Children’s bilateral advantage for grasp-to-eat actions becomes unimanual by age 10years

On the Neurocircuitry of Grasping: The influence of action intent on kinematic asymmetries in reach-to-grasp actions

Evidence from electrophysiology suggests that nonhuman primates produce reach-to-grasp movements based on their functional end goal rather than on the biomechanical requirements of the movement. However, the invasiveness of direct-electrical stimulation and single-neuron recording largely precludes analogous investigations in humans. In this review, we present behavioural evidence in the form of kinematic analyses suggesting that the cortical circuits responsible for reach-to-grasp actions in humans are organized in a similar fashion. Grasp-to-eat movements are produced with significantly smaller and more precise maximum grip apertures (MGAs) than are grasp-to-place movements directed toward the same objects, despite near identical mechanical requirements of the two subsequent (i.e., grasp-to-eat and grasp-to-place) movements. Furthermore, the fact that this distinction is limited to right-handed movements suggests that the system governing reach-to-grasp movements is asymmetric. We contend that this asymmetry may be responsible, at least in part, for the preponderance of right-hand dominance among the global population.

The left cerebral hemisphere may be dominant for the control of bimanual symmetric reach-to-grasp movements

Previous research has established that the left cerebral hemisphere is dominant for the control of continuous bimanual movements. The lateralisation of motor control for discrete bimanual movements, in contrast, is underexplored. The purpose of the current study was to investigate which (if either) hemisphere is dominant for discrete bimanual movements. Twenty-one participants made bimanual reach-to-grasp movements towards pieces of candy. Participants grasped the candy to either place it in their mouths (grasp-to-eat) or in a receptacle near their mouths (grasp-to-place). Research has shown smaller maximum grip apertures (MGAs) for unimanual grasp-to-eat movements than unimanual grasp-to-place movements when controlled by the left hemisphere. In Experiment 1, participants made bimanual symmetric movements where both hands made grasp-to-eat or grasp-to-place movements. We hypothesised that a left hemisphere dominance for bimanual movements would cause smaller MGAs in both hands during bimanual grasp-to-eat movements compared to those in bimanual grasp-to-place movements. The results revealed that MGAs were indeed smaller for bimanual grasp-to-eat movements than grasp-to-place movements. This supports that the left hemisphere may be dominant for the control of bimanual symmetric movements, which agrees with studies on continuous bimanual movements. In Experiment 2, participants made bimanual asymmetric movements where one hand made a grasp-to-eat movement while the other hand made a grasp-to-place movement. The results failed to support the potential predictions of left hemisphere dominance, right hemisphere dominance, or contralateral control.

Hear speech, change your reach: changes in the left-hand grasp-to-eat action during speech processing

Research has shown that the kinematic characteristics of right-hand movements change when executed during both speech production and processing. Despite the variety of prehension and manual actions used to examine this relationship, the literature has yet to examine potential movement effects using an action with a distinct kinematic signature: the hand-to-mouth (grasp-to-eat) action. In this study, participants performed grasp-to-eat and grasp-to-place actions in (a) a quiet environment and (b) while processing speech. Results during the quiet condition replicated the previous findings; consistently smaller grasp-to-eat (compared to grasp-to-place), maximum grip apertures appeared only when using the right hand. Interestingly, in the listen condition, smaller maximum grip apertures in the grasp-to-eat movement appeared in both the right and left hands, despite the fact that participants were right-handed. This paper addresses these results in relation with similar behaviour observed in children, and discusses implications for functional lateralization and neural organization.

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.

Wait wait, don't tell me: Handedness questionnaires do not predict hand preference for grasping

Handedness questionnaires are a common screening tool in psychology and neuroscience, used whenever a participant's performance on a given task may conceivably be affected by their laterality. Two widely-used examples of such questionnaires are the Edinburgh Handedness Inventory and the Waterloo Handedness Questionnaire. Both instruments ask respondents to report their hand preference for performing a variety of common tasks (e.g., throwing a ball, or opening a drawer). Here we combined questions from the two instruments (E-WHQ; 22 questions total) and asked participants to report their preferred hand for each via a five-point scale. The purpose of this study was to determine whether responses on the E-WHQ are accurate, reliable, and/or predictive of hand-preference for a simple grasp-to-construct task. Regarding accuracy, handedness scores were 5% lower when participants used a scrambled response key versus a consistent one. Test-retest reliability of the questionnaire was weak, with any given inventory item eliciting a different response from 34% of respondents upon retesting. Neither was the E-WHQ predictively useful-although both left- and right-handers preferred their dominant hands, E-WHQ score did not correlate with overall percentage of dominant-hand grasps in either group. We conclude that the E-WHQ is unsuited for predicting hand preference for grasping.

Impact of Handedness Consistency on Bimanual and Unimanual Continuous Movements

Bimanual coordination is an essential human function requiring efficient interhemispheric communication to produce coordinated movements. Previous research suggests a "bimanual advantage" phenomenon, where completing synchronized bimanual tasks results in less variability than unimanual tasks. Additionally, of hand dominance has been shown to influence coordinated performance. The present study examined the bimanual advantage in individuals with consistent and inconsistent handedness. It was predicted that participants with consistent handedness would not display a bimanual advantage unlike those with inconsistent handedness. Fifty-six young adults completed a finger-tapping paradigm in five conditions: unimanual tapping with either left or right hand, in-phase bimanual tapping, and out-of phase bimanual tapping led by either left or right hand. Results were not consistent with the hypothesis that participants with consistent handedness displayed the "bimanual advantage". However, the "bimanual advantage" was not evident for the inconsistent handers when the temporal consistency was measured with either the left or right hand only. Overall, the "bimanual advantage" may be dependent upon consistency of hand preference, as well as the direction of hand dominance.

Handedness and Reach-to-Place Kinematics in Adults: Left-Handers Are Not Reversed Right-Handers

The primary goal of this study was to examine the relations between limb control and handedness in adults. Participants were categorized as left or right handed for analyses using the Edinburgh Handedness Inventory. Three-dimensional recordings were made of each arm on two reach-to-place tasks: adults reached to a ball and placed it into the opening of a toy (fitting task), or reached to a Cheerio inside a cup, which they placed on a designated mark after each trial (cup task). We hypothesized that limb control and handedness were related, and we predicted that we would observe side differences favoring the dominant limb based on the dynamic dominance hypothesis of motor lateralization. Specifically, we predicted that the dominant limb would be straighter and smoother on both tasks compared with the nondominant limb (i.e., right arm in right-handers and left arm in left-handers). Our results only partially supported these predictions for right-handers, but not for left-handers. When differences between hands were observed, the right hand was favored regardless of handedness group. Our findings suggest that left-handers are not reversed right-handers when compared on interlimb kinematics for reach-to-place tasks, and reaffirm that task selection is critical when evaluating manual asymmetries.