Figure 1.
A. Percept electrodes (green) that produced a phosphene upon electrical stimulation and non-percept electrodes (red) that did not in three subjects. Subject 1 (s1) shows a posterior view of the right hemisphere; s2: posterior view of left hemisphere; s3: medial view of left hemisphere. Electrodes were implanted only in a single hemisphere for each subject (right for s1, left for s2 and s3). OP: occipital pole.
B. Maps showing the difference in gamma power between percept electrode stimulation and non-percept electrode stimulation in three subjects (same subjects as A). For each subject, one percept electrode and the nearest non-percept electrode in the implanted hemisphere was repeatedly stimulated, and the significance of post-stimulation difference in gamma power at each electrode (except for the stimulation electrodes) was calculated and mapped to the cortical surface. Black spheres show electrode locations. TPJ: temporoparietal junction.
C. TPJ response during electrical stimulation of occipital electrodes that did (left) or did not (right) produce a phosphene, averaged across subjects. Color scale indicates power at each frequency. Dark gray bar centered at t = 0 indicates stimulation artifact. Dashed white line at f = 30 Hz indicates boundary between two different frequency estimate techniques. Dashed black line indicates gamma band f-t window used to estimate power for single-trial analysis.
D. TPJ gamma responses for every trial during stimulation of a percept (left) or non-percept (right) electrode. Each horizontal line (raster) shows the power in a single trial over time, collapsed across 60–150 hz. Same color scale as C.
E. Receiver-operating curve analysis of single trial data.