Mapping of Olfactory Memory Circuits: Region-Specific c-fos Activation After Odor-Reward Associative Learning or After Its Retrieval
Comment in
Learn Mem. 2002 May-Jun;9(3):97-8.
Although there is growing knowledge about intracellular mechanisms underlying
neuronal plasticity and memory consolidation and reconsolidation after retrieval,
information concerning the interaction among brain areas during formation and
retrieval of memory is relatively sparse and fragmented. Addressing this question
requires simultaneous monitoring of activity in multiple brain regions during
learning, the post-acquisition consolidation period, and retrieval and subsequent
reconsolidation. Immunoreaction to the immediate early gene c-fos is a powerful
tool to mark neuronal activation of specific populations of neurons. Using this
method, we are able to report, for the first time, post-training activation of a
network of closely related brain regions, particularly in the frontal cortex and
the basolateral amygdala (BLA), that is specific to the learning of an
odor-reward association. On the other hand, retrieval of a well-established
associative memory trace does not seem to differentially activate the same
regions. The amygdala, in particular, is not engaged after retrieval, whereas the
lateral habenula (LHab) shows strong activation that is restricted to animals
having previously learned the association. Although intracellular mechanisms may
be similar during consolidation and reconsolidation, this study indicates that
different brain circuits are involved in the two processes, at least with respect
to a rapidly learned olfactory task.