Manual actions affect vocalizations of infants

Up right, not right up: Primacy of verticality in both language and movement

When describing motion along both the horizontal and vertical axes, languages from different families express the elements encoding verticality before those coding for horizontality (e.g., going up right instead of right up). In light of the motor grounding of language, the present study investigated whether the prevalence of verticality in Path expression also governs the trajectory of arm biological movements. Using a 3D virtual-reality setting, we tracked the kinematics of hand pointing movements in five spatial directions, two of which implied the vertical and horizontal vectors equally (i.e., up right +45° and bottom right −45°). Movement onset could be prompted by visual or auditory verbal cues, the latter being canonical in French (“en haut à droite”/up right) or not (“à droite en haut”/right up). In two experiments, analyses of the index finger kinematics revealed a significant effect of gravity, with earlier acceleration, velocity, and deceleration peaks for upward (+45°) than downward (−45°) movements, irrespective of the instructions. Remarkably, confirming the linguistic observations, we found that vertical kinematic parameters occurred earlier than horizontal ones for upward movements, both for visual and congruent verbal cues. Non-canonical verbal instructions significantly affected this temporal dynamic: for upward movements, the horizontal and vertical components temporally aligned, while they reversed for downward movements where the kinematics of the vertical axis was delayed with respect to that of the horizontal one. This temporal dynamic is so deeply anchored that non-canonical verbal instructions allowed for horizontality to precede verticality only for movements that do not fight against gravity. Altogether, our findings provide new insights into the embodiment of language by revealing that linguistic path may reflect the organization of biological movements, giving priority to the vertical axis.

Individual sensorimotor adaptation characteristics are independent across orofacial speech movements and limb reaching movements

Sensorimotor adaptation is critical for human motor control but shows considerable interindividual variability. Efforts are underway to identify factors accounting for individual differences in specific adaptation tasks. However, a fundamental question has remained unaddressed: Is an individual's capability for adaptation effector system specific or does it reflect a generalized adaptation ability? We therefore tested the same participants in analogous adaptation paradigms focusing on distinct sensorimotor systems: speaking with perturbed auditory feedback and reaching with perturbed visual feedback. Each task was completed once with the perturbation introduced gradually (ramped up over 60 trials) and, on a different day, once with the perturbation introduced suddenly. Consistent with studies of each system separately, visuomotor reach adaptation was more complete than auditory-motor speech adaptation (80% vs. 29% of the perturbation). Adaptation was not significantly correlated between the speech and reach tasks. Moreover, considered within tasks, 1) adaptation extent was correlated between the gradual and sudden conditions for reaching but not for speaking, 2) adaptation extent was correlated with additional measures of performance (e.g., trial duration, within-trial corrections) only for reaching and not for speaking, and 3) fitting individual participant adaptation profiles with exponential rather than linear functions offered a larger benefit [lower root mean square error (RMSE)] for the reach task than for the speech task. Combined, results suggest that the ability for sensorimotor adaptation relies on neural plasticity mechanisms that are effector system specific rather than generalized. This finding has important implications for ongoing efforts seeking to identify cognitive, behavioral, and neurochemical predictors of individual sensorimotor adaptation.NEW & NOTEWORTHY This study provides the first detailed demonstration that individual sensorimotor adaptation characteristics are independent across articulatory speech movements and limb reaching movements. Thus, individual sensorimotor learning abilities are effector system specific rather than generalized. Findings regarding one effector system do not necessarily apply to other systems, different underlying mechanisms may be involved, and implications for clinical rehabilitation or performance training also cannot be generalized.

