Functional plasticity of sensorimotor representations following short-term immobilization of the dominant versus non-dominant hands

The main purpose of the present study was to investigate the functional plasticity of sensorimotor representations for dominant versus non-dominant hands following short-term upper-limb sensorimotor deprivation. All participants were right-handed. A splint was placed either on the right hand or on the left hand of the participants during a brief period of 48 h and was used for the input/output signal restrictions. The participants were divided into 3 groups: right hand immobilization, left hand immobilization and control (without immobilization). The immobilized participants performed the hand laterality task before (pre-test) and immediately after (post-test) splint removal. The pre-/post-test procedure was similar for the control group. The main results showed a significant response time improvement when judging the laterality of hand stimuli in the control group. In contrast, the results showed a weaker response time improvement for the left-hand immobilization group and no significant improvement for the right-hand immobilization group. Overall, these results revealed that immobilization-induced effects were lower for the non-dominant hand and also suggested that 48 h of upper-limb immobilization led to an inter-limb transfer phenomenon regardless of the immobilized hand. The immobilization-induced effects were highlighted by the slowdown of the sensorimotor processes related to manual actions, probably due to an alteration in a general cognitive representation of hand movements.     

A functional role for the motor system in language understanding: evidence from theta-burst transcranial magnetic stimulation

Does language comprehension depend, in part, on neural systems for action? In previous studies, motor areas of the brain were activated when people read or listened to action verbs, but it remains unclear whether such activation is functionally relevant for comprehension. In the experiments reported here, we used off-line theta-burst transcranial magnetic stimulation to investigate whether a causal relationship exists between activity in premotor cortex and action-language understanding. Right-handed participants completed a lexical decision task, in which they read verbs describing manual actions typically performed with the dominant hand (e.g., "to throw," "to write") and verbs describing nonmanual actions (e.g., "to earn," "to wander"). Responses to manual-action verbs (but not to nonmanual-action verbs) were faster after stimulation of the hand area in left premotor cortex than after stimulation of the hand area in right premotor cortex. These results suggest that premotor cortex has a functional role in action-language understanding.     

“右好左坏”和“左好右坏”——利手与左右空间情感效价的关联性

人们会将“右”和“左”与积极或消极的事物相关联,这称为左右空间的情感效价.以具身认知理论和躯体特异性假设为基础的研究发现,右利手会将右侧空间与积极事物相关联,而左利手则会将左侧空间与积极事物相关连;左右空间情感效价是由利手与非利手的运动经验塑造的;利手与非利手运动经验的改变则会反转左右空间情感效价;趋近动机脑功能偏侧化与利手是一致的.未来的研究应进一步澄清利手运动与趋近动机在神经机制上的关联性,并探索文化因素与身体经验如何共同塑造左右空间情感效价.     

The GROOP effect: groups mimic group actions

Research on perception–action links has focused on an interpersonal level, demonstrating effects of observing individual actions on performance. The present study investigated perception–action matching at an inter-group level. Pairs of participants responded to hand movements that were performed by two individuals who used one hand each or they responded to hand movements performed by an individual who used both hands. Apart from the difference in the number of observed agents, the observed hand movements were identical. If co-actors form action plans that specify the actions to be performed jointly, then participants should have a stronger tendency to mimic group actions than individual actions. Confirming this prediction, the results showed larger mimicry effects when groups responded to group actions than when groups responded to otherwise identical individual actions. This suggests that representations of joint tasks modulate automatic perception–action links and facilitate mimicry at an inter-group level.     

Hand dominance, attention, and the choice between responses

Thirty pairs of matched right- and left-handed subjects carried out a serial C.RT task involving reaches between 2.4 cm square contact grids set at 2.4 cm intervals in a horizontal line. In one condition they responded with the right hand alone, in a second with the left and in a third they had to choose between hands on each trial responding to left side grids with the left hand and to right side grids with the right.

