Influence of prefrontal-visual associative cortical networks in a selective-attention, working memory paradigm.
Chadick, JZ, Rutman, A.J., Gazzaley, A.  Cognitive Neuroscience Meeting (2008)

Prefrontal cortex (PFC) has been shown to modulate activity in the visual association cortex (VAC) in a goal-directed fashion.  As older adults show a deficit in attention-driven modulation of VAC, these networks are a prime target for study in aging related cognitive decline.  Previous studies in our lab have focused on a selective-attention paradigm where relevant and irrelevant stimuli were presented sequentially.  Perhaps a more real-world based approach would be to study modulation associated with simultaneously presented stimuli, when a subject is required to concurrently enhance and suppress competing visual information. To explore this, we employed a working memory, selective-attention task in healthy, young adults (22-35 years old) in both an fMRI and EEG experiment.  Subjects were presented with simultaneously overlapping stimuli consisting of faces and scenes and were instructed to remember either faces or scenes, or to passively view the stimuli.  After a brief delay, a probe stimulus was presented and the subject’s responded if the probe matched either relevant stimuli.  We found significant modulation of BOLD signal in posterior stimulus-selective VAC regions based on task instruction, which corresponded with early modulation (~100 msec) of posterior EEG waveforms.  Preliminary multivariate analysis indicates this modulation is associated with a PFC-VAC network.  Currently, we are investigating the effects of aging on these networks with the hypothesis that aging-related changes in VAC modulation maybe due to loss of fidelity of PFC-VAC connections.