Figure 1.
Effects of pulse pattern on saccades from an example FEF site. A, Five patterns of electrical microstimulation current pulses were delivered to the FEF (shaded region). Each vertical bar represents a biphasic current pulse (enlarged in inset); the horizontal lines represent time (t) increasing from left to right and with the first pulse at t = 0. Individual IPIs are shown above each pulse train in milliseconds. Each train consisted of eight current pulses delivered over 35 ms, resulting in a mean IPI of 5 ms (the final random train excepted). The pulse patterns depicted are (top–bottom, left–right) as follows: fixed (constant IPI), decel (linearly increasing IPI), accel (linearly decreasing IPI symmetrically opposite of decel), ro (same IPIs as decel and accel but in random order), and ri (random assignment of 8 pulses to 2-ms-wide bins with one pulse per bin; question marks denote random values for IPIs). B–G, Data and example analysis from a single FEF site are shown. B, Raw traces of saccade trajectory evoked at a suprathreshold stimulation current (65 μA) using the fixed pulse pattern are plotted. Open circles indicate saccade endpoints. C, The saccade probability is plotted against the stimulation current for each pulse pattern. D–G, For each stimulation-evoked saccade, latency (D), amplitude (E), peak velocity (F), and duration (G) of individual evoked saccades are plotted against saccade probability of the pulse pattern as obtained for the block of trials in which the saccades were evoked. Lines are shown for significant (p < 0.05) linear regressions.