Congruent Movements Research Articles

Audio-Visual Interference During Motion Discriminationin Starlings.

Motion discrimination is essential for animals to avoid collisions, to escape from predators, to catch prey or to communicate. Although most terrestrial vertebrates can benefit by combining concurrent stimuli from sound and vision to obtain a most salient percept of the moving object, there is little research on the mechanisms involved in such cross-modal motion discrimination. We used European starlings as a model with a well-studied visual and auditory system. In a behavioural motion discrimination task with visual and acoustic stimuli, we investigated the effects of cross-modal interference and attentional processes. Our results showed an impairment of motion discrimination when the visual and acoustic stimuli moved in opposite directions as compared to congruent motion direction. By presenting an acoustic stimulus of very short duration, thus lacking directional motion information, an additional alerting effect of the acoustic stimulus became evident. Finally, we show that a temporally leading acoustic stimulus did not improve the response behaviour compared to the synchronous presentation of the stimuli as would have been expected in case of major alerting effects. This further supports the importance of congruency and synchronicity in the current test paradigm with a minor role of attentional processes elicited by the acoustic stimulus. Together, our data clearly show cross-modal interference effects in an audio-visual motion discrimination paradigm when carefully selecting real-life stimuli under parameter conditions that meet the known criteria for cross-modal binding.

Evolutionary Steps in the Development of a Patient-specific Temporomandibular Joint Prosthesis

Study Design Descriptive study (/review containing supporting case studies). Objective The temporomandibular joint has some distinctive features that were not taken into account during the initial development of temporomandibular joint prostheses, such as laterotrusive movements that are necessary for the proper grinding of food as well as synchronous and congruent movements made in conjunction with the healthy, contralateral joint. The aim of this article is to describe the development of a novel type of TMJ prosthesis that optimizes temporomandibular joint replacement. Methods The development was initiated by using contemporary technologies like computer-aided design customization, additive manufacturing, and surface treatments. Biocompatibility, proper fixation, and wear resistance, being prerequisites for the longevity of prostheses, were investigated next. Individual variables (condylar path, condylar axis angle, Bennet shift) were introduced as the main basis for physiological movements with the restoration of all functions. Early post-operative results ranging from 1 month to 4.5 years (11 patients, average follow-up period was 23.3 months) were assessed. Results The experience with 16 individualized total joint replacements in 11 patients is presented. The 3-year follow-up results of two-patient detailed studies are discussed, which show evidence of the promising restoration of all mandibular movements, when preoperatively present. Conclusions By incorporating various innovative and novel features (scaffold for re-attachment of lateral pterygoid, patient-specific functional parametrization, saddle-like design for retention, …) into a novel TMJ prosthesis concept, a major advance in function-reconstructive temporomandibular joint replacement was achieved. Early in vivo results (1 year after surgery) showed promising outcomes, involving both high increases in mandibular movements and decreases in pain scores.

Motor Compatibility Effect on the Comprehension of Complex Manual Action Sentences in L2: An ERP Study

Abstract Embodiment theories proposed that the comprehension of language involves sensory-motor simulation in the brain. The present study examined the brain response to motor compatibility effect in comprehending action-related linguistic materials for participants learning Chinese as a second language (L2). In this study, participants are required to read action-related sentences describing an agent performing two manual actions simultaneously or sequentially by manipulating temporal conjunctions. The sentences with simultaneous actions are marked by Chinese parallel structure 一边……一边…… (“while”) showing non-congruent motor condition while the sequential action sentences are marked by 先……然后…… (“after”) showing congruent motor condition. Event-Related Potentials (ERPs) were recorded with the second verb phrase. A larger fronto-central late positivity was observed for the sentences with simultaneous actions rather than the sentences with sequential actions due to body constraints, revealing that late L2 Chinese learners integrate embodied knowledge while processing action-related complex sentence despite demanding more cognitive resources, and longer processing time.

