Age-related occipito-temporal hypoactivation during visual search: relationships between mN2pc sources and performance.

Recently, an event-related potential (ERP) study (Lorenzo-López et al., 2008) provided evidence that normal aging significantly delays and attenuates the electrophysiological correlate of the allocation of visuospatial attention (N2pc component) during a feature-detection visual search task. To further explore the effects of normal aging on the N2pc neural sources, neuromagnetic activity during the execution of a visual search task was recorded in healthy young (N=14) and older (N=20) participants by using magnetoencephalography (MEG). The possible relationships between these neural sources and overt performance were explored by assessing the co-variation between the neural N2pc activity and both the task performance and the execution in the Trail Making Test Form A (TMT-A). Results revealed that young participants showed greater activity in occipito-temporal regions than older participants during the mN2pc (magnetic counterpart of the N2pc component) latency range (190-270ms). Moreover, older participants showed reduced relative activation in the right occipito-temporal source of mN2pc. These findings suggest that the previously observed age-related changes in N2pc parameters are associated with a significant hypoactivation of occipito-temporal N2pc sources that is more marked in the right hemisphere.