Optical imaging of digit topography in individual awake and anesthetized squirrel monkeys.

Topographic maps and columnar structures are fundamental to cortical sensory information processing. Most of the knowledge about detailed topographic maps and columnar structure comes mainly from experiments conducted on anesthetized animals. Towards the goal of evaluating whether topographic maps change with respect to behavioral demands, we used intrinsic signal optical imaging in alert monkeys to examine the spatial specificity of cortical topographic representation. Specifically, the somatotopies of neighboring distal finger pad representation in areas 3b and 1 were examined in the same awake and anesthetized squirrel monkey. In comparison to the anesthetized animal, we found larger cortical activation sizes in the alert animal in area 3b, where activation widths were found to overlap with even non-adjacent digits. This may suggest that in the alert animal, there is less inhibition across the somatotopic map within area 3b.