Conjugate lateral eye movements and cognitive mode: blindness as a control for visually-induced oculomotor effects

Cognitive consequences of asymmetrical visual distraction

The authors explored whether manipulating the location of distraction in the participants' visual field influences the degree of competition between visual and other cognitive processes. If a cognitive task is lateralized to a particular hemisphere, visual distraction directed toward that same hemisphere should impair performance on that task more than should visual distraction directed toward the other hemisphere. Consistent with this hypothesis, the authors found in Experiments 1 and 2 that participants better recalled words of high imageability in a verbal memory task when the examiner was in the participant's left visual field (right hemisphere) than when the examiner was in the participant's right visual field (left hemisphere). In Experiment 3, the authors found that this effect reversed for performance on a right-hemisphere spatial task.

Body asymmetry affects conjugate lateral eye movement

A. H. Baker (1989) and A. H. Baker and A. I. Ledner (1990) reported that asymmetrical visual stimulation affects conjugate lateral eye movement (CLEM). In the present article, the authors explored whether asymmetrical body position similarly affects CLEM. The authors assessed CLEMs twice in a counterbalanced design. In the control (symmetric) condition, each participant sat in a completely symmetrical position facing a wall devoid of any asymmetrical features. In the experimental (asymmetrical) condition, half the participants rotated their heads 68 degrees clockwise relative to their bodies to face the experimenter, and the other half rotated their heads 68 degrees counterclockwise, also to face the experimenter. CLEM was predominantly toward the body's position in the asymmetrical condition rather than toward the body's position in the symmetrical condition.

Reduction of cutaneous reaction time by directing eyes towards the source of stimulation

Reaction time to expected lateral cutaneous stimulation was measured in Man when the eyes were directed (1) towards the stimulated area, (2) towards another point within the same hemispace and (3) towards the other hemispace. As performance was better in the first case, this suggests that compatible eye postural activity reinforces the effect of spatial attention.

Relationship of lateral eye movements recorded in the dark to verbal and spatial question types

Lateral eye movements (LEMs) were recorded in normal subjects to verbal and spatial questions in the dark using infra-red recording techniques to assess whether clearer LEM-question type relationships are observed when the potentially confounding effects of visual stimulation are absent. Verbal questions elicited more rightward LEMs than spatial questions. However, spatial questions were not associated with leftward LEMs. It is argued that while infra-red recording techniques may be optimal for recording LEMs to verbal questions, the above results question the generalizability of strong LEM-spatial relationships obtained for a single blind subject by GRIFFITHS and WOODMAN [Neuropsychologia 23, 257-262, 1985].

Defective lateralized attention for non-verbal sounds in developmental dyslexia

The performance of dyslexic and control children--matched for age, sex, handedness and performance IQ--was compared on a dichotic listening task in which the stimuli were environmental sounds. Two findings emerged. First, the dyslexic group showed a normal, left ear perceptual advantage for these non-verbal materials. Second, the dyslexics were incapable of occluding dichotically presented sounds to the left ear when required to deploy attention only to sounds entering the right ear. This failure of unilateral selective attention was not found in the controls, nor in either group under a condition of left ear only attention. The data were interpreted as undermining the bihemispheric non-verbal processing hypothesis of developmental dyslexia. It was argued that the dyslexics' apparent inability to override voluntarily the reflexive lateral orienting mechanism was most consistent with explanatory models emphasizing defective functioning, or even malformation, of the left cerebral hemisphere alone.