The Sound of Grasp Affordances: Influence of Grasp-Related Size of Categorized Objects on Vocalization

Previous research shows that simultaneously executed grasp and vocalization responses are faster when the precision grip is performed with the vowel [i] and the power grip is performed with the vowel [ɑ]. Research also shows that observing an object that is graspable with a precision or power grip can activate the grip congruent with the object. Given the connection between vowel articulation and grasping, this study explores whether grasp-related size of observed objects can influence not only grasp responses but also vowel pronunciation. The participants had to categorize small and large objects into natural and manufactured categories by pronouncing the vowel [i] or [ɑ]. As predicted, [i] was produced faster when the object's grasp-related size was congruent with the precision grip while [ɑ] was produced faster when the size was congruent with the power grip (Experiment 1). The effect was not, however, observed when the participants were presented with large objects that are not typically grasped by the power grip (Experiment 2). This study demonstrates that vowel production is systematically influenced by grasp-related size of a viewed object, supporting the account that sensory-motor processes related to grasp planning and representing grasp-related properties of viewed objects interact with articulation processes. The paper discusses these findings in the context of size-sound symbolism, suggesting that mechanisms that transform size-grasp affordances into corresponding grasp- and articulation-related motor programs might provide a neural basis for size-sound phenomena that links small objects with closed-front vowels and large objects with open-back vowels.

Connection between movements of mouth and hand: Perspectives on development and evolution of speech

Mounting evidence shows interaction between manipulative hand movements and movements of tongue, lips and mouth in a vocal and non-vocal context. The current article reviews this evidence and discusses its contribution to perspectives of development and evolution of speech. In particular, the article aims to present novel insight on how processes controlling the two primary grasp components of manipulative hand movements, the precision and power grip, might be systematically connected to motor processes involved in producing certain articulatory gestures. This view assumes that due to these motor overlaps between grasping and articulation, development of these grip types in infancy can facilitate development of specific articulatory gestures. In addition, the hand-mouth connections might have even boosted the evolution of some articulatory gestures. This account also proposes that some semantic sound-symbolic pairings between a speech sound and a referent concept might be partially based on these hand-mouth interactions.

Does early object exploration support gesture and language development in extremely preterm infants and full-term infants?

BACKGROUND

An increasing body of research on typically and atypically developing infants has shown that motor skills play an important role in language development. To date, however, the role of specific object exploration skills for early gesture and vocabulary development has not been investigated in extremely low gestational age infants (ELGA, GA < 28 weeks), who are at greater risk for motor and language delays than full-term (FT) infants.

PURPOSE

This longitudinal study examined relations between 6-month active exploratory behaviors and 12- month word comprehension, gestures and vocal production, controlling for cognitive performance and neonatal condition (ELGA vs FT).

METHODS

Forty infants, 20 ELGA and 20 FT, and their mothers participated in the study. Mother-infant play interaction was video-recorded at 6 and 12 months. Oral and manual object exploration at 6 months and spontaneous gestures and vocal production at 12 months were coded. Word comprehension was evaluated with the Italian version of the MacArthur-Bates CDI parent questionnaire at 12 months. Cognitive performance was examined with the Griffiths Mental Developmental Scales at 6 months and the Bayley-III Scales at 12 months.

RESULTS

Regression analyses showed that after accounting for cognitive performance and neonatal condition, oral exploration was related to word comprehension, and manual exploration to gestures and vocal production in the overall sample.

CONCLUSIONS

Cascading effects of specific object exploration skills on gestures and language comprehension and production in preterm infants and FT infants are discussed. Clinical implications for early assessment of and interventions involving object exploration skills, which may affect language development, are considered for the preterm population.

Sensorimotor lateralization scaffolds cognitive specialization

In this chapter, we review hemispheric differences for sensorimotor function and cognitive abilities. Specifically, we examine the left-hemisphere specialization for visuomotor control and its interplay with language, executive function, and musical training. Similarly, we discuss right-hemisphere lateralization for haptic processing and its relationship to spatial and numerical processing. We propose that cerebral lateralization for sensorimotor functions served as a foundation for the development of higher cognitive abilities and their hemispheric functional specialization. We further suggest that sensorimotor and cognitive functions are inextricably linked. Based on the studies discussed in this chapter our view is that sensorimotor control serves as a loom upon which the fibers of language, executive function, spatial, and numerical processing are woven together to create the fabric of cognition.

