title: Cortico-cortical evoked potentials and stimulation-elicited gamma activity preferentially propagate from lower- to higher-order visual areas.
abstract: OBJECTIVE
  The lower-order visual cortex in the medial-occipital region is suggested to send feed-forward signals to the higher-order visual cortex including ventral-occipital-temporal and dorsal-occipital regions. We determined how stimulation-elicited cortical-signals propagate between lower- and higher-order visual cortices, and whether the magnitudes of stimulation-elicited cortical-signals recorded in the higher-order visual cortex differed from those recorded in the lower-order one.
  
  
  METHODS
  We studied 10 patients with focal epilepsy who underwent extraoperative electrocorticography recording. Trains of 1-Hz stimuli with an intensity of 3 mA were delivered to an electrode pair within the medial-occipital region; then, cortico-cortical evoked-potential (CCEP) and stimulation-elicited gamma-activity at 80-150 Hz were measured in the ventral-occipital-temporal and dorsal-occipital regions. Likewise, CCEP and stimulation-elicited gamma-activity, driven by stimuli within the higher-order visual cortex, were measured in the lower-order visual cortex.
  
  
  RESULTS
  CCEPs generated, via feed-forward propagations, in the higher-order visual cortex were significantly larger than those generated, via feed-back propagations, in the lower-order visual cortex. Stimulation of the lower-order visual cortex elicited augmentation of gamma-activity in the higher-order visual cortex after the preceding CCEP subsided.
  
  
  CONCLUSIONS
  The propagation manners of stimulation-elicited cortical-signals differ between feed-forward and feed-back directions in the human occipital lobe.
  
  
  CONCLUSIONS
  : Such difference may need to be taken into consideration for future clinical application of CCEPs and stimulation-elicited gamma-augmentation in presurgical evaluation for epilepsy surgery.
authors.affiliation: Department of Pediatrics, Children's Hospital of Michigan, Wayne State University, Detroit Medical Center, Detroit, MI 48201, USA.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Matsuzaki
authors.forename: Csaba
authors.initials: C
authors.lastname: Juhász
authors.forename: Eishi
authors.initials: E
authors.lastname: Asano
mesh_terms: D000293:Adolescent; D001703:Biophysics; D001931:Brain Mapping; D002648:Child; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004827:Epilepsy / Q000473:pathology*; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D009415:Nerve Net / Q000503:physiopathology*; D009434:Neural Pathways / Q000503:physiopathology*; D011930:Reaction Time; D014793:Visual Cortex / Q000503:physiopathology*