The self in action effects: selective attenuation of self-generated sounds

Augmented action observation: Theory and practical applications in sensorimotor rehabilitation

Sensory feedback is a fundamental aspect of effective motor learning in sport and clinical contexts. One way to provide this is through sensory augmentation, where extrinsic sensory information are associated with, and modulated by, movement. Traditionally, sensory augmentation has been used as an online strategy, where feedback is provided during physical execution of an action. In this article, we argue that action observation can be an additional effective channel to provide augmented feedback, which would be complementary to other, more traditional, motor learning and sensory augmentation strategies. Given these similarities between observing and executing an action, action observation could be used when physical training is difficult or not feasible, for example during immobilization or during the initial stages of a rehabilitation protocol when peripheral fatigue is a common issue. We review the benefits of observational learning and preliminary evidence for the effectiveness of using augmented action observation to improve learning. We also highlight current knowledge gaps which make the transition from laboratory to practical contexts difficult. Finally, we highlight the key areas of focus for future research.

High or low expectations: Expected intensity of action outcome is embedded in action kinetics

Goal-directed actions are performed in order to attain certain sensory consequences in the world. However, expected attributes of these consequences can affect the kinetics of the action. In a set of three studies (n = 120), we examined how expected attributes of stimulus outcome (intensity) shape the kinetics of the triggering action (applied force), even when the action kinetic and attribute are independent. We show that during action execution (button presses), the expected intensity of sensory outcome affects the applied force of the stimulus-producing action in an inverse fashion. Thus, participants applied more force when the expected intensity of the outcome was low (vs. high intensity outcome). In the absence of expectations or when actions were performed in response to the sensory event, no intensity-dependent force modulations were found. Thus, expectations of stimulus intensity and causality play an important role in shaping action kinetics. Finally, we examined the relationship between kinetics and perception and found no influence of applied force level on perceptual detection of low intensity (near-threshold) outcome stimuli, suggesting no causal link between the two. Taken together, our results demonstrate that action kinetics are embedded with high-level context such as the expectation of consequence intensity and the causal relationship with environmental cues.

Violation of identity-specific action-effect prediction increases pupil size and attenuates auditory event-related potentials at P2 latencies when action-effects are behaviorally relevant

Self-initiated sensory action effects are widely assumed to lead to less intense perception and reduced neural responses compared to externally triggered stimuli (sensory attenuation). However, it is unclear if sensory attenuation occurs in all cases of action-effect prediction. Specifically, when predicted action-effects are relevant to determine follow-up actions attenuation could be detrimental. We quantified auditory event-related potentials (ERP) in electroencephalography (EEG) when human participants created two-sound sequences by pressing two keys on a keyboard associated with different pitch, giving rise to identity-specific action-effect prediction after the first keypress. The first sound corresponded to (congruent) or violated (incongruent) the predicted pitch and was either relevant for the selection of the second keypress to correctly complete the sequence (Relevance) or irrelevant (Control Movement), or there was only one keypress and sound (Baseline). We found a diminished P2-timed ERP component in incongruent compared to congruent trials when the sound was relevant for the subsequent action. This effect of action-effect prediction was due to an ERP reduction for incongruent relevant sounds compared to incongruent irrelevant sounds at P2 latencies and correlated negatively with modulations of pupil dilation. Contrary to our expectation, we did not observe an N1 modulation by congruency in any condition. Attenuation of the N1 component seems absent for predicted identity-specific auditory action effects, while P2-timed ERPs as well as pupil size are sensitive to predictability, at least when action effects are relevant for the selection of the next action. Incongruent relevant stimuli thereby take a special place and seem to be subject to attentional modulations and error processing.

My choice, my actions: self-determination, not instrumental value of outcomes enhances outcome monitoring during learning

Freedom of choice enhances our sense of agency. During goal-directed behavior, the freedom to choose between different response options increases the neural processing of positive and negative feedback, indicating enhanced outcome monitoring under conditions of high agency experience. However, it is unclear whether this enhancement is predominantly driven by an increased salience of self- compared to externally determined action outcomes or whether differences in the perceived instrumental value of outcomes contribute to outcome monitoring in goal-directed tasks. To test this, we recorded electroencephalography while participants performed a reinforcement learning task involving free choices, action-relevant forced choices, and action-irrelevant forced choices. We observed larger midfrontal theta power and N100 amplitudes for feedback following free choices compared with action-relevant and action-irrelevant forced choices. In addition, a Reward Positivity was only present for free but not forced choice outcomes. Crucially, our results indicate that enhanced outcome processing is not driven by the relevance of outcomes for future actions but rather stems from the association of outcomes with recent self-determined choice. Our findings highlight the pivotal role of self-determination in tracking the consequences of our actions and contribute to an understanding of the cognitive processes underlying the choice-induced facilitation in outcome monitoring.

The neural network of sensory attenuation: A neuroimaging meta-analysis

Sensory attenuation refers to the reduction in sensory intensity resulting from self-initiated actions compared to stimuli initiated externally. A classic example is scratching oneself without feeling itchy. This phenomenon extends across various sensory modalities, including visual, auditory, somatosensory, and nociceptive stimuli. The internal forward model proposes that during voluntary actions, an efferent copy of the action command is sent out to predict sensory feedback. This predicted sensory feedback is then compared with the actual sensory feedback, leading to the suppression or reduction of sensory stimuli originating from self-initiated actions. To further elucidate the neural mechanisms underlying sensory attenuation effect, we conducted an extensive meta-analysis of functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) studies. Utilizing activation likelihood estimation (ALE) analysis, our results revealed significant activations in a prominent cluster encompassing the right superior temporal gyrus (rSTG), right middle temporal gyrus (rMTG), and right insula when comparing external-generated with self-generated conditions. Additionally, significant activation was observed in the right anterior cerebellum when comparing self-generated to external-generated conditions. Further analysis using meta-analytic connectivity modeling (MACM) unveiled distinct brain networks co-activated with the rMTG and right cerebellum, respectively. Based on these findings, we propose that sensory attenuation arises from the suppression of reflexive inputs elicited by self-initiated actions through the internal forward modeling of a cerebellum-centered action prediction network, enabling the "sensory conflict detection" regions to effectively discriminate between inputs resulting from self-induced actions and those originating externally.