All subjects took longer to respond when they had to choose between hands than when they used either hand alone. In the one-hand conditions neither group showed any effect of hand dominance. When choices had to be made between hands both groups responded faster with their dominant than with their nondominant hands.

Analysis of the results was undertaken in terms of two hypothetical systems of instructions which might control machines designed to carry out similar tasks. It is concluded that in some tasks hand dominance can be described in terms of an attentional bias towards the field of operation of one effector rather than another. In the present task the effects of such possible attentional biases were shown not to interact with other effects, such as the facilitation of successive responses by repeated use of the same limb. These latter effects seem to depend on processes underlying execution of responses rather than choices between responding limbs.     

Handedness in a virtual haptic environment: Assessments from kinematic behavior and modeling

This study evaluated hand asymmetries in performance of a dexterous, controlled task under haptic feedback. Participants punctured a virtual membrane with a pushing or pulling movement, using the left or right hand. For pulling movements, the dominant (right) hand exhibited faster average stopping latency and shorter skidding distance. When the kinematic data were fit to a three-phase model previously applied to this task (Klatzky et al., 2013), the right hand exhibited faster force decay attributable to biomechanical factors. Analyses of the aggregated performance measures and model parameters showed that the left and right hands are associated with two different distributions, supporting handedness effects. Furthermore, while the majority of participants expressed right-hand dominance, which was consistent with their self-reported hand preferences, others showed partial or no dominance. This approach could potentially be extended to quantify and differentiate individuals with difficulties in manual behavior due to abnormal motor control (e.g., dyspraxia), progressive deterioration (e.g., Parkinson's syndrome) or improvement (neural regrowth after transplant).     

The handedness of imagined bodies in action and the role of perspective taking

Past research at the nexus of motor control and perception investigated the role of perspective taking in many behavioral and neuroimaging studies. Some investigators addressed the issue of one's own vs. others' action imagination, but the possible effects of a front or a back view in imagining others' actions have so far been neglected. We report two 'single trial' experiments in which a total of 640 participants were asked to imagine a person performing a manual action - either in a front or in a back view - and then to indicate the hand used by the imagined person during movement execution. In such a task, we assume the existence of two distinct biases: a perceptual-mnemonic bias due to subjects' visual experience of others' actions, encouraging them to imagine right-handed movements, and a motor bias due to subjects' experience of self-made actions, encouraging them to imagine movements performed with the same hand as their dominant hand. We hypothesized that a greater involvement of motor representations in the back view compared to the front view could result in an increased correspondence between one's own manual preference and the hand used by the imagined agent in the former condition. The results of both experiments were consistent with this hypothesis, suggesting that while imagining others' actions we employ motor simulations in different degrees according to the perspective adopted.     

身体形式和社会环境对SNARC效应的影响:基于具身认知观的理解

目前SNARC效应在认知心理学领域得到了广泛研究,然而较少有研究考察身体形式和社会环境对SNARC效应的影响.研究以127名在校大学生为被试,使用奇偶判断任务、Go/No-go任务以及合作情境下的Go/No-go任务依次展开了三个研究,拟揭示身体形式和社会环境对SNARC效应的影响.实验一要求被试双手完成奇偶判断任务,结果出现了经典的SNARC效应.实验二要求被试完成Go/No-go任务,并让被试单手(左手或右手)对奇数或偶数进行反应,结果SNARC效应没有出现,这表明认知主体的身体形式对SNARC效应产生了影响.实验三要求被试合作完成Go/No-go任务,该实验按照被试所坐的位置(左边和右边)和反应手(左手和右手),设计了四个条件,结果只有身体位置和反应手完全一致时出现了 SNARC 效应.以上结果一方面表明了具身认知观的合理性,另外一方面扩展了以往对SNARC效应本质的理解.     

