memory Flashcards
how can you describe human memory?
the storage and retrieval of information between sensory, short-term and long-term
what do pre-frontal cortex lesions impair in macaques?
performance on tests of spatial working memory
(delayed alternation and delayed response tasks)
cannot select correct response on basis of info held in working memory
[Goldman 1984]
what and where is the prefrontal cortex
cerebral cortex covering the front part of the frontal lobe
orchestrates thoughts and actions in accordance with internal goals
what are the properties of dorsolateral PFC neurons?
have activity that is specific to particular locations + sustained across delays
representations are maintained in an active state even during delays
Funahashi 1991
what do PFC neurons have access to and how do they encode it?
information relevant to the current task
encode the spatial position of a stimulus or the identity of it depending on what is relevant in each task phase [Rao]
what does BOLD stand for?
blood oxygenation level dependent imaging
when does human PFC BOLD activity increase in the WCST?
at the point subjects get feedback about which dimension of a multiple dimension stimulus should be attended to in the Wisconsin Card Sorting Task [Konishi]
what is the wisconsin card sorting task? what is the point of it?
subjects are asked to match a stimulus card to 1 of 4 reference cards placed on the table with varying dimensions
dimensions = number, colour, shape
they are given feedback when matches are right or wrong
repeat with 64 or 128 cards
see if they get better at identifying what the key characteristic the cards should be matched on is
[to measure frontal lobe dysfunction]
why do patients with PFC lesions find the WCST difficult?
they struggle to use the feedback and keep it in their working memory to change the information they consider relevant for sorting the card
if told the match is wrong, on the next case, will not learn from that ?
what is the dorsolateral PFC critical for?
maintaining temporal organisation of memory
monitoring the contents of working memory
what is the recency effect?
tendency to remember the information most recently presented, best
what do prefrontal lesions impair?
recency judgements for information in working memory
gets worse as number of items to be remembered increases
don’t affect recognition judgements [Petrides]
what is a recency judgement?
a list of words presented sequentially
then subjects presented with 2 of the words at the same time and asked which was studied more recently
PFC activated
what do temporal lobe cortex lesions impair?
performance on recency judgement tests as length of delays increase [Petrides]
what were the findings of Sakai and Passingham (2002) about the PFC?
dorsolateral PFC activity increases during spatial working memory (also in posterior parietal cortex + frontal eye field)
if activity in dorsolateral PFC decreases then errors are more likely to be made
activity in PPC and FEF tightly correlated when performance is correct
activity in D PFC is high, correlation between PPC and FEF is high
what might be the functional specialisation of the PFC?
dorsolateral = spatial working memory
ventrolateral = verbal working memory
what is the role of hippocampus in memory?
implicated in spatial memory
what is the hippocampus a central component of?
the medial temporal lobe