Manual response preparation disrupts spatial attention: an electrophysiological investigation of links between action and attention

ERP evidence of attentional somatosensory processing and stimulus-response coupling under different hand and arm postures

We investigated (1) the effects of divided and focused attention on event-related brain potentials (ERPs) elicited by somatosensory stimulation under different response modes, (2) the effects of hand position (closely-placed vs. separated hands) and arm posture (crossed vs. uncrossed forearms) on the attentional modulation of somatosensory ERPs, and (3) changes in the coupling of stimulus- and response-related processes by somatosensory attention using a single-trial analysis of P300 latency and reaction times. Electrocutaneous stimulation was presented randomly to the thumb or middle finger of the left or right hand at random interstimulus intervals (700-900 ms). Subjects attended unilaterally or bilaterally to stimuli in order to detect target stimuli by a motor response or counting. The effects of unilaterally-focused attention were also tested under different hand and arm positions. The amplitude of N140 in the divided attention condition was intermediate between unilaterally attended and unattended stimuli in the unilaterally-focused attention condition in both the mental counting and motor response tasks. Attended infrequent (target) stimuli elicited greater P300 in the unilaterally attention condition than in the divided attention condition. P300 latency was longer in the divided attention condition than in the unilaterally-focused attention condition in the motor response task, but remained unchanged in the counting task. Closely locating the hands had no impact, whereas crossing the forearms decreased the attentional enhancement in N140 amplitude. In contrast, these two manipulations uniformly decreased P300 amplitude and increased P300 latency. The correlation between single-trial P300 latency and RT was decreased by crossed forearms, but not by divided attention or closely-placed hands. Therefore, the present results indicate that focused and divided attention differently affected middle latency and late processing, and that hand position and arm posture also differently affected attentional processes and stimulus-response coupling.

Upward action promotes selective attention to negative words

Space-valence metaphors (e.g., bad is down) are embedded within cognitive and emotional processing (e.g., negative stimuli at a lower space capture visual attention more than those at an upper space). Previous studies have revealed that motor action to vertical direction affects the emotional valence rating of stimuli in a metaphor-congruent manner only when the action was introduced after the stimuli presentation. In the present study, we hypothesized that motor action before the stimuli presentation does not affect valence rating while it may affect visual selective attention. In Experiment 1 (participants: 28 university students; mean age = 19.50 years), we partially replicated the previous result with repeated ANOVA and t-tests; manual action introduced before the stimuli presentation does not affect the valence rating. Then, in Experiment 2 (participants: 28 university students; mean age = 19.57 years), we employed a modified version of the dot-probe task as a measure of visual selective attention to emotional stimuli, where participants’ vertical or horizontal manual action was introduced before the presentation of a pair of emotional words. The results of the t-tests revealed that an upward manual action promoting selective attention to negative words, which was incongruent with the space-valence metaphorical correspondence. These results suggest that even though manual action does not affect the evaluative process of emotional stimuli prospectively, upward manual action introduced before stimuli presentation can promote visual attention to the subsequent negative stimuli in a way that is incongruent with the space-valence metaphor.

The brain dynamics of architectural affordances during transition

Action is a medium of collecting sensory information about the environment, which in turn is shaped by architectural affordances. Affordances characterize the fit between the physical structure of the body and capacities for movement and interaction with the environment, thus relying on sensorimotor processes associated with exploring the surroundings. Central to sensorimotor brain dynamics, the attentional mechanisms directing the gating function of sensory signals share neuronal resources with motor-related processes necessary to inferring the external causes of sensory signals. Such a predictive coding approach suggests that sensorimotor dynamics are sensitive to architectural affordances that support or suppress specific kinds of actions for an individual. However, how architectural affordances relate to the attentional mechanisms underlying the gating function for sensory signals remains unknown. Here we demonstrate that event-related desynchronization of alpha-band oscillations in parieto-occipital and medio-temporal regions covary with the architectural affordances. Source-level time-frequency analysis of data recorded in a motor-priming Mobile Brain/Body Imaging experiment revealed strong event-related desynchronization of the alpha band to originate from the posterior cingulate complex, the parahippocampal region as well as the occipital cortex. Our results firstly contribute to the understanding of how the brain resolves architectural affordances relevant to behaviour. Second, our results indicate that the alpha-band originating from the occipital cortex and parahippocampal region covaries with the architectural affordances before participants interact with the environment, whereas during the interaction, the posterior cingulate cortex and motor areas dynamically reflect the affordable behaviour. We conclude that the sensorimotor dynamics reflect behaviour-relevant features in the designed environment.

