title: Gamma activity modulated by naming of ambiguous and unambiguous images: intracranial recording.
abstract: OBJECTIVE
  Humans sometimes need to recognize objects based on vague and ambiguous silhouettes. Recognition of such images may require an intuitive guess. We determined the spatial-temporal characteristics of intracranially-recorded gamma activity (at 50-120Hz) augmented differentially by naming of ambiguous and unambiguous images.
  
  
  METHODS
  We studied 10 patients who underwent epilepsy surgery. Ambiguous and unambiguous images were presented during extraoperative electrocorticography recording, and patients were instructed to overtly name the object as it is first perceived.
  
  
  RESULTS
  Both naming tasks were commonly associated with gamma-augmentation sequentially involving the occipital and occipital-temporal regions, bilaterally, within 200ms after the onset of image presentation. Naming of ambiguous images elicited gamma-augmentation specifically involving portions of the inferior-frontal, orbitofrontal, and inferior-parietal regions at 400ms and after. Unambiguous images were associated with more intense gamma-augmentation in portions of the occipital and occipital-temporal regions.
  
  
  CONCLUSIONS
  Frontal-parietal gamma-augmentation specific to ambiguous images may reflect the additional cortical processing involved in exerting intuitive guess. Occipital gamma-augmentation enhanced during naming of unambiguous images can be explained by visual processing of stimuli with richer detail.
  
  
  CONCLUSIONS
  Our results support the theoretical model that guessing processes in visual domain occur following the accumulation of sensory evidence resulting from the bottom-up processing in the occipital-temporal visual pathways.
authors.affiliation: Department of Pediatrics, Children's Hospital of Michigan, Wayne State University, Detroit, MI 48201, USA; Department of Neurology, Children's Hospital of Michigan, Wayne State University, Detroit, MI 48201, USA.
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Cho-Hisamoto
authors.affiliation: Department of Pediatrics, Children's Hospital of Michigan, Wayne State University, Detroit, MI 48201, USA.
authors.forename: Katsuaki
authors.initials: K
authors.lastname: Kojima
authors.affiliation: MD-PhD Program, Wayne State University, School of Medicine, Detroit, MI 48201, USA.
authors.forename: Erik C
authors.initials: EC
authors.lastname: Brown
authors.affiliation: Department of Pediatrics, Children's Hospital of Michigan, Wayne State University, Detroit, MI 48201, USA.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Matsuzaki
authors.affiliation: Department of Pediatrics, Children's Hospital of Michigan, Wayne State University, Detroit, MI 48201, USA; Department of Neurology, Children's Hospital of Michigan, Wayne State University, Detroit, MI 48201, USA. Electronic address: eishi@pet.wayne.edu.
authors.forename: Eishi
authors.initials: E
authors.lastname: Asano
mesh_terms: D000293:Adolescent; D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D002648:Child; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000295:instrumentation* / Q000379:methods; D004827:Epilepsy / Q000175:diagnosis / Q000601:surgery; D005260:Female; D065818:Gamma Rhythm / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009778:Occipital Lobe / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods*; D011930:Reaction Time / Q000502:physiology; D021641:Recognition, Psychology / Q000502:physiology; D013702:Temporal Lobe / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology
keywords: Blurred images; Electrocorticography (ECoG); Event-related potentials (ERPs); High-frequency oscillations (HFOs); Low spatial frequencies; Pediatric epilepsy surgery; Ripples; Top-down processing; Visual recognition