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Byline: Renu. Rajan, Amit. Deb, Naresh. Kannan, Kim. Ramasamy Optic nerve (ON) aplasia is a rare congenital anomaly. It is characterised by the absence of optic nerve, nerve fibre layer, [...]

Findings suggest that in humans, sex and hand preference may be associated with the size of the corpus callosum (CC). The authors measured CC morphology from MRIs in 67 chimpanzees (Pan troglodytes) to see whether similar effects were present in this species. Hand preference was assessed by performance on 4 tasks, and chimpanzees were classified as left-handed, right-handed, or ambidextrous. In a subsequent analysis, the chimpanzees were reclassified into 2 groups: right-handed and left-handed. The results revealed no sex difference in CC area, but significant effects of hand preference were found for several CC regions (rostrum body, anterior midbody, posterior midbody, isthmus, and splenium) and for overall CC size, with left-handed chimpanzees exhibiting significantly smaller CC measurements than right-handed chimpanzees. The results indicate that lateralized hand use in chimpanzees, as in humans, is associated with variation in CC size. Keywords: Pan troglodytes, corpus callosum, handedness

Objective: By means of quantitative neuroanatomic imaging the authors assessed the hypothesis that there are structural brain abnormalities relevant to frontal lobe circuitry in children with attention deficit hyperactivity disorder (ADHD). Method: The midsagittal cross-sectional area of the corpus callosum, divided into seven sections, was measured from magnetic resonance images of 18 boys with ADHD and 18 carefully matched normal boys. Results: Two anterior regions, the rostrum and the rostral body, were found to have significantly smaller areas in the ADHD group. These areas correlated in the expected direction with teacher and parent ratings of hyperactivity/impulsivity. Conclusions: This finding supports theories of abnormal frontal lobe development and function in ADHD.

In the first of two experiments, rats with left or right parietal lesions and controls were tested in place and landmark navigation in the water maze. Right parietal lesions resulted in deficits in both tasks, but especially landmark navigation. Lateralized effects appeared mainly in latency to find the platform. Experiment 2 investigated the role of the corpus callosum. Split-brain rats with unilateral parietal lesions were tested on the same two tasks. Place and landmark deficits were particularly severe, but lateralization was weaker. Callosum section had its own effect, impairing the learning of both tasks. There appear to be additive effects of unilateral cortical lesions and bisection of the hemispheres. The impairment from left lesions equaled the right-lesion deficit because of the interruption of compensatory information from the intact right hemisphere and the effect of callosum section itself.

Objective: The corpus callosum, the largest white matter tract in the brain, is a midline structure associated with the formation of the hippocampus, septum pellucidum, and cingulate cortex, which have been implicated in the pathogenesis of schizophrenia. Corpus callosum shape deformation, therefore, may reflect a midline neurodevelopmental abnormality. Method: Corpus callosum area and shape were analyzed in 14 first-episode psychotic patients with schizophrenia, 19 first-episode psychotic patients with affective disorder, and 18 normal comparison subjects. Results: No statistically significant corpus callosum area differences between groups were found, but there were differences in the structure's shape between the patients with schizophrenia and the comparison subjects. A correlation between width and angle of the corpus callosum was found in patients with affective disorder. Conclusions: Corpus callosum shape abnormalities in first-episode psychotic patients with schizophrenia may reflect a midline neurodevelopmental abnormality. (Am J Psychiatry 2002; 159:866-868)