When perception is stronger than physics: Perceptual similarities rather than laws of physics govern the perception of interacting objects

When several multistable displays are viewed simultaneously, their perception is synchronized, as they tend to be in the same perceptual state. Here, we investigated the possibility that perception may reflect embedded statistical knowledge of physical interaction between objects for specific combinations of displays and layouts. We used a novel display with two ambiguously rotating gears and an ambiguous walker-on-a-ball display. Both stimuli produce a physically congruent perception when an interaction is possible (i.e., gears counterrotate, and the ball rolls under the walker’s feet). Next, we gradually manipulated the stimuli to either introduce abrupt changes to the potential physical interaction between objects or keep it constant despite changes in the visual stimulus. We characterized the data using four different models that assumed (1) independence of perception of the stimulus, (2) dependence on the stimulus’s properties, (3) dependence on physical configuration alone, and (4) an interaction between stimulus properties and a physical configuration. We observed that for the ambiguous gears, the perception was correlated with the stimulus changes rather than with the possibility of physical interaction. The perception of walker-on-a-ball was independent of the stimulus but depended instead on whether participants responded about a relative motion of two objects (perception was biased towards physically congruent motion) or the absolute motion of the walker alone (perception was independent of the rotation of the ball). None of the two experiments supported the idea of embedded knowledge of physical interaction.

The Z-Box illusion: dominance of motion perception among multiple 3D objects.

In the present article, we examine a novel illusion of motion-the Z-Box illusion-in which the presence of a bounding object influences the perception of motion of an ambiguous stimulus that appears within. Specifically, the stimuli are a structure-from-motion (SFM) particle orb and a wireframe cube. The orb could be perceived as rotating clockwise or counterclockwise while the cube could only be perceived as moving in one direction. Both stimuli were presented on a two-dimensional (2D) display with inferred three-dimensional (3D) properties. In a single experiment, we examine motion perception of a particle orb, both in isolation and when it appears within a rotating cube. Participants indicated the orb's direction of motion and whether the direction changed at any point during the trial. Accuracy was the critical measure while motion direction, the number of particles in the orb and presence of the wireframe cube were all manipulated. The results suggest that participants could perceive the orb's true rotation in the absence of the cube so long as it was made up of at least ten particles. The presence of the cube dominated perception as participants consistently perceived congruent motion of the orb and cube, even when they moved in objectively different directions. These findings are considered as they relate to prior research on motion perception, computational modelling of motion perception, structure from motion and 3D object perception.

Identifying Appropriate Neuropsychological Tests for Uneducated/Illiterate Older Individuals.

We investigated the utility of traditional neuropsychological tests in older uneducated/illiterate individuals without dementia to determine the possibility that they are likely not appropriate for this group. We assessed the neuropsychological performance of 1122 older adults [≥65 years old; mean age: 74.03 (SD = 5.46); mean education: 4.76 (SD = 2.5) years; women: n = 714], in the context of the Hellenic Longitudinal Investigation of Aging and Diet (HELIAD), a population-based study conducted in Greece. We based our analyses on three groups: high-functioning/cognitively healthy (i.e., without dementia) uneducated/illiterate individuals (n = 80), high-functioning/cognitively healthy educated/literate individuals (n = 932), and low-functioning/cognitively impaired educated/literate individuals (presumably with dementia; n = 110). We used binary regression analyses with Bonferroni correction to investigate whether test performance differentiated uneducated/illiterate from educated/literate individuals. Models were adjusted for age and sex; raw test scores were the predictor variables. The uneducated/illiterate cohort was at a disadvantage relative to the healthy educated/literate group on all variables but verbal memory recognition and consolidation, congruent motor responses, and phonological fluency clustering (p>.002). Moreover, only word list learning immediate and delayed free recall and delayed cued recall differentiated the high-functioning/cognitively healthy uneducated/illiterate from the low-functioning/cognitively impaired educated/literate group, favoring the former (p's<.002). Our findings suggest that only particular verbal memory test variables are fair in determining whether older uneducated/illiterate individuals have functional/cognitive impairment suggestive of a neurodegenerative process. On all other neuropsychological variables, this cohort was at a disadvantage. Therefore, we highlight the need for identifying appropriate methods of assessment for older uneducated/illiterate individuals.

