The comparative study of brain asymmetry in six species of living nonhuman primates and tree shrews distributed in China
Ma Yuanye, Cai Jingxia, Tian Yunfen
1992, 11(01):
60-68.
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The brain asymmetries of tree shrews(Tutpaia belangeri chinensis), the slow loris (Ny-cticebus coucang), rhesus monkeys (Macaca mulatta), leaf-eating monkeys ( Presbytis ntellus),golden hairmonkeys (Rhinopith·cus roxellanae). ( Rhinopithecus bieti), and gibbons ( Hylobates hoolock) have been observed with anatomical, electrophysiological, and behav ioural methods. The results are shown below (N = the numbers of animals):
Anatomy: The brain sulci of six species of primates were measured, the length of Sylviansulcus of right cortex in slow loris was longer than that of left side. In the leaf -eating monkcys, the shape of arcuate sulcus was different between two sides of the brain. Most sulci ofthe parietal, occipital and temporal lobes were located more posteriorly in the rightcorticescompared to the left for rhesus monkeys, golden hair monkeys and gibbons.And in six ofnine rhesus' monkeys, the left fron1a] poles were more posteriorly than that of right sides. lngolden hair monkeys and gibbons, the shape of some sulci in left cortices were more complexthan that of right cortex and sone sulci in right sides were longer than that of left sides. In treeshrews, the weights of left cortices were greater than the right, while the volume did not differ. This may reflect cell density.
Electroplhysiology: The amplitule of visualevoked poten!ials(VEP) were higher in leftcorticcs than right in 70% of tree shrews. Using VEP method to measure the areas ofvisualcortex, no differcnce was found between the areas of left and right visual cortex. Duringatten-tive tasks in rhesus monkeys the right prefrontal cortices showed EEG of higher frequency andlower amplitude compared to the left. After lesion left sides of dorsal hippocampus, in treeslrews, the heart rate became lower than before, but were not, if lesions were done in the rightsides.
Behaviour: The hand preference of rhesus monkeys, leaf-eating monkeys, golden hair monkeys, and gibbons in picking up food was observed. With the exception of the rhesus,there was' right handed perference in males but not in females.
Conclusion: The results suggest that there dre braina syninetries' in nonhuman prinnatescven in tree shrews; these asymmetries are more clear for species that are higher on the evolutionary ladder. There is also a difference in male and female animals in hand preference.
