Why is there an error negativity on correct trials? A reappraisal

In healthy subjects, the Error Negativity (Ne) was initially reported on errors and on partial errors, only. Later on, application of the Laplacian transformation to EEG data unmasked a Ne-like wave (Nc) that shares a main generator with the Ne, suggesting that the Nc is just a small Ne. However, the reason why a small Ne would persist on correct responses remains unclear. Now, sometimes, subthreshold EMG activations in the muscles corresponding to correct responses (not strong enough to reach the response threshold) can precede full-blown correct responses. These "partially correct" activities seem to correspond to (force) execution errors, as they evoke a sizeable Ne. Within the frames of the Reward Value and Prediction Model or of the Predicted Response-Outcome model we propose that the action monitoring system evokes a Ne/Nc on correct responses because, even when a correct choice has been made, the accuracy of response (force) execution cannot be fully predicted. If this interpretation is correct, it can be assumed that, once these execution errors have been corrected, the correctness of the (full-blown) correcting response is highly predictable. Consequently, they should evoke a smaller Nc/Ne than "pure" correct responses. We show, that for the response thresholds set in the present experiment, the correcting response of the trials containing a partially correct activation evoke no identifiable Nc at all. Therefore it seems that there usually is an Error Negativity on correct trials because the correctness of response (force) execution cannot be fully predicted.

The cerebellum monitors errors and entrains executive networks

Frontal midline θ (Fmθ) activity occurs in medial prefrontal cortices (mPFC), when expected and actual outcomes conflict. Cerebellar forward models could inform the mPFC about this mismatch. To verify this hypothesis we correlated the mPFC activation during a visuomotor tracking task (VM) with performance accuracy, in control and cerebellum-lesioned participants. Additionally, purely visual (V), motor (M) and a motor plus visual tasks (V + M) were performed. An Independent Component, with a mid-frontal topography scalp map and equivalent dipole location in the dorsal anterior cingulate cortex accounted for Fmθ. In control participants Fmθ power increased during VM, when the error level crossed a threshold, but not during V + M, M and V. This increase scaled with tracking error. Fmθ power failed to increase during VM in cerebellar participants, even at highest tracking errors. Thus, in control participants, activation of mPFC is induced when a continuous monitoring effort for online error detection is required. The presence of a threshold error for enhancing Fmθ, suggests the switch from an automatic to an executive tracking control, which recruits the mPFC. Given that the cerebellum stores forward models, the absence of Fmθ increases during tracking errors in cerebellar participants indicates that cerebellum is necessary for supplying the mPFC with prediction error-related information. This occurs when automatic control falters, and a deliberate correction mechanism needs to be triggered. Further studies are needed to verify if this alerting function also occurs in the context of the other cognitive and non-cognitive functions in which the cerebellum is involved.

More implicit and more explicit motor imagery tasks for exploring the mental representation of hands and feet in action

The mental representation of the body in action can be explored using motor imagery (MI) tasks. MI tasks can be allocated along a continuum going from more implicit to more explicit tasks, where the discriminant is the degree of action monitoring required to solve the tasks (which is the awareness of using the mental representation of our own body to monitor our motor imagery). Tasks based on laterality judgments, such as the Hand Laterality Task (HLT) and the Foot Laterality Task (FLT), provide an example of more implicit tasks (i.e., less action monitoring is required). While, an example of a more explicit task is the Mental Motor Chronometry task (MMC) for hands and feet, where individuals are asked to perform or imagine performing movements with their limbs (i.e., more action monitoring is required). In our study, we directly compared hands and feet at all these tasks for the first time, as these body districts have different physical features as well as functions. Fifty-five participants were asked to complete an online version of the HLT and FLT (more implicit measure), and an online version of the MMC task for hands and feet (more explicit measure). The mental representation of hands and feet in action differed only when the degree of action monitoring decreased (HLT ≠ FLT); we observed the presence of biomechanical constraints only for hands. Differently, when the degree of action monitoring increased hands and feet did not show any difference (MMC hands = MMC feet). Our results show the presence of a difference in the mental representation of hands and feet in action that specifically depends on the degree of action monitoring.

