title: Stimulus repetition modulates gamma-band synchronization in primate visual cortex.
abstract: When a sensory stimulus repeats, neuronal firing rate and functional MRI blood oxygen level-dependent responses typically decline, yet perception and behavioral performance either stay constant or improve. An additional aspect of neuronal activity is neuronal synchronization, which can enhance the impact of neurons onto their postsynaptic targets independent of neuronal firing rates. We show that stimulus repetition leads to profound changes of neuronal gamma-band (∼40-90 Hz) synchronization. Electrocorticographic recordings in two awake macaque monkeys demonstrated that repeated presentations of a visual grating stimulus resulted in a steady increase of visually induced gamma-band activity in area V1, gamma-band synchronization between areas V1 and V4, and gamma-band activity in area V4. Microelectrode recordings in area V4 of two additional monkeys under the same stimulation conditions allowed a direct comparison of firing rates and gamma-band synchronization strengths for multiunit activity (MUA), as well as for isolated single units, sorted into putative pyramidal cells and putative interneurons. MUA and putative interneurons showed repetition-related decreases in firing rate, yet increases in gamma-band synchronization. Putative pyramidal cells showed no repetition-related firing rate change, but a decrease in gamma-band synchronization for weakly stimulus-driven units and constant gamma-band synchronization for strongly driven units. We propose that the repetition-related changes in gamma-band synchronization maintain the interareal stimulus signaling and sharpen the stimulus representation by gamma-synchronized pyramidal cell spikes.
authors.affiliation: Donders Institute for Brain, Cognition, and Behaviour, Radboud University Nijmegen, 6525 EN Nijmegen, The Netherlands.
authors.forename: Nicolas M
authors.initials: NM
authors.lastname: Brunet
authors.forename: Conrado A
authors.initials: CA
authors.lastname: Bosman
authors.forename: Martin
authors.initials: M
authors.lastname: Vinck
authors.forename: Mark
authors.initials: M
authors.lastname: Roberts
authors.forename: Robert
authors.initials: R
authors.lastname: Oostenveld
authors.forename: Robert
authors.initials: R
authors.lastname: Desimone
authors.forename: Peter
authors.initials: P
authors.lastname: De Weerd
authors.forename: Pascal
authors.initials: P
authors.lastname: Fries
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D058256:Brain Waves / Q000502:physiology*; D004569:Electroencephalography; D008253:Macaca mulatta; D008297:Male; D010775:Photic Stimulation; D025341:Principal Component Analysis; D014793:Visual Cortex / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*
keywords: adaptation; learning; oscillation; plasticity; priming