Asynchrony in discrete bimanual aiming: Evidence for visual strategies of coordination

The bimanual coupling literature supposes an inherent drive for synchrony between the upper limbs when making discrete bimanual movements. The level of synchrony is argued to be task dependent, reliant on the visual demands of the two targets, and the result of a complex pattern of hand and eye movements (Bingham, Hughes, & Mon-Williams, 2008 ; Riek, Tresilian, Mon-Williams, Coppard, & Carson, 2003 ). However, recent work by Bruyn and Mason ( 2009 ) suggests that temporal coordination is not solely influenced by visual saccades. In this experimental series, a total of 8 participants performed congruent movements to targets either near or far from the midline. Targets far from the midline, requiring a visual saccade, resulted in greater terminal asynchrony. Initial and terminal asynchrony were not consistent, but linked to the task demands at that stage of the movement. If the asynchrony evident at the end of a bimanual movement is due to a complex pattern of hand and eye movements then the removal of visual feedback should result in an increase in synchrony. Sixteen participants then completed congruent and incongruent bimanual aiming movements to near and/or far targets. Movements were made with or without visual feedback of hands and targets. Analyses revealed that movements made without visual feedback showed increased synchrony between the limbs, yet movements to incongruent targets still showed greater asynchrony. We suggest that visual constraints are not the sole cause of asynchrony in discrete bimanual movements.     

Probing Representations of Gymnastics Movements: A Visual Priming Study

In this study, we designed a visual short‐term priming paradigm to investigate the mechanisms underlying the priming of movements and to probe movement representations in motor experts and matched controls. We employed static visual stimuli that implied or not human whole‐body movements, that is, gymnastics movements and static positions. Twelve elite female gymnasts and twelve matched controls performed a speeded two‐choice response time task. The participants were presented with congruent and incongruent prime‐target pairs and had to decide whether the target stimulus represented a gymnastics movement or a static position. First, a visual priming effect was observed in the two groups. Second, a stimulus–response rote association could not easily account for our results. Novel primes never presented as targets could also prime the targets. Third, by manipulating three levels of prime‐target relations in moving congruent pairs, we demonstrated that the more similar prime‐target pairs, the greater the facilitation in target. Lastly, gymnastics motor expertise impacted on priming effects.     

Neural correlates of partial transmission of sensorimotor information in the cerebral cortex

Using single neuron recordings in monkey primary motor (MI) cortex, two series of experiments were conducted in order to know whether response preparation can begin before perceptual processing finishes, thus providing evidence for a temporal overlap of perceptual and motor processes.

In Experiment 1, a “left/right, Go/No-Go” reaction time (RT) task was used. One monkey was trained to perform wrist flexion/extension movements to align a pointer with visual targets. The visual display was organized to provide a two-dimensional stimulus: side (an easy discrimination between left and right targets) which determined movement direction, and distance (a difficult discrimination between distal and proximal targets) which determined whether or not the movement was to be made. Changes in neuronal activity, when they were time-locked to the stimulus, were almost similar in the Go and No-Go trials, and when they were time-locked to movement onset, were markedly reduced in No-Go as compared to Go trials.

In Experiment 2, a stimulus-response compatibility (SRC) task was used. Two monkeys were trained to align a pointer with visual targets, on either left or right. In the spatially “compatible” trials, they had to point at the stimulus position, whereas in the “incompatible” trials, they had to point at the target located in the opposite side. For 12.5% of neurons, changes in activity associated with incompatible trials looked like changes in activity associated with movements performed in the opposite direction during compatible trials, thus suggesting the hypothesis of an automatic activation of the congruent, but incorrect response.

Results of both experiments provide evidence for a partial transmission of information from visual to motor cortical areas: that is, in the No-Go trials of the first task, information about movement direction, before the decision to perform or not this movement was made, and, in the incompatible trials of the SRC task, information about the congruent, but incorrect response, before the incongruent, but correct response was programmed.     