Motor dominance and movement-outcome congruency influence the electrophysiological correlates of sensory attenuation for self-induced visual stimuli

This study explores the impact of movement-outcome congruency and motor dominance on the action-associated modulations of early visual event-related potentials (ERPs). Employing the contingent paradigm, participants with varying degrees of motor dominance were exposed to stimuli depicting left or right human hands in the corresponding visual hemifields. Stimuli were either passively observed or evoked by voluntary button-presses with the dominant or non-dominant hand, in a manner that was either congruent or incongruent with stimulus laterality and hemifield. Early occipital responses (C1 and P1 components) revealed modulations consistent with sensory attenuation (SA) for self-evoked stimuli. Our findings suggest that sensory attenuation during the initial stages of visual processing (C1 component) is a general phenomenon across all degrees of handedness and stimulus/movement combinations. However, the magnitude of C1 suppression was modulated by handedness and movement-stimulus congruency, reflecting stronger SA in right-handed participants for stimuli depicting the right hand, when elicited by actions of the corresponding hand, and measured above the contralateral occipital lobe. P1 modulation suggested concurrent but opposing influences of attention and sensory prediction, with more pronounced suppression following stimulus-congruent button-presses over the hemisphere contralateral to movement, especially in left-handed individuals. We suggest that effects of motor dominance on the degree of SA may stem from functional/anatomical asymmetries in the processing of body parts (C1) and attention networks (P1). Overall, our results demonstrate the modulating effect of hand dominance and movement-outcome congruency on SA, underscoring the need for deeper exploration of their interplay. Additional empirical evidence in this direction could substantiate a premotor account for action-associated modulation of early sensory processing in the visual domain.

Self-initiation enhances perceptual processing of auditory stimuli in an online study

Understanding how the brain incorporates sensory and motor information will enable better theory building on human perception and behavior. In this study, we aimed to estimate the influence of predictive mechanisms on the magnitude and variability of sensory attenuation in two online samples. After the presentation of a visual cue stimulus, participants (Experiment 1: N = 224, Experiment 2: N = 84) compared the loudness of two consecutive tones in a two-alternative forced-choice task. In Experiment 1, the first tone was either self-initiated or not; in Experiment 2, the second tone was either self-initiated or not (active and passive condition, respectively). We further manipulated identity prediction (i.e., the congruence of pre-learned cue-sound combinations; congruent vs. incongruent), and the duration of the onset delay (to account for effects of attentional differences between the passive and active condition, 50 ms vs. 0 ms). We critically discuss our results within the framework of both classical (i.e., motor-based forward models) and contemporary approaches (i.e., predictive processing framework). Contrary to our preregistered hypothesis, we observed enhanced perceptual processing, instead of attenuation, for self-initiated auditory sensory input. Further, our results reveal an effect of fixed sound delays on the processing of motor and non-motor-based predictive information, and may point to according shifts in attention, leading to a perceptual bias. These results might best be captured by a hybrid explanatory model, combining predictions based on self-initiated motor action with a global predictive mechanism.

Short-Term Effect of Auditory Stimulation on Neural Activities: A Scoping Review of Longitudinal Electroencephalography and Magnetoencephalography Studies

Explored through EEG/MEG, auditory stimuli function as a suitable research probe to reveal various neural activities, including event-related potentials, brain oscillations and functional connectivity. Accumulating evidence in this field stems from studies investigating neuroplasticity induced by long-term auditory training, specifically cross-sectional studies comparing musicians and non-musicians as well as longitudinal studies with musicians. In contrast, studies that address the neural effects of short-term interventions whose duration lasts from minutes to hours are only beginning to be featured. Over the past decade, an increasing body of evidence has shown that short-term auditory interventions evoke rapid changes in neural activities, and oscillatory fluctuations can be observed even in the prestimulus period. In this scoping review, we divided the extracted neurophysiological studies into three groups to discuss neural activities with short-term auditory interventions: the pre-stimulus period, during stimulation, and a comparison of before and after stimulation. We show that oscillatory activities vary depending on the context of the stimuli and are greatly affected by the interplay of bottom-up and top-down modulational mechanisms, including attention. We conclude that the observed rapid changes in neural activitiesin the auditory cortex and the higher-order cognitive part of the brain are causally attributed to short-term auditory interventions.

Pre-movement event-related potentials and multivariate pattern of EEG encode action outcome prediction

Self-initiated movements are accompanied by an efference copy, a motor command sent from motor regions to the sensory cortices, containing a prediction of the movement's sensory outcome. Previous studies have proposed pre-motor event-related potentials (ERPs), including the readiness potential (RP) and its lateralized sub-component (LRP), as potential neural markers of action feedback prediction. However, it is not known how specific these neural markers are for voluntary (active) movements as compared to involuntary (passive) movements, which produce much of the same sensory feedback (tactile, proprioceptive) but are not accompanied by an efference copy. The goal of the current study was to investigate how active and passive movements are distinguishable from premotor electroencephalography (EEG), and to examine if this change of neural activity differs when participants engage in tasks that differ in their expectation of sensory outcomes. Participants made active (self-initiated) or passive (finger moved by device) finger movements that led to either visual or auditory stimuli (100 ms delay), or to no immediate contingency effects (control). We investigated the time window before the movement onset by measuring pre-movement ERPs time-locked to the button press. For RP, we observed an interaction between task and movement. This was driven by movement differences in the visual and auditory but not the control conditions. LRP conversely only showed a main effect of movement. We then used multivariate pattern analysis to decode movements (active vs. passive). The results revealed ramping decoding for all tasks from around -800 ms onwards up to an accuracy of approximately 85% at the movement. Importantly, similar to RP, we observed lower decoding accuracies for the control condition than the visual and auditory conditions, but only shortly (from -200 ms) before the button press. We also decoded visual vs. auditory conditions. Here, task is decodable for both active and passive conditions, but the active condition showed increased decoding shortly before the button press. Taken together, our results provide robust evidence that pre-movement EEG activity may represent action-feedback prediction in which information about the subsequent sensory outcome is encoded.

Playing with your ears: Audio-motor skill learning is sensitive to the lateral relationship between trained hand and ear

A salient feature of motor and sensory circuits in the brain is their contralateral hemispheric bias-a feature that might play a role in integration and learning of sensorimotor skills. In the current behavioral study, we examined whether the lateral configuration between sound-producing hand and feedback-receiving ear affects performance and learning of an audio-motor skill. Right-handed participants (n = 117) trained to play a piano sequence using their right or left hand while auditory feedback was presented monaurally, either to the right or left ear. Participants receiving auditory feedback to the contralateral ear during training performed better than participants receiving ipsilateral feedback (with respect to the training hand). Furthermore, in the Left-Hand training groups, the contralateral training advantage persisted in a generalization task. Our results demonstrate that audio-motor learning is sensitive to the lateral configuration between motor and sensory circuits and suggest that integration of neural activity across hemispheres facilitates such learning.

Multisensory decisions from self to world

Classic Bayesian models of perceptual inference describe how an ideal observer would integrate 'unisensory' measurements (multisensory integration) and attribute sensory signals to their origin(s) (causal inference). However, in the brain, sensory signals are always received in the context of a multisensory bodily state-namely, in combination with other senses. Moreover, sensory signals from both interoceptive sensing of one's own body and exteroceptive sensing of the world are highly interdependent and never occur in isolation. Thus, the observer must fundamentally determine whether each sensory observation is from an external (versus internal, self-generated) source to even be considered for integration. Critically, solving this primary causal inference problem requires knowledge of multisensory and sensorimotor dependencies. Thus, multisensory processing is needed to separate sensory signals. These multisensory processes enable us to simultaneously form a sense of self and form distinct perceptual decisions about the external world. In this opinion paper, we review and discuss the similarities and distinctions between multisensory decisions underlying the sense of self and those directed at acquiring information about the world. We call attention to the fact that heterogeneous multisensory processes take place all along the neural hierarchy (even in forming 'unisensory' observations) and argue that more integration of these aspects, in theory and experiment, is required to obtain a more comprehensive understanding of multisensory brain function. This article is part of the theme issue 'Decision and control processes in multisensory perception'.

