Mental tasks induce gamma EEG with reduced responsiveness in primary generalized epilepsies.
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.
Willoughby
John O
JO
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
Fitzgibbon
Sean P
SP
Pope
Kenneth J
KJ
Mackenzie
Lorraine
L
Davey
Matthew
M
Wilcox
Robert A
RA
Clark
C Richard
CR
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