[Temporal order judgment in the brain].

It is generally accepted that the brain can resolve the order of two stimuli that are separated in time by 20-50 ms, irrespective of their sensory modalities. This may support a traditional view that there is a single common decision mechanism of temporal order that compares arrival times of sensory signals of any modalities. However, the traditional view has been challenged recently in two ways. Firstly, it has been shown that human judgment of the temporal order is liable to change depending on our prior experiences, and in a modality specific manner. A constant tone-light pair presented repeatedly is judged as occurring simultaneously (lag adaptation), whereas opposite perceptual changes occur in judging the order of tactile stimuli delivered one to each hand. The latter change conforms to a Bayesian integration theory. Secondly, subjective temporal order has been shown to be inverted in some special conditions. Crossing the arms caused inverting of the temporal order of two tactile stimuli that were separated in time by 100-200 ms. The temporal order of visual and tactile stimuli separated by 50 ms was inverted when they were delivered just prior to the onset of a saccade. These recent results suggest that the mechanism of temporal order judgment is not so simple as previously hypothesized but would involve multiple processes whose results are later integrated to reconstruct a subjective order of events in time.