Temporal adaptation of sensory attenuation for self-touch

The sensory consequences of our actions appear attenuated to us. This effect has been reported for external sensations that are evoked by auditory or visual events and for body-related sensations which are produced by self-touch. In the present study, we investigated the effects of prolonged exposure to a delay between an action and the generated sensation on sensory attenuation for self-touch. Previously, it has been shown that after being presented to a systematic exposure delay, artificially delayed touch can feel more intense and non-delayed touches can appear less intense. Here, we investigated the temporal spread of the temporal recalibration effect. Specifically, we wondered whether this temporal recalibration effect would affect only the delay that was used during exposure trials or if it would also modulate longer test delays. In the first two experiments, we tested three test delays (0, 100 and 400 ms) either in randomized or in blocked order. We found sensory attenuation in all three test intervals but no effect of the exposure delay. In Experiment 3, we replicated the experiment by Kilteni et al. (ELife 8:e42888, 2019. https://doi.org/10.7554/eLife.42888 ) and found evidence for temporal recalibration by exposure delay. Our data show that the temporal selectivity of sensory attenuation of self-touch depends on presenting a singular test delay only. Presenting multiple test delays leads to a temporally broad spread of sensory attenuation.

Using event-related brain potentials to evaluate motor-auditory latencies in virtual reality

Actions in the real world have immediate sensory consequences. Mimicking these in digital environments is within reach, but technical constraints usually impose a certain latency (delay) between user actions and system responses. It is important to assess the impact of this latency on the users, ideally with measurement techniques that do not interfere with their digital experience. One such unobtrusive technique is electroencephalography (EEG), which can capture the users' brain activity associated with motor responses and sensory events by extracting event-related potentials (ERPs) from the continuous EEG recording. Here we exploit the fact that the amplitude of sensory ERP components (specifically, N1 and P2) reflects the degree to which the sensory event was perceived as an expected consequence of an own action (self-generation effect). Participants (N = 24) elicit auditory events in a virtual-reality (VR) setting by entering codes on virtual keypads to open doors. In a within-participant design, the delay between user input and sound presentation is manipulated across blocks. Occasionally, the virtual keypad is operated by a simulated robot instead, yielding a control condition with externally generated sounds. Results show that N1 (but not P2) amplitude is reduced for self-generated relative to externally generated sounds, and P2 (but not N1) amplitude is modulated by delay of sound presentation in a graded manner. This dissociation between N1 and P2 effects maps back to basic research on self-generation of sounds. We suggest P2 amplitude as a candidate read-out to assess the quality and immersiveness of digital environments with respect to system latency.

Perception and action as viewed from the Theory of Event Coding: a multi-lab replication and effect size estimation of common experimental designs

The Theory of Event Coding (TEC) has influenced research on action and perception across the past two decades. It integrates several seminal empirical phenomena and it has continued to stimulate novel experimental approaches on the representational foundations of action control and perceptual experience. Yet, many of the most notable results surrounding TEC originate from an era of psychological research that relied on rather small sample sizes as judged by today's standards. This state hampers future research aiming to build on previous phenomena. We, therefore, provide a multi-lab re-assessment of the following six classical observations: response-effect compatibility, action-induced blindness, response-effect learning, stimulus-response binding, code occupation, and short-term response-effect binding. Our major goal is to provide precise estimates of corresponding effect sizes to facilitate future scientific endeavors. These effect sizes turned out to be considerably smaller than in the original reports, thus allowing for informed decisions on how to address each phenomenon in future work. Of note, the most relevant results of the original observations were consistently obtained in the present experiments as well.

Auditory N1 and P2 Attenuation in Action Observation: An Event-Related Potential Study Considering Effects of Temporal Predictability and Individualism

Tones that are generated by self-performed actions elicit attenuated N1 and P2 amplitudes, as measured by electroencephalography (EEG), compared to identical external tones, which is referred to as neurophysiological sensory attenuation (SA). At the same time, self-generated tones are perceived as less loud compared to external tones (perceptual SA). Action observation led in part to a similar neurophysiological and perceptual SA. The perceptual SA in observers was found in comparison to tones that were temporally predictable, and one study suggested that perceptual SA in observers might depend on the cultural dimension of individualism. In this study, we examined neurophysiological SA for tones elicited by self-performed and observed actions during simultaneous EEG acquisitions in two participants, extending the paradigm with a visual cue condition controlling for effects of temporal predictability. Moreover, we investigated the effect of individualism on neurophysiological SA in action observation. Relative to un-cued external tones, the N1 was only descriptively reduced for tones that were elicited by self-performed or observed actions and significantly attenuated for cued external tones. A P2 attenuation effect relative to un-cued external tones was found in all three conditions, with stronger effects for self- and other-generated tones than for cued external tones. We found no evidence for an effect of individualism. These findings add to previous evidence for neurophysiological SA in action performance and observation with a paradigm well-controlled for the effect of predictability and individualism, showing differential effects of the former on the N1 and P2 components, and no effect of the latter.

The auditory P2 differentiates self- from partner-produced sounds during joint action: Contributions of self-specific attenuation and temporal orienting of attention

Sensory attenuation of the auditory P2 event-related potential (ERP) has been shown to differentiate the sensory consequences of one's own from others' action in joint action contexts. However, recent evidence suggests that when people coordinate joint actions over time, temporal orienting of attention might simultaneously contribute to enhancing the auditory P2. The current study employed a joint tapping task in which partners produced tone sequences together to examine whether temporal orienting influences auditory ERP amplitudes during the time window of self-other differentiation. Our findings demonstrate that the combined requirements of coordinating with a partner toward a joint goal and immediately adjusting to the partner's tone timing enhance P2 amplitudes elicited by the partner's tone onsets. Furthermore, our findings replicate prior evidence for self-specific sensory attenuation of the auditory P2 in joint action, and additionally demonstrate that it occurs regardless of the coordination requirements between partners. Together, these findings provide evidence that temporal orienting and sensory attenuation both modulate the auditory P2 during joint action and suggest that both processes play a role in facilitating precise interpersonal coordination between partners.

