NEURONAL-ACTIVITY WITHIN THE NUCLEUS BASALIS AND CONDITIONED NEOCORTICAL ELECTROENCEPHALOGRAPHIC ACTIVATION

The relationship between neuronal activity within the nucleus basalis (NB) and conditioned neocortical EEG activation was investigated in Ne w Zealand rabbits during Pavlovian differential conditioning. Twenty-s even of 56 neurons recorded in conditioned animals demonstrated a sign ificantly greater change in activity to a tone (CS+) that predicted th e occurrence of a mildly aversive unconditioned stimulus when compared to a tone (CS-) that did not. Twenty-four of these 27 neurons demonst rated a significant increase in activity to the CS+ compared to the CS -, while the remaining three neurons demonstrated a significant decrea se in activity to the CS+ compared to the CS-. In 24 of these 27 neuro ns (89%) these changes in neuronal activity during CS presentations co rrelated significantly with a decrease in the power of delta activity in the EEG. In addition, 13 of these 24 neurons (54%) demonstrated sig nificant correlations between neuronal activity and the power of delta activity during CS-free periods. In experimentally naive animals, the activity of 10 of 22 neurons (45%) recorded within the region of the NB correlated with the power of delta activity in the EEG during stimu lus-free periods. These results complement a growing body of evidence and provide strong support for the hypothesis that the NB contributes to neocortical activation in the conscious animal.