Tool use modulates early stages of visuo-tactile integration in far space: Evidence from event-related potentials

The neural representation of multisensory space near the body is modulated by the active use of long tools in non-human primates. Here, we investigated whether the electrophysiological correlates of visuo-tactile integration in near and far space were modulated by active tool use in healthy humans. Participants responded to a tactile target delivered to one hand while an irrelevant visual stimulus was presented ipsilaterally in near or far space. This crossmodal task was performed after the use of either short or long tools. Crucially, the P100 components elicited by visuo-tactile stimuli was enhanced on far as compared to near space trials after the use of long tools, while no such difference was present after short tool use. Thus, we found increased neural responses in brain areas encoding tactile stimuli to the body when visual stimuli were presented close to the tip of the tool after long tool use. This increased visuo-tactile integration on far space trials following the use of long tools might indicate a transient remapping of multisensory space. We speculate that performing voluntary actions with long tools strengthens the representation of sensory information arising within portions of space (i.e. the hand and the tip of the tool) that are most functionally relevant to one's behavioural goals.

Cortical processing of irrelevant somatosensory information from the leg is altered by attention during early movement preparation

The ability to actively suppress, or gate, irrelevant sensory information is needed for safe and efficient walking in sensory-rich environments. Both attention and the late phase of motor preparation alter somatosensory evoked potentials (SEPs) in healthy adults. The aim of this study was to examine the effect of attention on the processing of irrelevant somatosensory information during the early phase of preparation of plantarflexion movements. Young healthy individuals received tibial nerve stimulation while electroencephalography (EEG) recorded SEPs over the Cz electrode. Three conditions were tested in both legs: 1) Rest, 2) Attend To the stimulated limb, and 3) Attend Away from the stimulated limb. In conditions 2 and 3, vibration (80 Hz) was applied over the medial soleus muscle to cue voluntary plantarflexion movements of the stimulated (Attend To) or non-stimulated leg (Attend Away). Only SEPs delivered during early preparation were averaged for statistical analysis. Results demonstrated a main effect of condition for the N40 and N70 indicating that SEP amplitudes in the Attend To condition were smaller than rest (p ≤ 0.02). For the P50, no interaction effects or main effects were found (p ≥ 0.08). There was no main effect of leg for any component measured. The results indicate that gating of irrelevant sensory information during early preparation occurs in the leg when attention is directed within the same limb. If attention alters the somatosensory stimuli from a leg movement, then directing attention may affect safe community walking.

Attention orienting near the hand following performed and imagined actions

Recent studies have documented that the hand's ability to perform actions affects the visual processing and attention for objects near the hand, suggesting that actions may have specific effects on visual orienting. However, most research on the relation between spatial attention and action focuses on actions as responses to visual attention manipulations. The current study examines visual attention immediately following an executed or imagined action. A modified spatial cuing paradigm tested whether a brief, lateralized hand-pinch performed by a visually hidden hand near the target location, facilitated or inhibited subsequent visual target detection. Conditions in which hand-pinches were fully executed (action) were compared to ones with no hand-pinch (inaction) in Experiment 1 and imagined pinches (imagine) in Experiment 2. Results from Experiment 1 indicated that performed hand pinches facilitated rather than inhibited subsequent detection responses to targets appearing near the pinch, but target detection was not affected by inaction. In Experiment 2, both action and imagined action conditions cued attention and facilitated responses, but along differing time courses. These results highlight the ongoing nature of visual attention and demonstrate how it is deployed to locations even following actions.

