Cortical activity reduction with stimulus repetition: a whole-head MEG analysis.

Event related field responses to line drawings of novel visual objects were recorded in a simple target detection task using whole-head magnetoencephalography. Brain-current-source-density reconstruction indicated that, relative to initial presentations, immediately repeated nontarget stimuli elicited reduced neural activity in a region of cortex extending from the parietal lobe into the superior frontal lobe in a time window from 250 ms and 450 ms. There are at least two plausible accounts of this neural activity reduction between conditions. It may reflect facilitated stimulus processing due to the existence of a representation of the repeated stimulus or it may reflect differential levels of attentional allocation to initial and repeated stimulus presentations.