Figure 2

NREM-gated optogenetic waxing-and-waning stimulation of thalamic reticular nucleus (TRN) parvalbumin (PV) neurons increases cortical spindle density. (A,B) Representative raster plots of detected spindle-like events produced by optogenetic or sham stimulation (red lines) relative to non-rapid-eye-movement (NREM) sleep show a pronounced elevation in spindle density with optogenetic stimulation. Optogenetic waxing-and-waning stimulation was applied for 1 s with a minimum 9 s interval between stimulation trials repeatedly over 6 h of recording time. Stimulation was restricted to NREM sleep using a NREM detection system. (C,D) Histogram depiction shows a significant increase in averaged NREM spindle density with optogenetic stimulation when compared to sham (n = 5, ANOVA, **p < 0.01; *p < 0.05). There was no immediate arousal observed with optogenetic or sham stimulation (E,F). EEG power spectral density analysis of the 1 s pre-stimulus period (G) showed high delta activity typical of the NREM sleep state prior to both sham (black) and optogenetic stimulation (red) due to the use of the NREM detection system capturing high delta activity. (H) During the 1 s stimulus period, there was a statistically significant increase across the 10–12 Hz peak spindle frequency band with optogenetic stimulation (n = 5, Jackknifing U-Statistic, *p < 0.05) compared to sham. (I) No significant difference in EEG power was observed between sham and optogenetic stimulation during the 1 s post-stimulus period.