Inter- and intrahemispheric phase changes of diffuse 3 Hz spike-and-wave complex.

The inter- and intrahemispheric phase characteristics were investigated on diffuse 3 Hz spike-and-wave complex (D3SW) in eight epileptic patients who were diagnosed with typical absence. The phase of D3SW was analyzed sequentially using cross-power spectral arrays dividing D3SW into two components (spike-and-wave complex, spike component). The phase of spike-and-wave complex preceded most at the midline structure, and delayed symmetrically toward the lateral side of each hemisphere in all cases, while not in all cases when spike component was investigated. In spite of this symmetry, there was sparse correlation in phase change between the homologous hemispheres. There was almost no linear correlation between the phase of spike-and-wave complex and the corresponding spike component. The author concludes that the 'centrencephalic system' hypothesis still plays an important role for the generation of D3SW, and suggest a mechanism other than the cortical recurrent inhibition for the generation of wave component.