What's left in language? Beyond the classical model

Until recently it was widely held that language, and its left-hemispheric representation in the brain, were uniquely human, emerging abruptly after the emergence of Homo sapiens. Changing views of language suggest that it was not a recent and sudden development in human evolution, but was adapted from dual-stream circuity long predating hominins, including a system in nonhuman primates specialized for intentional grasping. This system was gradually tailored for skilled manual operations (praxis) and communication. As processing requirements grew more demanding, the neural circuits were increasingly lateralized, with the left hemisphere assuming dominance, at least in the majority of individuals. The trend toward complexity and lateralization was probably accelerated in hominins when bipedalism freed the hands for more complex manufacture and tool use, and more expressive communication. The incorporation of facial and vocal gestures led to the emergence of speech as the dominant mode of language, although gestural communication may have led to generative language before speech became dominant. This scenario provides a more Darwinian perspective on language and its lateralization than has been commonly assumed.

The motor system contributes to comprehension of abstract language

If language comprehension requires a sensorimotor simulation, how can abstract language be comprehended? We show that preparation to respond in an upward or downward direction affects comprehension of the abstract quantifiers "more and more" and "less and less" as indexed by an N400-like component. Conversely, the semantic content of the sentence affects the motor potential measured immediately before the upward or downward action is initiated. We propose that this bidirectional link between motor system and language arises because the motor system implements forward models that predict the sensory consequences of actions. Because the same movement (e.g., raising the arm) can have multiple forward models for different contexts, the models can make different predictions depending on whether the arm is raised, for example, to place an object or raised as a threat. Thus, different linguistic contexts invoke different forward models, and the predictions constitute different understandings of the language.

The sound of one-hand clapping: handedness and perisylvian neural correlates of a communicative gesture in chimpanzees

Whether lateralization of communicative signalling in non-human primates might constitute prerequisites of hemispheric specialization for language is unclear. In the present study, we examined (i) hand preference for a communicative gesture (clapping in 94 captive chimpanzees from two research facilities) and (ii) the in vivo magnetic resonance imaging brain scans of 40 of these individuals. The preferred hand for clapping was defined as the one in the upper position when the two hands came together. Using computer manual tracing of regions of interest, we measured the neuroanatomical asymmetries for the homologues of key language areas, including the inferior frontal gyrus (IFG) and planum temporale (PT). When considering the entire sample, there was a predominance of right-handedness for clapping and the distribution of right- and left-handed individuals did not differ between the two facilities. The direction of hand preference (right- versus left-handed subjects) for clapping explained a significant portion of variability in asymmetries of the PT and IFG. The results are consistent with the view that gestural communication in the common ancestor may have been a precursor of language and its cerebral substrates in modern humans.

Face scanning distinguishes social from communication impairments in autism

How closely related are the social and communicative impairments in Autism Spectrum Disorder (ASD)? Recent findings in typically developing children suggest that both types of impairment are highly heritable but have only moderate behavioural and genetic overlap. So far, their respective roles in social perception are poorly understood. Here we show that when looking at other people's faces, children with ASD who are better at socio-emotional behaviours than non-verbal communication look more at the eyes, while those with the opposite profile look more at the mouth (Study 1). For the mouth area, a similar pattern was observed for inverted faces, suggesting that information from this area is perceived on a featural basis. In Study 2, we found that when shown a person performing manual actions, 'eye-lookers' from Study 1 tended to look most at the face of the actor, while 'mouth-lookers' from Study 1 tended to look at the action itself (hand/objects). This result was found in both ASD and typical development. In Study 3, the main finding in Study 1 was replicated in a new sample. Taken together, we interpret these results as supporting the view that the neural systems underlying socio-emotional versus non-verbal communication skills are separable, a finding that has important theoretical and clinical implications. The results also suggest that a similar differentiation of looking behaviour may operate in normal development.

