Figure 2.

ST characteristics of cortical responses to local stimuli. A–C, ST representations of the evoked cortical response to, 10 ms (A, red), 50 ms (B, purple), and 100 ms (C, blue) local stimuli. To produce the ST representation, we averaged spatial data along the stimulus trajectory (Fig. 1C–G, rectangle in frame 216 ms). For each spatial point, the temporal data were fitted to a combination of two half Gaussians, as illustrated for one specific point in space (horizontal white line on the ST diagram) below the ST maps. Similarly, for each time frame, the spatial data were fitted to a Gaussian function as shown on the right side of each ST map for one specific point in time (vertical white line). D, Space constant of the Gaussian spatial fit (σ parameter) plotted as a function of time for the three considered durations (10 ms in red, 50 ms in magenta, and 100 ms in blue) and for the 2 monkeys (top: Monkey WA; bottom: Monkey BR). Error bars indicate SEs across sessions (n = 8 for each of the three duration conditions). E, Histograms of time constant at response onset (τ_on) estimated from the temporal fit of the response for the three considered durations and the 2 monkeys. F, Histograms of time constant at response offset (τ_off) estimated from the temporal fit of the response for the three considered durations and the 2 monkeys. G, Histograms of cortical speed of propagation estimated by linear regression on response latency (stairs-step contours, slanting lines, and slope of the linear regression in Fig. 2A–C) for the three considered durations and the 2 monkeys.