Emotional-call-Induced frequency-following responses in the rat's amygdala and inferior colliculus are unmasked by binaural integration

【摘要】：正In humans,perceived spatial separation of target sound from masker improves the target-sound recognition, and emotional attention mediated by the amygdala also improves target recognition against irrelevant stimuli.In rats,the lateral nucleus of the amygdala(LA) receives inputs from auditory structures and mediates the fear-conditioning-induced enhancement of responses to sounds in the auditory thalamus and cortex.This study investigated whether binaural integration in anesthetized rats enhances emotional-call-induced frequency-following responses(FFRs) recorded in the LA as well as in the inferior colliculus(IC).FFRs are sustained potentials that preserve low-frequency information of stimulus waveforms.Either a section of a rat's emotional call(with three harmonic frequency components of 2100,4200, and 6300 Hz) in response to tail grasping or a three-tone harmonic(with the frequency components of 700.2100,and 3500 Hz ) was used as the signal presented binaurally when a noise masker was also presented binaurally.For the signal,the interaural delay(IAD) was -1(right ear leading) or +1 ms;for the masker,the IAD was -1,0,or +1 ms.The results show that distinct FFRs to either the emotional call or the tone complex were evident in both the LA and IC.However,only FFRs to the emotional call were significantly affected by the IAD difference between the signal and masker.FFRs recorded in the LA were significantly stronger when the IAD between the signal and masker differed,as compared with the same IAD. Moreover the IAD-difference-induced enhancement of FFRs in the IC was weaker than that in the LA.Thus,the rat's LA is capable of processing fine-structure acoustic details based on phase-locked neural activity,and the hard-wired circuit for processing species-specific emotional call is involved in spatial unmasking of signal sounds critical for survival.