Structural Asymmetries of the Human Brain and Their Disturbance in Schizophrenia

Abstract

Asymmetries of the brain have been known about for at least a century, but they have been explored in detail only relatively recently. It has become clear that, although different asymmetries are common throughout the animal kingdom, they are most marked in the human brain. Disturbances in asymmetry are particularly striking in patients with schizophrenia and perhaps all psychotic illnesses, and may provide the neurological substrate for the etiology and clinical manifestations of the illness.

Increased inferior frontal activation during word generation: A marker of genetic risk for schizophrenia but not bipolar disorder?

“…Similarly, during a semantic categorization task, relatives of schizophrenia patients showed significantly greater response in the right inferior frontal gyrus than controls [Whyte et al, 2006]. Increased recruitment of the right homolog of Broca's area as part of the endophenotype predisposing to schizophrenia is also consistent with the conjecture by Crow that a loss of the normal lateralization for language is a defining feature of this disorder [Mitchell and Crow, 2005], linked not only to functional abnormalities but also to asymmetries in brain structure [Sommer et al, 2001a;Petty, 1999] and neuropsychological profile [Gruzelier, 1999].…”

Asymmetries of cortical shape: Effects of handedness, sex and schizophrenia

“…Indeed, lateralized brain insults occurring early during neurodevelopment have been shown to influence the direction of speech lateralization and handedness (Woods et al, 1988), where harmful environmental events in utero appear twice as likely to affect the left hemisphere (Geschwind et al, 2002). There is also wide agreement that neurodevelopmental disturbances induced by harmful genetic or environmental events contribute to schizophrenia pathophysiology (Harrison, 1999;Bilder, 2001) with some evidence suggesting a preponderance of left hemisphere pathology (Nopoulos et al, 1995;Gur, 1999;Petty, 1999). Particularly, it has been posited that disturbances in lateralization constitute a genetic and evolutionary basis for the disease, which is hypothesized to have developed in concert with hemispheric specialization for language via a gene influencing the direction and magnitude of cerebral dominance (Crow, 1997(Crow, , 2000.…”

“…Many studies have observed schizophrenia-related reductions (or reversals) in asymmetric perisylvian regions, but negative findings are common, for review see (Toga et al, in press;Harrison, 1999;Petty, 1999;Shapleske et al, 1999;Shenton et al, 2001;Sommer et al, 2001). Similarly, some CT studies report significant differences in left-biased occipital (Luchins et al, 1979;Falkai et al, 1995b) and right-biased frontal hemispheric width asymmetries (Falkai et al, 1995b), but several investigators have failed to replicate these findings in schizophrenia (Andreasen et al, 1982;Jernigan et al, 1982;Luchins and Meltzer, 1983;Crow et al, 1989).…”

Schizophrenia, neurodevelopment and corpus callosum

“…Clearly, the issue of right-left hemisphere differences in S requires further attention, and indeed a substantial although somewhat controversial literature exists in this domain. 151 Interestingly, some of the key anatomical findings supporting the notion of hypoconnectivity in S derive from studies of the left hemisphere. 44,63,68,69 A specific linkage between left hemisphere and S is also explicit in proposals relating the phylogenetic origins of language and S. [152][153][154] Unfortunately, the genes responsible for lateralization are undefined, and their number and modalities of phenotypic expression are matters of debate.…”