Congruent movement training as a rehabilitation method to ameliorate symptoms of neglect–proof of concept

Stroke patients with visuospatial neglect (VSN) have difficulties responding to visual information located in the contralesional hemifield, affecting many daily life activities (ADL) such as eating, reading and mobility. Visual Scanning Therapy (VST) is widely used in clinical practice to ameliorate symptoms of VSN. Yet, not all patients benefit from this training and many training sessions are needed in order to achieve stable results. One potentially promising improvement to the VST is based on the theory that different effectors of the motor systems (e.g., eyes, hands) independently allocate attention during the programming of the movement (i.e., Pre Motor Theory of Attention (PMT)). Here, we studied this direct implementation of the PMT and tested whether a congruent movement training (CMT: congruent -i.e., executed at the same time to the same location-eye and pointing movements) is more effective to attenuate symptoms of neglect compared to VST. This study can be seen as a proof of concept. Attenuation of neglect symptoms was found in the CMT group after just 5 h of training in the subacute phase of neglect. In contrast, no training effects were found in the VST group. These findings indicate the potential of CMT which is a minimal –yet crucial-upgrade of the standard VST protocol that can be easily implemented in the clinic.

Drawing lines and circles in Parkinson's Disease: The lateralized symptoms interfere with the movements of the unaffected hand

IntroductionEvidence about altered bimanual coordination has been reported in Parkinson's Disease. However, no previous study has explored such an alteration quantifying the interference effect that the trajectory of each hand might impose on the other one. Thus, in the present research, we applied the traditional Circles-Lines Coupling Task, which allowed assessing the motor coordination of the two hands, in the context of Parkinson's Disease. MethodsThirty-six individuals affected by Parkinson's Disease were consecutively recruited and assigned to two groups according to their symptoms' lateralization. Moreover, eighteen age-matched healthy controls participated in the study. We capitalized on the Circles-Lines Coupling Task, in which the performance during incongruent movements (drawing lines with one hand and circles with the other hand) was compared with the performance during congruent movements (drawing lines with both hands). A bimanual coupling index was computed to compare the interference effect of each hand on the other one. ResultsIn healthy controls, the bimanual coupling index did not differ between the two hands. Crucially, in both groups of individuals affected by Parkinson's Disease, the less affected hand showed a significantly higher bimanual coupling index, due to the abnormal interference exerted by the most affected one, than vice versa. ConclusionsOur results highlighted an altered spatial bimanual coupling in Parkinson's disease, depending on the symptoms' lateralization. We offered different explanations of our results according to the theoretical frameworks about the mechanisms subserving bimanual coordination.

Motor congruency and multisensory integration jointly facilitate visual information processing before movement execution

Attention allows us to select important sensory information and enhances sensory information processing. Attention and our motor system are tightly coupled: attention is shifted to the target location before a goal-directed eye- or hand movement is executed. Congruent eye–hand movements to the same target can boost the effect of this pre-movement shift of attention. Moreover, visual information processing can be enhanced by, for example, auditory input presented in spatial and temporal proximity of visual input via multisensory integration (MSI). In this study, we investigated whether the combination of MSI and motor congruency can synergistically enhance visual information processing beyond what can be observed using motor congruency alone. Participants performed congruent eye- and hand movements during a 2-AFC visual discrimination task. The discrimination target was presented in the planning phase of the movements at the movement target location or a movement irrelevant location. Three conditions were compared: (1) a visual target without sound, (2) a visual target with sound spatially and temporally aligned (MSI) and (3) a visual target with sound temporally misaligned (no MSI). Performance was enhanced at the movement-relevant location when congruent motor actions and MSI coincide compared to the other conditions. Congruence in the motor system and MSI together therefore lead to enhanced sensory information processing beyond the effects of motor congruency alone, before a movement is executed. Such a synergy implies that the boost of attention previously observed for the independent factors is not at ceiling level, but can be increased even further when the right conditions are met.

Corticospinal Modulations during Motor Imagery of Concentric, Eccentric, and Isometric Actions.

It is not known yet whether the neurophysiological specificity of eccentric, concentric, and isometric contractions can also be observed when these are mentally simulated. Therefore, our aim was to assess corticospinal excitability during motor imagery (MI) of different contraction types and to test whether a passive movement during MI could have additional effects. Twelve young participants imagined contractions of the wrist flexors, firstly with the arm motionless (static mode) and second, with a congruent passive movement (wrist extension during eccentric MI and wrist flexion during concentric MI). Motor-evoked potentials (MEP) and H-reflexes were elicited in flexor carpi radialis (FCR) at rest and during the three types of MI. As a secondary outcome, the MEP of one antagonist (extensor carpi radialis), elicited concomitantly with FCR MEP recording, were also analyzed. In static mode, FCR MEP were facilitated during isometric (P = 0.046) and concentric (P = 0.039) MI, but not during eccentric MI (P = 0.902). With passive congruent movements, FCR MEP were enhanced during all imagined contraction types, including eccentric (P = 0.047). FCR H-reflexes increased only during eccentric MI accompanied with wrist extension (P = 0.003). Extensor carpi radialis MEP were modulated only when a passive congruent movement was provided (P = 0.040). Like actual contractions, eccentric MI exhibits specific neural correlates, compared with isometric and concentric MI, which should be considered when using this modality for training. The present results showed that adding passive movements congruent to the eccentric MI task would enhance its impact over corticospinal structures.

