Cellular Basis for Contrast Gain Control over the Receptive Field Center of Mammalian Retinal Ganglion Cells

By D. L. Beaudoin, B. Borghuis, J. Demb. 2007

84 citations recorded by the source corpus.

Retinal ganglion cells fire spikes to an appropriate contrast presented over their receptive field center. These center responses undergo dynamic changes in sensitivity depending on the ongoing level of contrast, a process known as “contrast gain control.” Extracellular recordings suggested that gain control is driven by a single wide-field mechanism, extending across the center and beyond, that depends on inhibitory interneurons: amacrine cells. However, recordings in salamander suggested that the excitatory bipolar cells, which drive the center, may themselves show gain control independently of amacrine cell mechanisms. Here, we tested in mammalian ganglion cells whether amacrine cells are critical for gain control over the receptive field center. We made extracellular and whole-cell recordings of guinea pig Y-type cells in vitro and quantified the gain change between contrasts using a linear–nonlinear analysis. For spikes, tripling contrast reduced gain by ∼40%. With spikes blocked, ganglion cells showed similar levels of gain control in membrane currents and voltages and under conditions of low and high calcium buffering: tripling contrast reduced gain by ∼20–25%. Gain control persisted under voltage-clamp conditions that minimize inhibitory conductances and pharmacological conditions that block inhibitory neurotransmitter receptors. Gain control depended on adequate stimulation, not of ganglion cells but of presynaptic bipolar cells. Furthermore, horizontal cell measurements showed a lack of gain control in photoreceptor synaptic release. Thus, the mechanism for gain control over the ganglion cell receptive field center, as measured in the subthreshold response, originates in the presynaptic bipolar cells and does not require amacrine cell signaling.

Subfields: Cellular and Molecular Neuroscience, Cognitive Neuroscience, Molecular Biology

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Citations in the corpus

Normalization as a canonical neural computation (2011, background): “Light adaptation is thought to operate in photoreceptors and bipolar cells, whereas contrast normalization is thought to occur in bipolar cells and ganglion cell”
Functional mechanisms shaping lateral geniculate responses to artificial and natural stimuli. (2008, background): “Current research in retina is making steady progress in identifying the biophysical mechanisms underlying fast adaptation and is illuminating their variety (e.g., Beaudoin et al., 2007; Dunn et al., 2007).”
The challenges natural images pose for visual adaptation. (2009, unknown): “Adaptation in the synaptic inputs likely originates in the bipolar cells, and thus has limited spatial pooling (Rieke, 2001; Beaudoin et al., 2007).”