Binaural and commissural organization of the primary auditory cortex of the mustached bat

Abstract

In the mustached bat, the primary auditory cortex (AI) can be divided into three subdivisions: the Doppler-shifted constant-frequency processing (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 the ventral portion of the DSCF area and mainly consists of neurons excited bilaterally, while the I-E division is located in the dorsal portion and mainly consists of neurons which are inhibited by ipsilateral ear stimuli, but excited by contralateral ear stimuli. The E-E division is bilaterally connected by commissural fibers, while the I-E division is not. The AIa and AIp regions have neither E-E neurons nor commissural connections. In the AI of the cat, E-E and I-E neurons form alternating bands which are parallel to the frequency axis. E-E bands are bilaterally connected by commissural fibers, but I-E bands are not. The DSCF area shares a similar functional organization with the AI of the cat.

Development of functional organization of the pallid bat auditory cortex

“…The best studied of these is binaural selectivity. A consistent finding is that cortical neurons with similar binaural properties occur in clusters (Imig and Adrian, 1977;Middlebrooks et al, 1980;Reale and Kettner, 1986;Nakamoto et al, 2004;Kelly and Sally, 1988;Kelly and Judge, 1994;Liu and Suga, 1997;Shen et al, 1997;Recanzone et al, 1999;Rutkowski et al, 2000;Velenovsky et al, 2003). In cats and ferrets, clusters of neurons with different binaural properties such as binaural inhibition (EI) and excitation (EE) are represented orthogonal to the isofrequency contours (Imig and Adrian, 1977;Kelly and Judge, 1994).…”

Bilateral Cortical Interaction: Modulation of Delay-Tuned Neurons in the Contralateral Auditory Cortex

“…IE neurons show inhibitory responses (I) to ipsilateral stimuli, excitatory responses to contralateral stimuli, and weak or no excitatory responses to binaural stimuli. EE clusters are callosally connected, but IE clusters are not in cats (Imig and Brugge, 1978) and in mustached bats (Liu and Suga, 1997).…”

GABAergic organization of the auditory cortex in the mustached bat (Pteronotus p. parnellii)

“…Layer III had the second largest species differential in the sample after layer II (Table 1), though its functional impact is obscure. Perhaps the commissural system, which in the cat is represented chiefly by layer III pyramidal cells (Code and Winer, 1985), receives a larger ipsilateral GABAergic projection than its bat counterpart (Liu and Suga, 1997). The numerical difference does not likely reflect a decrease in the number of large multipolar cells since these are plentiful in layer III and all the neuronal classes present in the cat (Fig.…”