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An in vivo intracellular study of auditory thalamic neurons

Published online by Cambridge University Press:  18 April 2006

Ying Xiong ,
Yan-Qin Yu ,
Kenji Fujimoto ,
Ying-Shing Chan  and
Jufang He
Ying Xiong
Affiliation:
Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, PR China Present address: Department of Physiology, The Third Medical University, Chongqing, China
Yan-Qin Yu
Affiliation:
Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, PR China Zhejiang University, School of Medicine, Hangzhou, China
Kenji Fujimoto
Affiliation:
Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, PR China Present address: Department of Electrical and Electronic Engineering, The University of Tokushima, Tokushima, Japan
Ying-Shing Chan
Affiliation:
Department of Physiology, The University of Hong Kong, Sassoon Road, Hong Kong, PR China
Jufang He
Affiliation:
Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, PR China
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Abstract

The intrinsic electrophysiological properties of medial geniculate body (MGB) neurons and their responses to noise bursts/pure tones were examined in the pentobarbital anesthetized guinea pig through intracellular recording. Discharge rate was calculated in the absence of acoustic stimuli over varied membrane potentials which were changed by intracellular injection of current or through automatic drifting. The non-acoustically-driven firing rate was 45.8 ± 23.3 Hz (mean ± S.D., n = 8) at membrane potentials of −45 mV, 30.6 ± 19.4 Hz (n = 14) at −50 mV, 18.0 ± 12.9 Hz (n = 14) at −55 mV, and significantly decreased to 5.7 ± 7.4 Hz at −60 mV, and to 0.7 ± 1.5 Hz (n = 10) at −65 mV (ANOVA, P < 0.001). The maximum non-acoustically-driven rate observed in the present study was 160 Hz. The auditory responsiveness of the MGB neurons was examined at membrane potentials over a range of −45 to −75 mV: the higher the membrane potential, the greater the responsiveness and vice versa. A putative non-low-threshold calcium spike (non-LTS) burst was observed in the present study. It showed significantly longer inter-spike intervals (11.6 ± 6.0 ms, P < 0.001, t-test) than those associated with the putative LTS bursts (6.7 ± 2.4 ms, P < 0.001, t-test). The dependence of the temporal structure of the spikes/spike bursts on the stimulus may provide insight into the temporal coding of sound information in the auditory system.

Keywords

Medial geniculate bodyAction potentialResting membrane potentialCurrent injectionSpontaneous firingTuning curve
Type
Research Article
Information
Thalamus & Related Systems , Volume 2 , Issue 3 , August 2003 , pp. 253 - 260
Copyright
Elsevier Science Ltd

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