CIRCADIAN-RHYTHM PERIOD IN REACTION-TIME TO LIGHT SIGNALS - DIFFERENCE BETWEEN RIGHT-HAND AND LEFT-HAND SIDE

The study was designed to test the hypothesis that the prominent rhyth m period tau of simple reaction time (SRT) and three-choice reaction t ime (CRT) to light signals may vary between the dominant (DH) and non- dominant (NDH) hand. Eleven healthy subjects, 8 males (16-74 years, in cluding two left-handed) and 3 females (18-43 years), synchronized wit h a diurnal activity (congruent to 07.00 h to congruent to 23.00 h) an d a nocturnal rest, volunteered for the study, A battery-powered ambul atory device was used to self-record SRT to a yellow Light signal and CRT to yellow, green and red signals. Tests were performed 4-7 times/2 4 h during a 12- to 15-day span. Power spectra, ANOVA, cosinor, chi(2) and correlation tests were used to individually analyze time series. tau = 24 h in SRT rhythms of DH (8/11 cases) and NDH (6/11 cases) with chi(2) = 3.5 and p > 0.05. In CRT rhythms, tau = 24 h for DH (8/11 ca ses) while tau = 8 h for NDH (7/11 cases), a difference which was stat istically significant (chi(2) = 9.4 with p < 0.02). Concordant results were obtained with other statistical tests leading to the conclusion that the rather complex cognitive task (CRT) and, to a certain extent, SRT of certain individuals, were associated with tau = 24 h for DH an d tau = 8 h for NDH. These findings are in favor of the hypothesis tha t functional clocks are present in the human brain cortex, associated with the possible expression of rhythms with a prominent period differ ing from the right- and left-hand side. (C) 1997 Elsevier Science B.V.