In which two classes can memory be classified?
Information content —> What?
Time course —> How long?
Shortly explain difference between short-term and working memory!
short-term memory (passive sensory trace)
—> temporary storage of information
working memory (active exploitation of long-term memory)
storage and manipulation of information
What are the two parts the long-term memory is divided into?
long-term —> > minutes
implicit: procedural memory (skills like riding bike, learning to swim, …)
tied to subcortical areas (basal ganglia)
explicit: allow to store facts and episodes
tied to hippocampus
Explain the Baddeley and Hitch (1974) model.
three-component system:
Phonological loop: verbal material
Visuo-spatial sketch pad: visual material
Central executive: control stage
—> Core cognitive function for intelligent behavior
Describe the computer model for the working memory
brain’s RAM chip:
store information over short time periods
manipulate information to think and act
core cognitive function for intelligent behavior
Name three presented theories regarding working memory
Persistent activity
single-unit responses
Transient activity
gamma/ beta bursts
Silent activity
altered synaptic weights
Briefly explain the persistent activity regarding working memory.
single-unit responses —> individual prefrontal cortex (PFC) neurons fire persistently for memorized items
—> Experiments:
Fuster and Alexander (1971):
monkey remembers in which box a fruit was
Cue: show fruit
Delay: remember
Prompt: decide
Kandel (2013)
monkey remembers if first shape = second shape -> Delayed Match to sample (DMS)
Briefly explain the transient activity regarding working memory.
Similar monkey memory experiment:
—> Gamma bursts (~75Hz) are only found at informative spiking
—> Gamma burst —> Beta Burst —> Gamma …
What are the advantages of transient activity (oscillatory gamma/beta bursts) theory over persistent activity? What does it lack?
metabolically less expensive
encode multiple items
explains limits on working memory capacity
better at resisting distractors
—> But: lack of correlation between gamma bursting and animal performance in tests
Briefly explain the silent activity theory regarding working memory.
Task-relevant input is stored in the network by altered synaptic weights
—> Computational model -> no real experimental proof yet
Which brain regions are likely involved in storage/recovery of information from working memory?
—> cooperation of many high-level cortical parts from frontal, parietal, and temporal lobe
What do we know about the interplay of the pre-frontal cortex and the parietal neurons during working memory tasks?
PFC and parietal activity during working memory tasks
—> Lesion leads to absence of signal and worse performance
PFC and parietal signals have distinct channels
PFC —> theta (~3Hz)
Parietal —> alpha (~8-12Hz)
PFC timing of signal (phase) is important
in phase of parietal: target
out of phase: distractor
Stimulation of cortex with frequencies
PFC with theta —> better performance
Parietal with alpha —> better performance
What is the role of the visual cortex in working memory?
Working memory content can be decoded from the visual cortex
Define working memory
-> storage and active manipulation of information for organizational behavior
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