Keep your hands crossed: The valence-by-left/right interaction is related to hand,not side,in an incongruent hand–response key assignment

The body-specificity hypothesis (Casasanto, 2009) associates positive emotional valence and the space surrounding the dominant hand, and negative valence and the space surrounding the non-dominant hand. This effect has not only been found for manual responses, but also for the left and right side. In the present study, we investigated whether this compatibility effect still shows when hand and side carry incongruent information, and whether it is then related to hand or to side. We conducted two experiments which used an incongruent hand–response key assignment, that is, participants had their hands crossed. Participants were instructed to respond with their right vs. left hand (Experiment 1) or with the right vs. left key (Experiment 2). In both experiments, a compatibility effect related to hand emerged, indicating that the association between hand and valence overrides the one between side and valence when hand and side carry contradicting information.     

The influence of task instruction on action coding: constraint setting or direct coding?

In 3 experiments, the authors manipulated response instructions for 2 concurrently performed tasks. Specifically, the authors' instructions described left and right keypresses on a manual task either as left versus right or as blue versus green keypresses and required either "left" versus "right" or "blue" versus "green" concurrent verbalizations. When instructions for responses on the 2 tasks were in terms of location (Experiment 1) or color (Experiments 2a and 2b), then compatible responses on the tasks were faster than incompatible responses. However, when the verbal task required "left" versus "right" responses but instructions for manual keypresses referred to blue versus green (Experiments 3a and 3b), then no response compatibility effects were observed. These results suggest that response labels used in the instruction directly determine the codes that are used to control responding.     

Lateralisation of emotions: evidence from pupil size measurement

The way our brain processes emotional stimuli has been studied intensively. One of the main issues still under debate is the laterality of valence processing. Herein, we employed the fact that pupil size increases under conditions of higher mental effort and during emotional processing, in order to contrast three proposed hypotheses in the field. We used different manual response mapping for emotional stimuli: Participants responded with their right hand for positive and with their left hand for negative facial expressions, or vice versa. The hands position was either regular (Experiment 1) or crossed (Experiment 2) in order to rule out a “spatial-valence association” alternate explanation. A third experiment was conducted by employing a passive viewing procedure of peripheral emotional stimuli. In the first two experiments, pupil size was larger when participants responded to positive stimuli with their left hand and to negative with their right hand, compared with the opposite mapping. Results of Experiment 3 strengthen the findings of Experiments 1 and 2. These findings provide significant psychophysiological evidence for the valence hypothesis: Processing positive stimuli involves the left hemisphere, while processing negative stimuli involves the right hemisphere. These results are discussed in relation to contemporary theories of emotion processing.     

Manual asymmetries in the preparation and control of goal-directed movements

The primary purpose of this experiment was to determine if left hand reaction time advantages in manual aiming result from a right hemisphere attentional advantage or an early right hemisphere role in movement preparation. Right-handed participants were required to either make rapid goal-directed movements to small targets or simply lift their hand upon target illumination. The amount of advance information about the target for a particular trial was manipulated by precuing a subset of potential targets prior to the reaction time interval. When participants were required to make aiming movements to targets in left space, the left hand enjoyed a reaction advantage that was not present for aiming in right space or simple finger lifts. This advantage was independent of the amount or type of advance information provided by the precue. This finding supports the movement planning hypothesis. With respect to movement execution, participants completed their aiming movements more quickly when aiming with their right hand, particularly in right space. This right hand advantage in right space was due to the time required to decelerate the movement and to make feedback-based adjustments late in the movement trajectory.     

