EEG correlation of the discharge properties of identified neurons in the basal forebrain

The basal forebrain (BF) is a heterogeneous structure located in the ventra l aspect of the cerebral hemispheres. It contains cholinergic as well as di fferent types of noncholinergic corticopetal neurons and interneurons, incl uding GABAergic and peptidergic cells. The BF constitutes an extrathalamic route to the cortex, and its activity is associated with an increase in cor tical release of the neurotransmitter acetylcholine, concomitant with elect roencephalographic (EEG) low-voltage fast activity (LVFA). However, the spe cific role of the different BF cell types has largely remained unknown due to the lack of chemical identification of the recorded neurons. Here we sho w that the firing rate of immunocytochemically identified cholinergic and p arvalbumin-containing neurons increase during cortical LVFA. In contrast, i ncreased neuropeptide Y neuron firing is accompanied by cortical slow waves . Our results, furthermore, indicate that BF neurons posses a distinct temp oral relationship to different EEG patterns and suggest a more dynamic inte rplay within BF as well as between BF and cortical circuitries than previou sly proposed.