The basal forebrain (BF) is a heterogeneous structure located in the ventral aspect
of the cerebral hemispheres. It contains cholinergic as well as different types of
noncholinergic corticopetal neurons and interneurons, including GABAergic and peptidergic
cells. The BF constitutes an extrathalamic route to the cortex, and its activity is
associated with an increase in cortical release of the neurotransmitter acetylcholine,
concomitant with electroencephalographic (EEG) low-voltage fast activity (LVFA). However,
the specific role of the different BF cell types has largely remained unknown due
to the lack of chemical identification of the recorded neurons. Here we show that
the firing rate of immunocytochemically identified cholinergic and parvalbumin-containing
neurons increase during cortical LVFA. In contrast, increased neuropeptide Y neuron
firing is accompanied by cortical slow waves. Our results, furthermore, indicate that
BF neurons posses a distinct temporal relationship to different EEG patterns and suggest
a more dynamic interplay within BF as well as between BF and cortical circuitries
than previously proposed.
