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Frank Rösler, Philipps Universität Marburg

Wed 30 May 2007, 17:00
Campus Golm, building 24, room 033/34

In search of the engram: What does brain imaging tell us about the location of the memory trace?

Abstract:
Where are memories stored in the brain? Both empirical and theoretical
work suggests that memories are represented as activation patterns in
exactly those cortical areas in which online processing of information
during perception or motor planning does take place. I will review a
series of studies in which we recorded event-related brain potentials in
the EEG and the BOLD response with fMRI to monitor memory-related brain
activity. 
The experiments show that storage and retrieval of long-term memory
(LTM) contents produce material-specific activations, i.e.
topographically distinct patterns for spatial, verbal, or object
information. The topography evoked by LTM tasks was by and large the
same as when similar contents had to be manipulated in working memory
(WM). Moreover, in both cases, the activation patterns were not only
distinct for the different materials, rather, the maximum amplitude of
each activation pattern varied systematically with the task demands.
More demanding long-term memory search and more demanding working memory
transformations resulted in an increase of a negative slow wave
amplitude and the corresponding BOLD response. 

In sum, these studies not only prove a distinct topography for different
representations but also that each topography is specifically modulated
by the task demands. Moreover, the congruent topography strongly
supports the idea that working memory and long-term memory contents are
activated within the same cortical areas. The areas, however, which are
recruited for a particular LTM or WM task are not congenitally
predetermined. We observed that the very same haptic working memory task
activated systematically central-parietal areas in sighted controls but
occipital areas in congenitally blind people. This suggests kind of an
omnipotency of cortical areas for information processing and storage.


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