## Demonstrations

This is the README for the model associated with the paper: Zhou Y, Colburn HS (2010) A modeling study of the effects of membrane afterhyperpolarization on spike interval statistics and on ILD encoding in the lateral superior olive. J Neurophysiol 103:2355-71 This model was contributed by Yi Zhou.## A: Introduction

This simulation study investigated how membrane afterhyperpolarization (AHP) influences spiking activity of neurons in the Lateral Superior Olive (LSO). The model incorporates a general integrate-and-fire spiking mechanism with a first-order adaptation channel. Simulations focus on differentiating the effects of GAHP, tau_AHP, and input strength on (1) spike interval statistics, such as negative serial correlation and chopper onset, and (2) neural sensitivity to interaural level difference (ILD) of LSO neurons. The model simulated electrophysiological data collected in cat LSO (Tsuchitani and Johnson, 1985). The complete set of simulation results were reported in Zhou and Colburn (2010).## B: Download

This model was written in the NEURON simulation environment. After installing NEURON, download and unzip the model package LSO_ZhouColburn.zip to a local directory (e.g., C:/Neuron/LSO). Use nrnivmodl to compile mod files, and then execute the main NEURON programs (LSO_current_input.hoc or LSO_synaptic_input.hoc). The LSO model neuron receives synaptic inputs whose firing rate functions are stored in the input directory, e.g., "C:/Neuron/LSO/input". The simulation results are saved in the output directory, e.g., "C:/Neuron/LSO/output". Two Matlab scripts in the model package, func_current_stim.m and func_syn_stim.m, provide example commands for data importing and plotting.System Requirements:NEURON program. Please refer to the general NEURON documentation (http://www.neuron.yale.edu/neuron/docs) for furtherinstructions on compiling mod files and launching hoc files on different operating systems. Matlab software (http://www.mathworks.com).## C: Model Descriptions

Cell Model:An LSO cell was simulated using a modified leaky integrate-and-fire (LIF) model containing a capacitance Cm, a leak conductance GL, and two time-varying conductance-based channels, Gabs and gAHP(t), which produced the absolute and relative refractory periods, respectively, for a model cell. After the absolute refractory period (t_abs), the conductance of the adaptation channel gAHP(t) was increased by GAHP and decayed exponentially toward zero with a time constant tau_AHP. Responses of four model cells were tested in modeling, which have small or large GAHP and short or long tau_AHP. (See Table I in Zhou and Colburn, 2010.)Input Model:Stimulation was provided through either current injection (which simulated the ipsilateral-alone stimulation) or through synaptic-conductance channels (which simulated the combined effects of ipsilateral and contralateral acoustic stimulation).

- The current stimulation was implemented in LSO_current_input.hoc. The model cell received a random discrete current at a sampling rate of 4000 Hz. The amplitude of the current within each sample period (0.25 ms) was a Gaussian random variable with a mean of I and an SD of sigma_I; and both I and sigma_I were time-invariant.
- The synaptic stimuation was implemented in LSO_synaptic_input.hoc. Mathematically generated spike trains simulated the ipsilateral excitatory and contralateral inhibitory input spike trains (50 per side) to a LSO neuron. The input spike times were loaded during NEURON simulation. The excitatory and inhibitory synaptic time constant was 1ms.