Fig. 3

A Example of reductions in pulsation artifact. Raw (top 3 traces, indicated as detectors #1–#3) and pulsation artifact-removed optical signals (bottom 3 traces, indicated as detectors #1–#3) obtained at three different pixels are shown with the ECoG signal. Pixel #1 was located underneath the electrode spot (corresponding to electrode #3 in Fig. 2) where the electrocorticogram signal was recorded; the two other pixels were 1 mm away from #1. B Distribution of neural activity, as indicated by the asterisk or arrowhead in A. Dark-gray and light-gray areas indicate the areas in which this neural activity was clearly (similar to the arrowhead in pixel #3) or poorly (similar to the arrowhead in pixel #2) detected, respectively. Within the white area, no neural activity was detected at this time period [similar to pixel #1 (subtracted)]. C Comparison of artifact compensation based on two different neural activity-free periods, real (thick black lines) and pseudo (thick gray lines). The black and gray traces were based on the periods indicated by the thick black and gray bar in Fig. 3A, respectively. See the text for details