Slip or fallacy? Effects of error severity on own and observed pitch error processing in pianists

Errors elicit a negative, mediofrontal, event-related potential (ERP), for both own errors (error-related negativity; ERN) and observed errors (here referred to as observer mediofrontal negativity; oMN). It is unclear, however, if the action-monitoring system codes action valence as an all-or-nothing phenomenon or if the system differentiates between errors of different severity. We investigated this question by recording electroencephalography (EEG) data of pianists playing themselves (Experiment 1) or watching others playing (Experiment 2). Piano pieces designed to elicit large errors were used. While active participants' ERN amplitudes differed between small and large errors, observers' oMN amplitudes did not. The different pattern in the two groups of participants was confirmed in an exploratory analysis comparing ERN and oMN directly. We suspect that both prediction and action mismatches can be coded in action monitoring systems, depending on the task, and a need-to-adapt signal is sent whenever mismatches happen to indicate the magnitude of the needed adaptation.

Electrophysiological correlates of action monitoring in brain-damaged patients: A systematic review

Action monitoring is crucial to the successful execution of an action and understanding the actions of others. It is often impaired due to brain lesions, in particular after stroke. This systematic review aims to map the literature on the neurophysiological correlates of action monitoring in patients with brain lesions. Eighteen studies were identified and divided into two groups: studies on monitoring of one's own actions and studies on monitoring of the actions of others. The first group included EEG studies on monitoring of self-performed erroneous and correct actions. Impaired error detection (decreased error-related negativity) was observed in patients with lesions in the performance-monitoring network, as compared to healthy controls. Less consistent results were shown for error positivity and behavioral error monitoring performance. The second group of studies on monitoring of others' actions reported decreased mu frequency suppression, impaired readiness potential in the affected hemisphere and decreased EEG indices of error observation (observed error positivity and theta power) in stroke patients. As a whole, these results indicate distinct patterns of impaired neurophysiological activity related to monitoring one's own versus others' actions in patients with brain lesions. EEG recordings of this dissociation in the same patients might be a useful index of motor recovery, and therefore, potentially also beneficial in rehabilitation protocols.

Contrasting time and frequency domains: ERN and induced theta oscillations differentially predict post-error behavior

The present study investigated the neural dynamics of error processing in both the time and frequency domains, as well as associated behavioral phenomena, at the single-trial level. We used a technique that enabled us to separately investigate the evoked and induced aspects of the EEG signal (Cohen & Donner, 2013, Journal of Neurophysiology, 110[12], 2752-2763). We found that at the single-trial level, while the (evoked) error-related negativity (ERN) predicted only post-error slowing (PES)-and only when errors occurred on incongruent trials-induced frontal midline theta power served as a robust predictor of both PES and post-error accuracy (PEA) regardless of stimulus congruency. Mediation models of both electrophysiological indices demonstrated that although the relationship between theta and PEA was mediated by PES, there was not a relationship between the ERN and PEA. Our data suggest that although the ERN and frontal midline theta index functionally related underlying cognitive processes, they are not simply the same process manifested in different domains. In addition, our findings are consistent with the adaptive theory of post-error slowing, as PES was positively associated with post-error accuracy at the single-trial level. More generally, our study provides additional support for the inclusion of a time-frequency approach to better understand the role of medial frontal cortex in action monitoring.

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

INTRODUCTION

Evidence about altered bimanual coordination has been reported in Parkinson's Disease. However, no previous study has explored such an alteration quantifying the interference effect that the trajectory of each hand might impose on the other one. Thus, in the present research, we applied the traditional Circles-Lines Coupling Task, which allowed assessing the motor coordination of the two hands, in the context of Parkinson's Disease.

METHODS

Thirty-six individuals affected by Parkinson's Disease were consecutively recruited and assigned to two groups according to their symptoms' lateralization. Moreover, eighteen age-matched healthy controls participated in the study. We capitalized on the Circles-Lines Coupling Task, in which the performance during incongruent movements (drawing lines with one hand and circles with the other hand) was compared with the performance during congruent movements (drawing lines with both hands). A bimanual coupling index was computed to compare the interference effect of each hand on the other one.

RESULTS

In healthy controls, the bimanual coupling index did not differ between the two hands. Crucially, in both groups of individuals affected by Parkinson's Disease, the less affected hand showed a significantly higher bimanual coupling index, due to the abnormal interference exerted by the most affected one, than vice versa.

