Causal evidence for a shared mechanism linking language and tool use via the putamen

Both human language and tool use--two hallmark capacities of human cognition--depend on organizing discrete elements, i.e., symbols and actions, into highly constrained structured sequences to achieve a functional goal. However, the neural mechanism linking these capacities is unclear. We combined brain lesion analysis, developmental contrast, and functional neuroimaging to test whether the basal ganglia play a causal role in their shared capacity. In 100 adults with focal brain injury, damage to the putamen disrupted both sentence processing and tool use, with impairments specifically explained by reduced goal-dependent sequence integrity for both tasks. Further comparing populations with typical and deprived early language experience (congenitally deaf adults with vs. without early sign language exposure), we found that early language acquisition was associated with improved tool-use performance and strengthened putaminal responses to such goal dependency, which mediated the relationship between sentence sequence integrity and tool behavior. Together, these results identify the putamen as a key neural substrate supporting goal-dependent sequence integrity across language and action, and show how early language experience shapes this conserved control system. One-Sentence SummaryLanguage and tool use share a putamen-based mechanism that supports goal-dependent sequence integrity, and this mechanism is strengthened by early language experience.