Left-hand Advantage Research Articles

Right-left hand asymmetry in manual tracking: when poorer control is associated with better adaptation and interlimb transfer.

To date, interlimb transfer following visuomotor adaptation has been mainly investigated through discrete reaching movements. Here we explored this issue in the context of continuous manual tracking, a task in which the contribution of online feedback mechanisms is crucial, and in which there is a well-established right (dominant) hand advantage under baseline conditions. We had two objectives (1) to determine whether this preexisting hand asymmetry would persist under visuomotor rotation, (2) to examine interlimb transfer by assessing whether prior experience with the rotation by one hand benefit to the other hand. To address these, 44 right-handed participants were asked to move a joystick and to track a visual target following a rather unpredictable trajectory. Visuomotor adaptation was elicited by introducing a 90° rotation between the joystick motion and the cursor motion. Half of the participants adapted to the rotation first with the right hand, and then with the left, while the other half performed the opposite protocol. As expected during baseline trials, the left hand was less accurate while also exhibiting more variable and exploratory behavior. However, participants exhibited a left hand advantage during first exposure to the rotation. Moreover, interlimb transfer was observed albeit more strongly from the left to the right hand. We suggest that the less effective and more variable/exploratory control strategy of the left hand promoted its adaptation, which incidentally favored transfer from left to right hand. Altogether, this study speaks for further attention to the dominant/non-dominant asymmetry during baseline before examining interlimb transfer of adaptation.

Unilateral Spatial Neglect without Hemiplegia: The Output-Mode Effect Revisited

BackgroundThe occurrence of unilateral spatial neglect (USN) in non-hemiplegic right-hemisphere damaged patients is rare. Earlier studies of such patients revealed a significant advantage when typical neglect tests were performed by the patient's left hand as compared to the dominant right hand. The mechanism underlying this "output-mode effect" remains elusive. MethodsWe analyzed the temporal dynamics of this effect using line-bisection task in 9 non-hemiplegic stroke patients with left-USN. ResultsIn 4 patients tested shortly after stroke onset (≤ 6 weeks), the impact of hand laterality was variable (left-hand advantage in one patient; right-hand advantage in 2 patients; similar performance in both hands in one patient). Only later (> 6 weeks) a clear advantage of the left hand emerged in the majority of patients, similar to the earlier reports which were all based on late testing. ConclusionsWe found variable dynamics in the expression of the output-mode effect in the first weeks following stroke onset, which may reflect changes of inter-hemispheric balance, related to recovery processes. We propose that therapeutic interventions aiming to manipulate the inter-hemispheric balance (e.g., by non-invasive brain stimulation) take into account the existence of such dynamics and their highly variate nature.

Left-hand advantage and the right-sided selection hypothesis.

Left-hand advantage and the right-sided selection hypothesis.

Grammatical number elicits SNARC and MARC effects as a function of task demands.

Despite the robustness of the spatial-numerical association of response codes (SNARC) and linguistic markedness of response codes (MARC) effect, the mechanisms that underlie these effects are still under debate. In this paper, we investigate the extraction of quantity information from German number words and nouns inflected for singular and plural using two alternative forced choice paradigms. These paradigms are applied to different tasks to investigate how access to quantity representation is modulated by task demands. In Experiment 1, we replicated previous SNARC findings for number words-that is, a relative left-hand advantage for words denoting small numbers and a right-hand advantage for words denoting large numbers in semantic tasks (parity decision and quantity comparison). No SNARC effect was obtained for surface or lexical processing tasks (font categorization and lexical decision). In Experiment 2, we found that German words inflected for singular had a relative left-hand advantage, and German words inflected for plural a relative right-hand advantage, showing a SNARC-like effect for grammatical number. The effect interfered, however, with a MARC-like effect based on the markedness asymmetry of singulars and plurals. These two effects appear to be dissociated by response latency rather than task demands, with MARC being more pronounced in early responses and SNARC being more pronounced in late responses. The present findings shed light on the relationship of conceptual number and grammatical number and constrain current accounts of the SNARC and MARC effects.

