Transient and sustained responses in four extrastriate visual areas of the owl monkey.

Single neuron responses to stationary flashed bars were recorded from four extrastriate visual areas in the owl monkey: the middle temporal area (MT), the dorsal lateral area (DL), the dorsal medial area (DM), and the medial area (M). Data were collected at the optimum bar size and orientation for each cell. Each post-stimulus histogram was normalized to its maximum bin height. A cumulative histogram was produced for each area by adding together all the corresponding cell histograms. The cumulative histograms reveal a short latency, transient component and a longer latency, sustained component to the response for each of the areas. In all four areas there was a strong response, but the sustained component was much larger in DL and DM than in MT or M. The transient response in DL had a much longer latency than in the other areas. The dichotomy between areas which are slow-sustained responding and areas which are fast-transient responding is similar to the differences found between the magnocellular and parvocellular pathways.