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. Author manuscript; available in PMC: 2019 Feb 12.
Published in final edited form as: Microsyst Nanoeng. 2018 Jun 4;4:10. doi: 10.1038/s41378-018-0009-2

Figure 7: Control of multiple neural populations in vivo with ILD-GRIN waveguide probes.

Figure 7:

(a) Wide-band (0.1–7,500 Hz) spiking activity recorded on a four-shank probe from CA1 pyramidal cell layer of an awake mouse expressing ChR2 in pyramidal cells and ChrimsonR in parvalbumin expressing interneurons. The illuminated shank shows spiking activity and light-induced artifacts during a 200 μW 405 nm light pulse (100 ms, 40 mA) and 450 μW 635 nm light pulse (300 ms, 50 mA). Note spontaneous activity on all shanks and induced spiking during ILD driving on illuminated shank.

When simulated in our thermal model, the device can be driven for up to ~27 continuous seconds when driving 2 ILDs on the same shank with a total input electrical power of 320 mW (40mA × 5V for 635 nm + 50 mA × 2.4 V for 405 nm).

(b) Independent dual color excitation of pyramidal neurons (PYR) and interneurons (PV). The spiking data was quantified for 37 well-isolated cells (35 PYR and 2 PV interneurons) recorded simultaneously from CA1 (same animal and session as in Figure 7a). Inset of the probe tip shows the vertical location of three light-modulated cells (1 PYR and 2 PV) relative to the probe sites. Plots in the center show auto-correlation histogram and spike waveform (mean and SD) in the lack of any illumination. Histogram plots on the right show examples of spiking response to 50 ms long 405 pulses and 400 ms long 635 nm pulses (for three different intensities) in a ChR2+ PYR, and two ChrimsonR+ PV. Note the light-modulated increase in spiking response of PYR cells and PV cells with 405 nm and 635 nm light, respectively. Also note the decrease in spiking response of a putative PYR (not shown), possibly making a synaptic connection to the orange PV cell, with higher intensity of 635 nm illuminations. More experiments and analysis are ongoing to study these effects and similar circuit effects observed in other cells.

(c) Dual color modulation of single units (mean firing rate ± SEM are shown). Firing rate of 19 PYR (blue triangles) and 2 INT (red circles) were modulated by 405 nm (50 ms, 40 mA) and 635 nm light pulses (300ms, 25, 30 and 40 mA).