Sensory input to the nucleus basalis prosen- cephali, a feeding pecking centre in the pigeon

Summary. Evoked potentials were recorded from the nucleus basalis prosencephali (Bas) of the pi-geon through chronically implanted electrodes. The auditory sensitivity of the Bas was assessed by the amplitude of the potentials. Audiograms thus obtained were comparable to those similarly measured from stations of the orthodox auditory pathway and resembled those obtained by others with behavioural techniques from the same species. The sensitivity to vibration applied to the beak was also measured. The vibrogram revealed two separate optima, one located in the lower fre-quency and another in the higher frequency region. These were shown to be due to trigeminal mechan-oreceptive sensitivity and to bone/cochlea me-diated sound sensitivity, respectively. Evoked po-tentials of the Bas in response to vestibular stimu-lation are described for the first time. The possibili-ty that they were artefacts was excluded with sever-al control procedures. These findings confirm re-cent anatomical evidence of a direct pathway from the vestibular nucleus to the nucleus basalis pros-encephali. All afferents to the Bas are discussed in conjunction with the probable function of the nucleus as a sensorimotor coordinator of the pi-geon's pecking/feeding behaviour. Abbreviations: A archistriatum; aL area L of the medial neo-striatum caudale; Bas nucleus basalis prosencephali; Cb cere-bellum; FA tractus fronto-archistriatalis; HA hyperstriatum ac-cessorium; Hp hippocampus; HRP horseradish peroxidase; HV hyperstriatum ventrale; LLv nucleus lemnisci lateralis, pars ventralis; LPO lobus parolfactorius; MV nucleus motorius nervi trigemini; MLd nucleus mesencephalicus lateralis, pars dorsalis; nVI nucleus nervi facialis; nVI I I nervus vestibulo-cochlearis; N neostriatum; NFL neostriatum frontolaterale; OM tractus occipitomesencephalicus; Ov nucleus ovoidalis; PrV nucleus sensorius principalis nervi trigemini; QF tractus quintofrontalis; Rpv nucleus reticularis parvocellularis, pars lateralis; TrO tractus opticus; VS nucleus vestibularis superio