Effects of dopamine on response properties of ON-OFF RGCs in encoding stimulus durations

Lei Xiao,Pei-Ji Liang,Hai-Qing Gong,Pu-Ming Zhang

doi:10.3389/fncir.2014.00072

Abstract

Single retinal ganglion cell's (RGCs) response properties, such as spike count and response latency, are known to encode some features of visual stimuli. On the other hand, neuronal response can be modulated by dopamine (DA), an important endogenous neuromodulator in the retina. In the present study, we investigated the effects of DA on the spike count and the response latency of bullfrog ON-OFF RGCs during exposure to different stimulus durations. We found that neuronal spike count and response latency were both changed with stimulus durations, and exogenous DA (10 μM) obviously attenuated the stimulus-duration-dependent response latency change. Information analysis showed that the information about light ON duration was mainly carried by the OFF response and vice versa, and the stimulation information was carried by both spike count and response latency. However, during DA application, the information carried by the response latency was greatly decreased, which suggests that dopaminergic pathway is involved in modulating the role of response latency in encoding the information about stimulus durations.

Highlights

Neuronal response activities contain many aspects, including firing rate, response latency, correlated activity pattern among neurons, etc
Application of exogenous DA (10 μM) increased neuronal firing rate and shortened neuronal response latency, and it attenuated the stimulus-durationdependent response latency change, and significantly decreased the information carried by the response latency
These results suggest that dopaminergic pathway is involved in modulating the role of response latency in encoding the information about stimulus durations

Summary

Introduction

Neuronal response activities contain many aspects, including firing rate, response latency, correlated activity pattern among neurons, etc. Neuronal firing rate can vary when in exposure to different stimuli, and encodes stimulus information (Richmond et al, 1987; Risner et al, 2010). Some studies revealed that the timing of individual spikes, especially the timing of the first spike after stimulus onset (identified as response latency), played important roles in encoding the information about certain stimulus features, such as stimulus contrast, location, moving speed and direction, etc. (Witkovsky and Dearry, 1991; Maguire and Werblin, 1994; Bloomfield and Volgyi, 2009), which results in changes in the response characteristics of retinal ganglion cells (RGCs), such as firing rate, response latency, and receptive field size, etc. DA can modulate neuronal properties, including electrical coupling between retinal neurons and glutamate-gated ionic currents, etc. (Witkovsky and Dearry, 1991; Maguire and Werblin, 1994; Bloomfield and Volgyi, 2009), which results in changes in the response characteristics of retinal ganglion cells (RGCs), such as firing rate, response latency, and receptive field size, etc. (Bonaventure et al, 1980; Witkovsky, 2004; Li et al, 2012)

Methods

Results

Discussion

Conclusion