title: Multiple origins of the cortical γ rhythm.
abstract: Gamma rhythms (30-80 Hz) are a near-ubiquitous feature of neuronal population activity in mammalian cortices. Their dynamic properties permit the synchronization of neuronal responses to sensory input within spatially distributed networks, transient formation of local neuronal "cell assemblies," and coherent response patterns essential for intercortical regional communication. Each of these phenomena form part of a working hypothesis for cognitive function in cortex. All forms of physiological gamma rhythm are inhibition based, being characterized by rhythmic trains of inhibitory postsynaptic potentials in populations of principal neurons. It is these repeating periods of relative enhancement and attenuation of the responsivity of major cell groups in cortex that provides a temporal structure shared across many millions of neurons. However, when considering the origins of these repeating trains of inhibitory events considerable divergence is seen depending on cortical region studied and mode of activation of gamma rhythm generating networks. Here, we review the evidence for involvement of multiple subtypes of interneuron and focus on different modes of activation of these cells. We conclude that most massively parallel brain regions have different mechanisms of gamma rhythm generation, that different mechanisms have distinct functional correlates, and that switching between different local modes of gamma generation may be an effective way to direct cortical communication streams. Finally, we suggest that developmental disruption of the endophenotype for certain subsets of gamma-generating interneuron may underlie cognitive deficit in psychiatric illness.
authors.affiliation: Institute of Neuroscience, The Medical School, Newcastle University, Newcastle Upon Tyne NE2 4HH, United Kingdom. m.a.whittington@ncl.ac.uk
authors.forename: Miles A
authors.initials: MA
authors.lastname: Whittington
authors.forename: Mark O
authors.initials: MO
authors.lastname: Cunningham
authors.forename: Fiona E N
authors.initials: FE
authors.lastname: LeBeau
authors.forename: Claudia
authors.initials: C
authors.lastname: Racca
authors.forename: Roger D
authors.initials: RD
authors.lastname: Traub
mesh_terms: D000818:Animals; D001683:Biological Clocks / Q000502:physiology*; D058256:Brain Waves / Q000502:physiology*; D002540:Cerebral Cortex / Q000166:cytology / Q000502:physiology*; D003344:Cortical Synchronization / Q000502:physiology*; D006801:Humans; D007395:Interneurons / Q000166:cytology / Q000502:physiology*; D009415:Nerve Net / Q000166:cytology / Q000502:physiology*