自我概念威胁以及与重要他人的比较共同削弱自我面孔优势效应

内隐积极联想理论(implicit positive association, IPA)认为自我面孔识别以及与之伴随的自我意识激发了自我概念的积极属性, 促进了对自我面孔的识别优势, 因此通过自我概念威胁可以削弱自我面孔识别的优势效应。本研究旨在探讨自我概念威胁以及与重要他人的比较对自我面孔优势效应的共同影响。实验一为自我-朋友对比实验, 10对同性好友(20名被试)在接受完自我概念威胁启动或者非威胁性启动后对自我面孔和朋友面孔进行朝向的判断, 结果发现非威胁性启动后, 自我面孔的优势效应依然存在, 而在自我概念威胁启动后, 自我面孔优势效应消失。实验二为自我-陌生人对比实验, 另外20名被试在接受完自我概念威胁启动或者非威胁性启动后, 对自我面孔和陌生人面孔进行朝向的判断, 结果发现, 无论是自我概念威胁启动还是非威胁性启动后, 自我面孔识别优势效应都依然存在。两个实验的结果均主要体现在用左手进行反应的时候。结果表明：自我概念威胁以及与重要他人的比较共同削弱自我面孔优势效应; 而左手效应的发生似乎表明了大脑右半球对自我面孔识别的主导和调节作用。     

Bimanual reaching across the hemispace: Which hand is yoked to which?

When both hands perform concurrent goal-directed reaches, they become yoked to one another. To investigate the direction of this coupling (i.e., which hand is yoked to which), the temporal dynamics of bimanual reaches were compared with equivalent-amplitude unimanual reaches. These reaches were to target pairs located on either the left or right sides of space; meaning that in the bimanual condition, one hand's contralateral (more difficult) reach accompanied by the other hand's ipsilateral (easier) reach. By comparing which hand's difficult reach was improved more by the presence of the other hand's easier ipsilateral reach, we were able to demonstrate asymmetries in the coupling. When the cost of bimanual reaching was controlled for the contralateral reaching left hand's performance was improved, suggesting that the left hand is yoked to the right during motor output. In contrast, the right hand showed the greatest improvements for contralateral reaching in terms of reaction time, pointing toward a dominant role for the left hand in the processes prior to movement onset. The results may point toward a mechanism for integrating the unitary system of attention with bimanual coordination.     

Holding a manual response sequence in memory can disrupt vocal responses that share semantic features with the manual response

Holding an action plan in memory for later execution can delay execution of another action if the actions share a similar (compatible) feature. This compatibility interference (CI) occurs for actions that share the same response modality (e.g., manual response). We investigated whether CI can generalize to actions that utilize different response modalities (manual and vocal). In three experiments, participants planned and withheld a sequence of key-presses with the left- or right-hand based on the visual identity of the first stimulus, and then immediately executed a speeded, vocal response (‘left’ or ‘right’) to a second visual stimulus. The vocal response was based on discriminating stimulus color (Experiment 1), reading a written word (Experiment 2), or reporting the antonym of a written word (Experiment 3). Results showed that CI occurred when the manual response hand (e.g., left) was compatible with the identity of the vocal response (e.g., ‘left’) in Experiment 1 and 3, but not in Experiment 2. This suggests that partial overlap of semantic codes is sufficient to obtain CI unless the intervening action can be accessed automatically (Experiment 2). These findings are consistent with the code occupation hypothesis and the general framework of the theory of event coding (Behav Brain Sci 24:849–878, 2001a; Behav Brain Sci 24:910–937, 2001b).     

Judgment of other people's facial expressions of emotions is influenced by their concurrent affective hand movements

We investigated whether emotional information from facial expression and hand movement quality was integrated when identifying the expression of a compound stimulus showing a static facial expression combined with emotionally expressive dynamic manual actions. The emotions (happiness, neutrality, and anger) expressed by the face and hands were either congruent or incongruent. In Experiment 1, the participants judged whether the stimulus person was happy, neutral, or angry. Judgments were mainly based on the facial expressions, but were affected by manual expressions to some extent. In Experiment 2, the participants were instructed to base their judgment on the facial expression only. An effect of hand movement expressive quality was observed for happy facial expressions. The results conform with the proposal that perception of facial expressions of emotions can be affected by the expressive qualities of hand movements.     

