title: Neural correlation is stimulus modulated by feedforward inhibitory circuitry.
abstract: Correlated variability of neural spiking activity has important consequences for signal processing. How incoming sensory signals shape correlations of population responses remains unclear. Cross-correlations between spiking of different neurons may be particularly consequential in sparsely firing neural populations such as those found in layer 2/3 of sensory cortex. In rat whisker barrel cortex, we found that pairs of excitatory layer 2/3 neurons exhibit similarly low levels of spike count correlation during both spontaneous and sensory-evoked states. The spontaneous activity of excitatory-inhibitory neuron pairs is positively correlated, while sensory stimuli actively decorrelate joint responses. Computational modeling shows how threshold nonlinearities and local inhibition form the basis of a general decorrelating mechanism. We show that inhibitory population activity maintains low correlations in excitatory populations, especially during periods of sensory-evoked coactivation. The role of feedforward inhibition has been previously described in the context of trial-averaged phenomena. Our findings reveal a novel role for inhibition to shape correlations of neural variability and thereby prevent excessive correlations in the face of feedforward sensory-evoked activation.
authors.affiliation: Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA. jmiddlet@pitt.edu
authors.forename: Jason W
authors.initials: JW
authors.lastname: Middleton
authors.forename: Cyrus
authors.initials: C
authors.lastname: Omar
authors.forename: Brent
authors.initials: B
authors.lastname: Doiron
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Simons
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D005260:Female; D053444:Inhibitory Postsynaptic Potentials / Q000502:physiology; D008959:Models, Neurological; D009433:Neural Inhibition / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013003:Somatosensory Cortex / Q000502:physiology*