BALANCE OF COST AND INTERHEMISPHERIC RELAY - EVIDENCE FROM OMISSION ERRORS IN THE POFFENBERGER PARADIGM

The crossed-minus-uncrossed (field-hand) difference (CUD) in simple vi sual reaction time (SVRT) is typically termed interhemispheric transfe r time (Poffenbeger paradigm). No author has yet considered error freq uencies in normal participants in this paradigm, the error rates typic ally being too low and the participants too few. An error-CUD of posit ive valence suggests a cost in accuracy associated with interhemispher ic relay. Normal right-handers (N = 135) gave 5,815 omission errors in 7 SVRT experiments. A significant Field x Hand interaction was obtain ed in the omission errors, but of negative valence, F(1, 121) = 4.6, p = .03. Three possible and not necessarily mutually exclusive mechanis ms are discussed. Motor preparation for an individual response could g enerate neural noise within the responding hemisphere. Processing reso urces could become tonically modulated over a large number of trials a ccording to responding hand. The commissure(s) could have signal-to-no ise enhancement properties.