[Neuronal activity in the nucleus basalis magnocellularis during performance of an instrumental task].

Spike activity of 95 neurons in the rabbit basal forebrain forebrain magnocellular nucleus was recorded during spontaneous behavior and instrumental conditioned performance. Almost half of the neurons (48.4%) displayed a significant (p > 0.05) negative correlation between their spontaneous discharge rate and the power of the delta rhythm in the EEG of the frontal cortex; most of these cells can be classified as projection cholinergic neurons. During instrumental conditioned performance, neurons of this subgroup responded with excitation to the conditioned stimulus, whereas presumably noncholinergic nonprojection neurons responded to the conditioned stimulus with inhibition. Excitatory response of cells in the basal forebrain magnocellular nucleus was significantly more intense as compared to trials without the conditioned reaction. On the whole, our data testify that the basal forebrain magnocellular nucleus maintains the level of arousal and attention required for the instrumental conditioned performance.