title: Efficient "pop-out" visual search elicits sustained broadband γ activity in the dorsal attention network.
abstract: An object that differs markedly from its surrounding-for example, a red cherry among green leaves-seems to pop out effortlessly in our visual experience. The rapid detection of salient targets, independently of the number of other items in the scene, is thought to be mediated by efficient search brain mechanisms. It is not clear, however, whether efficient search is actually an "effortless" bottom-up process or whether it also involves regions of the prefrontal cortex generally associated with top-down sustained attention. We addressed this question with intracranial EEG (iEEG) recordings designed to identify brain regions underlying a classic visual search task and correlate neural activity with target detection latencies on a trial-by-trial basis with high temporal precision recordings of these regions in epileptic patients. The spatio-temporal dynamics of single-trial spectral analysis of iEEG recordings revealed sustained energy increases in a broad gamma band (50-150 Hz) throughout the duration of the search process in the entire dorsal attention network both in efficient and inefficient search conditions. By contrast to extensive theoretical and experimental indications that efficient search relies exclusively on transient bottom-up processes in visual areas, we found that efficient search is mediated by sustained gamma activity in the dorsal lateral prefrontal cortex and the anterior cingulate cortex, alongside the superior parietal cortex and the frontal eye field. Our findings support the hypothesis that active visual search systematically involves the frontal-parietal attention network and therefore, executive attention resources, regardless of target saliency.
authors.affiliation: INSERM U1028-CNRS UMR5292, Brain Dynamics and Cognition Team, Lyon Neuroscience Research Center, F-69500 Lyon-Bron, France.
authors.forename: Tomas
authors.initials: T
authors.lastname: Ossandón
authors.forename: Juan R
authors.initials: JR
authors.lastname: Vidal
authors.forename: Carolina
authors.initials: C
authors.lastname: Ciumas
authors.forename: Karim
authors.initials: K
authors.lastname: Jerbi
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Hamamé
authors.forename: Sarang S
authors.initials: SS
authors.lastname: Dalal
authors.forename: Olivier
authors.initials: O
authors.lastname: Bertrand
authors.forename: Lorella
authors.initials: L
authors.lastname: Minotti
authors.forename: Philippe
authors.initials: P
authors.lastname: Kahane
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Lachaux
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology*; D058256:Brain Waves / Q000502:physiology*; D002540:Cerebral Cortex / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods*; D011930:Reaction Time / Q000502:physiology; D013997:Time Factors; D055815:Young Adult