Further evidence of an association between handedness and neuroanatomical asymmetries in the primary motor cortex of chimpanzees (Pan troglodytes)

Abstract

The neurobiology of handedness is still poorly understood in nonhuman primates. Recently, an association between hand preference and precentral gyrus morphology in chimpanzees was reported. The aim of this study was to further evaluate the association between handedness and asymmetries in the precentral gyrus of chimpanzees (Pan troglodytes) and to evaluate the association between hand preference and brain asymmetry using a different approach to the classification of handedness in chimpanzees. The overall results suggest that differences in handedness groups are specific to a region of the precentral gyrus commonly known as the "knob" and that subjects that show different hand preferences differ in brain asymmetries for specific regions of the primary motor cortex. Moreover, using a continuous scale of measurement rather than discrete classification of handedness, significant associations were found between hand use and asymmetries within the precentral gyrus.

Exploring the relationship between cerebellar asymmetry and handedness in chimpanzees (Pan troglodytes) and capuchins (Cebus apella)

“…Together with recent studies on the relationship between handedness and areas of the primary motor cortex in chimpanzees (Dadda, Cantalupo, & Hopkins, 2006;Hopkins & Cantalupo, 2004) and capuchins (Phillips & Sherwood, 2005), these results contribute to the growing body of literature on the neurobiology of handedness. However, much remains to be addressed concerning the evolution of cerebellar specialization and its relationship to handedness.…”

“…A few studies have reported neural correlates associated with hand preference in nonhuman primates. For example, evidence from chimpanzees indicates that hand preferences for non-communicative actions are correlated with asymmetries of the KNOB, a region of the precentral gyrus, but not language area homologues (Dadda, Cantalupo, & Hopkins, 2006;Hopkins & Cantalupo, 2004). Similarly, asymmetries of the dorsal portion of the precentral gyrus are associated with hand preference in capuchin monkeys (Phillips & Sherwood, 2005).…”

Histological asymmetries of primary motor cortex predict handedness in chimpanzees (Pan troglodytes)

“…This central sulcus asymmetry appears to correlate with handedness only in males (Amunts et al, 2000). Similarly, morphological asymmetries of the central sulcus are also associated with hand preference on a coordinated bimanual task in chimpanzees (Hopkins and Cantalupo, 2004;Dadda et al, 2006) and New World capuchin monkeys (Phillips and Sherwood, 2005). Taken together, these findings suggest that structural asymmetries of the primary motor cortex reflect hemispheric specialization for controlling skilled actions of the dominant hand in primates (Hammond, 2002).…”

“…Gross anatomical asymmetries of the region of hand representation of the primary motor cortex have been shown to correlate with hand preferences in humans, chimpanzees, and capuchin monkeys (Amunts et al, 2000;Hopkins and Cantalupo, 2004;Phillips and Sherwood, 2005;Dadda et al, 2006), suggesting that handedness is facilitated by a greater total mass of neural tissue devoted to controlling the dominant hand. This hypothesis is further supported by evidence from magnetoencephalography in humans (Volkmann et al, 1998) and intracortical microstimulation in New World squirrel monkeys (Nudo et al, 1992) indicating that the size of forelimb movement representation is significantly increased in the primary motor cortex opposite to the preferred hand.…”

“…We collected brains postmortem from several of these chimpanzees, providing a unique opportunity to study brainbehavioral correlations. Based on previous studies linking handedness with morphological asymmetries in the precentral gyrus (Hopkins and Cantalupo, 2004;Dadda et al, 2006), we hypothesized that histological asymmetries of the primary motor cortex would predict individual differences in hand preferences. To examine this possibility, we measured asymmetry in a panel of histological variables in postmortem brains and determined their contribution to explaining variation in handedness as measured before death on an experimental bimanual coordination task.…”