Performance asymmetries in tool use are associated with corpus callosum integrity in chimpanzees (Pan troglodytes): A diffusion tensor imaging study.

Abstract

We examined the relationship of corpus callosum morphology and organization to hand preference and performance on a motor skill task in chimpanzees. Handedness was assessed using a complex tool use task that simulated termite fishing. Chimpanzees were initially allowed to perform the task wherein they could choose which hand to use (preference measure); then they were required to complete trials using each hand (performance measure). Two measures were used to assess the corpus callosum: midsagittal area obtained from in vivo magnetic resonance images and density of transcallosal connections as determined by fractional anisotropy values obtained from diffusion tensor imaging. We hypothesized that chimpanzees would perform better on their preferred hand compared to the non-preferred hand, and that strength of behavioral lateralization (rather the direction) on this task would be negatively correlated to regions of the corpus callosum involved in motor processing. Our results indicate that the preferred hand was the most adept hand. Performance asymmetries correlated with FA measures but not area measures of the CC.

Heritability in corpus callosum morphology and its association with tool use skill in chimpanzees (Pan troglodytes): Reproducibility in two genetically isolated populations

“…Second, it has been reported that asymmetries in tool use performance are associated with white matter integrity, as measured by fractional anisotropic values obtained in DTI scans, within the CC of chimpanzees. 42 Third, in two previous studies in chimpanzees, performance on a simulated termite fishing task was found to be significantly heritable and reproducible in the same cohort of chimpanzees used in this study. 60,61 These findings allowed for testing both phenotypic and genetic correlations between tool use performance and variation in CC surface area and thickness.…”

“…[33][34][35][36][37][38][39] Previous studies in chimpanzees and other nonhuman primates have also reported some evidence that right and left-handed individuals differ in CC surface area. [40][41][42][43] Here we sought to test for phenotypic and genetic associations between CC surface area and thickness with performance asymmetries on a tool use task in the chimpanzees for three reasons. First, chimpanzees are well known for their diversity in tool manufacture and use in both captivity and the wild [44][45][46] and there some evidence that hand preferences and skill for different forms of tool use are strongly lateralized at the individual and, in some cases, population-level.…”

Sex differences in the relationship between planum temporale asymmetry and corpus callosum morphology in chimpanzees (Pan troglodytes): A combined MRI and DTI analysis

“…These data were then regressed on directional and absolute PT asymmetries in a sample of > 200 chimpanzees. In addition, we also scanned a sample of 57 chimpanzees using diffusion tensor imaging (Phillips and Hopkins, 2012) and computed three measures of CC integrity including (a) raw streamline counts (b) mean fractional anisotropy and (c) the ratio of number of streamline counts to surface area (i.e., fiber density) using similar to those used in previous studies with humans and chimpanzees (Hofer and Frahm, 2006; Hofer et al, 2007; Phillips et al, 2013a, 2013b). Though the methods are dificult to compare, by quantifying streamline counts and their density from DTI, we sought to approximate the methods typically used in post-mortem material.…”

Context-dependent lateralization of trunk movements in wild Asian elephants

“…For example, in wild chimpanzees the efficiency of termite fishing positively correlates with the degree of an individual's hand preference (McGrew and Marchant, 1999). Other mammals such as: cats (Lorincz and Fabre-Thorpe, 1996); bonnet macaques (Mangalam et al, 2014); and, chimpanzees (Phillips et al, 2013) have been also shown to perform better with the preferred forelimb. Thus, at least in some animals, lateralized use of the forelimb is associated with potential fitness benefits.…”