The level of nitric oxide in the cortex correlates well with brain lateralization

A case of unilateral hemispheric encephalitis

Herein we report a case of encephalitis involving the unilateral hemisphere, with a clinical course different from that of Rasmussen syndrome. A 44-year-old man visited us because of headache and language abnormality. Cerebrospinal fluid examination showed lymphocytosis with increased level of protein. Brain MRI showed abnormal findings limited to the unilateral hemisphere. The symptoms and signs improved without any specific antiviral treatment in a week. However, language disturbance and right hemiparesis developed after a week. Steroid therapy was effective. He recovered without any neurologic sequelae. Our case was unusual encephalitis involving the unilateral hemisphere, which was benign and steroid-responsive.

Callosal agenesis affects consistency of laterality in a paw preference task in BALB/cCF mice

We tested the hypothesis that the ontogenetic development of the corpus callosum (CC) affects the consistency of laterality in a paw preference task. Adult male mice (55 normal and 29 acallosal) of the BALB/cCF strain were initially tested (twice; inter-test interval: 72 h) in an unbiased setup in which both forepaws could easily perform a reaching movement. In a subsequent test, animals were placed in a biased setup that favored the use of the non-preferred paw. Acallosal and normal mice were strongly lateralized in the unbiased setup. Additionally, while normal mice did not present a populational bias favoring one of the paws, acallosal mice presented a significant bias favoring the left paw. In the biased setup, left- and right-pawed normal mice were equally consistent (approximately 65% of the animals, in both groups, used the preferred paw of the initial two tests, in spite of the bias). Conversely, while left-pawed acallosal mice were as consistent (65%) as normal mice, only 20% of right-pawed mice were consistent. These results suggest that the development of the CC affects consistency of laterality in a side-dependent manner. These results are discussed considering the role of the CC in the establishment of behavioral lateralization.