On the use of visual motion perception to assess magnocellular integrity

It has been proposed, particularly in connection with dyslexia and schizophrenia, that motion perception can be used to assess magnocellular integrity. This suggestion is examined in this paper. The following observations are made: (1) motion information, i.e., information about direction and speed, is extracted at the cortical level, (2) the magnocellular system provides input to the motion selective cortical entities, and (3) so do the parvo- and koniocellular systems. Therefore, although the magnocellular system clearly has the ability to influence motion perception so do other parts of the visual system, e.g., cortical mechanisms. It is concluded that motion perception by itself is not a reliable test of magnocellular integrity.