ACOUSTIC FREQUENCY TUNING OF NEURONS IN THE BASAL FOREBRAIN OF THE WAKING GUINEA-PIG

The acoustic responses of cells in the basal forebrain were studied in the adult waking guinea pig. Frequency receptive fields were obtained across wide frequency (0.094-45.0 kHz) and intensity (0-90 dB) ranges . A total of 326 recordings were obtained in 26 electrode penetrations from five subjects; 205 from the globus pallidus (GP), 98 from the ca udate-putamen (CPu) and 23 from the central nucleus of the amygdala (A CE). Twenty-nine recordings exhibited acoustic responses (GP = 20 (9.8 %); CPu = 9 (9.2%); ACE = 0). Cells in the regions of the GP that proj ect to the primary auditory cortex (ACx) exhibited frequency tuning th at was dominantly suppressive. Responses in the CPu were excitatory, b ut poorly tuned. The spontaneous rate of discharge of GP cells that yi elded complete tuning data was positively correlated with power in the beta bands (12-25 and 25-50 Hz) and negatively correlated with power in the delta band (1-4 Hz) of the EEG of the ACx. These findings sugge st that acoustically tuned neurons in the GP that are inhibited by ton es are involved in the regulation of auditory cortical state, possibly promoting deactivation to unimportant sounds, and may be cholinergic in nature. (C) 1998 Elsevier Science B.V. All rights reserved.