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The nuclear arsenal and the use of nuclear technologies have enhanced the likelihood of whole-body/partial-body radiation exposure. The central nervous system is highly susceptible to even low doses of radiation. With the aim of detecting and monitoring the pathologic changes of radiation-induced damage in brain parenchyma, we used serial diffusion tensor magnetic resonance imaging (DTI) with a 7T magnetic resonance unit and neurobehavioral assessments mice irradiated with 3-, 5-, and 8-Gy doses of radiation. Fractional anisotropy (FA) and mean diffusivity (MD) values at each time point (baseline, day 1, day 5, and day 10) were quantified from hippocampus, thalamus, hypothalamus, cudate-putamen, frontal cortex, sensorimotor cortex, corpus callosum, cingulum, and cerebral peduncle. Behavioral tests were performed at baseline, day 5, and day 10. A decrease in FA values with time was observed in all three groups. At day 10, dose-dependent decreases in FA and MD values were observed in all of the regions compared with baseline. Behavioral data obtained in this study correlate with FA values. Radiation-induced affective disorders were not radiation dose dependent, insofar as the anxiety-like symptoms at the lower dose (3 Gy) mimics to the symptoms with the higher dose (8 Gy) level but not with the moderate dose. However, there was a dose-dependent decline in cognitive function as well as FA values. Behavioral data support the DTI indices, so it is suggested that DTI may be a useful tool for noninvasive monitoring of radiation-induced brain injury.

BackgroundMost humans are right handed, and most humans exhibit left-right asymmetries of the precentral corticospinal system. Recent studies indicate that chimpanzees also show a population-level right-handed bias, although it is less strong than in humans.Methodology/Principal FindingsWe used in vivo diffusion-weighted and T1-weighted magnetic resonance imaging (MRI) to study the relationship between the corticospinal tract (CST) and handedness in 36 adult female chimpanzees. Chimpanzees exhibited a hemispheric bias in fractional anisotropy (FA, left>right) and mean diffusivity (MD, right>left) of the CST, and the left CST was centered more posteriorly than the right. Handedness correlated with central sulcus depth, but not with FA or MD.Conclusions/SignificanceThese anatomical results are qualitatively similar to those reported in humans, despite the differences in handedness. The existence of a left>right FA, right>left MD bias in the corticospinal tract that does not correlate with handedness, a result also reported in some human studies, suggests that at least some of the structural asymmetries of the corticospinal system are not exclusively related to laterality of hand preference.