Cellular mechanisms underlying stimulus-dependent gain modulation in primary visual cortex neurons in vivo.
Gain modulation is a widespread neuronal phenomenon that modifies response amplitude without changing selectivity. Computational and in vitro studies have proposed cellular mechanisms of gain modulation based on the postsynaptic effects of background synaptic activation, but these mechanisms have not been studied in vivo. Here, we used intracellular recordings from cat primary visual cortex to measure neuronal gain while changing background synaptic activity with visual stimulation. We found that increases in the membrane fluctuations associated with increases in synaptic input do not obligatorily result in gain modulation in vivo. However, visual stimuli that evoked sustained changes in resting membrane potential, input resistance, and membrane fluctuations robustly modulated neuronal gain. The magnitude of gain modulation depended critically on the spatiotemporal properties of the visual stimulus. Gain modulation in vivo may thus be determined on a moment-to-moment basis by sensory context and the consequent dynamics of synaptic activation.
Cardin
Jessica A
JA
Department of Neuroscience, University of Pennsylvania School of Medicine, 215 Stemmler Hall, Philadelphia, PA 19106, USA.
Palmer
Larry A
LA
Contreras
Diego
D
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002415:Cats; D003198:Computer Simulation; D015350:Contrast Sensitivity; D004307:Dose-Response Relationship, Radiation; D004558:Electric Stimulation / Q000379:methods; D008959:Models, Neurological; D009474:Neurons / Q000502:physiology*; D018408:Patch-Clamp Techniques / Q000379:methods; D010775:Photic Stimulation / Q000379:methods; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*; D014793:Visual Cortex / Q000166:cytology*