Feature selectivity in area 21a of the cat.

We compared the feature tuning of neuronal activity in area 21a with the tuning in areas 17/18. Local field potentials and multi-unit activity recorded in alert animals showed similar selectivity to orientation in both areas, higher selectivity to spatial frequencies in areas 17/18 and higher selectivity and tuning significance to temporal frequencies in areas 17/18. In addition, only at sites in areas 17/18 did the local field potential exhibit locking to a horizontal motion pattern extracted from a natural movie. These results suggest that area 21a is concerned with the analysis of spatial features but lacks a faithful representation of temporal features. Hence, they foster the hypothesis that cortical area 21a is part of a ventral form pathway.