[Problems in the clinical use of steady state response]

Frequent stimulation induces a state of permanent evoked activity, i.e. the Steady State Response (SSR). An attempt was undertaken to assess the effects of various parameters on the SSR-configuration. 23 boys with normal brains and normal intelligence were studied under constant conditions. Light flashes were delivered in trains of 1 s at a flash repetition rate of 8 c/s. 60 trains were averaged. Three intensities of stimulation (1,2; 0,6; 0,3 Joule) were used. SSR could be observed in 87% of all volunteers (using intensity 1,2 Joule). Independently of the intensities of the stimulation a well-shaped SSR was found after the 3rd or 4th stimulus of the train. Considering the number of deflections four different types of SSR were detectable. There was a slight coherence between the types of SSR and the dominant alpha-frequency. Continuous enhancement of amplitude with increasing stimulus intensity was found only in 50%. Furthermore changing of the SSR-type was found in 5 cases. Taking into account the variability of SSR in healthy probands using of this method for clinical applications on a larger scale remains to be seen.