Figure 2.

State-dependent and cell-type-specific spontaneous firing. (A) An example of pedunculopontine tegmental (PPT) nucleus stimulation and neural population activity in the auditory cortex. LFP, multiple single-units, spectrogram, and a history of low-frequency LFP power are shown. (B) Examples of morphologically identified pyramidal cells (PCs) and the effects of PPT stimulation on their spiking. Rasters show response of these cells to repeated PPT stimuli; lower graphs show peri-stimulus time histograms. (C) Modulation index of morphologically identified PCs and extracellularly classified single-units. L5slP, L5 slender PCs; L5tP, L5 thick PCs; sP and dP putative superficial and deep PCs, respectively; sFS and dFS, putative superficial and deep fast-spiking interneurons (FSs), respectively. ^*p < 0.05, ^**p < 0.01, and ^***p < 0.005 (signed-rank test). (D) Mean firing rate during the synchronized state plotted against that during the desynchronized state (left column) and modulation index (right column) for morphologically identified and putative PCs (top row), and putative FSs (bottom row). Solid lines in left panels correspond to equality; those in right panels are linear regression fits. Please note that linear fitting was done with a semi-logarithmic scale.