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.     

Bimanual interference with compatible and incompatible tool transformations

The present study investigates bimanual interference in a tool-use task, in which two target locations had to be touched concurrently with two tools, one for each hand. Target locations were either in the same, or in different directions for the two hands. Furthermore, the tools implemented either a compatible or an incompatible relationship between the direction of target locations and the direction of associated bodily movements. Results indicated bimanual interference when the tools had to be moved to targets in different directions. Furthermore, this interference was much more pronounced when the tools required body movements that were spatially incompatible to the cued target locations as compared to when they were compatible. These results show that incompatible relationships between target directions and bodily movement directions can aggravate bimanual interference in tool use.     

Visual short-term memory is influenced by haptic perception

The present study investigated whether and how visual memory and haptic perception are related. Participants were required to compare a visual reference velocity with a visual test velocity separated by a 4-s interval. During the retention interval, a fast or slow hand movement was performed. Although the hand movement was not visible, effects of the speed of the distracting body movement occurred. Slow movements resulted in a lowering of the represented visual velocity, whereas fast movements heightened the represented velocity. Subsequent experiments extended the effect to body movements that differed from the visual motion and ruled out the possibility that the effect was due to changes in visual perception or interference from semantic, verbal, and acoustic memory codes. Perhaps haptic velocity information and visual velocity information stored in short-term memory are blended.     

Movement observation affects movement execution in a simple response task

The present study was designed to examine the hypothesis that stimulus-response arrangements with high ideomotor compatibility lead to substantial compatibility effects even in simple response tasks. In Experiment 1, participants executed pre-instructed finger movements in response to compatible and incompatible finger movements. A pronounced reaction time advantage was found for compatible as compared to incompatible trials. Experiment 2 revealed a much smaller compatibility effect for less ideomotor-compatible object movements compared to finger movements. Experiment 3 presented normal stimuli (hand upright) and flipped stimuli (hand upside-down). Two components were found to contribute to the compatibility effect, a dynamic spatial compatibility component (related to movement directions) and an ideomotor component (related to movement types). The implications of these results for theories about stimulus-response compatibility (SRC) as well as for theories about imitation are discussed.     

Is It Possible to Prepare the Second Component of a Movement Before the First One?

Experiment 1 utilized a choice reaction time paradigm to examine whether advance information about the second component of a movement has similar effects upon movement initiation and execution as advance information about the first component. Four stimuli were assigned to four goal keys. Subjects responded with the index finger of their preferred hand. They had to press one of two intermediate keys before pressing the assigned stimulus goal key. Advance information signaled one pair of goal keys in such a way that either the first or the second movement component was unequivocally specified before the response signal appeared. Shorter reaction times resulted when the first component was precued. Further control conditions showed that advance information about the second movement component could not be utilized for movement preparation. Experiment 2 ruled out a perceptual interpretation of this effect. Experiment 3 showed that preparation time for two-component movements are longer than for one-component movements. The study permits the conclusions that speeded two-component movements are controlled by motor programs and that advance information about the first movement component is required before the second movement component can be programmed.     

Is it possible to prepare the second component of a movement before the first one?

Experiment 1 utilized a choice reaction time paradigm to examine whether advance information about the second component of a movement has similar effects upon movement initiation and execution as advance information about the first component. Four stimuli were assigned to four goal keys. Subjects responded with the index finger of their preferred hand. They had to press on of two intermediate keys before pressing the assigned stimulus goal key. Advance information signaled one pair of goal keys in such a way that either the first or the second movement component was unequivocally specified before the response signal appeared. Shorter reaction times resulted when the first component was precued. Further control conditions showed that advance information about the second movement component could not be utilized for movement preparation. Experiment 2 ruled out a perceptual interpretation of this effect. Experiment 3 showed that preparation time for two-component movements are longer than for one-component movements. The study permits the conclusions that speeded two-component movements are controlled by motor programs and that advance information about the first movement component is required before the second movement component can be programmed.     

