title: Gamma oscillatory activity in a visual discrimination task.
abstract: We tested the hypothesis whether images of real objects elicit stronger gamma (>25 Hz) synchronization, when compared with scrambled objects. The background of this study is a recent debate about the functional meaning of evoked and induced gamma oscillations. Brain electrical source analysis (BESA) and low resolution electromagnetic tomography analysis (LORETA) was performed on the basis of the event-related potential (ERP) data. A component at around 230 ms (termed C230) showed strongest differences between objects and scrambled objects. Time-frequency analyses were run across electrodes and within the dipole sources. We found increased gamma event-related synchronization (ERS) between 200 and 300 ms for real objects. This effect was strongest in a fronto-medial source. Induced gamma, as also shown in previous studies, reflects the more task-relevant mechanism where object representations become activated.
authors.affiliation: Department of Psychology, University of Salzburg, Austria. roman.freunberger@sbg.ac.at
authors.forename: Roman
authors.initials: R
authors.lastname: Freunberger
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Klimesch
authors.forename: Paul
authors.initials: P
authors.lastname: Sauseng
authors.forename: Birgit
authors.initials: B
authors.lastname: Griesmayr
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Höller
authors.forename: Thomas
authors.initials: T
authors.lastname: Pecherstorfer
authors.forename: Simon
authors.initials: S
authors.lastname: Hanslmayr
mesh_terms: D000328:Adult; D001683:Biological Clocks / Q000502:physiology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D003344:Cortical Synchronization; D004193:Discrimination Learning / Q000502:physiology*; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D009474:Neurons / Q000502:physiology; D009483:Neuropsychological Tests; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology