Do Postures of Distal Effectors Affect the Control of Actions of Other Distal Effectors? Evidence for a System of Interactions between Hand and Mouth

Maurizio Gentilucci,Giovanna Cristina Campione,Angela Sirigu

doi:10.1371/journal.pone.0019793

Maurizio Gentilucci, Giovanna Cristina Campione + Show 1 more

Open Access

https://doi.org/10.1371/journal.pone.0019793

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Journal: PloS one	Publication Date: May 23, 2011
Citations: 68	License type: CC BY 4.0

Affiliation: University of Parma, Italian Institute of Technology

Abstract

The present study aimed at determining whether, in healthy humans, postures assumed by distal effectors affect the control of the successive grasp executed with other distal effectors. In experiments 1 and 2, participants reached different objects with their head and grasped them with their mouth, after assuming different hand postures. The postures could be implicitly associated with interactions with large or small objects. The kinematics of lip shaping during grasp varied congruently with the hand posture, i.e. it was larger or smaller when it could be associated with the grasping of large or small objects, respectively. In experiments 3 and 4, participants reached and grasped different objects with their hand, after assuming the postures of mouth aperture or closure (experiment 3) and the postures of toe extension or flexion (experiment 4). The mouth postures affected the kinematics of finger shaping during grasp, that is larger finger shaping corresponded with opened mouth and smaller finger shaping with closed mouth. In contrast, the foot postures did not influence the hand grasp kinematics. Finally, in experiment 5 participants reached-grasped different objects with their hand while pronouncing opened and closed vowels, as verified by the analysis of their vocal spectra. Open and closed vowels induced larger and smaller finger shaping, respectively. In all experiments postures of the distal effectors induced no effect, or only unspecific effects on the kinematics of the reach proximal/axial component. The data from the present study support the hypothesis that there exists a system involved in establishing interactions between movements and postures of hand and mouth. This system might have been used to transfer a repertoire of hand gestures to mouth articulation postures during language evolution and, in modern humans, it may have evolved a system controlling the interactions existing between speech and gestures.

Highlights

Arm actions, and in particular the grasp of objects, are among the most refined activities of primates
In monkeys the circuit formed by the anterior part of the intraparietal sulcus (AIP) [1] and F5 premotor area [2] is involved in the control of grasp movements [3]
According to the idea that spoken language derives, at least partially, from a primitive communication system based on arm gestures [7,8,9,10,11,12,13,14,15,16], Gentilucci and colleagues [17,18,19] suggested that during evolution, a system derived from F5 premotor area, where neurons commanding grasps with both hand and mouth were recorded, could have been used to transfer the repertoire of hand gestures to mouth articulation postures

Summary

Introduction

In particular the grasp of objects, are among the most refined activities of primates. A system of double motor commands to hand and mouth may be involved in controlling the interactions existing between speech and gestures [20,21] and it may be located in Broca’s area [22]. This view seems to be congruent with the Rizzolatti and Arbib’s hypothesis [15]: these authors, on cytoarchitectonic and functional grounds, proposed that Broca’s area derives phylogenetically from F5 premotor area. Broca’s area, and in particular area BA44, is anatomically adjacent to premotor area and it is thought to be involved in encoding phonetic representations in terms of mouth articulation gestures [23,24,25]

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