CONCLUSIONS

Our results highlighted an altered spatial bimanual coupling in Parkinson's disease, depending on the symptoms' lateralization. We offered different explanations of our results according to the theoretical frameworks about the mechanisms subserving bimanual coordination.

Acute effects of alcohol on error-elicited negative affect during a cognitive control task

RATIONALE

Alcohol intoxication can dampen negative affective reactions to stressors. Recently, it has been proposed that these acute anxiolytic effects of alcohol may extend to dampening of negative affective reactions to error commission during cognitive control tasks. Nonetheless, empirical verification of this claim is lacking.

OBJECTIVES

Test the acute effect of alcohol on negative affective reactions to errors during an effort-demanding cognitive control task.

METHODS

Healthy, young adult social drinkers (N = 96 [49 women], 21-36 years old) were randomly assigned to consume alcohol (0.80 g/kg; n = 33 [15 female]), active placebo (0.04 g/kg; n = 33 [18 women]), or a non-alcoholic control beverage (n = 30 [16 women]) before completing the Eriksen flanker task. Corrugator supercilii (Corr) activation, a psychophysiological index of negative affect, was tracked across the task. Two neurophysiological reactions to errors, the error-related negativity (ERN) and the error positivity (Pe), were also measured.

RESULTS

Erroneous actions increased Corr activation in the control and (to a lesser extent) placebo groups, but not in the alcohol group. Error-induced Corr activation was coupled to ERN and Pe in the control, but not in the alcohol and placebo groups. Error-induced Corr activation was not coupled to post-error performance adjustments in any group.

CONCLUSIONS

The ability of alcohol to dampen error-related negative affect was verified. It was also shown that placebo alone can disrupt coupling of affective and (neuro)cognitive reactions to errors. Although its behavioral relevance remains to be demonstrated, more attention should be paid to the role of affect in action monitoring and cognitive control processes.

The gamma model analysis (GMA): Introducing a novel scoring method for the shape of components of the event-related potential

BACKGROUND

Research using the event-related potential (ERP) method to investigate cognitive processes has usually focused on the analysis of either individual peaks or the area under the curve as components of interest. These approaches, however, do not analyse or describe the substantial variation in size and shape across the entire individual waveforms.

NEW METHOD

Here we show that the precision of ERP analyses can be improved by fitting gamma functions to components of interest. Gamma model analyses provide time-dependent and shape-related information about the component, such as the component's rise and decline. We demonstrated the advantages of the gamma model analysis in a simulation study and in a two-choice response task, as well as a force production task.

RESULTS

The gamma model parameters were sensitive to experimental variations, as well as variations in behavioural parameters.

COMPARISON WITH EXISTING METHODS

Gamma model analyses provide researchers with additional reliable indicators about the shape of an ERP component's waveform, which previous analytical techniques could not.

CONCLUSION

This approach, therefore, provides a novel toolset to better understand the exact relationship between ERP components, behaviour and cognition.

Patients with mutations of the Thyroid hormone beta-receptor show an ADHD-like phenotype for performance monitoring: an electrophysiological study

•

Mutations in the thyroid hormone receptor beta (THRB) lead to relative hyperthyroidism in the brain.

•

Electrophysiological biomarkers of performance monitoring (ERN and Pe components) show a pattern similar to ADHD in carriers of THRB mutations.

•

The phenotype of THRB mutation carriers is indistinguishable from ADHD with regard to performance monitoring.

Resistance to thyroid hormone beta (RTHβ) is a syndrome of reduced responsiveness of peripheral tissue to thyroid hormone, caused by mutations in the thyroid hormone receptor beta (THRB). Its cognitive phenotype has been reported to be similar to attention deficit hyperactivity disorder (ADHD). This study used electrophysiological biomarkers of performance monitoring in RTHβ to contribute further evidence on its phenotypical similarity to ADHD. Twenty-one participants with RTHβ aged 18–67 years and 21 matched healthy controls performed a modified flanker task during EEG recording. The RTHβ and control groups were compared on behavioural measures and components of event related potentials (ERPs), i.e. the error related negativity (ERN), the error positivity (Pe) and P3 component. There were no significant group differences with regard to behaviour. RTHβ subjects displayed significantly reduced ERN and Pe amplitudes compared to the controls in the response-locked ERPs. In addition, we observed reduced P3 amplitudes in both congruent and incongruent trials, as well as prolonged P3 latencies in RTHβ subjects in the stimulus-locked ERPs. Our findings reveal alterations in error detection and performance monitoring of RTHβ patients, likely indicating reduced error awareness. The electrophysiological phenotype of RTHß subjects with regard to action monitoring is indistinguishable from ADHD.

