Eye movement physiology : Saccadic hypometria in drug-naive and drug treated schizophrenia patients: a working memory deficit?

Hutton, S. B. and Cuthbert, I. and Crawford, T. J. and Kennard, C. and Barnes, T. R. E. and Joyce, E. (1999) Eye movement physiology : Saccadic hypometria in drug-naive and drug treated schizophrenia patients: a working memory deficit? Schizophrenia Research, 36 (1-3). p. 264. ISSN 0920-9964

Abstract

Attempts to determine the physiological nature of smoothpursuit dysfunction in schizophrenia have included many investigations of saccade rates, but the findings have been variable. The present investigation tested the hypothesis that the misclassification of blinks as saccades affects saccade rates in studies using only infrared oculography (IROG). Both IROG and vertical electro-oculography (VEOG), the latter of which provides an objective measure of blinking, were collected while 17 schizophrenia patients and 19 healthy control subjects were presented 0.4 Hz sinusoidal stimuli. Of the blinks identified with the VEOG, 42% were not identified, and 37% were misclassified as saccades when only the IROG was used. Most misclassified saccades masqueraded as catch-up saccades (CUS)(66%) and anticipatory saccades (AS) (34%). However, CUS and total saccade rates were significantly elevated in schizophrenia patients both before and after correction for misclassified blinks. Rates of other saccade subtypes and blinks did not differ. Therefore, the misclassification of blinks as saccades is likely to introduce some measurement error into estimates of saccade rates, but it is unlikely to account for the variability in estimates evidenced in the literature. However, when the blinkto-saccade ratio is larger, as it is in saccadic paradigms, saccade metrics may be vulnerable to the effects of blink misclassification