Science - USA (2021-11-12)

RESEARCH ARTICLE SUMMARY

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NEUROSCIENCE

Tool use and language share syntactic processes

and neural patterns in the basal ganglia

Simon Thibault, Raphaël Py, Angelo Mattia Gervasi, Romeo Salemme, Eric Koun, Martin Lövden,
Véronique Boulenger†, Alice C. Roy†, Claudio Brozzoli†

INTRODUCTION:Tool use is a hallmark of hu-
man evolution. Beyond its sensorimotor com-
ponents, the complexity of which has been
extensively investigated, tool use affects cog-
nition from a different perspective. Indeed, tool
use requires integrating an external object
as a body part and embedding its functional
structure in the motor program. This adds a
hierarchical level into the motor plan of man-
ual actions, subtly modifying the relationship
between interdependent subcomponents. Em-
bedded structures also exist in language, and
syntax is the cognitive function handling these
linguistic hierarchies. One example is center-
embedded object-relative clauses:“The poet
[that the scientist admires]reads the paper.”
Accordingly, researchers have advanced a role
forsyntaxinactionandtheexistenceofsim-

ilarities between the processes underlying tool

use and language, so that shared neural re-

sources for a common cognitive function could

be at stake.

RATIONALE:We first tested the existence of

shared neural substrates for tool use and syn-

tax in language. Second, we tested the pre-

diction that training one ability should affect

performance in the other. In a first experi-

ment, we measured participants’brain activity

with functional magnetic resonance imaging

during tool use or, as a control, manual ac-

tions. In separate runs, the same participants

performed a linguistic task on complex syn-

tactic structures. We looked for common ac-

tivations between tool use and the linguistic

task, predicting similar patterns of activity if

they rely on common neural resources. In fur-

ther behavioral experiments, we tested wheth-

er motor training with the tool selectively

improves syntactic performance in language

and if syntactic training in language, in turn,

selectively improves motor performance with

the tool.

RESULTS:Tool-use planning and complex syn-

tax processing (i.e., object relatives) elicited

neural activity anatomically colocalized within

the basal ganglia. A control experiment ruled

out verbal working memory and manual (i.e.,

without a tool) control processes as an under-

lying component of this overlap. Multivariate

analyses revealed similar spatial distributions

of neural patterns prompted by tool-use plan-

ning and object-relative processing. This agrees

with the recruitment of the same neural re-

sources by both abilities and with the exis-

tence of a supramodal syntactic function. The

shared neurofunctional resources were more-

over reflected behaviorally by cross-domain

learning transfer. Indeed, tool-use training

significantly improved linguistic performance

with complex syntactic structures. No learning

transfer was observed on language syntactic

abilities if participants trained without the

tool. The reverse was also true: Syntactic train-

ing with complex sentences improved motor

performance with the tool more than motor

performance in a task without the tool and

matched for sensorimotor difficulty. No learn-

ing transfer was observed on tool use if par-

ticipants trained with simpler syntactic

structures in language.

CONCLUSION:These findings reveal the exis-

tence of a supramodal syntactic function that

is shared between language and motor pro-

cesses. As a consequence, training tool-use

abilities improves linguistic syntax and, recip-

rocally, training linguistic syntax abilities im-

proves tool use. The neural mechanisms allowing

for boosting performance in one domain by

training syntax in the other may involve priming

processes through preactivation of common

neural resources, as well as short-term plastic-

ity within the shared network. Our findings

point to the basal ganglia as the neural site of

supramodal syntax that handles embedded

structures in either domain and also support

longstanding theories of the coevolution of

tool use and language in humans.▪

RESEARCH

SCIENCEscience.org 12 NOVEMBER 2021•VOL 374 ISSUE 6569 841

The list of author affiliations is available in the full article online.

*Corresponding author. Email: [email protected]

(S.T.); [email protected] (C.B.)

These authors contributed equally to this work.

Cite this article as S. Thibaultet al.,Science 374 , eabe0874

(2021). DOI: 10.1126/science.abe0874

READ THE FULL ARTICLE AT

https://doi.org/10.1126/science.abe0874

Learning transfer

Tool use Linguistic syntax

Tool use performance Linguistic performance

Pre

Post

Pre

Post

Training Training

The writer that the

poet admires

writes the paper

The writer that the

writes the paperpoet admires

Similar neural patterns

Tool use and language share syntactic processes.Functional magnetic resonance imaging revealed that tool use
and syntax in language elicit similar patterns of brain activation within the basal ganglia. This indicates common neural
resources for the two abilities. Indeed, learning transfer occurs across the two domains: Tool-use motor training improves
syntactic processing in language and, reciprocally, linguistic training with syntactic structures improves tool use.