Parallel Evolution of Cortical Areas Involved in Skilled Hand Use

TLDR

Dexterous hands are a hallmark of primate evolution, yet the neural basis of fine manual control remains unclear; cebus monkeys uniquely possess a well‑developed area 5 and proprioceptive area 2, enabling precision grip similar to macaques, suggesting a conserved cortical organization linked to manual dexterity. The study aims to describe the functional organization of parietal cortical areas 2 and 5 in the cebus monkey. The authors examined the functional organization of these areas in the cebus monkey. The similarity of these fields in cebus and macaque monkeys indicates that cortical organization is constrained and shaped by conserved developmental mechanisms.

Abstract

Dexterous hands, used to manipulate food, tools, and other objects, are one of the hallmarks of primate evolution. However, the neural substrate of fine manual control necessary for these behaviors remains unclear. Here, we describe the functional organization of parietal cortical areas 2 and 5 in the cebus monkey. Whereas other New World monkeys can be quite dexterous, and possess a poorly developed area 5, cebus monkeys are the only New World primate known to use a precision grip, and thus have an extended repertoire of manual behaviors. Unlike other New World Monkeys, but much like the macaque monkey, cebus monkeys possess a proprioceptive cortical area 2 and a well developed area 5, which is associated with motor planning and the generation of internal body coordinates necessary for visually guided reaching, grasping, and manipulation. The similarity of these fields in cebus monkeys and distantly related macaque monkeys with similar manual abilities indicates that the range of cortical organizations that can emerge in primates is constrained, and those that emerge are the result of highly conserved developmental mechanisms that shape the boundaries and topographic organizations of cortical areas.