Article Figures & Data
Figures
- Fig. 1.
Experimental paradigm. A: behavioral task. On each trial, the monkeys compared the direction of motion of 2 sequentially presented stimuli, the sample and test, separated by a 1.5-s delay. The sample was composed of dots moving within a predetermined range of directions producing a net direction of motion in 1 of 4 orthogonal directions. One of the 4 directions always matched the preferred direction of the stimulated site in the middle temporal area (MT). The dots in the test stimulus moved coherently in the direction that was either the same as or opposite to the direction of motion in the sample. The monkeys indicated whether the stimuli moved in the same or different directions by pressing 1 of 2 response buttons. The monkeys were required to maintain fixation throughout the duration of the trial. B: stimulation protocol. Stimulation occurred either throughout the duration of the sample (500 ms) or during the middle 3rd of the delay (500 ms).
- Fig. 2.
Effect of stimulation during the presentation of sample.A: the direction selectivity profile for the example stimulation site. The radial axes show the firing rate (Hz) for the multiunit site measured with coherently moving dots. The preferred direction was rightward (0°). B: the performance of the monkey on nonstimulation (gray columns) and stimulation trials (black columns). The data are plotted separately for each of the 4 sample directions. The dashed line shows the level of chance performance. C: the percentage of trials in which the animal equated the direction of the sample with the direction of the test on nonstimulation (gray columns) and stimulation (black columns) trials. The data are plotted separately for each test direction. Statistical significance between nonstimulation and stimulation trials was tested using Fisher's Exact test (* P < 0.05).
- Fig. 3.
Summary of the effects of stimulation during sample for 44 MT sites.A: the distribution of stimulation effects [1 − (percent correct on stimulation trials/percent correct on nonstimulation trials)]. Top: data from trials in which the sample moved in the preferred direction. Middle: data from trials in which the sample moved in the null direction.Bottom: data from trials in which the sample moved in directions orthogonal to the preferred. B: percentage of sites in which the monkeys reported that the sample moved in the direction of the test. Top: test stimulus moved in preferred direction. Middle: test moved in the null direction. Bottom: test stimulus moved in directions orthogonal to the preferred. Light gray outlines of columns: “same as test” choices recorded during nonstimulation trials. Lower values (toward 0%) represent sites in which the monkeys frequently judged the direction of the sample to be different from the test. Higher values (toward 100%) represent sites for which the monkeys consistently reported that the direction of the sample was the same as that of the test. Gray columns: sites in which the proportion of the “same as test” reports during stimulation trials was significantly different from the proportion of these reports during nonstimulation trials (Fisher's Exact test, P < 0.05). Hollow columns: sites in which the proportion of the “same as test” reports during stimulation trials was not different from the proportion of these reports during nonstimulation trials.
- Fig. 4.
Effect of stimulation during the delay for the site illustrated in Fig.2. A: performance during nonstimulation (gray columns) and stimulation (black columns) trials. The data are plotted separately for each sample direction. B: the percentage of trials in which the animal equated the direction of the sample with the direction of the test on nonstimulation (gray columns) and stimulation (black columns) trials. The data are plotted separately for each test direction. Statistical significance between nonstimulation and stimulation trials was tested using Fisher's Exact test (* P < 0.05).
- Fig. 5.
Summary of the effects of stimulation during the delay measured for 31 sites. A: the distribution of stimulation effects.B: percentage of sites in which the monkeys reported that the sample moved in the direction of the test. See Fig. 3 for detailed explanation.
- Fig. 6.
Stimulation during a stationary sample stimulus. A: the direction selectivity profile for the stimulated site in MT. The preferred direction was leftward (180°). B: the percentage of stimulated trials in which the monkey equated the moving (black bars) or stationary (striped bars) sample with the direction of test. In this plot the angular axes show the directions of the test stimulus, and the radial axes show the proportion of trials for which the monkey reported that the sample moved in the same direction as the test. Note the consistency in the reports for the stationary and the moving sample. C: percentage of stimulated trials for which the monkeys equated the stationary sample with the direction of the test, plotted against the percentage of trials for which the monkeys equated the moving sample with the test. Each point represents a single test direction from each of the 6 sites. ●, directions significantly effected by stimulation under both conditions (Fisher's Exact test, P < 0.05); ○, directions not effected in both conditions. Linear regression of the solid points (solid line) was significant (P < 0.001) with a correlation coefficient R = 0.832. For more detailed explanation of axis units, see results.
- Fig. 7.
Remote stimulation experiment. A: schematic illustration of the experimental protocol. The visual stimulus was always placed either in the visual quadrant diagonally opposite to the site of stimulation or in the location of stimulation. Stimulation was applied during the presentation of sample. B: direction selectivity profile of the stimulated site and performance during stimulation on nonstimulation trials (░), stimulation trials with stimuli placed in the location of stimulation (■), and stimulation trials with the visual stimuli in location remote from the receptive field of the stimulated site (▧). The preferred direction of the site was 45°. Statistical significance between nonstimulation and stimulation trials was tested using Fisher's Exact test (* P < 0.05).
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