The personalized auditory cortex of the mustached bat: adaptation for echolocation
Journal of Neurophysiology
AND CONCLUSIONS 1. In the mustached bat, Pteronotus parnellii, the "resting" frequency of the constant-frequency component of the second harmonic (CFz) of the orientation sound (biosonar signal) is different among individuals within a range from 59.69 to 63.33 kHz. The standard deviation of CF2 resting frequency is 0.091 kHz on the average for individual bats. The male's CF2 resting frequency (61.250 + 0.534 kHz, n : 58) is 1.040 kHz lowerthan the female's 62.290 + 0.539 kHz, n : 58) on the
... n : 58) on the average. Females' resting frequencies measured in December are not different from those measured in April when almost all of them are pregnant. Therefore, the orientation sound is sexually dimorphic. 2. In the DSCF (Doppler-shifted CF processing) area of the auditory cortex, tonotopic representation differs among individual bats. The higher the CF2 resting frequency of the bat's own sound, the higher the frequencies represented in the DSCF area of that bat. There is a unique match between the tonotopic representation and the CFz resting frequency. This match indicates that the auditory cortex is "personalized" for echolocation and that the CFz resting frequency is like a signature ofthe orientation sound. 3. If a bat's resting frequency is normalized to 6 I .00 kHz, the DSCF area overrepresents 60.6-62.3 kHz. The central region of this overrepresented band is 6l.l-61.2 kHz. This focal band matches the "reference" frequency to which the CF2 frequency of a Doppler-shifted echo is stabilized by Doppler-shift compensation. 4. Since DSCF neurons are extraordinar-ily sharply tuned in frequency, the personalization ofthe auditory cortex or system is not only suited for the detection of wing beats of insects, but also for the reduction of the masking effect on echolocation of conspecific's biosonar signals. 5. Because the orientation sound is sexually dimorphic and the auditory cortex is personalized, the tonotopic representation of the auditory cortex is also sexually dimorphic.