Figure 6.

Orientation tuning in cortical neurons of the primary visual cortex (V1). (A) Orientation tuning exhibited by a simple cell in cat V1. The cell responded with spiking to a vertical bar. The response decreased when the bar angle became more horizontal, showing that the cell was tuned to a vertical angle orientation. Adapted with permission from Hubel and Wiesel (79). (B) A representative simple cell receptive field from and orientation column in tree shrew V1, which shows ON (red) and OFF (blue) subfields. An OFF subfield is flanked by two ON subfields. The angle of the two ON subfields determines the tuning orientation (yellow bar). Adapted with permission from Lee et al. (81).