Cultural differences in drawing movements between right-handed Japanese and German participants

Differences in drawing movements with the dominant and nondominant hands by 41 right-handed students from Japan (9 men, 12 women; M age = 20.3 yr., SD = 1.4) and Germany (13 men, 7 women; M age = 23.4 yr., SD = 3.0) were investigated. Participants were asked to use each hand to draw a circle, a pentagon, and a rhombus in one stroke. Analysis showed that Japanese participants drew a circle clockwise with the dominant right hand, starting from 6 or 7 o'clock on the face of a clock, while the German participants drew the circle counterclockwise, starting from 11 or 12 o'clock. Moreover, when drawing a pentagon and a rhombus with the right hand, Japanese participants drew counterclockwise from the top-center vertex, whereas almost half of German participants drew clockwise from the left side and others drew counterclockwise from the top-center vertex. Using the left hand, no significant difference was found in starting positions or directionality. Cultural differences in the starting positions and directionality when using the dominant right hand probably reflect the influence of writing habits on the drawing movement of the dominant hand.     

Action-feature integration blinds to feature-overlapping perceptual events: evidence from manual and vocal actions

Previous studies showed that the identification of a left- or right-pointing arrowhead is impaired when it appears while planning and executing a spatially compatible left or right keypress (Müsseler & Hommel, 1997a). We attribute this effect to stimulus processing and action control operating on the same feature codes so that, once a code is integrated in an action plan, it is less available for perceptual processing. In three pairs of experiments we tested the generality of this account by using stimulus-response combinations other than arrows and manual keypresses. Planning manual left-right keypressing actions impaired the identification of spatially corresponding arrows but not of words with congruent meaning. On the contrary, planning to say "left" or "right" impaired the identification of corresponding spatial words but not of congruent arrows. Thus, as the feature-integration approach suggests, stimulus identification is impaired only with overlap of perceptual or perceptually derived stimulus and response features while mere semantic congruence is insufficient.     

Coloring an action: Intending to produce color events eliminates the Stroop effect

The implications of an ideomotor approach to action control were investigated. In Experiment 1, participants made manual responses to letter stimuli and they were presented with response-contingent color patches, i.e., colored action effects. This rendered stimuli of the same color as an action's effect effective primes of that action, suggesting that bilateral associations were created between actions and the effects they produced. Experiment 2 combined this set-up with a manual Stroop task, i.e., participants responded to congruent, neutral, or incongruent color-word compounds. Standard Stroop effects were observed in a control group without action effects and in a group with target-incompatible action effects, but the reaction time Stroop effect was eliminated if actions produced target-compatible color effects (e.g., blue word --> left key --> blue patch). Experiment 3 did not replicate this interaction between target-effect compatibility and color-word congruency with color words as action effects, which rules out semantically based accounts. Theoretical implications for both action-effect acquisition and the Stroop effect are discussed. It is suggested that learning action effects, the features of which overlap with the target, allows and motivates people to recode their actions in ways that make them more stimulus-compatible. This provides a processing shortcut for translating the relevant stimulus into the correct response and, thus, shields processing from the impact of competing word distractors.     

Emotional valence and physical space: limits of interaction

According to the body-specificity hypothesis, people associate positive things with the side of space that corresponds to their dominant hand and negative things with the side corresponding to their nondominant hand. Our aim was to find out whether this association holds also true for a response time study using linguistic stimuli, and whether such an association is activated automatically. Four experiments explored this association using positive and negative words. In Exp. 1, right-handers made a lexical judgment by pressing a left or right key. Attention was not explicitly drawn to the valence of the stimuli. No valence-by-side interaction emerged. In Exp. 2 and 3, right-handers and left-handers made a valence judgment by pressing a left or a right key. A valence-by-side interaction emerged: For positive words, responses were faster when participants responded with their dominant hand, whereas for negative words, responses were faster for the nondominant hand. Exp. 4 required a valence judgment without stating an explicit mapping of valence and side. No valence-by-side interaction emerged. The experiments provide evidence for an association between response side and valence, which, however, does not seem to be activated automatically but rather requires a task with an explicit response mapping to occur.