Action-effect related motor adaptation in interactions with everyday devices

Human action planning relies on integrated representations of motor acts and the associated consequences, which implies that changing the set of effects associated to a motor act might directly influence action planning and control. The present study investigated the hypothesis that action-effect manipulations also affected the motor components of the actions even when only a single action option was available. Participants performed simple everyday actions (pinched a plastic sheet, pressed a button, tapped on a table) in two conditions. In the motor-auditory condition actions resulted in the presentation of a tone, whereas no tones were presented in the motor condition. The applied force was softer in the motor-auditory than in the motor condition for all three types of actions. The temporal characteristics of force application showed that action-effect related motor adaptation occurred during action planning, but possibly also during action execution. This demonstrates that even in simple, well-defined interactions with everyday devices we take all (even seemingly task-irrelevant) action-effects into account during action planning, which affects the motor component of the action. The results also imply that in experiments manipulating contingent action effects, one cannot rely on the assumption that the motor part of the action is invariant between conditions.

The effect of pre-cueing on spatial attention across perception and action

It is well established that processes of perception and action interact. A key question concerns the role of attention in the interaction between perception-action processes. We tested the hypothesis that spatial attention is shared by perception and action. We created a dual-task paradigm: In one task, spatial information is relevant for perception (spatial-input task) but not for action, and in a second task, spatial information is relevant for action (spatial-output task) but not for perception. We used endogenous pre-cueing, with two between-subjects conditions: In one condition the cue was predictive only for the target location in the spatial-input task; in a second condition the cue was predictive only for the location of the response in the spatial-output task. In both conditions, the cueing equally affected both tasks, regardless of the information conveyed by the cue. This finding directly supports the shared input-output attention hypothesis.

Spatial attention across perception and action

We hypothesize that a shared spatial attention mechanism is used for both perception and action. To this end we created a new dual-task version of the classical Simon task. In one task, the spatial-input task, associated with input spatial attention, participants named one shape out of two bilaterally presented colored shapes. In a second task, the spatial-output task, associated with output spatial attention, participants discriminated between high and low pitch tones by pressing either a left or a right key. In Experiment 1, input for both tasks appeared simultaneously, and participants were instructed not to prioritize either task. A between tasks Simon-like effect was found for responses to both tasks. Reaction times were shorter when the side of the relevant shape in the spatial-input task and the side of the correct response in the spatial-output task were congruent. In Experiment 2, we manipulated the stimulus-onset asynchrony (SOA) between the inputs for the two tasks and showed that the Simon-like effect remained intact at all SOAs. Experiment 3 was similar to Experiment 1 except that the vocal response for the spatial-input task was not speeded. A Simon-like effect was still observed. Experiment 4 was the same as Experiment 3 except that the non-speeded response for the spatial-input task was manual rather than vocal. No Simon-like effect was observed in this experiment. Our results support a shared spatial attention mechanism involved in the Simon effect and indicate that this spatial attention mechanism is shared by perception and action.

Functional Equivalence of Imagined vs. Real Performance of an Inhibitory Task: An EEG/ERP Study

Early neuroimaging and electrophysiological studies suggested that motor imagery recruited a different network than motor execution. However, several studies have provided evidence for the involvement of the same circuits in motor imagery tasks, in the absence of overt responses. The present study aimed to test whether imagined performance of a stop-signal task produces a similar pattern of motor-related EEG activity than that observed during real performance. To this end, mu and beta event-related desynchronization (ERD) and the Lateralized Readiness Potential (LRP) were analyzed. The study also aimed to clarify the functional significance of the Stop-N2 and Stop-P3 event-related potential (ERPs) components, which were also obtained during both real and imagined performance. The results showed a common pattern of brain electrical activity, and with a similar time course, during covert performance and overt execution of the stop-signal task: presence of LRP and Stop-P3 in the imagined condition and identical LRP onset, and similar mu and beta ERD temporal windows for both conditions. These findings suggest that a similar inhibitory network may be activated during both overt and covert execution of the task. Therefore, motor imagery may be useful to improve inhibitory skills and to develop new communicating systems for Brain-Computer Interface (BCI) devices based on inhibitory signals.

