CO-OCCURRING PLASTICITY IN DISTRIBUTED NEURAL NETWORKS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Introduction: Repeated conceptual processing of a stimulus results in behavioral facilitation (priming) and functional activation reductions in left ventrolateral prefrontal cortex (VLPFC) and posterior neocortical regions. While initially posited to reflect neocortical tuning, repetition-induced activation reductions have been recently associated with stimulus-response learning. Specific Aims: To investigate whether cortical tuning and response learning co-occur and to determine the representational level at which response learning impacts cortical activation, event-related fMRI was used to examine repetition effects at three levels: (a) conceptual repetition, (b) stimulus-decision repetition, and (c) stimulus-response repetition. Methods & Materials: Event-related fMRI measured BOLD activity during both study and test blocks of the experiment. During study, participants performed one of two semantic classification tasks on words. Subsequently, studied words were represented (conceptual repetition) along with a set of novel words (no repetition). Half of the old words were classified under the same decision as at study (within-task repetition), and half were classified according to the other decision (across-task repetition). Of the across-task trials, half required the same response as at study (response repetition) and half a different response (response switch).