Stimulus velocity effect in a complex interceptive task in right- and left-handers

This study investigated stimulus velocity effect on manual asymmetry during planning and execution of a complex coincidence-anticipation task. Left- and right-handers were required to press six buttons sequentially in conjunction with visual stimulus provided by a coincidence-anticipation device. Results showed that (1) stimulus velocity affected timing response and timing accuracy only for right-handers, who responded faster but less accurately in the fast stimulus velocity, (2) manual asymmetries for both handedness groups revealed a left-hand advantage for initiating the movement, and a preferred-hand advantage for movement time. The preferred-hand advantage in timing accuracy was only observed in the fast stimulus velocity. These findings are discussed in the framework of the hemispheric functional lateralisation.

Hemispheric specialisation in haptic processing

This study investigated the organising principles of touch. We examined specialisations within the haptic system and their hemispheric distribution. Haptic processing consists of the integration of data from multiple sources to form a single percept. Previous research provides strong support for a hierarchical and functional distribution within haptic processing. We investigated hemispheric asymmetry in haptic discrimination of objects with differing textures and centres of mass. By analogy with vision it was hypothesised that participants would demonstrate a left-hand advantage for centre of mass discrimination (a ‘global’, presumed right hemisphere, judgement) and a right-hand advantage for surface texture judgements (a ‘local’, presumed left hemisphere discrimination). We found that left-handed participants showed these effects to a lesser degree than did the right-handers, consistent with the notion that left-handed people generally show weaker asymmetries in bimanual tasks. In a second experiment the effect of conflicting information on haptic percept formation was investigated. Following from the previous hypotheses it was predicted that participants would be more accurate with their right hands at judging conflicting surfaces. Contrary to predictions an advantage was demonstrated for the left hand for texture discrimination and for the right hand for centre of mass judgement.

The processing of auditory and visual recognition of self-stimuli

This study examined self-recognition processing in both the auditory and visual modalities by determining how comparable hearing a recording of one's own voice was to seeing photograph of one's own face. We also investigated whether the simultaneous presentation of auditory and visual self-stimuli would either facilitate or inhibit self-identification. Ninety-one participants completed reaction-time tasks of self-recognition when presented with their own faces, own voices, and combinations of the two. Reaction time and errors made when responding with both the right and left hand were recorded to determine if there were lateralization effects on these tasks. Our findings showed that visual self-recognition for facial photographs appears to be superior to auditory self-recognition for voice recordings. Furthermore, a combined presentation of one's own face and voice appeared to inhibit rather than facilitate self-recognition and there was a left-hand advantage for reaction time on the combined-presentation tasks.

Motor Preparation of Manual Aiming at a Visual Target Manipulated in Size, Luminance Contrast, and Location

We conducted two experiments to investigate whether the motor preparation of manual aiming to a visual target is affected by either the physical characteristics (size or luminance contrast) or spatial characteristics (location) of the target. Reaction time (RT) of both finger lifting (ie stimulus-detection time) and manual aiming (ie movement-triggering time) to the onset of the target was measured. The difference of RT (DRT) between two tasks (ie the difference of task complexity) was examined to clarify the temporal characteristics of manual aiming per se during visuomotor integration. Results show classical characteristics: RT decreased as either the target size or luminance contrast increased. Furthermore, the task-complexity and target-location factors significantly interacted with each other, where the aiming RT was longer than the finger-lifting RT and the effects of target location on RT differed for each task. However, the task factor did not interact with either the size or luminance-contrast factor, implying that the motor preparation of manual aiming is associated with the spatial characteristics rather than the physical characteristics of the target. Inspection of DRT revealed that the time needed for motor preparation for an ipsilateral target was significantly shorter than that for a contralateral target. This was the case both for the left and for the right hand. Foveal targets required longer processing time, implying a disadvantageous function of motor preparation for the gazed target. The left-hand superiority for the target appearing in the left visual field was also observed. Such lateralised effect and left-hand advantage to the left visual field in manual aiming suggest that visuospatial information processing is activated during the preparation of aiming action, with faster processing in the right hemisphere.

Constant error in aiming movements without visual feedback is higher in the preferred hand

There is convincing evidence for a left hand advantage for the spatial planning of aiming movements in right-handers. However, little is known about equivalent proficiency in left-handers. Therefore, 48 participants (24 right-handers and 24 left-handers) performed aiming movements of the hand without visual feedback. While the variable aiming error tended to be lower for the preferred hand, the constant aiming error was consistently lower for the non-preferred hand. Data are consistent with the idea of a spatial accuracy advantage for the controller of the non-preferred hand. Data from an ambidextrous participant suggest that this functional difference might be innate rather than acquired through practice.

