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Simple Models Show the General Advantages of Dendrites in Coincidence Detection

¹Department of Biomedical Engineering, ²Hearing Research Center, and ³Center for BioDynamics, Boston University, Boston, Massachusetts

Submitted 27 June 2005; accepted in final form 26 July 2006

Dendrites can influence and improve information processing in single neurons. Here, simple models are used to elucidate mechanisms underlying the dendritic enhancement of coincidence detection. We focus on coincidence-detecting cells in the auditory system, which have bipolar dendrites and show acute sensitivity to interaural time difference (ITD), a critical cue for spatial hearing. A three-compartment model consisting of a single-compartment soma and two single-compartment dendrites is primarily used, although multiple-compartment dendrites are also tested. Two varieties of somata, with and without active ion channels, are studied. Using constant conductance inputs, we show analytically that the somatic response to balanced bilateral inputs is largest, whereas the response monotonically decreases as the input distribution becomes increasingly monolateral. This enhancement is a consequence of the sublinear saturating dendritic voltage response to conductance input and occurs when dendrites are composed of a single compartment or either a finite number or an infinite number (i.e., a cable) of compartments. Longer, thinner dendrites or greater numbers of compartments increase the enhancement of the somatic response to bilateral input. The time-independent dendritic enhancement, moreover, underlies improved coincidence detection of time-varying input. Coincidence sensitivity to a pair of conductance pulses and rate–ITD modulation to low-frequency (400-Hz) periodic inputs increases with dendritic length. These findings are related to the length gradient in the avian system, where low characteristic frequency (CF) cells have long dendrites and high CF cells have short dendrites. We conclude that dendrites fundamentally improve coincidence detection, increasing the computational power of many neurons in the nervous system.

This article has been cited by other articles:

				Z.-Q. Tang, H. Gao, and Y. Lu Control of a Depolarizing GABAergic Input in an Auditory Coincidence Detection Circuit J Neurophysiol, September 1, 2009; 102(3): 1672 - 1683. [Abstract] [Full Text] [PDF]