Figure 3.

No-control-response neuron with integrative surround modulation. Responses to the four global motions of stimuli are shown as PSTHs and response vectors (black lines) in which angles indicate the direction of global motion (i.e., of the surround stimulus) and lengths indicate response magnitude for that direction. A, Responses to corner stimuli. The motion period (dark bar) was, for all stimuli, from 500 to 1000 ms after stimulus onset. For this neuron, the P direction was up and to the left. We define the global prediction (blue arrow) as the direction of the average of the four corner response vectors (see Results, Responses of MT neurons to contour stimuli: integrative modulation). B, Responses to contour stimuli. Local motion refers to the motion of the contour within the CRF. For this example, the local motion was either upward or downward. The P direction of global motion resulted in upward local motion. For this example, the PP direction is thus up and to the right. Responses to the P direction were larger than to the PP direction indicating integrative surround modulation. The contour preferred direction (red arrow) is the direction of the average of the four contour response vectors. C, We classified this neuron as a no-control-response neuron because control stimuli did not elicit significant responses. D, Directional tuning measured with drifting gratings. Responses to gratings moving in the two local motion directions determine the local prediction. For this neuron the two local directions were upward and downward. Since responses to upward motion were greater than to downward motion, the local prediction (green arrow) points upward. E, The contour preferred direction (red arrow) is superimposed on the local (green arrow) and global (blue arrow) predictions. The contour preferred direction is biased away from the local prediction toward the global prediction indicating integrative surround modulation.