The dual facet of gamma oscillations: separate visual and decision making circuits as revealed by simultaneous EEG/fMRI.
It remains an outstanding question whether gamma-band oscillations reflect unitary cognitive processes within the same task. EEG/MEG studies do lack the resolution or coverage to address the highly debated question whether single gamma activity patterns are linked with multiple cognitive modules or alternatively each pattern associates with a specific cognitive module, within the same coherent perceptual task. One way to disentangle these issues would be to provide direct identification of their sources, by combining different techniques. Here, we directly examined these questions by performing simultaneous EEG/fMRI using an ambiguous perception paradigm requiring holistic integration. We found that distinct gamma frequency sub-bands reflect different neural substrates and cognitive mechanisms when comparing object perception states vs. no categorical perception. A low gamma sub-band (near 40 Hz) activity was tightly related to the decision making network, and in particular the anterior insula. A high gamma sub-band (∼60 Hz) could be linked to early visual processing regions. The demonstration of a clear functional topography for distinct gamma sub-bands within the same task shows that distinct gamma-band modulations underlie sensory processing and perceptual decision mechanisms.
Visual Neuroscience Laboratory, IBILI-Institute for Biomedical Imaging and Life Sciences, Faculty of Medicine, University of Coimbra, Coimbra, Portugal; ICNAS-Institute for Nuclear Sciences Applied to Health, University of Coimbra, Coimbra, Portugal.
João
J
Castelhano
Isabel Catarina
IC
Duarte
Michael
M
Wibral
Eugénio
E
Rodriguez
Miguel
M
Castelo-Branco
D000328:Adult; D000704:Analysis of Variance; D001921:Brain / Q000098:blood supply* / Q000502:physiology*; D001931:Brain Mapping; D003657:Decision Making / Q000502:physiology*; D004569:Electroencephalography; D005145:Face; D005260:Female; D065818:Gamma Rhythm / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D013997:Time Factors; D055815:Young Adult
D010100:Oxygen
cognitive modules; gamma-band oscillations; multimodal imaging; simultaneous EEG/fMRI; source localization; visual perception