Fig. 15.

Bottom. Preferences for orientation and direction examined by electrical recording along a tangential track. Multiunit data were collected in locations separated 50 μm from one another. The image illustrates the exposed cortex, the electrode, and the recording track. The set of stimuli was composed of eight oriented gratings, each of which was moved in two directions. Thered lines represent at each location the vectorial sum of responses to all orientations. The green arrows represent the vectorial sum of responses to all directions of motion. For clear presentation, the length of the arrows was doubled relative to that of the lines. The preferred direction changed in a continuous manner along the track, except for several locations at which reversals occurred. The magnitude of the direction preference next to reversals was low along at least 150 μm. Similar to the optical imaging results, the preferred direction was approximately orthogonal to the preferred orientation.