Is congruent movement training more effective than standard visual scanning therapy to ameliorate symptoms of visuospatial neglect? Study protocol of a randomised control trial

IntroductionApproximately 30% of all patients with stroke show visuospatial neglect (VSN). Currently, visual scanning therapy (VST) is applied in clinical settings to attenuate neglect symptoms. VST builds on the premise...

Earth-Gravity Congruent Motion Facilitates Ocular Control for Pursuit of Parabolic Trajectories

There is evidence that humans rely on an earth gravity (9.81 m/s²) prior for a series of tasks involving perception and action, the reason being that gravity helps predict future positions of moving objects. Eye-movements in turn are partially guided by predictions about observed motion. Thus, the question arises whether knowledge about gravity is also used to guide eye-movements: If humans rely on a representation of earth gravity for the control of eye movements, earth-gravity-congruent motion should elicit improved visual pursuit. In a pre-registered experiment, we presented participants (n = 10) with parabolic motion governed by six different gravities (−1/0.7/0.85/1/1.15/1.3 g), two initial vertical velocities and two initial horizontal velocities in a 3D environment. Participants were instructed to follow the target with their eyes. We tracked their gaze and computed the visual gain (velocity of the eyes divided by velocity of the target) as proxy for the quality of pursuit. An LMM analysis with gravity condition as fixed effect and intercepts varying per subject showed that the gain was lower for −1 g than for 1 g (by −0.13, SE = 0.005). This model was significantly better than a null model without gravity as fixed effect (p < 0.001), supporting our hypothesis. A comparison of 1 g and the remaining gravity conditions revealed that 1.15 g (by 0.043, SE = 0.005) and 1.3 g (by 0.065, SE = 0.005) were associated with lower gains, while 0.7 g (by 0.054, SE = 0.005) and 0.85 g (by 0.029, SE = 0.005) were associated with higher gains. This model was again significantly better than a null model (p < 0.001), contradicting our hypothesis. Post-hoc analyses reveal that confounds in the 0.7/0.85/1/1.15/1.3 g condition may be responsible for these contradicting results. Despite these discrepancies, our data thus provide some support for the hypothesis that internalized knowledge about earth gravity guides eye movements.

Vestibular cerebellar evoked potentials in humans and their modulation during optokinetic stimulation.

We recorded evoked potentials (EPs) from over the posterior fossa and in parallel ocular vestibular evoked myogenic potentials (OVEMPs) during visuo-vestibular stimulation in a sample of 7 male and 11 female human subjects. In 9 of the 18 subjects we were able to record EPs reliably in the form of an early biphasic positive-negative wave with latencies ~12 and 17 ms ipsilateral to head acceleration direction (P12-N17) and a slightly later, contralateral, biphasic positive-negative wave with latencies ~19 and 23 ms (P19-N23). The amplitudes of the responses varied widely between subjects. Both P12 and N23 EPs were modulated by the mode of visual stimulation, larger for vection (sense of movement) compared with optokinetic nystagmus and for congruent movement. We suggest that the EPs measured over the posterior fossa are a manifestation of climbing fiber responses of cerebellar cortical Purkinje cells, i.e., a form of vestibular cerebellar EP (VsCEP). The two subject groups with and without VsCEPs were distinguished by the magnitude of their OVEMPs and their subjective experience of vection. The modulation of VsCEPs by visual context may be a manifestation of cerebellar control of linear vestibular ocular reflex gain. NEW & NOTEWORTHY We report likely vestibular cerebellar evoked potentials (VsCEPs) produced by lateral head impulses recorded in intact humans over the posterior fossa. VsCEPs occurred as short-latency P12-N17 waves ipsilateral to the direction of head motion and as P19-N23 contralaterally and were present in half our subjects. Their properties suggest that the VsCEPs may be of a climbing-fiber origin. VsCEPs are related to the perception of motion and, possibly, control of linear vestibular ocular reflex gain.

