Fig. 4: Using Neuropixels Opto to drive local circuits.

a, We inserted a Neuropixels Opto probe in the dorsal cortex of mice expressing red-sensitive depolarizing opsin ChrimsonR–tdTomato in putative inhibitory neurons (using a DLX2.0 enhancer virus). b, Left: electrical signals at 20 recording sites during red-light stimulation from emitter 9. Colors indicate the spikes of two nearby units, one activated (unit 189; green) and one inactivated (unit 208; purple) by light. Right: waveforms across peak channels confirm neural activity. In this panel and subsequent ones, the shaded rectangle indicates the time of optical activation. c, Spike rasters for a pair of example units, one inactivated (unit 177) and one activated (unit 232) by light, ordered by the stimulating emitter (ordinate). d, Average firing rate (bin size: 40 ms) relative to light onset for those units and for two additional units (199 and 180). Shading indicates ±1 s.e. Insets: waveforms show spike shapes across six peak recordings sites. e, Spike width (trough to peak) of average waveforms versus effect of light stimulation, measured by a modulation index (R₁ − R₀)/(R₁ + R₀), where R₀ and R₁ are firing rates before and during stimulus, showing significantly activated units (green) and inactivated units (purple) at P < 0.005 (paired two-sided t-test). Narrow spikes were defined as width <0.4 ms (vertical line). f, CCG between units 199 and 180. g, Recording versus emitter depth for significantly modulated neurons. Each neuron appears at one recording depth and at one or more emitter depths (if modulated by light from multiple emitters).