"Silent" NMDA Synapses Enhance Motion Sensitivity in a Mature Retinal Circuit.
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Retinal direction-selective ganglion cells (DSGCs) have the remarkable ability to encode motion over a wide range of contrasts, relying on well-coordinated excitation and inhibition (E/I). E/I is orchestrated by a diverse set of glutamatergic bipolar cells that drive DSGCs directly, as well as indirectly through feedforward GABAergic/cholinergic signals mediated by starburst amacrine cells. Determining how direction-selective responses are generated across varied stimulus conditions requires understanding how glutamate, acetylcholine, and GABA signals are precisely coordinated. Here, we use a combination of paired patch-clamp recordings, serial EM, and large-scale multi-electrode array recordings to show that a single high-sensitivity source of glutamate is processed differentially by starbursts via AMPA receptors and DSGCs via NMDA receptors. We further demonstrate how this novel synaptic arrangement enables DSGCs to encode direction robustly near threshold contrasts. Together, these results reveal a space-efficient synaptic circuit model for direction computations, in which "silent" NMDA receptors play critical roles.
SubjectRetinal Ganglion Cells
Retinal Bipolar Cells
Published Version (Please cite this version)10.1016/j.neuron.2017.09.058
Publication InfoSethuramanujam, Santhosh; Yao, Xiaoyang; deRosenroll, Geoff; Briggman, Kevin L; Field, Greg D; & Awatramani, Gautam B (2017). "Silent" NMDA Synapses Enhance Motion Sensitivity in a Mature Retinal Circuit. Neuron, 96(5). pp. 1099-1111.e3. 10.1016/j.neuron.2017.09.058. Retrieved from https://hdl.handle.net/10161/17869.
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Assistant Professor of Neurobiology
My laboratory studies how the retina processes visual scenes and transmits this information to the brain. We use multi-electrode arrays to record the activity of hundreds of retina neurons simultaneously in conjunction with transgenic mouse lines and chemogenetics to manipulate neural circuit function. We are interested in three major areas. First, we work to understand how neurons in the retina are functionally connected. Second we are studying how light-adaptation and circadian rhythms a