MONAURAL INTERACTION OF EXCITATION AND INHIBITION IN THE MEDIAL SUPERIOR OLIVE OF THE MOUSTACHED BAT - AN ADAPTATION FOR BIOSONAR

被引:49
作者
GROTHE, B
VATER, M
CASSEDAY, JH
COVEY, E
机构
[1] UNIV MUNICH,INST ZOOL,W-8000 MUNICH 2,GERMANY
[2] DUKE UNIV,MED CTR,DEPT NEUROBIOL,DURHAM,NC 27710
关键词
AUDITION; BRAIN-STEM; NEUROPHARMACOLOGY; ELECTROPHYSIOLOGY; NEUROANATOMY;
D O I
10.1073/pnas.89.11.5108
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
In most mammals, the superior olive is the first stage for binaural interaction. Neurons in the medial superior olive (MSO) receive excitatory input from both ears and are sensitive to interaural time or phase differences of low-frequency sounds. The mustached bat (Pteronotus parnellii parnellii), a small echolocating species with high-frequency hearing, probably does not use interaural time or phase differences as cues for sound localization. Although the mustached bat has a large MSO, there is some evidence that it is functionally different from the MSO in nonecholocating mammals. Most MSO neurons in the mustached bat are monaural, excited by a contralateral sound. Their responses are phasic and correlated with either the onset or the offset of a sound. As a first step in determining the origin of these phasic monaural responses, we traced the connections of the MSO by using both retrograde and anterograde transport methods. Excitatory inputs to the MSO originate from spherical cells in the anteroventral cochlear nucleus, almost exclusively from the contralateral side. Glycinergic inhibitory input is relayed from the contralateral cochlear nucleus through the medial nucleus of the trapezoid body. To investigate the interactions of the contralateral excitatory and inhibitory inputs at the level of the MSO cell, we recorded sound-evoked responses and applied glycine or its antagonist by using microiontophoresis. The results show that the phasic response to a contralateral sound is created by interaction of a sustained excitatory input with a sustained inhibitory input, also from the contralateral ear. Whether the response is to the onset or offset of a sound is determined by the relative timing between the excitatory and inhibitory inputs. Thus, in MSO of the mustached bat, the ipsilateral excitatory pathway from the cochlear nucleus seen in animals with low-frequency hearing is virtually absent, and the MSO is adapted for timing analysis by using input from only the contralateral ear.
引用
收藏
页码:5108 / 5112
页数:5
相关论文
共 30 条