Echolocation calls and communication calls are controlled differentially in the brainstem of the bat Phyllostomus discolor

Both structures were probed simultaneously in a single experimental approach. Two stimulation electrodes were chronically implanted within the PAG in order to elicit either echolocation or communication calls. Blockade of the ipsilateral PLA site with iontophoretically application of the glutamate antagonist kynurenic acid did not impede either echolocation or communication calls elicited from the PAG. However, blockade of the contralateral PLA suppresses PAG-elicited echolocation calls but not communication calls. In both cases the blockade was reversible.The neural control of echolocation and communication calls seems to be differentially organized below the level of the PAG. The PLA is an essential functional unit for echolocation call control before the descending pathways share again the final common pathway for vocalization.Bats use echolocation calls for orientation in space and hunting for prey. Communication calls serve the purpose of inter- and intraspecific social communication. Neural control of both types of calls has access at the level of the medulla to the final common pathway for vocalization. Motoneurons controlling the larynx, the vocal tract and the respiratory muscles are accessed via interneurons from the nucleus ambiguus/retroambiguus complex [1]. One major subcortical structure for the control of vocalizations above the level of the medulla is the periaqueductal gray matter (PAG). Here, communication calls can be elicited by electrical or pharmacological stimulation in many mammalian species like squirrel monkey [2], rhesus monkey [3], rat [4], guinea pig [5], gibbon [6] and bat [7,8]. While in most areas where vocalizations can be elicited, long persisting stimulation causes a fading of the vocal reaction, the PAG is one of the very few regions where natural communication calls can be elicited without changes in the emotional state of the animal and without habituation to the stimulus, even over extended stimulation periods [9]. PAG stimulat