Developing language in a developing body: the relationship between motor development and language development

ABSTRACTDuring the first eighteen months of life, infants acquire and refine a whole set of new motor skills that significantly change the ways in which the body moves in and interacts with the environment. In this review article, I argue that motor acquisitions provide infants with an opportunity to practice skills relevant to language acquisition before they are needed for that purpose; and that the emergence of new motor skills changes infants' experience with objects and people in ways that are relevant for both general communicative development and the acquisition of language. Implications of this perspective for current views of co-occurring language and motor impairments and for methodology in the field of child language research are also considered.

The observation of manual grasp actions affects the control of speech: a combined behavioral and Transcranial Magnetic Stimulation study

Does the mirror system affect the control of speech? This issue was addressed in behavioral and Transcranial Magnetic Stimulation (TMS) experiments. In behavioral experiment 1, participants pronounced the syllable /da/ while observing (1) a hand grasping large and small objects with power and precision grasps, respectively, (2) a foot interacting with large and small objects and (3) differently sized objects presented alone. Voice formant 1 was higher when observing power as compared to precision grasp, whereas it remained unaffected by observation of the different types of foot interaction and objects alone. In TMS experiment 2, we stimulated hand motor cortex, while participants observed the two types of grasp. Motor Evoked Potentials (MEPs) of hand muscles active during the two types of grasp were greater when observing power than precision grasp. In experiments 3-5, TMS was applied to tongue motor cortex of participants silently pronouncing the syllable /da/ and simultaneously observing power and precision grasps, pantomimes of the two types of grasps, and differently sized objects presented alone. Tongue MEPs were greater when observing power than precision grasp either executed or pantomimed. Finally, in TMS experiment 6, the observation of foot interaction with large and small objects did not modulate tongue MEPs. We hypothesized that grasp observation activated motor commands to the mouth as well as to the hand that were congruent with the hand kinematics implemented in the observed type of grasp. The commands to the mouth selectively affected postures of phonation organs and consequently basic features of phonological units.

Deictic word and gesture production: Their interaction

We examined whether and how deictic gestures and words influence each other when the content of the gesture was congruent or incongruent with that of the simultaneously produced word. Two experiments were carried out. In Experiment 1, the participants read aloud the deictic word 'QUA' ('here') or 'LA" ('there'), printed on a token placed near to or far from their body. Simultaneously, they pointed towards one's own body, when the token was placed near, or at a remote position, when the token was placed far. In this way, participants read 'QUA' ('here') and pointed towards themselves (congruent condition) or a remote position (incongruent condition); or they read 'LA" ('there') and pointed towards a remote position (congruent condition) or themselves (incongruent condition). In a control condition, in which a string of 'X' letters was printed on the token, the participants were silent and only pointed towards themselves (token placed near) or a remote position (token placed far). In Experiment 2, the participants read aloud the deictic word placed in the near or far position without gesturing. The results showed that the congruence/incongruence between the content of the deictic word and that of the gesture affected gesture kinematics and voice spectra. Indeed, the movement was faster in the congruent than in the control and incongruent conditions; and it was slower in the incongruent than in the control condition. As concerns voice spectra, formant 2 (F2) decreased in the incongruent conditions. The results suggest the existence of a bidirectional interaction between speech and gesture production systems.

When the hands speak

In the present review we will summarize evidence that the control of spoken language shares the same system involved in the control of arm gestures. Studies of primate premotor cortex discovered the existence of the so-called mirror system as well as of a system of double commands to hand and mouth. These systems may have evolved initially in the context of ingestion, and later formed a platform for combined manual and vocal communication. In humans, manual gestures are integrated with speech production, when they accompany speech. Lip kinematics and parameters of voice spectra during speech production are influenced by executing or observing transitive actions (i.e. guided by an object). Manual actions also play an important role in language acquisition in children, from the babbling stage onwards. Behavioural data reported here even show a reciprocal influence between words and symbolic gestures and studies employing neuroimaging and repetitive transcranial magnetic stimulation (rTMS) techniques suggest that the system governing both speech and gesture is located in Broca's area.