Fig. 2

Two examples of a single sweep optical signal from the rat cerebral cortex obtained with the plano-concave lens (left) and with 4 % agarose (right). Somatic evoked cortical response was induced by electrical stimulation (0.5 ms, 1 mA) of the contralateral forelimb. The vertical line indicates the timing of the electrical stimulation. The direction of the arrow in the lower-right corner indicates a decrease in fluorescence (corresponding to depolarization) and the length of the arrow represents the stated value of the fractional change (change in fluorescence intensity divided by the resting fluorescence intensity). The right drawing indicates relative position of the matrix array photodiode and that of the plano-concave lens to the image of the left cerebral cortex. Each square corresponds to each element in the photodiode array used in our laboratory. The 3 × 3 gray squares indicate the position of the nine contiguous photodiode elements at the marginal zone of the image used for analyzing in Table 1. Two black squares among the gray ones indicate the positions in the matrix where the optical signals shown in the left were recorded. The notation 18–14 or 18–15 indicates the element position in row 18 and column 14 or 15 of the matrix array, respectively