TEMPORAL INTEGRATION OF EVENTS WITHIN AND BETWEEN THE CEREBRAL HEMISPHERES

The effect of interhemispheric transmission time (IHTT) on temporal pe rception was investigated by comparing, simultaneity thresholds under unimanual and bimanual stimulation conditions. In the unimanual condit ions the tactile stimuli were delivered to the same hand and were rece ived by the same hemisphere, but in bimanual conditions, where stimuli were delivered to different hands, interhemispheric communication was necessary in order to compare the timing of the two stimuli. Randomis ed order of stimulating the fingers of the hands was compared with con sistent stimulation of each hand. Previous studies have used only cons istent stimulation. Thirty-two undergraduate university students (16 m ales and 16 females) were tested. Bimanual simultaneity thresholds wer e significantly higher than unimanual. Previous research showing an ab sence of laterality effects for simultaneity judgements was confirmed, supporting a hemispheric equivalence model of temporal processing. Si multaneity thresholds were not affected by randomisation of stimulus l ocation, indicating that expectancy effects were not responsible for t he difference between bimanual and unimanual thresholds. The implicati on of these findings is that temporal perceptions are affected by the process of interhemispheric transmission.