Complex motion perception and its deficits.

Within the hierarchy of motion perception, the dorsolateral middle superior temporal area (MSTd) is optimally suited for the analysis of the complex motion patterns that are directly useful for visually guided behaviour (e.g. computation of heading). Recent electrophysiological and psychophysical evidence suggests the existence of 'detectors' in MSTd that are specialised for complex motion patterns and advocates the necessity of combining retinal and extraretinal signals received by MSTd neurones for the accurate perception of heading. In some neurological patients, of which only a small number have been reported to date, lesions involving the human homologue of MST have devastating effects on their ability to navigate in their surroundings. It has been reported that these patients have impaired performance of psychophysical tasks of complex motion discrimination.