Priming reduces input activity in right posterior cortex during stem completion

A recent positron emission tomography (PET) study showed reduced blood flow in the right posterior cortex for primed words during a stem completion task, suggesting reduction in processing demand in this area for primed tasks. The time course of this attenuation was studied using event-related potentials (ERPs) in 40 normal subjects. As compared to the unprimed stems, primed stems elicited significantly less positive ERP in the right posterior channels between 60 and 200 ms after presentation of the stem. The results, while confirming the PET findings, implicate involvement of right posterior cortex in bottom-up processing of primed stimuli. In addition to right posterior channels, the primed stems also had attenuated positivity in the right frontal channels after 250 ms of stem presentation, indicating reduced requirement for explicit recall process.