The VECP represents a brain reaction evoked by fairly abrupt visually perceived changes of one or several environmental features. If the stimulus consists of a finite temporal luminance rise, then the VECP is triggered later as compared to an abruptly appearing stimulus. This delay is an expression of the dynamic input properties of a VECP trigger mechanism. This system evaluates sudden changes of luminance slope and the temporal luminance integral in the first 50 ms after commencement of the stimulus. It may be assumed that deficiencies of the processing of visual information are manifested especially and first of all in a change of the dynamic trigger conditions of VECP. This is shown for colour stimulation (under isolation of the green and red colour mechanism) in different deficiencies of the visual system.