Perception of self-generated and externally-generated visual stimuli: Evidence from EEG and behavior

Efference copy-based forward model mechanisms may help us to distinguish between self-generated and externally-generated sensory consequences. Previous studies have shown that self-initiation modulates neural and perceptual responses to identical stimulation. For example, event-related potentials (ERPs) elicited by tones that follow a button press are reduced in amplitude relative to ERPs elicited by passively attended tones. However, previous EEG studies investigating visual stimuli in this context are rare, provide inconclusive results, and lack adequate control conditions with passive movements. Furthermore, although self-initiation is known to modulate behavioral responses, it is not known whether differences in the amplitude of ERPs also reflect differences in perception of sensory outcomes. In this study, we presented to participants visual stimuli consisting of gray discs following either active button presses, or passive button presses, in which an electromagnet moved the participant's finger. Two discs presented visually 500-1250 ms apart followed each button press, and participants judged which of the two was more intense. Early components of the primary visual response (N1 and P2) over the occipital electrodes were suppressed in the active condition. Interestingly, suppression in the intensity judgment task was only correlated with suppression of the visual P2 component. These data support the notion of efference copy-based forward model predictions in the visual sensory modality, but especially later processes (P2) seem to be perceptually relevant. Taken together, the results challenge the assumption that N1 differences reflect perceptual suppression and emphasize the relevance of the P2 ERP component.

Cancelling cancellation? Sensorimotor control, agency, and prediction

For decades, classic theories of action control and action awareness have been built around the idea that the brain predictively 'cancels' expected action outcomes from perception. However, recent research casts doubt over this basic premise. What do these new findings mean for classic accounts of action? Should we now 'cancel' old data, theories and approaches generated under this idea? In this paper, we argue 'No'. While doubts about predictive cancellation may urge us to fundamentally rethink how predictions shape perception, the wider pyramid using these ideas to explain action control and agentic experiences can remain largely intact. Some adaptive functions assigned to predictive cancellation can be achieved through quasi-predictive processes, that influence perception without actively tracking the probabilistic structure of the environment. Other functions may rely upon truly predictive processes, but not require that these predictions cancel perception. Appreciating the role of these processes may help us to move forward in explaining how agents optimise their interactions with the external world, even if predictive cancellation is cancelled from theory.

Action-based predictions affect visual perception, neural processing, and pupil size, regardless of temporal predictability

Sensory consequences of one's own action are often perceived as less intense, and lead to reduced neural responses, compared to externally generated stimuli. Presumably, such sensory attenuation is due to predictive mechanisms based on the motor command (efference copy). However, sensory attenuation has also been observed outside the context of voluntary action, namely when stimuli are temporally predictable. Here, we aimed at disentangling the effects of motor and temporal predictability-based mechanisms on the attenuation of sensory action consequences. During fMRI data acquisition, participants (N = 25) judged which of two visual stimuli was brighter. In predictable blocks, the stimuli appeared temporally aligned with their button press (active) or aligned with an automatically generated cue (passive). In unpredictable blocks, stimuli were presented with a variable delay after button press/cue, respectively. Eye tracking was performed to investigate pupil-size changes and to ensure proper fixation. Self-generated stimuli were perceived as darker and led to less neural activation in visual areas than their passive counterparts, indicating sensory attenuation for self-generated stimuli independent of temporal predictability. Pupil size was larger during self-generated stimuli, which correlated negatively with the blood oxygenation level dependent (BOLD) response: the larger the pupil, the smaller the BOLD amplitude in visual areas. Our results suggest that sensory attenuation in visual cortex is driven by action-based predictive mechanisms rather than by temporal predictability. This effect may be related to changes in pupil diameter. Altogether, these results emphasize the role of the efference copy in the processing of sensory action consequences.

Dissociable effects of attention and expectation on perceptual sensitivity to action-outcomes

Self-generated sensations evoke attenuated neural response - physiological attenuation - and is perceived with less intensity - perceptual attenuation. This phenomenon is referred as sensory attenuation and is proposed to reflect the silencing of predicted sensations. The present study aimed to investigate the independent contribution of expectation and attention on sensory attenuation. The expectation associated with the stimulus feature and the focus of attention was manipulated independently by orthogonal cues. We found pronounced sensory attenuation at the unattended location when the stimulus was self-generated (Experiment 1). When the stimulus was externally-generated (Experiment 2), sensory attenuation was observed at the attended location. Sensory attenuation of expected action-outcome was not observed when the attention cue was uninformative (Experiment 3A). The findings corroborate the claim from Bayesian models that attention mediates sensory attenuation. The results also highlight the paradoxes in Bayesian proposals of perception-action interaction.

Turning a blind eye to motor differences leads to bias in estimating action-related auditory ERP attenuation

Event-related potential (ERP) studies investigating the processing of self-induced stimuli often rely on the assumption that ballistic actions and motor ERPs are constant across different sets of action effects. Since recent studies challenge this motor equivalence assumption, we examined whether neglecting effect-related motor differences can bias the estimation of auditory ERPs in a typical action-related ERP attenuation paradigm. We increased action variability with a force production task and selected an event subset in which the motor equivalence assumption was true. ERP attenuation estimated in this subset was compared with attenuation obtained in the standard task, where motor differences were not controlled. Violation of the motor equivalence assumption resulted in a positive deflection overlapping auditory ERPs elicited by self-induced sounds, resulting in the overestimation of N1- and underestimation of P2-attenuation. This demonstrates that sensory-effect-related motor differences should be considered when separating sensory and motor components in ERPs elicited by self-induced stimuli.

Non-motor cues do not generate the perception of self-agency: A critique of cue-integration

How does one know that (s)he is the causal agent of their motor actions? Earlier theories of sense of agency have attributed the capacity for perception of self-agency to the comparator process of the motor-control/action system. However, with the advent of the findings implying a role of non-motor cues (like affective states, beliefs, primed concepts, and social instructions or previews of actions) in the sense of agency literature, the perception of self-agency is hypothesized to be generated even by non-motor cues (based on their relative reliability or weighting estimate); and, this theory is come to be known as the cue-integration of sense of agency. However, the cue-integration theory motivates skepticism about whether it is falsifiable and whether it is plausible that non-motor cues that are sensorily unrelated to typical sensory processes of self-agency have the capacity to produce a perception of self-agency. To substantiate this skepticism, I critically analyze the experimental operationalizations of cue-integration-with the (classic) vicarious agency experiment as a case study-to show that (1) the participants in these experiments are ambiguous about their causal agency over motor actions, (2) thus, these participants resort to reports of self-agency as heuristic judgments (under ambiguity) rather than due to cue-integration per se, and (3) there might not have occurred cue-integration based self-agency reports if these experimental operationalizations had eliminated ambiguity about the causal agency. Thus, I conclude that the reports of self-agency (observed in typical non-motor cues based cue-integration experiments) are not instances of perceptual effect-that are hypothesized to be produced by non-motor cues-but are of heuristic judgment effect.

Enhancement of loudness discrimination acuity for self-generated sound is independent of musical experience

Musicians tend to have better auditory and motor performance than non-musicians because of their extensive musical experience. In a previous study, we established that loudness discrimination acuity is enhanced when sound is produced by a precise force generation task. In this study, we compared the enhancement effect between experienced pianists and non-musicians. Without the force generation task, loudness discrimination acuity was better in pianists than non-musicians in the condition. However, the force generation task enhanced loudness discrimination acuity similarly in both pianists and non-musicians. The reaction time was also reduced with the force control task, but only in the non-musician group. The results suggest that the enhancement of loudness discrimination acuity with the precise force generation task is independent of musical experience and is, therefore, a fundamental function in auditory-motor interaction.

