DYNAMIC CHANGE OF ERPS RELATED TO SELECTIVE ATTENTION TO SIGNALS FROMLEFT AND RIGHT VISUAL-FIELD DURING HEAD-DOWN TILT

To study further the effect of head-down tilt(HDT) on slow positive po tential in the event-related potentials(ERPs), the temporal and spatia l features of visual ERPs changes during 2 hour HDT(-10 degrees) were compared with that during HUT(+20 degrees) in 15 normal subjects.-The stimuli were consisted of two color LED flashes appeared randomly in l eft or right visual field(LVF or RVF) with same probability. The subje cts were asked to make switch response to target signals(T) differenti ally: switching to left for T in LVF and to right for T in RVF, ignori ng non-target signals(N). Five sets of tests were made during HUT and HDT ERPs were obtained from 9 locations on scalp. The mean value of th e ERPs in the period from 032 similar to 0.55 a was taken as the ampli tude of slow positive potential(P400). The main results were as follow s. 1)The mean amplitude of P400 decreased during HDT which was more si gnificant at the 2nd, 3rd and 5th set of tests; 2)spatially, the reduc tion of mean P400 amplitude during HDT was more significant for signal s from RVF and was more significant at posterior and; central brain re gions than that on frontal locations. As that the positive potential p robably reflects the active inhibition activity in-the brain during at tention process, these data provide further evidence showing that the higher brain function was affected by the simulated weightlessness and ;that this effect was not only transient but also with interesting spa tial characteristics. (C) 1998 Elsevier Science Ltd. All rights reserv ed.