Conjugate Lateral Eye Movements: A Second Look

Abstract

It has been suggested that conjugate lateral eye movements (CLEM) are related to cerebral lateralization. Two types of research have developed: studies examining individual differences (hemisphericity) and studies examining the type of questions used to elicit eye movements (hemispheric specialization). In a 1978 review, Ehrlichman and Weinberger questioned the notion that CLEM is related to cerebral lateralization, particularly with regard to individual differences. However, since their review, a substantial number of studies have been published which are pertinent to the validity of CLEM. The following paper reviewed the validity of CLEM through three avenues, neurophysiological evidence, relationships with other measures of laterality and relation to spatial and verbal stimuli. Overall, it was concluded that there is sufficient evidence to support the CLEM model. Converging evidence from studies on EEG, electrical stimulation, ablation, brain damage, sodium amytal testing, blood flow, positron emission tomography, dichotic listening, and visual half fields was found to be, for the most part, supportive. The results for verbal and spatial task performance were mixed. Studies examining verbal abilities or a verbal to spatial comparison were generally supportive. The findings for spatial abilities alone were more equivocal. Evidence on question-type was found to be weak but positive, with about half the studies showing the predicted asymmetry and the other half reporting nonsignificant results. The implications of an interaction between hemisphericity or characteristic arousal and hemispheric specialization were also discussed.

Quantitative Assessment of Five Behavioural Laterality Measures: Distributions of Scores and Intercorrelations Among Right-handers

“…How ever, evidence for the validity of degree of handedness and all other applied measures can be found in the literature, for instance, significant relationships to other psychological, physiological, or anatom ical characteristics, or changes after brain lesions (e.g. Annett, 1992;Bow ers & Heilman, 1980;Charlton et al, 1989;Cow ell et al, 1993;Efron & Crandall, 1983;Efron, Dennis, & Yund, 1977;Laeng et al, 1996;Miller, 1982;Porac & Coren, 1976;Rippon , 1991;Schachter, 1994;Tan, 1990;Tenke et al, 1993;W itelson & Goldsm ith, 1991).…”

“…If subjects have to be groupe d on the basis of their ocular dom inance, therefore, these results suggest a division into three groups rather than two. In an extensive review of lateral eye movements, Charlton et al (1989) noted that the evidence suggests a greater percentage of left-movers than rightmovers in the popula tion. This observation can be confirm ed by the present results and may be in accordance with findings from cerebral blood flow studies which have demonstrated greater right hem isphere flow in norm al participants (Charlton et al, 1989;Gur & Reivich, 1980).…”

“…It was suggested that the preferred direction of CLE Ms may indicate individual differences in lateral preference, that is, in the tendency of a person to consistently activate the left or right hemisphere m ore intensely (Bakan, 1969). An extensive review on this issue has concluded that there is now substantial neurophy siological evidence supporting the assumption of a link between hemispheric activation and contralateral eye movements (Charlton, Bakan, & M oretti, 1989). Characteristic arousal asym metries m ay account for individua l variations in hem isphere dom inance measures (Levy, Heller, Banich, & Burton, 1983).…”

Conjugated lateral eye movements and EEG: a study on schizophrenic and depressive patients

“…Weinberger (1988) has already described the importance of disorders of frontocortical areas in schizophrenics. Moreover, the frontocortical areas are considered to be paramount for CLEM-generation (Charlton et al, 1989). Tonic hemispheric priming effects could have confounded the results: insiructions were given that the purpose of the experiment was to test verbal expressivity.…”

“…Ehrlichman and Weinberger's review (1978) has cast some doubt on the proposed relationship between the interaction of CLEMs, hemispheric activity, and content of question. However, a more recent review of the experimental literature by Charlton et al (1989) provided supportive evidence for the CLEM-model on the basis of neurophysiological studies, whose findings indicated positive relationships with other measures of laterality and correlations with stimulus content. EEG validation studies supported the CLEM-model only in part (Bakan and Svorad, 1969;Morgan et al, 1971;Warren and Haueter, 1981;Neubauer el al, 1988) because this can be due to different EEG designs.…”