Programming of expected and unexpected movements: effects on the onset of the lateralized readiness potential

When participants utilize prime information to prepare some or all aspects of the forthcoming movement, reaction time (RT) costs are obtained when the imperative response signal demands an unexpected rather than an expected movement. Longer RT in trials for which primes are invalid rather than valid, i.e., the response validity effect, are taken to reflect prolonged motoric processing time. The present study was designed to test this assumption by using the lateralized readiness potential (LRP) in order to reveal influences of response validity at motoric processes, pre-motoric processes, or both. In two response priming experiments LRP onset latency was examined when valid and invalid advance information about direction (Experiment 1) or about direction and hand (Experiment 2) was provided. RT revealed large response validity effects in both experiments. Analysis of LRP onsets provided strong evidence against the common assumption of a motoric locus of the RT increase in invalid trials. Rather, the present results suggest a pre-motoric locus of the response validity effect within information processing.     

Evidence for effects of phonological correspondence between visible speech and written syllables

The present study investigated compatibility effects between written and spoken syllables. Participants saw the syllables "Ba" or "Da" printed on a speaker's mouth that was articulating either /b wedge / or /d wedge /. Participants classified either the printed syllable or the mouth movement by pressing a left or right key. Responses were faster when mouth movement and letters were congruent regardless of imperative stimulus dimension. As the two stimulus dimensions (mouth movements and letters) showed dimensional overlap, but did not overlap with the response, stimulus-response compatibility was ruled out according to some models. It is argued that the compatibility effect was due to the competition of phonological codes at a stage preceding response selection. Also, the results lend support to the view that Stroop-like tasks are ambiguous with regard to the locus of compatibility effects. Stimulus-response and stimulus-stimulus compatibility may be observed.     

Visual tracking of active and passive movements of the hand

Two experiments were performed to evaluate the influence of movement frequency and predictability on visual tracking of the actively and the passively moved hand. Four measures of tracking precision were employed: (a) saccades/cycle, (b) percent of pursuit movement, (c) eye amplitude/arm amplitude, (d) asynchrony of eye and hand at reversal. Active and passive limb movements were tracked with nearly identical accuracy and were always vastly superior to tracking an external visual target undergoing comparable motion. Proprioceptive information about target position appears to provide velocity and position information about target location. Its presence permits the development of central eye-movement programmes that move the eyes in patterns that approximate but do not exactly match, temporally or spatially, the motion of the hand.     

Temporal predictive mechanisms modulate motor reaction time during initiation and inhibition of speech and hand movement

Skilled movement is mediated by motor commands executed with extremely fine temporal precision. The question of how the brain incorporates temporal information to perform motor actions has remained unanswered. This study investigated the effect of stimulus temporal predictability on response timing of speech and hand movement. Subjects performed a randomized vowel vocalization or button press task in two counterbalanced blocks in response to temporally-predictable and unpredictable visual cues. Results indicated that speech and hand reaction time was decreased for predictable compared with unpredictable stimuli. This finding suggests that a temporal predictive code is established to capture temporal dynamics of sensory cues in order to produce faster movements in responses to predictable stimuli. In addition, results revealed a main effect of modality, indicating faster hand movement compared with speech. We suggest that this effect is accounted for by the inherent complexity of speech production compared with hand movement. Lastly, we found that movement inhibition was faster than initiation for both hand and speech, suggesting that movement initiation requires a longer processing time to coordinate activities across multiple regions in the brain. These findings provide new insights into the mechanisms of temporal information processing during initiation and inhibition of speech and hand movement.     

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.     

On the locus of the divided-attention effects

Reaction times in a choice reaction task were used to localize the livided-attention effect (less proficient performance under dual than under ingle-taks conditions) in a sequential-stage model of human information processing. Experiment 1 eliminated a central (memory-dependent) processing tage, while Experiment 2 suggested that a stimulus sampling process within the hitial encoding stage was the locus of the effect. Thus, the effect was localized in the input, not the central or an output stage of processing. A slower stimulus ampling rate was indicated under dual-than under single-task conditions.     