The impact of response frequency on spatial stimulus-response correspondence effects

The present study explored how response preparation, varied by relative response frequency, affects response conflict as expressed in the Simon effect. Previous studies showed that valid response cues, when presented before the imperative stimulus, increase rather than decrease the Simon effect. This finding was explained by the hypothesis that response cues trigger shifts of attention to the side of the prepared response, and that these attention shifts modulate processing of the imperative stimulus. We investigated whether cues are necessary for inducing shifts of attention and thereby modulating the Simon effect, or whether response preparation without cues is sufficient. In two experiments, participants performed a Simon task with one response being more frequent than the other. Results showed larger Simon effects for the more frequent (i.e. prepared) response than for the less frequent (i.e. unprepared) response. These results suggest that response preparation (rather than the cue that induces the preparation) triggers a shift of spatial attention which modulates the Simon effect.

Atypical Caudate Anatomy in Children Who Stutter

A temporal motor defect in speech preparation and/or planning may contribute to the development of stuttering. This defect may be linked to a dysfunctional cortical-subcortical network at the level of the striatum. To determine whether structural differences exist and whether group differences are associated with stuttering severity or manual laterality, the caudate was measured in 14 children who stutter (CWS) and in a control group of right-handed boys, ages 8–13 years. There was a statistically significant hemisphere by group effect for caudate volume. CWS had reduced right caudate volume and atypical leftward asymmetry compared to controls. Nine of the 13 CWS with atypical caudate asymmetry had atypical manual laterality. These anomalies may represent a vulnerability that perturbs speech planning/preparation and contributes to inefficiencies in action-perception coupling that may be an indicator of stuttering susceptibility. These results suggest that right-handed boys who stutter may have a defect in the feedforward cortico-striato-thalamo-cortical networks.

Investigating ideomotor cognition with motorvisual priming paradigms: key findings, methodological challenges, and future directions

Ideomotor theory claims that perceptual representations of action-effects are functionally involved in the planning of actions. Strong evidence for this claim comes from a phenomenon called motorvisual priming. Motorvisual priming refers to the finding that action planning directly affects perception, and that the effects are selective for stimuli that share features with the planned action. Motorvisual priming studies have provided detailed insights into the processing of perceptual representations in action planning. One important finding is that such representations in action planning have a categorical format, whereas metric representations are not anticipated in planning. Further essential findings regard the processing mechanisms and the time course of ideomotor cognition. Perceptual representations of action-effects are first activated by action planning and then bound into a compound representation of the action plan. This compound representation is stabilized throughout the course of the action by the shielding of all involved representations from other cognitive processes. Despite a rapid growth in the number of motorvisual priming studies in the current literature, there are still many aspects of ideomotor cognition which have not yet been investigated. These aspects include the scope of ideomotor processing with regard to action types and stimulus types, as well as the exact nature of the binding and shielding mechanisms involved.

The planning and control model (PCM) of motorvisual priming: reconciling motorvisual impairment and facilitation effects

Previous research on dual-tasks has shown that, under some circumstances, actions impair the perception of action-consistent stimuli, whereas, under other conditions, actions facilitate the perception of action-consistent stimuli. We propose a new model to reconcile these contrasting findings. The planning and control model (PCM) of motorvisual priming proposes that action planning binds categorical representations of action features so that their availability for perceptual processing is inhibited. Thus, the perception of categorically action-consistent stimuli is impaired during action planning. Movement control processes, on the other hand, integrate multi-sensory spatial information about the movement and, therefore, facilitate perceptual processing of spatially movement-consistent stimuli. We show that the PCM is consistent with a wider range of empirical data than previous models on motorvisual priming. Furthermore, the model yields previously untested empirical predictions. We also discuss how the PCM relates to motorvisual research paradigms other than dual-tasks.