Interhemispheric connectivity and executive functioning in adults with Tourette syndrome.

The prefrontal cortex (PFC) is relatively smaller, and the corpus callosum (CC) larger, in adults with Tourette syndrome (TS). The authors explored the possible roles of the PFC and the CC in mediating interhemispheric interference and coordination in TS adults. They measured performance on M. Kinsbourne and J. Cook's (1971) verbal-manual interference task and on the bimanual Purdue Pegboard in 38 adults with TS and 34 healthy adults. Compared with controls, TS subjects were impaired on the bimanual Purdue Pegboard. On the dual task, right-hand performance did not differ between groups, but the normally expected left-hand advantage (opposite hemisphere condition) was absent in TS subjects. In the control group only, better left-hand performance accompanied larger PFC volumes but not CC cross-sectional area. PFC dysfunction might have precluded executive control of interference in the TS group.

Asymmetrical neural substrates of tactile discrimination in humans: a functional magnetic resonance imaging study.

The left-hand advantage seen during tactile discrimination tasks suggests hemispheric-processing asymmetry, although its neural substrates are not well known. We used functional magnetic resonance imaging to evaluate the laterality of the neural substrates involved in tactile discrimination in 19 normal volunteers. Passive tactile discrimination tasks, along with appropriate control tasks, were performed with both the right and left hands to evaluate the effects of the hand used and hemispheric effects (i.e., laterality of the activation pattern). Regardless of the hand used, the right dorsolateral prefrontal cortex, posterior parietal cortex, pre-supplementary motor area, and rostral portion of the dorsal premotor cortex (PMdr) were activated asymmetrically during tactile discrimination. This confirms the previous finding of a right-sided asymmetry for tactile shape discrimination. Hand effects were found in the left caudal portion of PMd (PMdc) adjacent to the central sulcus, which showed prominent activation during right-handed but not left-handed discrimination tasks. This asymmetric activation in the left PMdc might be related to the asymmetric interhemispheric interaction during right-handed tactile discrimination.

Aiming in adults: Sex and laterality effects

The purpose of the study was to twofold: to investigate gender‐related differences in the asymmetry of aiming with the preferred and non‐preferred hand in right‐handed adults, and to examine the effect of the spatial requirements of the task on these asymmetries. The hypothesis was that if cognitive functions are more asymmetrically localised in men than in women, one should observe greater left–right differences on some variables in men than in women. Eleven men and eleven women were required to aim fast and accurately at one of three possible targets under a choice reaction time protocol. Performance and kinematics data were analysed. Results revealed an effect of target location on the left hand advantage in reaction time, and gender‐related effects on movement time, accuracy, and on the velocity profiles. Overall, women performed more slowly and accurately than men. This gender‐related effect could not be accounted for by differential strategies with regard to speed or accuracy, lending support to the idea that differences exist in the neural mechanisms of movement control between the two genders. Finally, although the results show a hand effect on terminal accuracy in men only, they do not support the hypothesis of a greater asymmetry of movement control in men.

Cross-modal self-recognition: The role of visual, auditory, and olfactory primes

Three priming experiments were conducted to determine how information about the self from different sensory modalities/cognitive domains affects self-face recognition. Being exposed to your body odor, seeing your name, and hearing your name all facilitated self-face recognition in a reaction time task. No similar cross-modal facilitation was found among stimuli from familiar or novel individuals. The finding of a left-hand advantage for self-face recognition was replicated when no primes were presented. These data, along with other recent results suggest the brain processes/represents information about the self in highly integrated ways.

A left-hand advantage for self-description: the impact of schizotypal personality traits

Consistent with the possibility that the right hemisphere is responsible for processing information about the self, subjects responded faster with their left hand to adjectives that were self-descriptive. However, those who scored high on the Schizotypal Personality Questionnaire (SPQ) did not show a left-hand advantage. These data add to a growing body of evidence that implicates the right hemisphere in processing information about the self and supports the hypothesis that self-processing may be impaired in schizophrenic-like populations.