Reduced Motor Interference in Preschoolers with Autism Spectrum Disorder and Williams Syndrome

ABSTRACTMotor interference occurs when action execution is hindered by the observation of an incongruent action. The present study used a novel eye-tracking paradigm to test the motor interference effect in 22 preschoolers with autism spectrum disorder (ASD), 14 preschoolers with Williams syndrome (WS), and 18 typically developing (TD) peers. In TD children, performance of a pre-determined action was slower after the observation of an incongruent motor action and faster following observation of a congruent motor action, indicating a motor interference effect. In both the ASD and WS groups, performance was unaffected by the congruent versus incongruent nature of the observed motor action.

Effects of Congruency on Bereitschaftspotential While Performing a Bimanual Motor Task

The bereitschaftspotential (BP)—also known as the readiness potential—is a measure of brain activity that precedes voluntary movement by approximately one second in the supplementary motor area and the contralateral primary motor cortex. Motor task reaction time for bimanual task performance is affected by both the individual and the environment; however, it is unclear whether motor task reaction time (as measured via the BP) is significantly affected by congruency. A congruent motor task is an ipsilateral stimulus (e.g., a stimulus on the right is responded to by the right hand), and an incongruent task is a contralateral stimulus (e.g., a stimulus on the right is responded to by the left hand). Congruency is re-emerging as an important topic in motor learning as it may require different levels of cortical processing. The purpose of this study was to examine the effect of congruency on the BP. Participants were asked to complete the computer task, Keyboard Hero, where they pressed keys with both their left and right hands in response to discrete congruent and incongruent stimuli. A MUSE™ apparatus recorded brain activity 1000 ms prior to, and 1000 ms after each stimulus. Results from every participant for the incongruent and congruent trials were averaged and compared using a grand average waveform. Means of accuracy (how often participants pressed the key correctly) and BP for each condition were averaged and compared using a 95% Confidence Interval (CI). Across congruent and incongruent conditions, a non-significant difference (p &gt; 0.05 ) was found in BP (p &gt; 0.59 ), accuracy (p &gt; 0.64 ), and BP within −200 ms to 200 ms (p &gt; 0.31 ). BP and mean accuracy scores were not significantly different between congruent and incongruent conditions, which may be due to only minute differences in brain activity or due to the study’s design. Further research should analyze individual variations of the present study, such as stimulus location, differences in the responding limb, correctness of responses, and the sensory modality being tested

Immersive VR and Education: Embodied Design Principles That Include Gesture and Hand Controls.

This article explores relevant applications of educational theory for the design of immersive virtual reality (VR). Two unique attributes associated with VR position the technology to positively affect education: (1) the sense of presence, and (2) the embodied affordances of gesture and manipulation in the 3rd dimension. These are referred to as the two profound affordances of VR. The primary focus of this article is on the embodiment afforded by gesture in 3D for learning. The new generation of hand controllers induces embodiment and agency via meaningful and congruent movements with the content to be learned. Several examples of gesture-rich lessons are presented. The final section includes an extensive set of design principles for immersive VR in education, and finishes with the Necessary Nine which are hypothesized to optimize the pedagogy within a lesson.

The effect of motor context on semantic processing: A TMS study

BackgroundStrong embodiment theories claimed that action language representation is grounded in the sensorimotor system, which would be crucially to semantic understanding. However, there is a large disagreement in literature about the neural mechanisms involved in abstract (symbolic) language comprehension. ObjectiveIn the present study, we investigated the role of motor context in the semantic processing of abstract language. We hypothesized that motor cortex excitability during abstract word comprehension could be modulated by previous presentation of a stimuli which associated a congruent motor content (i.e., a semantically related gesture) to the word. Methods and resultsWe administered a semantic priming paradigm where postures of gestures (primes) were followed by semantically congruent verbal stimuli (targets, meaningful or meaningless words). Transcranial Magnetic Stimulation was delivered to left motor cortex 100, 250 and 500 ms after the presentation of each target. Results showed that Motor evoked potentials of hand muscle significantly increased in correspondence to meaningful compared to meaningless words, but only in the earlier phase of semantic processing (100 and 250 ms from target onset). ConclusionResults suggested that the gestural motor representation was integrated with corresponding word meaning in order to accomplish (and facilitate) the lexical task. We concluded that motor context resulted crucial to highlight motor system involvement during semantic processing of abstract language.

