BINAURAL AND COMMISSURAL ORGANIZATION OF THE PRIMARY AUDITORY-CORTEX OF THE MOUSTACHED BAT

In the mustached bat, the primary auditory cortex (AI) can be divided into three subdivisions: the Doppler-shifted constant-frequency proces sing (DSCF) area, and the anterior (AIa) and posterior (AIp) regions. The DSCF area is composed of two subdivisions: excitatory-excitatory ( E-E) and inhibitory-excitatory (I-E). The E-E division is located in t he ventral portion of the DSCF area and mainly consists of neurons exc ited bilaterally, while the I-E division is located in the dorsal port ion and mainly consists of neurons which are inhibited by ipsilateral ear stimuli, but excited by contralateral ear stimuli. The E-E divisio n is bilaterally connected by commissural fibers, while the I-E divisi on is not. The AIa and AIp regions have neither E-E neurons nor commis sural connections. In the AI of the cat, E-E and I-E neurons form alte rnating bands which are parallel to the frequency axis. E-E bands are bilaterally connected by commissural fibers, but I-E bands are not. Th e DSCF area shares a similar functional organization with the AI of th e cat.