Fig. 1: Electrical stimulation at 40 Hz, 140 Hz, and 1 kHz evoked robust cellular calcium activity.

a, b An illustration of the animal preparation for the (a) CA1 and (b) cortex, showing optical imaging chambers with nearby stimulation and ground electrodes. c Schematic of the widefield calcium imaging experimental setup in freely locomoting head-fixed mice. d (left) An example max-min projected imaging field of view of the GCaMP7f fluorescence during a CA1 recording session testing 140 Hz stimulation, (middle) a heatmap depicting the theoretical electric field strength dissipation, and (right) the overlay of the left and middle panels. White dotted circles mark every 50 µm from the center of the electrode tip. The fluorescence traces of four example modulated neurons (outlined in yellow in the left and right panels) are shown in f. e The normalized fluorescence traces of example CA1 neurons during 40 Hz stimulation, aligned to stimulation onset. Every trial is shown in gray (10 trials total); the average fluorescence trace across all trials is shown in red for activated neurons and blue for suppressed neurons. f–j Additional example modulated neurons for the other experimental conditions, with electrical stimulation period highlighted by the bar on the top (green, for CA1; yellow for cortex). (e) 40 Hz in the CA1, (f) 140 Hz in the CA1, (g) 1 kHz in the CA1, (h) 40 Hz in the cortex, (i) 140 Hz in the cortex, and (j) 1 kHz in the cortex.