title: Gain modulation of synaptic inputs by network state in auditory cortex in vivo.
abstract: The cortical network recurrent circuitry generates spontaneous activity organized into Up (active) and Down (quiescent) states during slow-wave sleep or anesthesia. These different states of cortical activation gain modulate synaptic transmission. However, the reported modulation that Up states impose on synaptic inputs is disparate in the literature, including both increases and decreases of responsiveness. Here, we tested the hypothesis that such disparate observations may depend on the intensity of the stimulation. By means of intracellular recordings, we studied synaptic transmission during Up and Down states in rat auditory cortex in vivo. Synaptic potentials were evoked either by auditory or electrical (thalamocortical, intracortical) stimulation while randomly varying the intensity of the stimulus. Synaptic potentials evoked by the same stimulus intensity were compared in Up/Down states. Up states had a scaling effect on the stimulus-evoked synaptic responses: the amplitude of weaker responses was potentiated whereas that of larger responses was maintained or decreased with respect to the amplitude during Down states. We used a computational model to explore the potential mechanisms explaining this nontrivial stimulus-response relationship. During Up/Down states, there is different excitability in the network and the neuronal conductance varies. We demonstrate that the competition between presynaptic recruitment and the changing conductance might be the central mechanism explaining the experimentally observed stimulus-response relationships. We conclude that the effect that cortical network activation has on synaptic transmission is not constant but contingent on the strength of the stimulation, with a larger modulation for stimuli involving both thalamic and cortical networks.
authors: Institut d'Investigacions Biomèdiques August Pi i Sunyer, 08036 Barcelona, Spain.
authors: Ramon
authors: http://orcid.org/0000-0002-6475-4181
authors: R
authors: Reig
authors: Unité de Neurosciences, Information et Complexité, CNRS, 91198 Gif sur Yvette, France, and.
authors: Yann
authors: http://orcid.org/0000-0003-0322-749X
authors: Y
authors: Zerlaut
authors: Institut d'Investigacions Biomèdiques August Pi i Sunyer, 08036 Barcelona, Spain.
authors: Ramiro
authors: http://orcid.org/0000-0001-6052-9318
authors: R
authors: Vergara
authors: Unité de Neurosciences, Information et Complexité, CNRS, 91198 Gif sur Yvette, France, and.
authors: Alain
authors: http://orcid.org/0000-0001-7405-0455
authors: A
authors: Destexhe
authors: Institut d'Investigacions Biomèdiques August Pi i Sunyer, 08036 Barcelona, Spain, Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain msanche3@clinic.ub.es.
authors: Maria V
authors: http://orcid.org/0000-0002-8437-9083
authors: MV
authors: Sanchez-Vives
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001303:Auditory Cortex / Q000502:physiology*; D004558:Electric Stimulation; D008297:Male; D008959:Models, Neurological; D009415:Nerve Net / Q000502:physiology*; D009431:Neural Conduction / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology; D013788:Thalamus / Q000502:physiology
keywords: Up states; cerebral cortex; computational model; oscillations; synaptic inputs; thalamocortical