Dear SPM’ers,
I have theoretical question about DCM. I am a cognitive psychologist, and in
my field, an important feature of some cognitive theories is the assumption
of localist processing/representations.
A number of published DCM studies have successfully shown that a change in
activity between two conditions in one region can be explained by a specific
strengthening/ weakening of afferent connections from other areas. These
findings are very valuable for the improvement/formulation of
neuro-cognitive theories.
However, several neuro-cognitive theories would suggest that a change in
activity between two conditions in one brain region is due to the intrinsic
properties of this brain area (in the presence of constant connectivity with
other brain areas). For example, experimental condition A causes
instantiation of a specific neural representation in a certain brain region
and experimental condition B does not. Hence, stonger lateral inhibition
within this brain region would be expected for experimental condition A.
I think it would be nice to compare DCMs that encorporate either of these
theoretical mechanisms – changes in connection strength vs changes in local
response properties.
Now my question is how to model a “localist” mechanism. Do you think a
modulation of an inhibitory self connection (enable for example parameter
B(1,1)) could represent such a differences in the intrinsic response
behaviour of one area, e.g. lateral inhibition? Or should one model a
localist mechanism as a direct effect (C parameter)? Or do you think neither
is appropriate?
I’m looking forward to hear your opinions/advices.
Yours sincerely,
Matthias
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Mag. Matthias Schurz
Institut für Psychologie &
Zentrum für Neurokognitive Forschung
Universität Salzburg
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Tel. 0662/8044/5162
Hellbrunner Straße 34,
5020 Salzburg
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