Orientation sounds evoked from echolocating bats by electrical stimulation of the brain.

Abstract

The brains of several representative species of echolocating bats were found to contain regions concerned with the emission of species-specific orientation sounds. When the dorsal part of the reticular formation in the midbrain or the lateral part of the central gray matter is stimulated with a short train of electric pulses, the bat moves its mouth and pinnae and emits sounds identical to orientation sounds, with a latency of 25 to 60 msec. The acoustic parameters of the electrically elicited sounds and the temporal patterns of emissions vary with the location of the stimulating electrodes. Bats of the genus Myotis (little brown bat) emitted short frequency-modulated (FM) sounds both in nature and when electrically stimulated. Pteronotus parnellii (mustache bat) responded with sounds containing long constant-frequency (CF) and short FM components that were typical of the species. Eptesicus fuscus (big brown bat), Pteronotus suapurensis (naked-backed bat), and Noctilio leporinus (fish-catching bat) also made characteristic orientation sounds when electrically stimulated. It appears that the midbrain contains neural circuits for the emission of species-specific orientation sounds and that a part of the vocalization system is located in the regions juxtaposed to the inferior colliculus, an important neural center for echolocation.