Dopamine, affordance and active inference

The role of dopamine in behaviour and decision-making is often cast in terms of reinforcement learning and optimal decision theory. Here, we present an alternative view that frames the physiology of dopamine in terms of Bayes-optimal behaviour. In this account, dopamine controls the precision or salience of (external or internal) cues that engender action. In other words, dopamine balances bottom-up sensory information and top-down prior beliefs when making hierarchical inferences (predictions) about cues that have affordance. In this paper, we focus on the consequences of changing tonic levels of dopamine firing using simulations of cued sequential movements. Crucially, the predictions driving movements are based upon a hierarchical generative model that infers the context in which movements are made. This means that we can confuse agents by changing the context (order) in which cues are presented. These simulations provide a (Bayes-optimal) model of contextual uncertainty and set switching that can be quantified in terms of behavioural and electrophysiological responses. Furthermore, one can simulate dopaminergic lesions (by changing the precision of prediction errors) to produce pathological behaviours that are reminiscent of those seen in neurological disorders such as Parkinson's disease. We use these simulations to demonstrate how a single functional role for dopamine at the synaptic level can manifest in different ways at the behavioural level.

Active inference, attention, and motor preparation

Perception is the foundation of cognition and is fundamental to our beliefs and consequent action planning. The Editorial (this issue) asks: "what mechanisms, if any, mediate between perceptual and cognitive processes?" It has recently been argued that attention might furnish such a mechanism. In this paper, we pursue the idea that action planning (motor preparation) is an attentional phenomenon directed toward kinesthetic signals. This rests on a view of motor control as active inference, where predictions of proprioceptive signals are fulfilled by peripheral motor reflexes. If valid, active inference suggests that attention should not be limited to the optimal biasing of perceptual signals in the exteroceptive (e.g., visual) domain but should also bias proprioceptive signals during movement. Here, we investigate this idea using a classical attention (Posner) paradigm cast in a motor setting. Specially, we looked for decreases in reaction times when movements were preceded by valid relative to invalid cues. Furthermore, we addressed the hierarchical level at which putative attentional effects were expressed by independently cueing the nature of the movement and the hand used to execute it. We found a significant interaction between the validity of movement and effector cues on reaction times. This suggests that attentional bias might be mediated at a low level in the motor hierarchy, in an intrinsic frame of reference. This finding is consistent with attentional enabling of top-down predictions of proprioceptive input and may rely upon the same synaptic mechanisms that mediate directed spatial attention in the visual system.

Independent Allocation of Attention to Eye and Hand Targets in Coordinated Eye-Hand Movements

When reaching for objects, people frequently look where they reach. This raises the question of whether the targets for the eye and hand in concurrent eye and hand movements are selected by a unitary attentional system or by independent mechanisms. We used the deployment of visual attention as an index of the selection of movement targets and asked observers to reach and look to either the same location or separate locations. Results show that during the preparation of coordinated movements, attention is allocated in parallel to the targets of a saccade and a reaching movement. Attentional allocations for the two movements interact synergistically when both are directed to a common goal. Delaying the eye movement delays the attentional shift to the saccade target while leaving attentional deployment to the reach target unaffected. Our findings demonstrate that attentional resources are allocated independently to the targets of eye and hand movements and suggest that the goals for these effectors are selected by separate attentional mechanisms.

Modulation of sensory and motor cortex activity during speech preparation

Previous studies have shown that speaking affects auditory and motor cortex responsiveness, which may reflect the influence of motor efference copy. If motor efference copy is involved, it would also likely influence auditory and motor cortical activity when preparing to speak. We tested this hypothesis by using auditory event-related potentials and transcranial magnetic stimulation (TMS) of the motor cortex. In the speech condition subjects were visually cued to prepare a vocal response to a subsequent target, which was compared to a control condition without speech preparation. Auditory and motor cortex responsiveness at variable times between the cue and target were probed with an acoustic stimulus (Experiment 1, tone or consonant-vowels) or motor cortical TMS (Experiment 2). Acoustic probes delivered shortly before targets elicited a fronto-central negative potential in the speech condition. Current density analysis showed that auditory cortical activity was attenuated at the beginning of the slow potential in the speech condition. Sensory potentials in response to probes had shorter latencies (N100) and larger amplitudes (P200) when consonant-vowels matched the sound of cue words. Motor cortex excitability was greater in the speech than in the control condition at all time points before picture onset. The results suggest that speech preparation induces top-down regulation of sensory and motor cortex responsiveness, with different time courses for auditory and motor systems.