The implicit sense of agency is not a perceptual effect but is a judgment effect

The sense of agency (SoA) is characterized as the sense of being the causal agent of one's own actions, and it is measured in two forms: explicit and implicit. In the explicit SoA experiments, the participants explicitly report whether they have a sense of control over their actions or whether they or somebody else is the causal agent of seen actions; the implicit SoA experiments study how do participants' agentive or voluntary actions modify perceptual processes (like time, vision, tactility, and audition) without directly asking the participants to explicitly think about their causal agency or sense of control. However, recent implicit SoA literature reported contradictory findings of the relationship between implicit SoA reports and agency states. Thus, I argue that the purported implicit SoA reports are not agency-driven perceptual effects per se but are judgment effects, by showing that (a) the typical operationalizations in implicit SoA domain lead to perceptual uncertainty on the part of the participants, (b) under uncertainty, participants' implicit SoA reports are due to heuristic judgments which are independent of agency states, and (c) under perceptual certainty, the typical implicit SoA reports might not have occurred at all. Thus, I conclude that the instances of implicit SoA are judgments (or response biases)-under uncertainty-rather than perceptual effects.

Movement Planning Determines Sensory Suppression: An Event-related Potential Study

Sensory suppression refers to the phenomenon that sensory input generated by our own actions, such as moving a finger to press a button to hear a tone, elicits smaller neural responses than sensory input generated by external agents. This observation is usually explained via the internal forward model in which an efference copy of the motor command is used to compute a corollary discharge, which acts to suppress sensory input. However, because moving a finger to press a button is accompanied by neural processes involved in preparing and performing the action, it is unclear whether sensory suppression is the result of movement planning, movement execution, or both. To investigate this, in two experiments, we compared ERPs to self-generated tones that were produced by voluntary, semivoluntary, or involuntary button-presses, with externally generated tones that were produced by a computer. In Experiment 1, the semivoluntary and involuntary button-presses were initiated by the participant or experimenter, respectively, by electrically stimulating the median nerve in the participant's forearm, and in Experiment 2, by applying manual force to the participant's finger. We found that tones produced by voluntary button-presses elicited a smaller N1 component of the ERP than externally generated tones. This is known as N1-suppression. However, tones produced by semivoluntary and involuntary button-presses did not yield significant N1-suppression. We also found that the magnitude of N1-suppression linearly decreased across the voluntary, semivoluntary, and involuntary conditions. These results suggest that movement planning is a necessary condition for producing sensory suppression. We conclude that the most parsimonious account of sensory suppression is the internal forward model.

The Interplay Between Affective Processing and Sense of Agency During Action Regulation: A Review

Sense of agency is the feeling of being in control of one's actions and their perceivable effects. Most previous research identified cognitive or sensory determinants of agency experience. However, it has been proposed that sense of agency is also bound to the processing of affective information. For example, during goal-directed actions or instrumental learning we often rely on positive feedback (e.g., rewards) or negative feedback (e.g., error messages) to determine our level of control over the current task. Nevertheless, we still lack a scientific model which adequately explains the relation between affective processing and sense of agency. In this article, we review current empirical findings on how affective information modulates agency experience, and, conversely, how sense of agency changes the processing of affective action outcomes. Furthermore, we discuss in how far agency-related changes in affective processing might influence the ability to enact cognitive control and action regulation during goal-directed behavior. A preliminary model is presented for describing the interplay between sense of agency, affective processing, and action regulation. We propose that affective processing could play a role in mediating the influence between subjective sense of agency and the objective ability to regulate one's behavior. Thus, determining the interrelation between affective processing and sense of agency will help us to understand the potential mechanistic basis of agency experience, as well as its functional significance for goal-directed behavior.

The auditory brain in action: Intention determines predictive processing in the auditory system-A review of current paradigms and findings

According to the ideomotor theory, action may serve to produce desired sensory outcomes. Perception has been widely described in terms of sensory predictions arising due to top-down input from higher order cortical areas. Here, we demonstrate that the action intention results in reliable top-down predictions that modulate the auditory brain responses. We bring together several lines of research, including sensory attenuation, active oddball, and action-related omission studies: Together, the results suggest that the intention-based predictions modulate several steps in the sound processing hierarchy, from preattentive to evaluation-related processes, also when controlling for additional prediction sources (i.e., sound regularity). We propose an integrative theoretical framework—the extended auditory event representation system (AERS), a model compatible with the ideomotor theory, theory of event coding, and predictive coding. Initially introduced to describe regularity-based auditory predictions, we argue that the extended AERS explains the effects of action intention on auditory processing while additionally allowing studying the differences and commonalities between intention- and regularity-based predictions—we thus believe that this framework could guide future research on action and perception.

No evidence for somatosensory attenuation during action observation of self-touch

The discovery of mirror neurons in the macaque brain in the 1990s triggered investigations on putative human mirror neurons and their potential functionality. The leading proposed function has been action understanding: Accordingly, we understand the actions of others by 'simulating' them in our own motor system through a direct matching of the visual information to our own motor programmes. Furthermore, it has been proposed that this simulation involves the prediction of the sensory consequences of the observed action, similar to the prediction of the sensory consequences of our executed actions. Here, we tested this proposal by quantifying somatosensory attenuation behaviourally during action observation. Somatosensory attenuation manifests during voluntary action and refers to the perception of self-generated touches as less intense than identical externally generated touches because the self-generated touches are predicted from the motor command. Therefore, we reasoned that if an observer simulates the observed action and, thus, he/she predicts its somatosensory consequences, then he/she should attenuate tactile stimuli simultaneously delivered to his/her corresponding body part. In three separate experiments, we found a systematic attenuation of touches during executed self-touch actions, but we found no evidence for attenuation when such actions were observed. Failure to observe somatosensory attenuation during observation of self-touch is not compatible with the hypothesis that the putative human mirror neuron system automatically predicts the sensory consequences of the observed action. In contrast, our findings emphasize a sharp distinction between the motor representations of self and others.

Self-generation and sound intensity interactively modulate perceptual bias, but not perceptual sensitivity

The ability to distinguish self-generated stimuli from those caused by external sources is critical for all behaving organisms. Although many studies point to a sensory attenuation of self-generated stimuli, recent evidence suggests that motor actions can result in either attenuated or enhanced perceptual processing depending on the environmental context (i.e., stimulus intensity). The present study employed 2-AFC sound detection and loudness discrimination tasks to test whether sound source (self- or externally-generated) and stimulus intensity (supra- or near-threshold) interactively modulate detection ability and loudness perception. Self-generation did not affect detection and discrimination sensitivity (i.e., detection thresholds and Just Noticeable Difference, respectively). However, in the discrimination task, we observed a significant interaction between self-generation and intensity on perceptual bias (i.e. Point of Subjective Equality). Supra-threshold self-generated sounds were perceived softer than externally-generated ones, while at near-threshold intensities self-generated sounds were perceived louder than externally-generated ones. Our findings provide empirical support to recent theories on how predictions and signal intensity modulate perceptual processing, pointing to interactive effects of intensity and self-generation that seem to be driven by a biased estimate of perceived loudness, rather by changes in detection and discrimination sensitivity.

