Fig 1. Response properties of MT neurons to constant motion stimuli.

Blue indicates experiments on alert subjects and orange indicates experiments on anesthetized subjects throughout. (A) A cartoon of the experimental setup for measuring the response of MT neurons to steps of coherent random dot pattern motion. Monkeys maintained fixation while stimuli translated at constant speed in one of 13 or 24 directions behind a stationary aperture scaled to the excitatory receptive field. See Materials and methods for detail. (B) Sample peri-stimulus time histogram (PSTH) from a representative unit showing the time course of firing rate for different motion directions, averaged over a 10 ms sliding window. Motion onset is at 0 ms and motion offset is at 250 ms. (C) Average spike count across neurons in the alert experiments (blue) and anesthetized (orange) by direction. Circles indicate mean, error bars indicate standard deviation, and the solid traces indicates a Gaussian best fit. Responses are aligned such that the preferred stimulus direction for each neuron is taken to be 0°. (D) Average spike count variance across populations of neurons in the same manner as (C). (E) Histogram of direction selectivity indexes, DI, across both populations. (F) Histogram of variance spike count tuning indexes. (G) Histogram of response latency distributions. (H) Distribution of single-unit mutual information (Shannon) values for alert (blue bars) and anesthetized (orange bars) states, based on spike count 250 ms after stimulus motion onset, Value are corrected for finite sample size (see Materials and methods). Arrows below indicate average information for alert (1.11 bits) and anesthetized (0.40 bits). Inset: time course of the mutual information between the cumulative spike count and motion direction over time with respect to stimulus motion onset. Blue traces indicate alert-state units, orange traces anesthetized state.