Figure 4

Optogenetic inhibition of thalamic reticular nucleus (TRN) parvalbumin (PV) neurons alters spontaneous electroencephalogram (EEG) activity leading to an abnormal auditory steady state response (ASSR). (A,B) Grand-average spectrograms of the 40 Hz ASSR under control conditions (A) and with bilateral ArchT inhibition of TRN-PV neurons (B). (C) Overall, optical inhibition of TRN-PV neurons using archaerhodopsin (ArchT) resulted in a trend level (p = 0.07) decrease in the relative change in 40 Hz ASSR power. (D) Background 40 Hz power prior to auditory stimuli (0–0.8 s) was significantly increased whereas (E) evoked 40 Hz power during the auditory stimuli (1.2–2 s) was unchanged. Thus, the reduction in the ASSR with ArchT inhibition of TRN-PV neurons is due to a significant (p < 0.05) increase in spontaneous activity prior to the auditory stimuli. (F) Further examination of the power spectral density during the ASSR task show that background activity is significantly elevated in power across the delta & theta (0.5–9 Hz), low beta (~18 Hz), and gamma (~40 Hz) bands with optical inhibition of TRN-PV neurons. (G) Evoked activity during the 40 Hz train of auditory stimuli shows only a small elevation in power in the delta range when compared to control. (n = 5, Jackknifing U-Statistics, *p < 0.05).