During normal development of the fetal brain, the left hemisphere lags behind the right hemisphere in intrauterine growth, causing the left hemisphere to be smaller than the right hemisphere throughout the early and mid-prenatal period. By the end of the second trimester, the right hemisphere has achieved almost full-term size; thus second-trimester injuries affecting neurons, that is, anoxic, ischemic, toxic, or infectious insults that are systemic and bilateral, will affect the left hemisphere more than the right hemisphere. While other explanations for brain asymmetries in schizophrenia have been proposed, the embryological literature is consistent with the hypothesis that a prenatal injury may be one etiological factor in producing the structural brain asymmetries seen in psychotic adult patients.

There is a growing body of evidence implicating prenatal insults in the etiology of schizophrenia, although the etiological process is unclear. In this article we propose that prenatal exposure to alcohol may relate to a small fraction of patients who later develop schizophrenia.

A significant relationship was found between a bias to make complete counter-clockwise (leftward) turns and performance levels on tests of visuospatial function. Subjects who turned preferentially to the left over a four-day period performed above average on visuospatial tests with those having the greatest turning bias performing the best. Subjects who tended to turn to the right performed below average on tests of visuospatial function. There was no relationship between rotational bias and verbosequential skills, but there was a significant relationship between turning bias and a cognitive profile defined as the difference between visuospatial ability and verbosequential ability. The cognitive profile effectively partialed out overall ability suggesting that the turning bias is related to the bias for better visuospatial processing rather than the level of visuospatial performance per se. Asymmetric turning has been shown to be related to asymmetries of dopamine activity in rats. Therefore, the present results are discussed in relation to the possibility that the dopamine neurotransmitter system may underlie both rotational behavior and visuospatial cognitive function in humans.

Studies associate psychotic disorders with various forms of subtle inattention to the right hemispace (left-turning behavior). The authors examined the correlation between this dopamine-related sign and severity of delusions (presumably dopaminergic symptoms) in 20 psychotic patients. Delusions were significantly correlated with severity of left-turning bias, and this neurological sign accounted for 33% of the variance in severity of delusions.

This pilot study examined and quantified rotational asymmetry (the tendency to turn preferentially to the right or left side). An automated device was used to measure turning (circling) in 9 children with autism and 27 normal control subjects and confirmed clinical observations of stereotypical spinning behavior in patients with autism. This behavior was significantly preferential toward the left side relative to control subjects (P = 0.0009, two-tailed). Group membership accounted for approximately 40% of variance. Although the precise causes of autism are not known, these preliminary data suggest that the spinning behavior often seen in children with neurodevelopmental disorders can be reliably measured. Furthermore, spinning in autism may most often manifest as specific right-hemispace neglect.