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Figure 8.2. Directionally selective responses of one cell (J68_29.25) to object movement and projected large-field pattern movment. Upper part: The cell was tested with 8 directions of object movement in the fronto-poraiiei plane (0=up,

180=down). The cell responded (mean +/- ISE) to three directions of object movement (180, 225 and 135, p<0.001) significantly more (PLSD, each comparison p<0.001), than to motion at angles of 0,45,90, 315, and 270 or to static control object or spontaneous activity (s.a.). (Overall effect of condition, ANOVA; F8.36=18.7, p<0.001, n=5 in each conditions). The curve is the best fit cardioid function, relating response to direction of movement (R2=0.68; F4,35=18.2, p<0.001). Lower part: ceil responses to the projected video image of the cylinder used in the experiments. The rasterogroms show individual neuronal spikes (short vertical dashes) during post- stimuius time period collected from nine different trials. Poststimuius time histograms (PSTH) show averaged response from nine trials (bin width = 20 ms). The cell responded strongly to the pattern movement directed downwards but failed to respond to similar movement directed upwards (stimulus onset at time 0). The ordinate axes of the PSTHs denote the ceil responsivity for 100 spikes/s.

otlier cells exhibited response discrimination in the cells preferred direction of movement for the stimulation induced by the experimenter compared to self-induced stimulation. Additionally the cells responded at a reduced level to the externally

induced non-preferred direction of movement and to the self-induced motion in both directions without showing any response discrimination (Fig. 8.3).

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Figure 8.3. Directionally selective responses of one ceil (J30_27.05) to externally

Induced pattern movement. Upper row: response to the externally induced motion to

the left and right; middle row: self-induced motion to the left and right; bottom left: response to the static pattern. Externally-induced pattern motion to the right elicited statistically stronger responses than any other stimulus condition (p<0.005 each comparison). The ceil responded above spontaneous activity (=static pattern) also to the externally-induced motion directed to the left and to both self-produced directions of motion (p<0.02 each comparison). These responses, however, were graded so that the externally-induced motion to the left did not exceed the self­ induced motion to the right (p>0.1), but was anyway stronger than the self-produced

motion in this direction (p<0.02). There was no difference in responses between the self-induced conditions (p>0.3). (ANOVA, F4.3o= 17.7, p<0.0005, n=7 in each

condition). Stimulus onset at the beginning of the rasterogroms and PSTHs (bin width = 20 ms). Calibration marks on the right bottom comer give the scale of the responsivity (spikes/s) and time (ms).

Motion velocity. The experimenter tried to match the velocity of the handle rotation with that generated by the monkey. The velocity between individual rotations naturally varied in both cases, but within the range of velocities generated by the experimenter or the monkey, no effect of velocity on the cell responses was observed. Figure 8.4 depicts the results of testing with one cell which responded selectively to

the externally-induced motion and the figure also shows the average velocity curve of the pattern motion across the collected trials.

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