This project will show that the recognition potential is a new brain wave phenomenon that bears a superior relationship to psychological processes, compared to other event-related potentials. From previous research it is known to be evoked by recognizable images (e.g. words, pictures, and faces). Its short latency and scalp distribution distinguish it from the vertex-positive wave known as P3 or P300 and a related negative potential that precedes it (N2). For N2, polarity is also a distinguishing feature. The lead closer to the vertex becomes initially positive for the recognition potential, not negative. N2 and P3 are sensitive to probability of occurrence. The rarer stimulus evokes the response. Either a low or a high frequency tone could be rarer, so either could evoke N2-P3. Exchanging the roles of low and high frequency tones has been used to rule out the possibility that the N2-P3 effects were produced by differences in the physical attributes of the stimuli. This doesn't work for the recognition potential. It is relatively insensitive to the probability of occurrence, and it depends on the recognizability of the images. The picture of a fish would evoke it, but a scrambled, unrecognizable version of it would not. The roles of these two stimuli cannot be exchanged. A solution to this problem took advantage of differences in learning experience among subjects. Chinese-speaking subjects discerned at a glance the meaning of Chinese ideographs. Subjects unfamiliar with Chinese derived no meaning from them. Recognizability was the important factor, not the physical attributes, so the Chinese ideographs evoked the recognition potential only for the Chinese speaking subjects. Many studies showed increased N2 or P3 latency for more difficult perceptual tasks, but the increase was only a fraction of the increase observed for RT. The recognition potential showed a superior relationship; its latency increase equalled the RT increase. The N400 component was found to be relatively independent of frequency of usage, as defined by words occurring at least 50 times/million words versus 0-5 times/million words. Preliminary evidence shows recognition potential latency increases for less commonly used words as much as RT does. The proposed research will confirm these results in a larger group of subjects. This will (1) provide additional evidence that the recognition potential is not the same as the event-related potentials previously studied, (2) demonstrate the superiority of the recognition potential for studying psychophysical processes, and (3) encourage its use for the study of reading disorders.
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