Integrating multisensory information across external and motor-based frames of reference

In the mirror box illusion, participants often report that their hand is located where they see it, even when the position of the reflected hand differs from the actual position of their hand. This illusory shift (an index of multisensory integration) is stronger when the two hands engage in synchronous bimanual movement, in which visual and proprioceptive information is congruent in both motor-based (i.e. coordinate centered on the effector) and external (i.e. coordinates centered on elements external to the effector) frames of reference. To investigate the separate contributions of external and motor-based congruence in multisensory integration, we instructed participants to make synchronous or asynchronous tapping movements in either the same (i.e. both hands palms up) or opposing (palm up, palm down) postures. When in opposing postures, externally congruent movements were incongruent in a motor-based frame of reference, and vice versa. Across three experiments, participants reported more illusory shift and stronger ownership of the viewed hand in the mirror for external versus motor-based congruence trials regardless of motor outflow or motor effort, indicating that information from an externally-based representation is more strongly weighted in multisensory integration. These findings provide evidence that not only information across sensory modalities, but also information regarding crossmodal congruence represented in different spatial frames of reference, is differentially weighted in multisensory integration. We discuss how our findings can be incorporated into current computational models on multisensory integration.

The Emotional Modulation of Facial Mimicry: A Kinematic Study

It is well-established that the observation of emotional facial expression induces facial mimicry responses in the observers. However, how the interaction between emotional and motor components of facial expressions can modulate the motor behavior of the perceiver is still unknown. We have developed a kinematic experiment to evaluate the effect of different oro-facial expressions on perceiver's face movements. Participants were asked to perform two movements, i.e., lip stretching and lip protrusion, in response to the observation of four meaningful (i.e., smile, angry-mouth, kiss, and spit) and two meaningless mouth gestures. All the stimuli were characterized by different motor patterns (mouth aperture or mouth closure). Response Times and kinematics parameters of the movements (amplitude, duration, and mean velocity) were recorded and analyzed. Results evidenced a dissociated effect on reaction times and movement kinematics. We found shorter reaction time when a mouth movement was preceded by the observation of a meaningful and motorically congruent oro-facial gesture, in line with facial mimicry effect. On the contrary, during execution, the perception of smile was associated with the facilitation, in terms of shorter duration and higher velocity of the incongruent movement, i.e., lip protrusion. The same effect resulted in response to kiss and spit that significantly facilitated the execution of lip stretching. We called this phenomenon facial mimicry reversal effect, intended as the overturning of the effect normally observed during facial mimicry. In general, the findings show that both motor features and types of emotional oro-facial gestures (conveying positive or negative valence) affect the kinematics of subsequent mouth movements at different levels: while congruent motor features facilitate a general motor response, motor execution could be speeded by gestures that are motorically incongruent with the observed one. Moreover, valence effect depends on the specific movement required. Results are discussed in relation to the Basic Emotion Theory and embodied cognition framework.

Revisiting the link between body and agency: visual movement congruency enhances intentional binding but is not body-specific

Embodiment and agency are key aspects of how we perceive ourselves that have typically been associated with independent mechanisms. Recent work, however, has suggested that these mechanisms are related. The sense of agency arises from recognising a causal influence on the external world. This influence is typically realised through bodily movements and thus the perception of the bodily self could also be crucial for agency. We investigated whether a key index of agency – intentional binding – was modulated by body-specific information. Participants judged the interval between pressing a button and a subsequent tone. We used virtual reality to manipulate two aspects of movement feedback. First, form: participants viewed a virtual hand or sphere. Second, movement congruency: the viewed object moved congruently or incongruently with the participant’s hidden hand. Both factors, form and movement congruency, significantly influenced embodiment. However, only movement congruency influenced intentional binding. Binding was increased for congruent compared to incongruent movement feedback irrespective of form. This shows that the comparison between viewed and performed movements provides an important cue for agency, whereas body-specific visual form does not. We suggest that embodiment and agency mechanisms both depend on comparisons across sensorimotor signals but that they are influenced by distinct factors.