Effects of Form Perception and Meaning on the Visual Evoked Potential with Author's Update
ARMY AEROMEDICAL RESEARCH LAB FORT RUCKER AL
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Visual evoked responses VER from different interpretations of reversible figures, simple geometrical forms, and consonant-vowel-consonant cvc trigrams with differently ordered consonants were studied over a 2-year period in three adult human subjects. Stimuli were all black line figures subtending less than 2 degrees, seen against a white, square, 10-degree background and presented in random order with a random interstimulus interval. VERs were obtained from six active electrode sites. VER wave forms resulting from unlike stimuli or stimulus interpretations were defined as disparate when amplitude differences of one or more frequency components were greater than the amplitude differences from replications of the same stimulus or stimulus interpretation. Results were then placed in binary arrays for within and between subject comparisons. Distinctly different VERs were found for the different interpretations of reversible figures. This was interpreted as resulting from perceptual, rather than sensory processes. VER differences were also found resulting from differences in simple geometrical figure forms and angular subtenses. These differences were all attributed to sensory processes. VERs did not distinguish between trigram meanings based on changes in consonant order, but may distinguish between meaningful and nonsense trigram classes.
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