Figure 4

Superior colliculus neurons have large receptive fields with principal whiskers. A: An example of a neuron with a 17-vibrissa receptive field. Responses to individual deflections of 10 vibrissae with the piezoelectric device are depicted, with the vibrissa deflected indicated above each PSTH. Vibrissae were deflected in eight different directions (0° is caudal, 90° is dorsal), and ON responses to each direction were used to create the polar tuning curves. Distance from the center of the polar tuning curve represents the magnitude of the response for deflections in that direction. The radii of the octagons represent one spike/stimulus. The PSTHs were constructed by pooling spikes recorded in response to each of the eight directions. B: Histogram of receptive field sizes of collicular neurons, defined as the number of vibrissae evoking responses to manual stimulation. C: Difference in response magnitude to stimulation of different vibrissae. For each neuron, vibrissae were ordered according to their response magnitudes ("V1" evoked the largest magnitude response, "V2" the second largest magnitude, etc). Eleven of 16 neurons showed a significant difference in magnitude between V1 and V2 (solid lines, paired t-test, P < 0.005). D: Difference in onset latency to stimulation of different vibrissae. For each neuron, vibrissae were ordered according to their response latency ("V1" evoked responses at the shortest latency, etc). Six of 16 neurons showed a significant difference in latency between V1 and V2 (solid lines, paired t-test, P < 0.005).