Cortical modulation by nucleus basalis magnocellularis corticopetal cholinergic neurons during anxiety-like states is reflected by decreases in delta

Previous research has demonstrated that nucleus basalis magnocellularis (nbm) corticopetal cholinergic neurons modulate anxiety-like states, but cortical modulation by these neurons during anxiety-like states has not been characterized. In order to address this, we documented the effect of nbm corticopetal cholinergic lesions on cortical activity in direct (prefrontal cortex) and indirect (retrosplenial cortex) targets of nbm corticopetal cholinergic neurons during footshock induced operant suppression. The gamma/delta ratio and theta were used as indices of cortical activity, because these components of the electroencephalogram (EEG) are sensitive to basal forebrain corticopetal cholinergic modulation. During operant suppression, increases in the gamma/delta ratio and augmented theta were observed in both cortical EEGs. Lesions attenuated operant suppression and the gamma/delta ratio, but had no effect on increased theta. The effect of nbm corticopetal cholinergic lesions on the gamma/delta ratio was driven by the effect of the lesions on the delta band. The results of the study demonstrate that during anxiety-like states 1) decreases in delta reflect the action of nbm corticopetal cholinergic neurons, 2) nbm corticopetal cholinergic neurons alter neural processes in direct and indirect cortical targets, and 3) cortical theta is not dependent on the integrity of nbm corticopetal cholinergic neurons. (C) 2008 Elsevier B.V. All rights reserved.