Response Selection Contributes to the Preparation Cost for Bimanual Asymmetric Movements

Movement preparation of bimanual asymmetric movements takes more time than bimanual symmetric movements in choice reaction-time conditions. This bimanual asymmetric cost may be caused by increased processing demands on any stage of movement preparation. The authors tested the contributions of each stage of movement preparation to the asymmetric cost by using the additive factors method. This involved altering the stimulus contrast, response compatibility, and response complexity. These manipulations changed the processing demands on stimulus identification, response selection, and response programming, respectively. Any manipulation with a larger reaction time cost than control suggests that stage contributes to the bimanual asymmetric cost. The bimanual asymmetric cost was larger for incompatible stimuli, which supports that response selection contributes to the bimanual asymmetric cost.     

Cognitive adaptations arising from nonnative experience of sign language in hearing adults

Three experiments examined spatial transformation abilities in hearing people who acquired sign language in early adulthood. The performance of the nonnative hearing signers was compared with that of hearing people with no knowledge of sign language. The two groups were matched for age and gender. Using an adapted Corsi blocks paradigm, the experimental task simulated spatial relations in sign discourse but offered no opportunity for linguistic coding. Experiment 1 showed that the hearing signers performed significantly better than the nonsigners on a task that entailed 180 degree rotation, which is the canonical spatial relationship in sign language discourse. Experiment 2 found that the signers did not show the typical costs associated with processing rotated stimuli, and Experiment 3 ruled out the possibility that their advantage relied on seen hand movements. We conclude that sign language experience, even when acquired in adulthood by hearing people, can give rise to adaptations in cognitive processes associated with the manipulation of visuospatial information.     

The effects of delayed and displaced visual feedback on motor control

Developments in television technology have made possible new approaches to the study of the role of visual feedback in motor control. In two experiments using a special videodisc recording and playback system, the effects of delaying for 66 msec a subject's view of his own hand during a target-directed movement was investigated. The observed effects of such visually delayed feedback compared to spatially distorted feedback produced by prisms led to three major conclusions: (a) despite the behavioral similarity (overshooting) induced by the two kinds of altered feedback, the role of each in the visual-motor control loop is different; (b) adaptation to and the after effect of the two kinds of altered feedback are based on different control mechanisms (c) the processing and use of visual information in hand control requires less time than previous experiments have indicated.     

Embodiment effects in memory for facial identity and facial expression

Research suggests that states of the body, such as postures, facial expressions, and arm movements, play central roles in social information processing. This study investigated the effects of approach/avoidance movements on memory for facial information. Faces displaying a happy or a sad expression were presented and participants were induced to perform either an approach (arm flexion) or an avoidance (arm extension) movement. States of awareness associated with memory for facial identity and memory for facial expression were then assessed with the Remember/Know/Guess paradigm. The results showed that performing avoidance movements increased Know responses for the identity, and Know/Guess responses for the expression, of valence-compatible stimuli (i.e., sad faces as compared to happy faces), whereas this was not the case for approach movements. Based on these findings, it is suggested that approach/avoidance motor actions influence memory encoding by increasing the ease of processing for valence-compatible information.     

Effects of motor intention on the perception of somatosensory events: A behavioural and functional magnetic resonance imaging study

The intention to execute a movement can modulate our perception of sensory events, and this modulation is observed ahead of both ocular and upper limb movements. However, theoretical accounts of these effects, and also the empirical data, are often contradictory. Accounts of “active touch”, and the premotor theory of attention, have emphasized how movement intention leads to enhanced perceptual processing at the target of a movement, or on the to-be-moved effector. By contrast, recent theories of motor control emphasize how internal “forward” model (FM) estimates may be used to cancel or attenuate sensory signals that arise as a result of self-generated movements. We used behavioural and functional brain imaging (functional magnetic resonance imaging, fMRI) to investigate how perception of a somatosensory stimulus differed according to whether it was delivered to a hand that was about to execute a reaching movement or the alternative, nonmoving, hand. The results of our study demonstrate that a somatosensory stimulus delivered to a hand that is being prepared for movement is perceived to have occurred later than when that same stimulus is delivered to a nonmoving hand. This result indicates that it takes longer for a tactile stimulus to be detected when it is delivered to a moving limb and may correspond to a change in perceptual threshold. Our behavioural results are paralleled by the results of our fMRI study that demonstrated that there were significantly reduced blood-oxygen-level-dependent (BOLD) responses within the parietal operculum and insula following somatosensory stimulation of the hand being prepared for movement, compared to when an identical stimulus was delivered to a nonmoving hand. These findings are consistent with the prediction of FM accounts of motor control that postulate that central sensory suppression of somatosensation accompanies self-generated limb movements, and with previous reports indicating that effects of sensory suppression are observed in higher order somatosensory regions.     

