Interhemispheric asymmetry in EEG photic driving coherence in childhood autism

ObjectiveExamination of the EEG photic driving coherence during intermittent photic stimulation in autistic patients with relatively intact verbal and intellectual functions in order to enhance the likely latent interhemispheric asymmetry in neural connectivity.MethodsFourteen autistic boys, aged 6–14 years, free of drug treatment, with I.Q. 91.4 ± 22.8, and 19 normally developing boys were subject to stimulation of 12 fixed frequencies of 3–27 Hz. The number of high coherent connections (HCC) (coherence >0.6–0.8) was estimated among 7 leads in each hemisphere.ResultsIn contrast to the spectral characteristics showing the right hemisphere deficit in the photic driving reactivity, the number of HCC differentiated the groups only in the left hemisphere where it was higher in autistics at the EEG frequencies corresponding to those of stimulation at 6–27 Hz without asymmetry at other frequencies, the left-side prevalence increasing with frequency. No asymmetry was observed in the resting state.ConclusionsSpectral and coherence characteristics of the EEG photic driving show different aspects of latent abnormal interhemispheric asymmetry in autistics: the right hemisphere “hyporeactivity” and potential “hyperconectivity” of likely compensatory nature in the left hemisphere.SignificanceThe EEG photic driving can reveal functional topographic alterations not present in the spontaneous EEG.