Sensory Attenuation of the Auditory P2 Differentiates Self- from Partner-Produced Sounds during Joint Action

Successful human interaction relies on people's ability to differentiate between the sensory consequences of their own and others' actions. Research in solo action contexts has identified sensory attenuation, that is, the selective perceptual or neural dampening of the sensory consequences of self-produced actions, as a potential marker of the distinction between self- and externally produced sensory consequences. However, very little research has examined whether sensory attenuation distinguishes self- from partner-produced sensory consequences in joint action contexts. The current study examined whether sensory attenuation of the auditory N1 or P2 ERPs distinguishes self- from partner-produced tones when pairs of people coordinate their actions to produce tone sequences that match a metronome pace. We did not find evidence of auditory N1 attenuation for either self- or partner-produced tones. Instead, the auditory P2 was attenuated for self-produced tones compared to partner-produced tones within the joint action. These findings indicate that self-specific attenuation of the auditory P2 differentiates the sensory consequences of one's own from others' actions during joint action. These findings also corroborate recent evidence that N1 attenuation may be driven by general rather than action-specific processes and support a recently proposed functional dissociation between auditory N1 and P2 attenuation.

Self-initiation Inhibits the Postural and Electrophysiological Responses to Optic Flow and Button Pressing

As we move through our environment, our visual system is presented with optic flow, a potentially important cue for perception, navigation and postural control. How does the brain anticipate the optic flow that arises as a consequence of our own movement? Converging evidence suggests that stimuli are processed differently by the brain if occurring as a consequence of self-initiated actions, compared to when externally generated. However, this has mainly been demonstrated with auditory stimuli. It is not clear how this occurs with optic flow. We measured behavioural, neurophysiological and head motion responses of 29 healthy participants to radially expanding, vection-inducing optic flow stimuli, simulating forward transitional motion, which were either initiated by the participant's own button-press ("self-initiated flow") or by the computer ("passive flow"). Self-initiation led to a prominent and left-lateralized inhibition of the flow-evoked posterior event-related alpha desynchronization (ERD), and a stabilisation of postural responses. Neither effect was present in control button-press-only trials, without optic flow. Additionally, self-initiation also produced a large event-related potential (ERP) negativity between 130-170 ms after optic flow onset. Furthermore, participants' visual induced motion sickness (VIMS) and vection intensity ratings correlated positively across the group - although many participants felt vection in the absence of any VIMS, none reported the opposite combination. Finally, we found that the simple act of making a button press leads to a detectable head movement even when using a chin rest. Taken together, our results indicate that the visual system is capable of predicting optic flow when self-initiated, to affect behaviour.

Modulation of Bodily Self-Consciousness by Self and External Touch

The full body illusion (FBI) is a bodily illusion based on the application of multisensory conflicts that induce changes in bodily self-consciousness (BSC). This has been used to study cognitive brain mechanisms underlying body ownership and related aspects of self-consciousness. Typically, such paradigms employ external passive multisensory stimulation, thus neglecting the possible contributions of self-generated action and haptic cues to body ownership. In this article, the effects of both external and voluntary self-touch on BSC were examined with a robotics-based FBI paradigm. We compared the effects of classical passive visuotactile stimulation and active self-touch (in which experimental participants had a sense of agency over the tactile stimulation) on the FBI. We evaluated these effects using a questionnaire, crossmodal congruency task, and measurements of changes in self-location. The results indicated that both synchronous passive visuotactile stimulation and synchronous active self-touch induced illusory ownership over a virtual body, without significant differences in their magnitudes. However, the FBI induced by active self-touch was associated with a larger drift in self-location towards the virtual body. These results show that movement-related signals arising from self-touch impact the BSC not only for hand ownership but also for torso-centered body ownership and related aspects of BSC.

Action-locked Neural Responses in Auditory Cortex to Self-generated Sounds

Sensory perception is a product of interactions between the internal state of an organism and the physical attributes of a stimulus. It has been shown across the animal kingdom that perception and sensory-evoked physiological responses are modulated depending on whether or not the stimulus is the consequence of voluntary actions. These phenomena are often attributed to motor signals sent to relevant sensory regions that convey information about upcoming sensory consequences. However, the neurophysiological signature of action-locked modulations in sensory cortex, and their relationship with perception, is still unclear. In the current study, we recorded neurophysiological (using Magnetoencephalography) and behavioral responses from 16 healthy subjects performing an auditory detection task of faint tones. Tones were either generated by subjects' voluntary button presses or occurred predictably following a visual cue. By introducing a constant temporal delay between button press/cue and tone delivery, and applying source-level analysis, we decoupled action-locked and auditory-locked activity in auditory cortex. We show action-locked evoked-responses in auditory cortex following sound-triggering actions and preceding sound onset. Such evoked-responses were not found for button-presses that were not coupled with sounds, or sounds delivered following a predictive visual cue. Our results provide evidence for efferent signals in human auditory cortex that are locked to voluntary actions coupled with future auditory consequences.

Sensorimotor conflicts induce somatic passivity and louden quiet voices in healthy listeners

Sensorimotor conflicts are known to alter the perception of accompanying sensory signals, and deficits in sensory attenuation have been observed in schizophrenia. In the auditory domain, self-generated tones or voices (compared to tones or voices presented passively or with temporal delays) have been associated with changes in loudness perception and attenuated neural responses. It has been argued that for sensory signals to be attenuated, predicted and sensory consequences must have a consistent spatiotemporal relationship, between button presses and reafferent signals, via predictive sensory signaling, a process altered in schizophrenia. Here, we investigated auditory sensory attenuation for a series of morphed voices while healthy participants applied sensorimotor stimulations that had no spatiotemporal relationship to the voice stimuli and that have been shown to induce mild psychosis-like phenomena. In two independent groups of participants, we report a loudening of silent voices and found this effect only during maximal sensorimotor conflicts (versus several control conditions). Importantly, conflicting sensorimotor stimulation also induced a mild psychosis-like state in the form of somatic passivity and participants who experienced stronger passivity lacked the sensorimotor loudening effect. We argue that this conflict-related sensorimotor loudness amplification may represent a reduction of auditory self-attenuation that is lacking in participants experiencing a concomitant mild psychosis-like state. We interpret our results within the framework of the comparator model of sensorimotor control, and discuss the implications of our findings regarding passivity experiences and hallucinations in schizophrenia.

