Together with previous studies in the locust olfactory system showing that reduced synchronization impairs odor discrimination (Stopfer et al., 1997), our results suggest that there is an optimal level of neural synchronization for the processing of overlapping sensory representations. Sensory information contained in the temporal dimension of the representation may be altered by resting NVP-BKM120 clinical trial states of synchronization and yield to a slower integration time in downstream structures. In this context, abnormal oversynchronization of neural

assemblies observed in brain disorders such as schizophrenia during resting state may disrupt the neural integration of related check details stimuli and account for the lengthening of reaction time described in schizophrenic patients (Reinhart et al., 2011 and Tikka et al., 2012). Our work illustrates

to what extent impairments in local inhibitory circuits, and therefore in the excitation/inhibition balance, may represent a key process leading to γ oversynchronization and abnormal electroencephalogram signals responsible for psychophysical altered responses seen in some brain disorders. Single-unit activity was recorded using a 3 MΩ tungsten electrode array (FHC) glued to a miniature cannula (polyimide tubing, 0.0035”). For behaving animals, mice were chronically implanted with a bipolar electrode (coated-platinium wires, 0.2–0.5 MOhm, A-M Systems) closely linked to a steel guide cannula and stabilized

with dental cement. An additional stimulation bipolar electrode was positioned in the LOT for antidromic stimulation (1–2 mA; ISI, 30 ms). Breathing was monitored with a thermocouple (5TC-TT-JI-40-1M, Omega) and the reference electrode was positioned on the occipital crest. Local field potentials and spiking activity were amplified (×1,000–10,000), filtered (1–300 Hz for LFP, 0.3–8 kHz for spikes), and digitized (Micro1401-3, CED). Drugs were unless injected via a 10 μl Hamilton syringe (0.1 μl/min). Head-fixed Thy1:ChR2-YFP mice were stimulated using an LED-coupled optic fiber (220 μm; NA 0.5; 470 nm; Doric Lenses) positioned on the surface of the dura, with output light intensity set to 2–5 mW/mm2. See also Supplemental Experimental Procedures. Short-time Fourier transform (Hanning window, 2.44 Hz resolution) was used to measure the absolute spectral power and the mean frequency of γ (40–100 Hz), β (15–40 Hz) and theta (1–10 Hz) bands. MC spiking was characterized from 500 s signal epoch before and after drug injection. Phase histogram was computed to measure the phase preference and the length of the normalized vector as a measure of the modulation strength and was tested with Rayleigh’s uniformity test (significance p < 0.005) and Hotelling paired test (significance p < 0.05).