A DTI Investigation of Neural Substrates Supporting Tool Use

Abstract

Recent functional neuroimaging and brain lesion studies have implicated a network of left hemisphere regions in human tool use: 1) posterior middle temporal cortex involved in conceptual knowledge of tools, 2) posterior inferior parietal cortex for representations of learned tool use gestures, and 3) anterior inferior parietal cortex, along with posterior inferior frontal and ventral premotor cortices, involved in grasping and manipulating objects. Here, we use diffusion tensor imaging (DTI) to investigate the anatomical connections that support this putative network. DTI scans were acquired from nineteen right-handed males and a deterministic tractography algorithm was used to identify connections between these regions implicated in tool use. Three of the resulting pathways were larger in the left than the right hemisphere. One connected posterior middle temporal cortex and the anterior inferior parietal cortex, a second connected posterior middle temporal cortex and the posterior inferior parietal cortex, and a third connected anterior inferior parietal cortex and the frontal lobe. In contrast, the connection between the posterior inferior parietal cortex and the frontal lobe was highly rightwardly asymmetric. Although further study is necessary to establish the functions of these pathways, we integrate our findings with previous evidence from functional neuroimaging and apraxia studies to suggest some possible functions.

Stone tools, language and the brain in human evolution

“…Indeed, this hemispheric 'division of labour' may be reflected anatomically in the greater global interconnectedness of the right hemisphere when compared with the more discrete, nodal organization of the left hemisphere [142]. This structural asymmetry appears to be shared with macaques [142], in keeping with the hypothesis that hemispheric specialization predates both language and tool use [143]; however, a recently reported rightward asymmetry of pathways connecting posterior inferior parietal cortex to frontal premotor cortex may reflect more specific human adaptations for toolmaking [58].…”

Functional mastery of percussive technology in nut-cracking and stone-flaking actions: experimental comparison and implications for the evolution of the human brain

“…; e.g. [95][96][97]), and those involved in the selection and effective use of a functional tool to solve a mechanical problem [98,99]. Thus, human tool use activates a fronto-parietal praxis network involved in hand manipulation skills, as well as regions of the cerebellum and the basal ganglia [95], while macaque tool use also activates several cortical areas (intraparietal cortex, presupplementary motor area, premotor cortex) as well as the cerebellum and the basal ganglia [100].…”

The First Appearance of Symmetry in the Human Lineage: Where Perception Meets Art

“…This is further supported by the fact that, in order to be able to use tools beyond which chimpanzees are capable, involving increased ability to shape materials with more structured strategies, skills are required that recruit the fronto-parietal circuit. The inferior parietal area may therefore represent a crucial point where the "what" and "where/how" as well as the mirror system intersect to enable the production and use of more complex tools, including those with greater symmetry, as part of a left lateralized system employing conceptually mediated abilities [66][67][68]. The interaction of such factors seems to have become particularly prominent during the late Acheulean that eventually led to the ability to intentionally direct the course of innovation in ways that increasingly benefitted those involved [69], which is obvious in the ability to produce more complex handaxes with twisted symmetry and the highly crafted javelin-like 400,000 year old wooden spears from Schoeningen [4,5].…”