Conflict-induced perceptual filtering

In a variety of conflict paradigms, target and distractor stimuli are defined in terms of perceptual features. Interference evoked by distractor stimuli tends to be reduced when the ratio of congruent to incongruent trials is decreased, suggesting conflict-induced perceptual filtering (i.e., adjusting the processing weights assigned to stimuli associated with the target and with the distractor features). In search of evidence for such a mechanism, we administered a flanker task, in which targets and distractors were defined in terms of stimulus location (Experiment 1) or color (Experiment 2). The efficiency of processing stimuli associated with target and distractor features was assessed in intermixed trials of a visual search task, in which a target had to be detected irrespective of these features. In both experiments search times were shorter for stimuli associated with the target feature than with the distractor feature of the flanker task. This effect was increased under conditions of a reduced congruent/incongruent ratio, thereby providing evidence for conflict-dependent perceptual filtering.     

Eye movements may cause motor contagion effects

When a person executes a movement, the movement is more errorful while observing another person’s actions that are incongruent rather than congruent with the executed action. This effect is known as “motor contagion”. Accounts of this effect are often grounded in simulation mechanisms: increased movement error emerges because the motor codes associated with observed actions compete with motor codes of the goal action. It is also possible, however, that the increased movement error is linked to eye movements that are executed simultaneously with the hand movement because oculomotor and manual-motor systems are highly interconnected. In the present study, participants performed a motor contagion task in which they executed horizontal arm movements while observing a model making either vertical (incongruent) or horizontal (congruent) movements under three conditions: no instruction, maintain central fixation, or track the model’s hand with the eyes. A significant motor contagion-like effect was only found in the ‘track’ condition. Thus, ‘motor contagion’ in the present task may be an artifact of simultaneously executed incongruent eye movements. These data are discussed in the context of stimulation and associative learning theories, and raise eye movements as a critical methodological consideration for future work on motor contagion.     

Tracking hand movements captures the response dynamics of the evaluative priming effect

We tested the response dynamics of the evaluative priming effect (i.e. facilitation of target responses following evaluatively congruent compared with evaluatively incongruent primes) using a mouse tracking procedure that records hand movements during the execution of categorisation tasks. In Experiment 1, when participants performed the evaluative categorisation task but not the non-evaluative semantic categorisation task, their mouse trajectories for evaluatively incongruent trials curved more toward the opposite response than those for evaluatively congruent trials, indicating the emergence of evaluative priming effects based on response competition. In Experiment 2, implementing a task-switching procedure in which evaluative and non-evaluative categorisation tasks were intermixed, we obtained reliable evaluative priming effects in the non-evaluative semantic categorisation task as well as in the evaluative categorisation task when participants assigned attention to the evaluative stimulus dimension. Analyses of hand movements revealed that the evaluative priming effects in the evaluative categorisation task were reflected in the mouse trajectories, while evaluative priming effects in the non-evaluative categorisation tasks were reflected in initiation times (i.e. the time elapsed between target onset and first mouse movement). Based on these findings, we discuss the methodological benefits of the mouse tracking procedure and the underlying processes of evaluative priming effects.     

Painful semantic context modulates the relationship between action words and biological movement perception

Studies have revealed a close relationship between action–word processing and the detection of point-light biological movements and that this effect can be modulated by the context of action-verb presentation. The goal of the present study was to further examine the extent to which motor representation activation plays a role in this relationship by testing the influence of painless/painful sentence understanding during a listening task. Participants judged the presence or absence of a point-light biological movement that was embedded in a scrambled mask after a congruent or incongruent action sentence was presented. The sentences varied according to the context of action-verb presentation (painful, painless). Perceptual judgments of human movements improved after a prior presentation of a congruent action sentence but only in the painless context. Thus, our findings show that pain included in a semantic context of sentence presentation can preclude the relationship between action–word understanding and point-light biological movement judgments.     

