title: Mental tasks induce gamma EEG with reduced responsiveness in primary generalized epilepsies.
abstract: OBJECTIVE
  We previously revealed an interictal increase in intensity of EEG rhythms during quiescent mental activity in the 30- to 100-Hz frequency (gamma) range in primary generalized epilepsy (PGE). We have evidence that there is induction of gamma EEG in normal subjects in response to controlled mental activity. Here we test whether mental tasks further augment interictal gamma oscillations in people with PGE.
  
  
  METHODS
  We recorded interictal EEG from patients with PGE and partial epilepsy and compared EEG power spectral responses (increases over resting) during mental tasks.
  
  
  RESULTS
  In partial epilepsy, mental tasks (except for alternating checkerboard visual stimulation) induced 1.5- to 2.5-fold increases in power of gamma EEG. In generalized epilepsy, generalized increases of 1.5-fold in gamma EEG were induced by only two mental tasks (reading and subtraction), and enhancement of 1- to 1.5-fold in the remaining six (checkerboard, expectancy, music, learning, recalling, and a video).
  
  
  CONCLUSIONS
  Gamma EEG is less responsive to mental activation in PGE than in partial epilepsy, confirming an abnormality in gamma mechanisms in PGE. Our findings also provide a possible mechanistic link between mental activity and seizures in reading- and arithmetic-induced seizures.
authors.affiliation: Centre for Neuroscience and Department of Medicine (Neurology), School of Psychology School of Informatics & Engineering, Flinders University, Adelaide, South Australia, Australia. John.Willoughby@flinders.edu.au
authors.forename: John O
authors.initials: JO
authors.lastname: Willoughby
authors.forename: Sean P
authors.initials: SP
authors.lastname: Fitzgibbon
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Pope
authors.forename: Lorraine
authors.initials: L
authors.lastname: Mackenzie
authors.forename: Matthew
authors.initials: M
authors.lastname: Davey
authors.forename: Robert A
authors.initials: RA
authors.lastname: Wilcox
authors.forename: C Richard
authors.initials: CR
authors.lastname: Clark
mesh_terms: D000328:Adult; D001143:Arousal / Q000502:physiology*; D001288:Attention / Q000502:physiology*; D002540:Cerebral Cortex / Q000502:physiology; D004569:Electroencephalography; D004829:Epilepsy, Generalized / Q000503:physiopathology*; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D008297:Male; D008606:Mental Processes / Q000502:physiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D011340:Problem Solving / Q000502:physiology*; D011932:Reading; D012815:Signal Processing, Computer-Assisted