The spatial specificity of sensory attenuation for self-touch

Self-touch is sensed less intense as touch produced by another person. According to the standard explanation, if predicted and actual sensations match, the intensity of the touch will be reduced. Here, we asked whether sensory attenuation is spatially specific. To this end, participants laid their left hand under a metal arc on which a force sensor was mounted. Pressing the sensor caused one of two motors to rotate a lever that either touched the index or the ring finger. We took care that no cues would reveal in advance which of the motors would move in order to leave participants uninformed about the finger that will be stimulated. Any reduction in felt intensity of the touch could therefore be induced only by the efference copy of the touching movement. We found strong spatial specificity of sensory attenuation of self-touch, selecting between two fingers of the same hand.

Precise force controls enhance loudness discrimination of self-generated sound

Motor executions alter sensory processes. Studies have shown that loudness perception changes when a sound is generated by active movement. However, it is still unknown where and how the motor-related changes in loudness perception depend on the task demand of motor execution. We examined whether different levels of precision demands in motor control affects loudness perception. We carried out a loudness discrimination test, in which the sound stimulus was produced in conjunction with the force generation task. We tested three target force amplitude levels. The force target was presented on a monitor as a fixed visual target. The generated force was also presented on the same monitor as a movement of the visual cursor. Participants adjusted their force amplitude in a predetermined range without overshooting using these visual targets and moving cursor. In the control condition, the sound and visual stimuli were generated externally (without a force generation task). We found that the discrimination performance was significantly improved when the sound was produced by the force generation task compared to the control condition, in which the sound was produced externally, although we did not find that this improvement in discrimination performance changed depending on the different target force amplitude levels. The results suggest that the demand for precise control to produce a fixed amount of force may be key to obtaining the facilitatory effect of motor execution in auditory processes.

Action-related auditory ERP attenuation is not modulated by action effect relevance

Event-related potentials (ERPs) elicited by self-induced sounds are often smaller than ERPs elicited by identical, but externally generated sounds. This action-related auditory ERP attenuation is more pronounced when self-induced sounds are intermixed with similar sounds generated by an external source. The current study explored whether attentional factors contributed to this phenomenon. Participants performed tone-eliciting actions, while the action-tone contingency and the set of additional action effects (tactile only, tactile and visual) were manipulated in a blocked manner. Previous action-tone contingence-effects were replicated, but the addition of other sensory action consequences did not influence the magnitude of auditory ERP attenuation. This suggests that the amount of attention allocated to concurrent non-auditory action effects does not substantially affect the magnitude of action-related auditory ERP attenuation and is on a par with the assumption that action-related auditory ERP attenuation might be related to the process of distinguishing self-induced stimuli from externally generated ones.

Commonalities and differences in predictive neural processing of discrete vs continuous action feedback

Sensory action consequences are highly predictable and thus engage less neural resources compared to externally generated sensory events. While this has frequently been observed to lead to attenuated perceptual sensitivity and suppression of activity in sensory cortices, some studies conversely reported enhanced perceptual sensitivity for action consequences. These divergent findings might be explained by the type of action feedback, i.e., discrete outcomes vs. continuous feedback. Therefore, in the present study we investigated the impact of discrete and continuous action feedback on perceptual and neural processing during action feedback monitoring. During fMRI data acquisition, participants detected temporal delays (0-417 ms) between actively or passively generated wrist movements and visual feedback that was either continuously provided during the movement or that appeared as a discrete outcome. Both feedback types resulted in (1) a neural suppression effect (active<passive) in a largely shared network including bilateral visual and somatosensory cortices, cerebellum and temporoparietal areas. Yet, compared to discrete outcomes, (2) processing continuous feedback led to stronger suppression in right superior temporal gyrus (STG), Heschl´s gyrus, and insula suggesting specific suppression of features linked to continuous feedback. Furthermore, (3) BOLD suppression in visual cortex for discrete outcomes was specifically related to perceptual enhancement. Together, these findings indicate that neural representations of discrete and continuous action feedback are similarly suppressed but might depend on different predictive mechanisms, where reduced activation in visual cortex reflects facilitation specifically for discrete outcomes, and predictive processing in STG, Heschl´s gyrus, and insula is particularly relevant for continuous feedback.

Similarities and Differences between Performers and Observers in Processing Auditory Action Consequences: Evidence from Simultaneous EEG Acquisition

In our social environment, we easily distinguish stimuli caused by our own actions (e.g., water splashing when I fill my glass) from stimuli that have an external source (e.g., water splashing in a fountain). Accumulating evidence suggests that processing the auditory consequences of self-performed actions elicits N1 and P2 ERPs of reduced amplitude compared to physically identical but externally generated sounds, with such reductions being ascribed to neural predictive mechanisms. It is unexplored, however, whether the sensory processing of action outcomes is similarly modulated by action observation (e.g., water splashing when I observe you filling my glass). We tested 40 healthy participants by applying a methodological approach for the simultaneous EEG recording of two persons: An observer observed button presses executed by a performer in real time. For the performers, we replicated previous findings of a reduced N1 amplitude for self- versus externally generated sounds. This pattern differed significantly from the one in observers, whose N1 for sounds generated by observed button presses was not attenuated. In turn, the P2 amplitude was reduced for processing action- versus externally generated sounds for both performers and observers. These findings show that both action performance and observation affect the processing of action-generated sounds. There are, however, important differences between the two in the timing of the effects, probably related to differences in the predictability of the actions and thus also the associated stimuli. We discuss how these differences might contribute to recognizing the stimulus as caused by self versus others.

Sensory attenuation of action outcomes of varying amplitude and valence

Stimuli caused by self-initiated actions are perceived as less intense than those caused externally; this effect is called sensory attenuation (SA). In two experiments, we aimed to assess the impact of the amplitude of outcomes and its affective valence on SA and explicit ratings of sense of agency. This allowed us to test the predictions of the available SA frameworks and better understand the link between SA, affect, and agency. The results indicated that SA can be reversed, and such sensory amplification is driven by low-amplitude and positive-valence outcomes. We also show that intentional action influences the perceived valence of outcomes, and that modulations of explicit sense of agency are divergent from those of SA. Our study shows that valence influences the processing of the amplitude of intentional action outcomes and suggests that none of the currently available frameworks give full justice to SA's variability.

Sense of Agency in Multi-Step Actions

In our daily lives, we frequently execute actions that require several steps to bring about the outcome. However, investigations on how the sense of agency—the sense of controlling our actions and their outcomes—evolves in multi-step actions are still lacking. The purpose of the present research is to fill this gap. In the present study, the participants executed one-step, two-step, and three-step actions in which one, two, or three keys had to be pressed consecutively to generate a tone. We used sensory attenuation as an implicit measure of the sense of agency. Sensory attenuation means that self-produced sensory effects are perceived as less intense than externally generated effects. In the present experiment, sensory attenuation was measured in a psychophysical paradigm and increased in multi-step actions compared to the one-step action. We also asked the participants to explicitly rate the amount to which they felt that they had generated the tone. Ratings were highest in the one-step condition and dropped for multi-step actions, thus showing the opposite pattern of the sensory attenuation data. We assume that enhanced sensory attenuation in multi-step actions could be due to increased effort or more accurate sensorimotor predictions of action effects. The decrease in explicit ratings for multi-step actions might be attributed to reduced perception of causality.

