Previous studies by our group have demonstrated fMRI signal changes
and synchronized gamma rhythm EEG oscillations between thalamus and
cortical regions as subjects recall objects from visually presented
features. Here, we extend this work by estimating the time course of
fMRI signal changes in the cortical and subcortical regions found to
exhibit evidence for task-related activation. Our results indicate that
there are separate loci of signal changes in the thalamus (dorsomedial
and pulvinar) that exhibit notable differences in times of onset, peak
and return to baseline of signal changes. The signal changes in the
pulvinar demonstrate the slowest transients of all the cortical and
subcortical regions we examined. Evaluation of cortical regions
demonstrated salient differences as well, with the signal changes in
Brodmann area 6 (BA6) rising, peaking, and returning to baseline
earlier than those detected in other regions. We conclude that BA6
mediates early designation or refinement of search criteria, and that
the pulvinar may be involved in the binding of feature stimuli for an
integrated object memory. (JINS, 2003, 9,
1031–1040.)