The temporal distribution of stimulus information in the visual evoked potential.

Research in psychophysics (Bloch's law) and perceptual experiments concerned with the integration of successively presented stimuli suggest that the perception of form is a process that occurs over a period of as much as 200-300 msec. Such results prompted the question of whether the visual evoked potential (VEP) might contain information about the distribution over time of perceptual processing. Subjects viewed lines formed from combinations of three lengths and four angles while the EEG was recorded. Analysis of the VEPs indicated that the length and angle of the lines produced temporal distributions of information in the VEP and that the distributions for length and angle were somewhat different. The major difference was that the processing of angle begins earlier and is completed sooner than the processing of length. A conclusion of the experiment was that an alternative or supplement to analyzing VEPs for specific waveform features is to consider the encoding of stimulus information in the VEP as a density or concentration over time.