower response when presented again
Decrease in firing associated with familiarity in anterior TE and perirhinal cortex
Decrease in firing to recency in anterior TE and perirhinal cortex

Question 24

what are the implications of perceptuo-mneumonic theory

Answer 24

amnesia results in impoverished perceptual representations as well as memory deficits
challenge prevailing concepts that MTL is only involved in memory processes
rather than damage to a declarative memory system may be better characterised as impoverished representations of the stimuli these regions maintain

Question 25

summary

Answer 25

the perirhinal cortex in both humans and macaques is important for processing stimuli at an object level

this has been demonstrated in tasks traditionally regarded to be declarative, tasks regarded as non-declarative and perceptual tasks

the notion that MTL houses a MTL memory system exlusively involved in declarative memory is challenged

the notion that MTL houses a memory system that is homogenous is challenged

there is strong evidence for doamin specific (object vs spatial) and funcitonal (recollection vs familiarity) subdivisions

If perception, recognition, memory, knowledge and understanding about objects appear to be mediated by the perirhinal region, what might the role of the hippocampus be?