Voluntary Actions Modulate Perception and Neural Representation of Action-Consequences in a Hand-Dependent Manner

Evoked neural activity in sensory regions and perception of sensory stimuli are modulated when the stimuli are the consequence of voluntary movement, as opposed to an external source. It has been suggested that such modulations are due to motor commands that are sent to relevant sensory regions during voluntary movement. However, given the anatomical-functional laterality bias of the motor system, it is plausible that the pattern of such behavioral and neural modulations will also exhibit a similar bias, depending on the effector triggering the stimulus (e.g., right/left hand). Here, we examined this issue in the visual domain using behavioral and neural measures (fMRI). Healthy participants judged the relative brightness of identical visual stimuli that were either self-triggered (using right/left hand button presses), or triggered by the computer. Stimuli were presented either in the right or left visual field. Despite identical physical properties of the visual consequences, we found stronger perceptual modulations when the triggering hand was ipsi- (rather than contra-) lateral to the stimulated visual field. Additionally, fMRI responses in visual cortices differentiated between stimuli triggered by right/left hand. Our findings support a model in which voluntary actions induce sensory modulations that follow the anatomical-functional bias of the motor system.

Distinct Roles for the Cerebellum, Angular Gyrus, and Middle Temporal Gyrus in Action-Feedback Monitoring

Action-feedback monitoring is essential to ensure meaningful interactions with the external world. This process involves generating efference copy-based sensory predictions and comparing these with the actual action-feedback. As neural correlates of comparator processes, previous fMRI studies have provided heterogeneous results, including the cerebellum, angular and middle temporal gyrus. However, these studies usually comprised only self-generated actions. Therefore, they might have induced not only action-based prediction errors, but also general sensory mismatch errors. Here, we aimed to disentangle these processes using a custom-made fMRI-compatible movement device, generating active and passive hand movements with identical sensory feedback. Online visual feedback of the hand was presented with a variable delay. Participants had to judge whether the feedback was delayed. Activity in the right cerebellum correlated more positively with delay in active than in passive trials. Interestingly, we also observed activation in the angular and middle temporal gyri, but across both active and passive conditions. This suggests that the cerebellum is a comparator area specific to voluntary action, whereas angular and middle temporal gyri seem to detect more general intersensory conflict. Correlations with behavior and cerebellar activity nevertheless suggest involvement of these temporoparietal areas in processing and awareness of temporal discrepancies in action-feedback monitoring.

Listening to music while running alters ground reaction forces: a study of acute exposure to varying speed and loudness levels in young women and men

PURPOSE

Music listening while running enhances physiological and psychological features, resulting in a more enjoyable experience. The possible influence of music on ground reaction forces (GRF) during running, however, is unknown. Considering the 'distracting' role of music on runner's attention, we hypothesized that music would cover foot impacts against the ground. This study verified such hypothesis by testing the effects of different music volumes while running at different velocities.

METHODS

Fifty fit volunteers (F:M = 22:8; 23 ± 2 years) performed 2-min running stints over 3 random conditions (80-dB, 85-dB music; 'no music'), at 3 velocities (8, 10, 12 km/h). Participants ran on a sensorized treadmill that recorded GRF during all experiments.

RESULTS

Listening to 85-dB music resulted in greater GRF at 8 (p = 0.0005) and 10 km/h (p = 0.04) but not 12 km/h (p = 0.35) and not with 80-dB volume. Gender-based analyses revealed significant Condition × gender interactions only for 85-dB music vs. 'no music'. Bonferroni-adjusted comparisons revealed significant music-induced increases in GRF only in men at 8 km/h (+ 4.1 kg/cm², p < 0.0005; women: + 0.8 kg/cm², p = 0.47) and 10 km/h (+ 3.3 kg/cm², p = 0.004; women: + 0.8 kg/cm², p = 0.51) but not at 12 km/h.

CONCLUSION

In active men, listening to loud music while running results in increased GRF, whereas no effect was observed in women. The lack of music effect in women may be related to structural factors, such as larger hip width-to-femoral length ratio, possibly resulting in different loading patterns. The present preliminary findings introduce high-volume music listening as a new potential risk factor for injury in young runners.

Sensorimotor Integration Can Enhance Auditory Perception

Whenever we move, speak, or play musical instruments, our actions generate auditory sensory input. The sensory consequences of our actions are thought to be predicted via sensorimotor integration, which involves anatomical and functional links between auditory and motor brain regions. The physiological connections are relatively well established, but less is known about how sensorimotor integration affects auditory perception. The sensory attenuation hypothesis suggests that the perceived loudness of self-generated sounds is attenuated to help distinguish self-generated sounds from ambient sounds. Sensory attenuation would work for louder ambient sounds, but could lead to less accurate perception if the ambient sounds were quieter. We hypothesize that a key function of sensorimotor integration is the facilitated processing of self-generated sounds, leading to more accurate perception under most conditions. The sensory attenuation hypothesis predicts better performance for higher but not lower intensity comparisons, whereas sensory facilitation predicts improved perception regardless of comparison sound intensity. A series of experiments tested these hypotheses, with results supporting the enhancement hypothesis. Overall, people were more accurate at comparing the loudness of two sounds when making one of the sounds themselves. We propose that the brain selectively modulates the perception of self-generated sounds to enhance representations of action consequences.

Connecting action control and agency: Does action-effect binding affect temporal binding?

The sense of agency, i.e., the notion that we, as agents, are in control of our own actions and can affect our environment by acting, is an integral part of human volition. Recent work has attempted to ground agency in basic mechanisms of human action control. Along these lines, action-effect binding has been shown to affect explicit judgments of agency. Here, we investigate if such action-effect bindings are also related to temporal binding which is often used as an implicit measure of agency. In two experiments, we found evidence for the establishment of short-term action-effect bindings as well as temporal binding effects. However, the two phenomena were not associated with each other. This finding suggests that the relation of action control and agency is not a simple one, and it adds to the evidence in favor of a dissociation between subjective agency and perceptual biases such as temporal binding.

Compress global, dilate local: Intentional binding in action-outcome alternations

Intentional binding refers to subjective temporal attraction between an action and its outcome. However, the nature of intentional binding in multiple actions remains unclear. We examined intentional binding in alternated action-outcome dyads. Participants actively or passively pressed a key, followed by a tone, and they again pressed the key; resulting in four keypress-tone dyads in a trial. Participants reproduced the duration of alternated keypress-tone dyads or the temporal interval between a dyad embedded in the alternations. The reproduced duration was shorter in the active than in the passive condition, suggesting the intentional binding in action-outcome alternations. In contrast, the reproduced interval between a dyad was longer in the active condition and did not correlate with the reproduced duration. These results suggest that subjective time during actions relies not only on an internal clock but also on postdictive biases that are switched based on what we recall.