Visual Cortical Neurons: Are Bars or Gratings the Optimal Stimuli?

Neurons in the visual cortex of monkeys and cats have been characterized as either (i) bar and edge detectors or (ii) cells selective for certain spatial frequencies. To assess which of these functional descriptions is more accurate, we measured (i) the selectivity and (ii) the responsivity-sensitivity of these neurons to bars of various widths and gratings of various spatial frequencies. All of the cells recorded from were considerably more selective along the dimension of spatial frequency than along the dimension of bar width. Further, most were more responsive and sensitive to the grating of optimal frequency than to the bar of optimal width.