Effects of motor intention on the perception of somatosensory events: a behavioural and functional magnetic resonance imaging study

The intention to execute a movement can modulate our perception of sensory events, and this modulation is observed ahead of both ocular and upper limb movements. However, theoretical accounts of these effects, and also the empirical data, are often contradictory. Accounts of "active touch", and the premotor theory of attention, have emphasized how movement intention leads to enhanced perceptual processing at the target of a movement, or on the to-be-moved effector. By contrast, recent theories of motor control emphasize how internal "forward" model (FM) estimates may be used to cancel or attenuate sensory signals that arise as a result of self-generated movements. We used behavioural and functional brain imaging (functional magnetic resonance imaging, fMRI) to investigate how perception of a somatosensory stimulus differed according to whether it was delivered to a hand that was about to execute a reaching movement or the alternative, nonmoving, hand. The results of our study demonstrate that a somatosensory stimulus delivered to a hand that is being prepared for movement is perceived to have occurred later than when that same stimulus is delivered to a nonmoving hand. This result indicates that it takes longer for a tactile stimulus to be detected when it is delivered to a moving limb and may correspond to a change in perceptual threshold. Our behavioural results are paralleled by the results of our fMRI study that demonstrated that there were significantly reduced blood-oxygen-level-dependent (BOLD) responses within the parietal operculum and insula following somatosensory stimulation of the hand being prepared for movement, compared to when an identical stimulus was delivered to a nonmoving hand. These findings are consistent with the prediction of FM accounts of motor control that postulate that central sensory suppression of somatosensation accompanies self-generated limb movements, and with previous reports indicating that effects of sensory suppression are observed in higher order somatosensory regions.     

Modulation of the affordance effect through transfer of learning

Consistent evidence shows that practising with spatially incompatible stimulus–response trials modulates performance on following tasks requiring the solution of cognitive conflict such as the Simon and Stroop tasks. In the present study we assessed whether a spatially incompatible practice can modulate another effect that is thought to be due to a conflict between two response alternatives, the affordance effect. To this end, we requested participants to categorize pictures of common objects on the basis of their upright or inverted orientation. A group of participants performed the categorization task alone, while the other two groups performed the categorization task after practising with a spatial compatibility task with either a compatible or an incompatible mapping. Results showed that the spatially incompatible practice eliminated the affordance effect. These results indicate that the conflict at the basis of the affordance effect is not unavoidable but it rather permeable to modulations affecting the response selection stage. Indeed the “emit the alternative spatial response” rule acquired during the spatially incompatible task can transfer to and modulate how the subsequent affordance task is performed.     

The role of vision in the control of continuous multijoint movements

The authors investigated whether visual fixations during a continuous graphical task were related to arm endpoint kinematics, joint motions, or joint control. The pattern of visual fixations across various shapes and the relationship between temporal and spatial events of the moving limb and visual fixations were assessed. Participants (N=16) performed movements of varying shapes by rotating the shoulder and elbow joints in the transverse plane at a comfortable pace. Across shapes, eye movements consisted of a series of fixations, with the eyes leading the hand. Fixations were spatially related to modulation of joint motion and were temporally related to the portions of the movement where curvature was the highest. Gathering of information related to modulation of interactive torques arising from passive forces from movement of a linked system occurred when the velocity of the movement (a) was the lowest and (b) was ahead of the moving limb, suggesting that that information is used in a feedforward manner.