Figure 2

Optogenetic activation of cholinergic and GABAergic basal forebrain inputs to the OB modulates spontaneous as well as sensory-evoked MTC spiking. (A) Spike raster and rate histograms (bin width, 50 ms) from presumptive MTCs showing spontaneous spiking in the absence of inhalation (no sniff). Spike rate decreased during optical stimulation of the dorsal OB (“stim”, blue shaded area) in GAD-Cre mice and increased in ChAT-Cre animals. (B) Left, Plot of spontaneous firing rate in the 9 s before (no stim) and during (stim) optical stimulation for all tested units (ChAT-Cre, n = 27 units, purple; GAD-Cre, n = 44 units, orange). Squares indicated significantly modulated units. Right, Time course of changes in firing rate (mean ± SEM across all units) during optical stimulation (blue bar). The trace indicates changes in mean spike rate in 1 s bins relative to the mean rate before stimulation. The time axis is relative to the time of stimulation onset. (C) Spike raster and rate histogram of MTC spiking during inhalation of clean air and optical stimulation (blue shaded area). Inhalation-evoked spike rates decrease (top) or increase (bottom) during optical stimulation in GAD-Cre mice while only excitation in response to optical stimulation is observed in ChAT-Cre mice. The top trace (sniff) shows artificial inhalation as measured by a pressure sensor connected to the nasopharyngeal cannula. (D) Left, Plot of inhalation-evoked firing rates during clean air inhalation, averaged for the nine inhalations just before (no stim) and after (stim) optical stimulation (ChAT-Cre, n = 62 units, purple; GAD-Cre, n = 25 units, orange). Data were analyzed and plotted as in B. Squares indicate significantly modulated units. Right: Time course of changes in firing rate (mean ± SEM across all units) during optical stimulation (blue bar).