Impact of action planning on spatial perception: Attention matters

Previous research suggested that perception of spatial location is biased towards spatial goals of planned hand movements. In the present study I show that an analogous perceptual distortion can be observed if attention is paid to a spatial location in the absence of planning a hand movement. Participants judged the position of a target during preparation of a mouse movement, the end point of which could deviate from the target by a varying degree in Exp. 1. Judgments of target position were systematically affected by movement characteristics consistent with perceptual assimilation between the target and the planned movement goal. This effect was neither due to an impact of motor execution on judgments (Exp. 2) nor due to characteristics of the movement cues or of certain target positions (Exp. 3, Exp. 5A). When the task included deployment of attention to spatial positions (former movement goals) in preparation for a secondary perceptual task, an effect emerged that was comparable with the bias associated with movement planning (Exp. 4, Exp. 5B). These results indicate that visual distortions accompanying manipulations of variables related to action could be mediated by attentional mechanisms.     

Age-related differences in automatic stimulus-response associations: Insights from young and older adults’ parity judgments

Young and older adults completed a parity judgment task (i.e., judging whether a target digit was odd or even) in which target numbers were preceded by masked prime numbers presented for 43 msec. Targets were either congruent (i.e., they had the same parity status as their primes) or incongruent (i.e., odd primes were paired with even targets, and even primes were paired with odd targets). Response times, percent errors, and event-related potentials (ERPs) were recorded for all items to compare automatic stimulus—response association (ASRA) and congruence effects (i.e., better performance on congruent than on incongruent trials) across age groups. Two important original sets of findings were obtained in this sample of participants. First, both age groups showed ASRA effects in behavioral measures. Second, age-related differences were observed in amplitude, timing, and scalp distributions for each congruent and incongruent ERP. These findings have implications for furthering the understanding of ASRA effects and of general characteristics of cognitive processes affected (or not affected) by aging.     

The influence of environmental context in interpersonal observation–execution

Cyclical upper-limb movements involuntarily deviate from a primary movement direction when the actor concurrently observes incongruent biological motion. We examined whether environmental context influences such motor interference during interpersonal observation–execution. Participants executed continuous horizontal arm movements while observing congruent horizontal or incongruent curvilinear biological movements with or without the presence of an object positioned as an obstacle or distractor. When participants were observing a curvilinear movement, an object located within the movement space became an obstacle, and, thus, the curvilinear trajectory was essential to reach into horizontal space. When acting as a distractor, or with no object, the curvilinear trajectory was no longer essential. For observing horizontal movements, objects were located at the same relative locations as in the curvilinear movement condition. We found greater involuntary movement deviation when observing curvilinear than horizontal movements. Also, there was an influence of context only when observing horizontal movements, with greater deviation exhibited in the presence of a large obstacle. These findings suggest that the influence of environmental context is underpinned by the (mis-)matching of observed and executed actions as incongruent biological motion is primarily coded via bottom-up sensorimotor processes, whilst the congruent condition incorporates surrounding environmental features to modulate the bottom-up sensorimotor processes.     

Effects of mental fatigue on the capacity limits of visual attention

The literature indicates that mental fatigue, due to Time-on-Task (ToT), compromises the ability to ignore distractors. The present study elaborates on this effect by testing whether perceptual load of the target stimuli moderates the ability to ignore distractors under fatigue. Participants (N = 27) performed a visual attention task (an Eriksen flanker task) for 2.5 hours without rest. Target letters were presented at three different perceptual loads and with a peripheral distractor letter. Three target–distractor conditions were tested: congruent, incongruent, and neutral. Results showed that, overall, error rates and reaction times increased with ToT. The detrimental effect of fatigue on performance was most pronounced in the high perceptual load condition. Importantly, however, we also found that fatigue-related ignorance of distractors was compromised in the low perceptual load condition, but not in the medium or high perceptual load condition. This finding is in accordance with the perceptual load theory and refines the knowledge about the declining cognitive performance under fatigue.     

Motion as input: a functional explanation of movement effects on cognitive processes

Motion is often thought of as the result of perceptual and higher cognitive processes. Although this idea has been investigated in myriad ways, the understanding of how movements tune cognitive processes is still in its infancy. The present study examined the nonaffective tuning of movements (arm extension and arm flexion) on heuristic and systematic processes. In a departure from recent cognitive tuning models, a model was derived that defines the tuning effect based on the movement goal and not on the movement position. In the experiment, participants moved toward an extension or flexion position with a movement goal which connected the movement with either an avoidance or an approach function. Analysis indicated that cognitive tuning is a product of the movement goal rather than the movement position. Implications for models of motor control as well as for cognitive tuning models are presented.     

Planning and control of straight-ahead and angled planar movements in adults and young children.

In the present study we wanted to determine why straight-ahead movements performed along one's mid-line are directionally more accurate than movements toward eccentric targets. We also wanted to determine whether the processes underlying this difference were the same in young children as in adults. Six-to-seven-year-old children and adults practiced a video-aiming task using different starting base and target combinations without vision of their ongoing movements. The results indicated that adults and children were directionally more accurate and less variable when pointing toward targets located straight ahead of the starting base rather than eccentric or concentric targets. This was true, regardless of whether the movement was performed along one's midline or not. These results suggest that angled movements are directionally less accurate than straight-ahead movements because of difficulty in defining the orientation of the appropriate movement vector in the workspace and/or in transforming it into appropriate motor commands. A kinematic analysis revealed large coefficients of direction and of extent variability early after movement initiation. However, these coefficients of variability were largely reduced by the occurrence of peak extent velocity, revealing that noise in initial movement planning was quickly reduced by on-line control processes. Finally, the results indicated largely similar planning and control processes for young children and adults.     

Motivational and cognitive determinants of control during conflict processing

Previous studies suggest that both reward anticipation and expected or experienced conflicts activate cognitive control. The present study investigated how these factors interact during conflict processing. In two experiments, participants performed a variant of the Stroop task, receiving performance-dependent monetary rewards in some blocks. In addition, we manipulated the level of conflict-triggered reactive and expectancy-driven proactive control: In Experiment 1, we compared the Stroop effect after previously congruent and incongruent trials to examine the conflict adaptation effect (reactive control). We found that the level of motivation did not interact with conflict adaptation. In Experiment 2, we varied the proportion of congruent and incongruent trials to manipulate conflict expectancy (proactive control). The data suggest the effects of motivation to be less pronounced under conditions of high conflict expectancy. We conclude that the interaction of motivation with cognitive determinants of control depends on whether these activate proactive or reactive control processes.     

Cognitive constraints on motor imagery

Executed bimanual movements are prepared slower when moving to symbolically different than when moving to symbolically same targets and when targets are mapped to target locations in a left/right fashion than when they are mapped in an inner/outer fashion [Weigelt et al. (Psychol Res 71:238–447, 2007)]. We investigated whether these cognitive bimanual coordination constraints are observable in motor imagery. Participants performed fast bimanual reaching movements from start to target buttons. Symbolic target similarity and mapping were manipulated. Participants performed four action conditions: one execution and three imagination conditions. In the latter they indicated starting, ending, or starting and ending of the movement. We measured movement preparation (RT), movement execution (MT) and the combined duration of movement preparation and execution (RTMT). In all action conditions RTs and MTs were longer in movements towards different targets than in movements towards same targets. Further, RTMTs were longer when targets were mapped to target locations in a left/right fashion than when they were mapped in an inner/outer fashion, again in all action conditions. RTMTs in imagination and execution were similar, apart from the imagination condition in which participants indicated the start and the end of the movement. Here MTs, but not RTs, were longer than in the execution condition. In conclusion, cognitive coordination constraints are present in the motor imagery of fast (<1600 ms) bimanual movements. Further, alternations between inhibition and execution may prolong the duration of motor imagery.     

Performance of unimanual and bimanual multiphased prehensile movements

By manipulating task action demands in 2 experiments, the author investigated whether the context-dependent effects seen in unimanual multiphase movements are also present in bimanual movements. Participants (N = 14) in Experiment 1 either placed or tossed objects into targets. The results indicated that the intention to perform a subsequent action with an object could influence the performance of an earlier movement in a sequence in both unimanual and bimanual tasks. Furthermore, assimilation effects were found when the subsequent tasks being performed by the 2 hands were incongruent. In Experiment 2, the author investigated in 12 participants whether planning in a multiphase movement includes some representation of the accuracy demands of the subsequent task. The accuracy demands of a subsequent task did not appear to influence initial movement planning. Instead, the present results support the notion that it is the action requirements of the subsequent movement that lead to context-dependent effects.     

Manual asymmetries in bimanual reaching: the influence of spatial compatibility and visuospatial attention

The goal of the present investigation was to explore the possible expression of hemispheric-specific processing during the planning and execution of a bimanual reaching task. Participants (N = 9) completed 80 bimanual reaching movements (requiring simultaneous, bilateral production of arm movements) to peripherally presented targets while selectively attending to either their left or right hand. Further, targets were presented in spatially compatible (ipsilateral to the aiming limb) and incompatible (contralateral to the aiming limb) response contexts. It was found that the left hand exhibited temporal superiority over the right hand in the response planning phase of bimanual reaching, indicating a left hand/right hemisphere advantage in the preparation of a bimanual response. During response execution, and consistent with the view that interhemispheric processing time (Barthelemy & Boulinguez, 2002) or biomechanical constraints (Carey, Hargreaves, & Goodale, 1996) generate temporal delays, longer movement times were observed in response to spatially incompatible target positions. However, no hemisphere-specific benefit was demonstrated for response execution. Based on these findings, we propose lateralized processing is present at the time of response planning (i.e., left hand/right hemisphere processing advantage); however, lateralized specialization appears to be annulled during dynamic execution of a bimanual reaching task.     

Priming outside of awareness and subsequent stimulus identification.

The influence of priming outside of awareness on performance of a color-recognition task was investigated. Using a tachistoscope, a color word that matched ("congruent prime") or did not match ("incongruent prime") the target color or a blank prime was followed by a pattern mask and the target color. Identification performance was superior on the blank prime trials to the congruent prime trials, with performance on the incongruent prime trials being the lowest. A subsequent study included a meaningless (XXX) prime condition, and it was found that meaningless primes interfered with target-color identification more than the congruent and blank prime conditions, but less than the incongruent prime condition, suggesting that primes, in addition to producing semantic activation, impose demands on information-processing capacity of the perceptual system.     

Gender differences on the semantic flanker task using transposed-letter target words

Previous research has demonstrated that men and women are differentially influenced by irrelevant distractors. Other lines of evidence have suggested that increasing the perceptual load of a task reduces distractor interference for participants generally. The present study examined these effects using a semantic version of the flanker task; participants made speeded responses to category target words that were flanked by irrelevant distractors. The response mapping between the target and flanker words was either congruent (mapped to the same motor response) or incongruent (target word mapped to a different motor response to that of the flankers). Target words were presented either normally (e.g., table: low perceptual load) or with the beginning letters transposed (e.g., atble: high perceptual load). The results revealed that women showed a larger congruency effect than men but this was not due to greater interference on incongruent trials. While men and women made faster responses to normal than to transposed target words, this was similar in magnitude. The magnitude of the flanker effect for normal and transposed target words was significantly correlated in men but not in women. These findings are consistent with the view that women may process target words to a deeper level than men and therefore may engage in more conflict monitoring then men.     

Gender differences on the semantic flanker task using transposed-letter target words

Previous research has demonstrated that men and women are differentially influenced by irrelevant distractors. Other lines of evidence have suggested that increasing the perceptual load of a task reduces distractor interference for participants generally. The present study examined these effects using a semantic version of the flanker task; participants made speeded responses to category target words that were flanked by irrelevant distractors. The response mapping between the target and flanker words was either congruent (mapped to the same motor response) or incongruent (target word mapped to a different motor response to that of the flankers). Target words were presented either normally (e.g., table: low perceptual load) or with the beginning letters transposed (e.g., atble: high perceptual load). The results revealed that women showed a larger congruency effect than men but this was not due to greater interference on incongruent trials. While men and women made faster responses to normal than to transposed target words, this was similar in magnitude. The magnitude of the flanker effect for normal and transposed target words was significantly correlated in men but not in women. These findings are consistent with the view that women may process target words to a deeper level than men and therefore may engage in more conflict monitoring then men.