Sensorimotor conflicts alter metacognitive and action monitoring

While sensorimotor signals are known to modulate perception, little is known about their influence on higher-level cognitive processes. Here, we applied sensorimotor conflicts while participants performed a perceptual task followed by confidence judgments. Results showed that sensorimotor conflicts altered metacognitive monitoring by decreasing metacognitive performance. In a second experiment, we replicated this finding and extended our results by showing that sensorimotor conflicts also altered action monitoring, as measured implicitly through intentional binding. In a third experiment, we replicated the same effects on intentional binding with sensorimotor conflicts related to the hand rather than to the trunk. However, effects of hand sensorimotor conflicts on metacognitive monitoring were not significant. Taken together, our results suggest that metacognitive and action monitoring may involve endogenous, embodied processes involving sensorimotor signals which are informative regarding the state of the decider.

Gesture impairments in schizophrenia are linked to increased movement and prolonged motor planning and execution

Schizophrenia patients present with a variety of impaired nonverbal communication skills. Performance of hand gestures is frequently impaired and associated with ratings of motor abnormalities. However, the impact of motor abnormalities to gesture performance remains unclear. To test the association between quantitative measures of motor behavior and qualitative ratings of gesture performance, we quantified movement parameters semi-automatically in videotaped recordings of gesture assessment. Thirty-one patients with schizophrenia (77.4%), schizophreniform (19.4%) or schizoaffective disorder (3.2%) and 32 healthy controls matched for age, gender and education underwent clinical assessment. Performance of the test of upper limb apraxia (TULIA) was video-taped in all subjects. The videos were analyzed with motion energy analysis software (MEA) to determine motion and time parameters. Patients and controls differed significantly in quantitative gesture performance: patients required more movement and more time to complete the tasks. Differences increased in patients with qualitatively impaired gesture production ratings (p<0.01). Group differences were most pronounced in the pantomime domain, when gestures are performed following verbal instruction. In patients, ratings of motor abnormalities correlated with duration of movement, while behavioral disorganization correlated with the amount of movements during gesture performance. Disorder related motor symptoms, aberrant action observation, planning and monitoring as well as internal clock abnormalities may explain the poor performance of hand gestures in schizophrenia. Quantitative video analysis offers a unique possibility to analyze movement patterns as a direct functional output of the motor system. In the future, it may assist monitoring, staging and prognosis in schizophrenia.

Violation of expectations about movement and goal achievement leads to Sense of Agency reduction

The control of one's own movements and of their impact on the external world generates a feeling of control referred to as Sense of Agency (SoA). SoA is experienced when actions match predictions and is reduced by unpredicted events. The present study investigated the contribution of monitoring two fundamental components of action-movement execution and goal achievement-that have been most often explored separately in previous research. We have devised a new paradigm in which participants performed goal-directed actions while viewing an avatar's hand in a mixed-reality scenario. The hand performed either the same action or a different one, simultaneously or after various delays. Movement of the virtual finger and goal attainment were manipulated, so that they could match or conflict with the participants' expectations. We collected judgments of correspondence (an explicit index of SoA that overcomes the tendency to over-attribute actions to oneself) by asking participants if the observed action was synchronous or not with their action. In keeping with previous studies, we found that monitoring both movement execution and goal attainment is relevant for SoA. Moreover, we expanded previous findings by showing that movement information may be a more constant source of SoA modulation than goal information. Indeed, an incongruent movement impaired SoA irrespective of delay duration, while a missed goal did so only when delays were short. Our novel paradigm allowed us to simultaneously manipulate multiple action features, a characteristic that makes it suitable for investigating the contribution of different sub-components of action in modulating SoA in healthy and clinical populations.