Orienting visuospatial attention generates manual reaction time asymmetries in target detection and pointing

Right-handers exhibit a left hand advantage in response preparation when pointing to targets. These manual asymmetries are generally attributed to a right hemisphere specialization for spatial processing. More precisely, the left hand reaction time (RT) advantage was recently supposed to reflect specifically the right hemisphere superiority for movement planning. This study proposes to investigate a possible attentional origin for manual RT asymmetries. In a first experiment, we used the covert orienting of attention paradigm to measure subjects' RTs when reaching at targets (pointing task) both in valid, neutral and invalid conditions, either in the left or in the right visual fields and with the left and the right hand. In a second experiment, we applied the same paradigm to a detection task (key-pressing). Results revealed that orienting of attention to spatial locations was more time consuming when responding with the right than with the left hand, whether movement planning was required or not. It is suggested that the right hemisphere dominance for orienting of visuospatial attention account, partly at least, for the RT asymmetries classically observed in manual aiming.

Motor Control of the Hands: The Effect of Familial Sinistrality

Left-and right-handed subjects, selected on the basis of degree of hand preference and for the presence or absence of familial sinistrality, responded to monaurally presented tonal stimuli (440 Hz note played on four different instruments) using their right and left hands on separate occasions. It was found that in both the strong left-handers and the inconsistent strong right-handers, motor control of the hands was related to familial sinistrality (FS). Specifically, strong left-handers and inconsistent strong right-handers with FS have a difference in the motor control of the hands in the left hemisphere, with a left hemisphere-left hand advantage. Strong left-handers and inconsistent strong righthanders with no FS have a difference in the motor control of the hands in the right hemisphere, with a right hemisphere-left hand advantage.

Manual laterality in haptic and visual reaching tasks by tufted capuchin monkeys ( Cebus apella). An association between hand preference and hand accuracy for food discrimination

Manual laterality was examined in 26 tufted capuchins ( Cebus apella) in three tasks differing in their sensorimotor demands and the availability of visual cues. The Haptic discrimination task required the monkeys to discriminate haptically between two pumpkin seeds and two tinfoil items stuck into a tray inside an opaque box. The other two tasks required the monkeys to reach for two pumpkin seeds stuck into the tray within a transparent box with vision (Visually guided reaching task) or without vision (Visual-Tactual reaching task) during reaching. A significant group-level left hand bias was found for food retrieval in both the Haptic discrimination and Visual-Tactual tasks, and a significant group-level right hand bias in the Visually guided reaching task. The strength of hand preferences did not differ among the tasks. It was found that the accuracy of food recognition in the Haptic discrimination task was greater for the left than the right hand. The results suggest that the differences in the manipulo-spatial requirements of the tasks and in the availability of visual cues can variously affect manual laterality in capuchins. The left-hand preferences for the Haptic discrimination and Visual-Tactual tasks as well as the left-hand advantage for food discrimination may reflect a greater involvement of the right hemisphere in processing haptic information.

Left hand advantage in a self-face recognition task

Subjects were exposed to pictures of self and others (e.g., friend, stranger, and famous people) to determine if there was an advantage in reaction time and accuracy in identifying the self. It was found that upright and inverted self-faces were identified more rapidly than non-self faces when subjects responded with their left hand, which in other tasks has corresponded with contralateral hemispheric dominance. These data suggest that self-recognition may be correlated with neural activity in the right hemisphere, and that the differences observed may not be unique to self-face recognition. These results are in agreement with previous research indicating that self-directed awareness is correlated with right prefrontal activity.

One hand is better than two: motor extinction of left hand advantage in unilateral neglect

One hand is better than two: motor extinction of left hand advantage in unilateral neglect

Continuity in tactual-visual cross-modal transfer: infancy to 11 years.

The present study demonstrated that individual differences in cross-modal transfer showed continuity over a 10-year span. Tactual-visual tasks, requiring visual recognition of shapes that had previously been felt but not seen, were given to full-term and preterm children at 2 ages, 1 and 11 years. Cross-modal performance showed a left-hand advantage at 11 years and, for both groups, cross-age correlations were significant when tactual exploration at 11 years was done with the left hand (r = .34-.36). The continuity showed some specificity in that the infant measure did not relate to other types of cross-modal performance at 11 years and was not dependent on aspects of spatial ability involving form perception. This continuity accounted for most of the previously reported relation of infant cross-modal ability to 11-year IQ.