title: Loss of visually driven synaptic responses in layer 4 regular-spiking neurons of rat visual cortex in absence of competing inputs.
abstract: Monocular deprivation (MD) during development shifts the ocular preference of primary visual cortex (V1) neurons by depressing closed-eye responses and potentiating open-eye responses. As these 2 processes are temporally and mechanistically distinct, we tested whether loss of responsiveness occurs also in absence of competing inputs. We thus compared the effects of long-term MD in layer 4 regular-spiking pyramidal neurons (L4Ns) of binocular and monocular V1 (bV1 and mV1) with whole-cell recordings. In bV1, input depression was larger than potentiation, and the ocular dominance shift was larger for spike outputs. MD-but not retinal inactivation with tetrodotoxin-caused a comparable loss of synaptic and spike responsiveness in mV1, which is innervated only by the deprived eye. Conversely, brief MD depressed synaptic responses only in bV1. MD-driven depression in mV1 was accompanied by a proportional reduction of visual thalamic inputs, as assessed upon pharmacological silencing of intracortical transmission. Finally, sub- and suprathreshold responsiveness was similarly degraded in L4Ns of bV1 upon complete deprivation of patterned vision through a binocular deprivation period of comparable length. Thus, loss of synaptic inputs from the deprived eye occurs also in absence of competition in the main thalamorecipient lamina, albeit at a slower pace.
authors: Neuroscience and Brain Technologies Department, Italian Institute of Technology, Genova, Italy.
authors: Giuliano
authors: G
authors: Iurilli
authors: Fabio
authors: F
authors: Benfenati
authors: Paolo
authors: P
authors: Medini
mesh_terms: D000818:Animals; D005074:Evoked Potentials, Visual / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010775:Photic Stimulation; D051381:Rats; D020318:Rats, Long-Evans; D009435:Synaptic Transmission / Q000502:physiology*; D015349:Vision, Monocular / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology*