The temporal representation of in-phase and anti-phase movements

We have proposed that the stability of bimanual coordination is influenced by the complexity of the representation of the task goals. Here, we present two experiments to explore this hypothesis. First, we examined whether a temporal event structure is present in continuous movements by having participants vocalize while producing bimanual circling movements. Participants tended to vocalize once per movement cycle when moving in-phase. In contrast, vocalizations were not synchronized with anti-phase movements. While the in-phase result is unexpected, the latter would suggest anti-phase continuous movements lack an event structure. Second, we examined the event structure of movements marked by salient turn-around points. Participants made bimanual wrist flexion movements and were instructed to move 'in synchrony' with a metronome, without specifying how they should couple the movements to the metronome. During in-phase movements, participants synchronized one hand cycle with every metronome beat; during anti-phase movements, participants synchronized flexion of one hand with one metronome beat and extension of the other hand with the next beat. The results are consistent with the hypothesis that the instability of anti-phase movements is related to their more complex (or absent) event representation relative to that associated with in-phase movements.     

Coding controlled and triggered cursor movements as action effects: influences on the auditory Simon effect for wheel-rotation responses

Four experiments investigated influences of irrelevant action effects on response selection in Simon tasks for which tone pitch was relevant and location irrelevant, and responses were clockwise- counterclockwise wheel rotations. When the wheel controlled left-right movement of a cursor in a direction opposite an instructed left-right hand-movement goal, the Simon effect was reduced. When the wheel was held at the bottom, this reduction was due to some participants coding responses relative to the cursor and others relative to the hands. However, when the wheel was held at the top, it was due to participants integrating cursor movements with hand movements as a single action concept. In contrast, a cursor triggered by the wheel movement showed little influence on the Simon effect, even when contiguity and contingency with the wheel movements were high. Experience with the controlled cursor in a prior trial block or between trials established a causal relation that enabled participants to code the triggered cursor as belonging to the action concept and thus reduce the Simon effect. Multiple factors determine the influence of an irrelevant action effect on performance.     

Emergence of spontaneous anticipatory hand movements in a probabilistic environment

In this article, we present a novel experimental approach to the study of anticipation in probabilistic cuing. We implemented a modified spatial cuing task in which participants made an anticipatory hand movement toward one of two probabilistic targets while the (x, y)-computer mouse coordinates of their hand movements were sampled. This approach allowed us to tap into anticipatory processes as they occurred, rather than just measuring their behavioral outcome through reaction time to the target. In different conditions, we varied the participants’ degree of certainty of the upcoming target position with probabilistic pre-cues. We found that participants initiated spontaneous anticipatory hand movements in all conditions, even when they had no information on the position of the upcoming target. However, participants’ hand position immediately before the target was affected by the degree of certainty concerning the target’s position. This modulation of anticipatory hand movements emerged rapidly in most participants as they encountered a constant probabilistic relation between a cue and an upcoming target position over the course of the experiment. Finally, we found individual differences in the way anticipatory behavior was modulated with an uncertain/neutral cue. Implications of these findings for probabilistic spatial cuing are discussed.     

Oculomotor evidence of sequence learning on the serial reaction time task

Manual and oculomotor measures of sequence learning were examined on the serial reaction time (SRT) task Participants were assigned into four groups differing on response modality (manual, oculomotor) and trial type (sequence, pseudorandom). The pattern of manual RTs replicated previous studies. Frequency of anticipatory eye movements followed similar patterns as RTs. Participants made many anticipations, even in pseudorandom blocks, and frequency of anticipations did not depend on presence of concurrent manual responses. Excluding participants with explicit awareness did not change results. Anticipations were negatively related to RTs in both incidental and intentional learning. Anticipations were positively related to sequence recall in intentional, but not incidental, learning. Results suggest that (1) anticipatory eye movements reflected sequence learning and (2) participants made overt and covert shifts of visuospatial attention to likely stimulus locations prior to stimulus onset, whether or not they made manual responses and whether or not there was a sequence.     

Intentions and expectations in temporal binding

Recently, it has been shown that the perceived times of voluntary movements and their effects are perceived as shifted towards each other. This temporal binding phenomenon was explained by an integrated representation of movement and effect, facilitating operant learning and the experience of intentionality. Here, we investigated whether temporal binding depends on explicit intentional attributions. In Experiment 1, participants intended to either produce or avoid producing an effect (a tone) by the timing of their movements, with the ratio of success being fixed at 2:1. In Experiments 2 and 3, the influence of the action-effect contingency ratio on temporal binding was controlled for by removing the intentional attribution of the effect. The results indicate that temporal binding is a general associative mechanism that facilitates the learning of movement-effect contingencies. Beyond that, temporal binding is sensitive to explicit intentional attributions, which selectively enhance the link between an intentional movement and the effect a moving agent intends to produce.     

On the signals underlying conscious awareness of action

To investigate whether conscious judgments of movement onset are based solely on pre-movement signals (i.e., premotor or efference copy signals) or whether sensory feedback (i.e., reafferent) signals also play a role, participants judged the onset of finger and toe movements that were either active (i.e., self initiated) or passive (i.e., initiated by the experimenter). Conscious judgments were made by reporting the position of a rotating clock hand presented on a computer screen and were then compared to the actual measured time of movement onset. In line with previous studies, judgment errors were found to be anticipatory for both finger and toe movements. There was a significant difference between judgment errors for active and passive movements, with judgments of active movements being more anticipatory than judgments of passive movements. This is consistent with a pre-movement (from here on referred to as an “efferent”) account of action awareness because premotor and efference copy signals are only present in active movements, whereas the main source of movement information in passive movements is sensory feedback which is subject to time delays of conduction (and hence predicts later judgment times for passive movements). However, judgments of active toe movement onset time were less anticipatory than judgments of active finger movement onset time. This pattern of results is not consistent with a pure efferent account of conscious awareness of action onset - as this account predicts more anticipatory judgments for toe movements compared to finger movements. Instead, the data support the idea that conscious judgments of movement onset are based on efferent (i.e., premotor, efference copy) and reafferent (i.e., feedback from the movement) components.     

Emotional state and initiating cue alter central and peripheral motor processes

Evidence indicates that voluntary and involuntary movements are altered by affective context as well as the characteristics of an initiating cue. The purpose of this study was to determine the contribution of central and peripheral mechanisms to this phenomenon. During the presentation of pleasant, unpleasant, neutral, and blank images, participants (N = 33) responded to auditory stimuli (startle, 107 dB startle or 80 dB tone) by initiating a bimanual isometric contraction of the wrist and finger extensor muscles. Analyses of electromyography and force measures supported the hypothesis that exposure to unpleasant images accelerates central processing times and increases the gradient of slope of peripheral movement execution. In addition, startle cues as compared with tone cues accelerated and magnified all temporal and amplitude indices. Collectively, these findings have noteworthy implications for (a) those seeking to facilitate the speed and force of voluntary movement (i.e., movement rehabilitation), (b) understanding the higher incidence of motor difficulty in individuals with affective disorders, and (c) those seeking to regulate emotional input so as to optimize the quality of intended movements.     

Anticipatory Planning of Sequential Hand and Finger Movements

ABSTRACT

Hand movements may be anticipatorily planned to reach an immediate target and at the same time facilitate movements to subsequent targets. Researchers have proposed that in anticipatory planning, information about subsequent targets needs to be processed to engage in the planning of the next movement. To test this hypothesis, the authors varied the information 48 participants had about to-be-executed two-step hand and finger movement sequences prior to a choice reaction signal. Movements were initialized faster if participants had advance information about the second target of the sequence than if participants had no advance information at all. The results imply that movement segments to late targets in a movement sequence may be at least partially planned, even if information about earlier targets is not yet available.     

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.     

Modulating the sense of agency with external cues

We investigate the processes underlying the feeling of control over one’s actions (“sense of agency”). Sense of agency may depend on internal motoric signals, and general inferences about external events. We used priming to modulate the sense of agency for voluntary and involuntary movements, by modifying the content of conscious thought prior to moving. Trials began with the presentation of one of two supraliminal primes, which corresponded to the effect of a voluntary action participants subsequently made. The perceived interval between movement and effect was used as an implicit measure of sense of agency. Primes modulated perceived intervals for both voluntary and involuntary movements, but the modulation was greatest for involuntary movements. A second experiment showed that this modulation depended on prime–movement (temporal) contiguity. We propose that sense of agency is based on a combination of internal motoric signals and external sensory evidence about the source of actions and effects.     

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.     

Delayed auditory feedback in repetitive tapping: A role for the sensory goal

The open-loop model by Wing and Kristofferson has successfully explained many aspects of movement timing. A later adaptation of the model assumes that timing processes do not control the movements themselves, but the sensory consequences of the movements. The present study tested direct predictions from this “sensory-goals model”. In two experiments, participants were instructed to produce regular intervals by tapping alternately with the index fingers of the left and the right hand. Auditory feedback tones from the taps of one hand were delayed. As a consequence, regular intervals between taps resulted in irregular intervals between feedback tones. Participants compensated for this auditory irregularity by changing their movement timing. Compensation effects increased with the magnitude of feedback delay (Experiment 1) and were also observed in a unimanual variant of the task (Experiment 2). The pattern of effects in alternating tapping suggests that compensation processes were anticipatory—that is, compensate for upcoming feedback delay rather than being reactions to delay. All experiments confirmed formal model predictions. Taken together, the findings corroborate the sensory-goals adaptation of the Wing–Kristofferson model.     

Changes in the relationship between movement velocity and movement distance in primary focal hand dystonia

The authors examined the relationship between movement velocity and distance and the associated muscle activation patterns in 18 individuals with focal hand dystonia (FHD) compared with a control group of 18 individuals with no known neuromuscular condition. Participants performed targeted voluntary wrist and elbow flexion movements as fast as possible across 5 movement distances. Individuals with FHD were slower than controls across all distances, and this difference was accentuated for longer movements. Muscle activation patterns were triphasic in the majority of individuals with FHD, and muscle activation scaled with distance in a similar manner to controls. Cocontraction did not explain movement slowing in individuals with dystonia, but there was a trend toward underactivation of the 1st agonist burst in the dystonic group. The authors concluded that slowness is a consistent feature of voluntary movement in FHD and is present even in the absence of dystonic posturing. Underactivation of the 1st agonist burst appears to be the most likely reason to explain slowing.     

Individual differences in approach and avoidance movements: how the avoidance motive influences response force

The present research is based on the assumption that people differ in their responsiveness to incentives and threats. In two experiments we examined whether the trait corresponding to the responsiveness to threats (avoidance motive) and the trait corresponding to the responsiveness to incentives (approach motive) influence voluntary motor behavior toward or away from stimuli. In Experiment 1, stimuli consisted of positive and negative words within a lexical decision task. Participants moved their arms backward in order to withdraw from the stimuli or forward in order to approach them. In Experiment 2, participants responded with forward or backward arm movements to neutral sounds coming from behind or in front of them. The main dependent variable was the strength of the approach and avoidance movements. In both experiments this variable was related to participants' avoidance-motive disposition but not to their approach-motive disposition. Avoidance-motivated individuals generally showed more forceful avoidance movements than approach movements. There was no effect of stimulus valence on the strength of the movements in Experiment 1. Furthermore, the results of Experiment 2 suggest that it is not the physical direction (forward or backward) but rather the movement's effect of distance reduction (approach) or distance increase (avoidance) in regard to the stimulus that defines a movement as an approach or an avoidance movement.     

Anticipatory modulation of precision grip force with variations in limb velocity of a curvilinear movement

The authors examined the relationship between peak velocity of a discrete horizontal elbow flexion movement in which the hand path was curvilinear and premovement modulation of precision grip force. The velocity of the movements of 7 participants was varied from maximal velocity to a velocity that required several seconds to reach a target. An object instrumented with force transducers for the forefinger and thumb measured precision grip force. There was a positively accelerating quadratic relationship between grip force change before movement and peak velocity of the ensuing limb movement. On some low-velocity trials, premovement grip force modulation reflected a net decrease. In contrast, high-velocity trials were preceded by net increases in grip force. Using cluster analysis, the authors classified grip forces in low-velocity movements as an empirically distinct set of entities from grip forces in high-velocity movements. The cluster of high-value grip forces suggested an anticipatory strategy that allowed participants a large safety margin in grip force to avoid object slip on movement initiation. The cluster of low-value grip forces at movement initiation suggested a second anticipatory strategy in which participants changed grip force very little, perhaps to increase the ability of proprioceptors in the hand to sense force changes. Those findings suggest that modulation of grip force before initiation of movements in which the hand path is curvilinear may be governed by two distinct velocity-dependent anticipatory strategies.     

Interplay between action and movement intentions during social interaction

Observing the movements of another person influences the observer's intention to execute similar movements. However, little is known about how action intentions formed prior to movement planning influence this effect. In the experiment reported here, we manipulated the congruency of movement intentions and action intentions in a pair of jointly acting individuals (i.e., a participant paired with a confederate coactor) and investigated how congruency influenced performance. Overall, participants initiated actions faster when they had the same action intention as the coactor (i.e., when participants and the coactor were pursuing the same conceptual goal). Participants' responses were also faster when their and the coactor's movement intentions were directed to the same spatial location, but only when participants had the same action intention as the coactor. These findings suggest that observers use the same representation to implement their own action intentions that they use to infer other people's action intentions and also that a dynamic, multitiered intentional mechanism is involved in the processing of other people's actions.     

Anticipatory Postural Adjustments for Altering Direction During Walking

The authors examined how individuals adapt their gait and regulate their body configuration before altering direction during walking. Eight young adults were asked to change direction during walking with different turning angles (0deg;, 45deg;, 90deg;), pivot foot (left, right), and walking speeds (normal and fast). The authors used video and force platform systems to determine participants' whole-body center of mass and the center of pressure during the step before they changed direction. The results showed that anticipatory postural adjustments occurred during the prior step and occurred earlier for the fast walking speed. Anticipatory postural adjustments were affected by all 3 variables (turn angle, pivot foot, and speed). Participants leaned backward and sideward on the prior step in anticipation of the turn. Those findings indicate that the motor system uses central control mechanisms to predict the required anticipatory adjustments and organizes the body configuration on the basis of the movement goal.     

Linguistically guided anticipatory eye movements in scene viewing

The present study replicated the well-known demonstration by Altmann and Kamide (1999) that listeners make linguistically guided anticipatory eye movements, but used photographs of scenes rather than clip-art arrays as the visual stimuli. When listeners heard a verb for which a particular object in a visual scene was the likely theme, they made earlier looks to this object (e.g., looks to a cake upon hearing The boy will eat …) than when they heard a control verb (The boy will move …). New data analyses assessed whether these anticipatory effects are due to a linguistic effect on the targeting of saccades (i.e., the where parameter of eye movement control), the duration of fixations (i.e., the when parameter), or both. Participants made fewer fixations before reaching the target object when the verb was selectionally restricting (e.g., will eat). However, verb type had no effect on the duration of individual eye fixations. These results suggest an important constraint on the linkage between spoken language processing and eye movement control: Linguistic input may influence only the decision of where to move the eyes, not the decision of when to move them.     

Altered Arm-Body Coordination with Triggered Pointing Responses as Influenced by Task Predictability

Abstract

Reaching movements generate reaction forces that affect postural stability, requiring sophisticated coordination between body and arm movement to maintain balance. In voluntary movement, this coordination involves feedforward shifts of posture, and such anticipatory postural muscle activity also accompanies the rapid modulation of an ongoing point to suddenly a shifting target (double-step). However, it is unknown if this early postural activity depends on target-shift predictability and whether arm and body motion are similar coordinated to voluntary movement. Body and arm motion coordination during double-step pointing movements from standing were done under differing conditions of target-shift predictability. In a proportion of trials, the pointing target was displaced, with the predictability of target-shift direction varied between two peripheral targets (target-shift direction known) and two central targets (target-shift direction uncertain). The target jump evoked an adjustment in the arm then body response, opposite to the pointing responses to the initial target. The triggered arm-then-body ordering was consistent across target-shift predictability, although known target-shift direction resulted in closer timing of arm and body onsets. The altered coordination in triggered corrections suggests that the body component in triggered reactions depend on response predictability, showing an altered control of arm and body motion.