Cerebral Sulcal Asymmetry in Macaque Monkeys

Abstract

The asymmetry of the cerebral sulcal morphology is particularly obvious in higher primates. The sulcal asymmetry in macaque monkeys, a genus of the Old World monkeys, in our previous studies and others is summarized, and its evolutionary significance is speculated. Cynomolgus macaques displayed fetal sulcation and gyration symmetrically, and the sulcal asymmetry appeared after adolescence. Population-level rightward asymmetry was revealed in the length of arcuate sulcus (ars) and the surface area of superior temporal sulcus (sts) in adult macaques. When compared to other nonhuman primates, the superior postcentral sulcus (spcs) was left-lateralized in chimpanzees, opposite of the direction of asymmetry in the ars, anatomically-identical to the spcs, in macaques. This may be associated with handedness: either right-handedness in chimpanzees or left-handedness/ambidexterity in macaques. The rightward asymmetry in the sts surface area was seen in macaques, and it was similar to humans. However, no left/right side differences were identified in the sts morphology among great apes, which suggests the evolutionary discontinuity of the sts asymmetry. The diversity of the cortical lateralization among primate species suggests that the sulcal asymmetry reflects the species-related specialization of the cortical morphology and function, which is facilitated by evolutionary expansion in higher primates.

Neonatal valproic acid exposure produces altered gyrification related to increased parvalbumin-immunopositive neuron density with thickened sulcal floors

“…Sulcogyral development has been documented in the cerebrum of several mammalian species, including humans [1], baboons [2], cynomolgus monkeys [3][4][5][6][7], common marmosets [8], bovine [9], dogs [10], and ferrets [11][12][13]. The cerebral cortex can be roughly differentiated into four types of surface morphology.…”

Genetic determinants of individual variation in the superior temporal sulcus of chimpanzees (Pan troglodytes)

“…More generally, the overall significant rightward asymmetries in the STAP region clearly challenge the claim that these asymmetries are uniquely human, though admittedly, the magnitude of the bias is decidedly smaller in chimpanzees compared to humans. We also note that significant rightward asymmetries have been reported in the overall surface area of the STS in macaques (Bogart et al 2012;Suwada 2020), though it is unclear if these effects are attributable to lateralization within the STAP region because these previous studies did not delineate the STS in the manner that was utilized in this report. Future studies in other species should seek to clarify the nature of STS asymmetry in the context of the location of STAP region.…”

The evolution of linguistic iconicity and the cross-modal cognitive suite

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