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. 1998 Mar 17;95(6):3263–3268. doi: 10.1073/pnas.95.6.3263

Figure 5.

Figure 5

Control experiments. (A) After the recordings in anesthetized animals, figure-ground modulation still could be recorded in the awake condition. Shown are average responses for the two types of stimuli with RFs either within the boundaries of the square figure (thick lines) or overlying background (thin lines). The gray shading indicates the difference between figure and ground responses, i.e., the figure-ground specific contextual modulation. (B) Figure-ground modulation in the awake animals is not caused by eye movements. Shown are the average eye velocities during fixation (Top) (eye movements were recorded during about 40% of the data collection resulting in Figs. 2 and 3), showing that the stimulus does not evoke any eye movements beyond the already present low level of micro-saccades within the fixation window. The second and third rows show the figure-ground responses either before or after correcting for eye movements. Correction consisted of removing those 50% of the trials where eye movements within the fixation window were largest. Figure-ground modulation does not appear to depend quantitatively on eye movements. The fourth row shows figure-ground responses for flashed stimuli (see Results), indicating that figure-ground modulation could not have been caused by eye movements over the textures generating responses. (C) Figure-ground modulation in the awake is not an effect of focal attention. Quantitatively similar figure-ground modulation is observed when two figures are presented (Lower) as when one figure is presented (Upper), whereas an effect of focal attention would be expected to split in about equal halves when two figures are presented, thereby diminishing figure-ground modulation for each figure. Format of all figures is: figure responses, thick lines; ground responses, thin lines; SEM of figure responses, dotted lines; prestimulus level of activity, short horizontal dashes; difference between figure and ground responses, gray shading. Not all of these control experiments were performed in both animals.