Figure 7.

Stochastic model of MT responses. A, Example of a return map for neuron sj116d for stimulus speed of 64°/s. We computed such a return map for each of the seven stimulus speeds (other speeds not shown). Probability of observing a particular firing rate is color coded: white corresponds to a high probability, and black corresponds to a low probability. The y-axis depicts the rate found in a given time bin, and the x-axis refers to the rate found in the next time bin. For example, when the neuron fired with ∼16 Hz to a stimulus moving at 64°/s, there was a high probability that it would fire with ∼6 Hz in the next bin (i.e., 50 ms later). B, Comparison of the temporal response profile of model prediction and actual neuronal response. Response rate (y-axis) is plotted against time of stimulation (x-axis). The gray dashed line represents the mean response of the neuron sampled in 50 ms bins. The gray area around the mean depicts the SD of the response over trials. The model prediction is shown by the black line; it captures both the initial onset and the more sustained part of the response. C, Comparison between actual speed tuning curve (gray dotted line) of neuron sj116d and the tuning curve prediction of the model for this particular neuron (black solid line). Mean response (y-axis) is plotted against the speed of the stimulus (x-axis). The model prediction lies almost perfectly on top of the measured tuning curve.