The retinal periphery of nine healthy subjects was stimulated with computer-generated random-dot kinematograms. These stimuli provided almost isolated visual motion information and minimal position cues. Pattern-reversal stimuli at the same location in the visual field were used for control. Stimulus-related electrical brain activity was recorded from 29 scalp electrodes. Total mean and individual data were analyzed with a spatiotemporal multiple dipole model. The scalp potentials showed a different spatial distribution for motion and pattern stimulation in the time range of 160-200 ms. In this epoch, the predominant motion-related source activity was localized in the region of the contralateral occipital-temporal-parietal border. A significant ipsilateral source activity was not found. The predominant source activity related to the pattern stimulus occurred in the same epoch. The corresponding equivalent dipole was localized more medially and deeper in the brain. The orientation of these major dipole activities was markedly different. These dipoles appeared to represent activity of distinct extrastriate areas, in contrast to earlier activity which was modelled by more posterior dipoles in the occipital lobe. The latter dipoles were at comparable contralateral locations and had similar peak activities around 100 ms, suggesting an origin in the striate cortex.

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Transcranial magnetic stimulation (TMS) of the human brain is mainly used for the diagnosis of diseases with disturbed central motor conduction. Recent studies revealed controversial results concerning the possibility of a TMS-induced specific activation of epileptogenic foci in patients with localization-related epilepsies, which would make TMS an additional diagnostic tool for the presurgical localization of the primary epileptogenic zone. We applied TMS to 19 patients with complex-partial seizures and investigated its effects and safety. In 12 patients we performed TMS during scalp electroencephalogram (EEG) recordings. The remaining 7 patients with localization-related epilepsies of mesiobasal limbic seizure origin underwent EEG with additionally implanted foramen-ovale-electrodes (FOE). We did not notice any significant spike activation and even observed bilateral reduction of epileptic activity in some patients. On the contrary, hyperventilation induced a marked activation of the epileptic focus. Our findings support that TMS is safe since adverse effects did not occur. However, due to possible safety hazards, TMS in epileptic patients still requires cautious application until more data will be available.

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