Declarative Memory Flashcards
parallel distributed processing’ (PDP) model
Knowledge is represented in the distributed pattern of activity of many units (or ‘nodes’)
Weights
(values between 0 and 1) at each of the many connections determine how signals sent from a given unit will either increase or decrease the activity of the next unit when transmitted through that particular connection
PDP models
conceptual in many ways, yet the fact that the essential ‘pieces’ look/work a whole lot like how we understand neurons look/work means it has a biologically plausible form that we could consider a sort of ‘neural network’
The way PDP models operate has some similarity to how
repeated firing of connected neurons can strengthen those connections (long-term potentiation, LTP: ‘Neurons that fire together wire together’: Donald Hebb)
Can also relate PDP models to
ling term depression models
relate long-term depression (LTD
) to these models, in which repeated firing can also (depending on how everything is connected) selectively weaken connections
PDP networks consist of 3 ‘layers’ of units
Input units, hidden units, output units
input units (and e.g.)
activated by stimulation from the environment (e.g. retinal activity when viewing pictures of faces during an experiment
Hidden units (and example)
receive signals from input units feature detectors in visual cortex that receive signals from the retina, neurons involved in perceptual judgments and decisions making
output units (and e.g.)
receive signals from hidden units(e.g. neurons involved in delivering the response provided by the person making the judgment
rogers et al 2004 and PDP
programmed simulated ‘lesions’ into the system to see how disabling/compromising a random assortment of units affects the output
rogers et al 2004 found
the errors made by the compromised system were qualitatively similar to those shown by patents with semantic dementia
not a must but
could
PDP models demonstrate
Graceful adaptation
graceful degradation,
which means selectively damaging certain units doesn’t necessarily result in a complete breakdown of the whole system
PDP general explanation
interaction of all the parts of the system that encode not necessarily one unit firing the collective connectivity is what allows you to represent objects
Petersen et al block design
block of one trial and a block of another trial and used subtractive logic looking at fixation blocks and word blocks he was able to subtract activity from fixation blocks from brain scans when looking at word blocks and then what might be left is the activity specific to those blocks
Tulving et al study
compares neural activation during the presentation of novel stimuli with the same during familiar stimuli based on the assumption that the inherent novelty would, on average, result in more robust encoding mechanisms being automatically recruited
Tulving et al study procedure
showed one photo on one day and then brought participants back a second day and showed them old photos as well as new ones
tulving et al study results
Found greater hippocampus and parahippocampal activation during the presentation of ‘new’ stimuli, as compared to ‘old’
Stern et al. procedure
showed 40 novel images with instructions to encode them for a later memory test Compared activation in a ‘one-item’ condition in which only a single image is presented on each trial, to that in a ‘many-items’ condition in which several images are presented on each trial
Stern et al. results
Found greater activation in the ‘many-item’ condition, as compared to the ‘one-item’ condition, within several regions (including posterior hippocampus, parahippocampal gyrus, and fusiform gyri)
EPR and long term memory steps
Present a series of stimuli, one at a time,Average ERP’s time-locked to stimulus onset, Test memory of participants for stimuli, Compare ERP’s recorded during initial stimulus presentation, as a function of subsequent memory performance
Advantage to using ERPs to test long term memory
One advantage of this design could be that participants perform the same task on every trial (unlike some of the other PET/fMRI work we discussed, e.g. comparing blocks of fixation to blocks of encoding
disadvantage to using ERPs to test long term memory
lots of variability in how predictive the signal is, which seems to (at least in part) be related to the form the test takes (free recall vs. cued recall vs. comprehension)
mechanism related to spatial cognition
Hippocampus
Maguire, Woolett, & Spiers and taxi drievers
Found that the taxi drivers had more gray matter in mid-posterior hippocampus, and less in anterior hippocampus, as compared to the bus drivers
incidental encoding
is said to occur when encoding proceeds automatically, or without specific intention
Contextual reinstatement involves 2 things
First activating knowledge about more general properties, Then using that general knowledge to focus your memory search
contextual restrainment is related to the idea of
mental time travel
Polyn et al.
had members remember images while in a brain scan and then were later asked to recall images…based on image results researchers were able to accurately predict which objects were being remembered
Ranganath et al.
Found that activation in the left dorsolateral PFC and left hippocampus shortly after stimulus presentation predicted performance, In other words, objects presented during the memory test that were correctly responded to were associated with greater activation in those areas during initial processing
Functional connectivity
refers to two or more regions whose activity is correlated (implying they ‘talk’ to each other)
Ranganeth et al experiment showed
Functional connectivity
Noetic
knowing, or self-knowing, which can take two general forms
Anoetic
not knowing