Impulse control disorder and response-inhibition alterations in Parkinson's disease. A rare case of totally absent functionality of the medial-prefrontal cortex and review of literature

This report illustrates a Parkinson’s disease (PD) patient with impulse-control disorder (ICD) and selective impairment in response-inhibition abilities as revealed by the performance in a functional magnetic resonance imaging (fMRI) anterior cingulate cortex - sensitive go-nogo task. In line with hypothesis on the role of response-inhibition disabilities in the arising of impulsivity in PD, the patient completely failed the go-nogo task. Moreover, fMRI acquisition revealed absent task-sensitive activity in the anterior cingulate cortex, medial prefrontal, and orbitofrontal cortices for the contrast nogo versus go, which signifying that a hypo-function of this network could be associated with ICD. A fronto-striatal and cingulo-frontal dysfunction may reflect impairment in metacognitive-executive abilities (such as response-inhibition, action monitoring, and error awareness) and promote compulsive repetition of behavior. Response-inhibition tasks may be useful in PD post-diagnostic phase, to better identify individuals at risk of developing ICD with dopaminergic medication.

Uniqueness of action monitoring in children with autism spectrum disorder: Response types and temporal aspects

BACKGROUND

Action monitoring, the process for evaluating the appropriateness of one's own actions, is reported to be atypical in individuals with autism spectrum disorder (ASD).

METHOD

We examined the characteristics of action monitoring in 11 children with ASD and 12 children with typical development (TD), analyzing stimulus-locked and response-locked event-related potential components (i.e., N2; error-related negativity, ERN; and error positivity, Pe) related to execution of a flanker task.

RESULTS

We found a smaller N2 amplitude in children with ASD than in those with TD. Children with ASD also had a larger amplitude of ERN for partial error responses (electromyographic activity corresponding to the inappropriate hand side before response execution) than did children with TD. Additionally, the ERN amplitude for the partial error response was correlated with the Autistic Mannerisms of the Social Responsiveness Scale. There were no significant differences in Pe amplitudes between children with ASD and those with TD.

CONCLUSION

The results suggest that action monitoring in children with ASD is significantly different both before and after response execution. We hypothesized that the detail-focused processing style of ASD reduces the demands of action monitoring before response execution; however, autistic mannerisms evoke excessive concern regarding trivial mistakes after response execution.

Self-initiated actions result in suppressed auditory but amplified visual evoked components in healthy participants

Self-suppression refers to the phenomenon that sensations initiated by our own movements are typically less salient, and elicit an attenuated neural response, compared to sensations resulting from changes in the external world. Evidence for self-suppression is provided by previous ERP studies in the auditory modality, which have found that healthy participants typically exhibit a reduced auditory N1 component when auditory stimuli are self-initiated as opposed to externally initiated. However, the literature investigating self-suppression in the visual modality is sparse, with mixed findings and experimental protocols. An EEG study was conducted to expand our understanding of self-suppression across different sensory modalities. Healthy participants experienced either an auditory (tone) or visual (pattern-reversal) stimulus following a willed button press (self-initiated), a random interval (externally initiated, unpredictable onset), or a visual countdown (externally initiated, predictable onset-to match the intrinsic predictability of self-initiated stimuli), while EEG was continuously recorded. Reduced N1 amplitudes for self- versus externally initiated tones indicated that self-suppression occurred in the auditory domain. In contrast, the visual N145 component was amplified for self- versus externally initiated pattern reversals. Externally initiated conditions did not differ as a function of their predictability. These findings highlight a difference in sensory processing of self-initiated stimuli across modalities, and may have implications for clinical disorders that are ostensibly associated with abnormal self-suppression.

Neurophysiological evidence for diminished monitoring of own, but intact monitoring of other's errors in schizophrenia

Schizophrenia is characterized by social deficits. Correctly monitoring own and others' performance is crucial for efficient social behavior. Deficits in monitoring own performance as reflected in reduced error-related negativity (rERN) amplitudes, have been demonstrated repeatedly in schizophrenia. A similar ERP component (observed ERN; oERN) is elicited when observing others' mistakes. However, possible deficits in monitoring others' performance have never been investigated in schizophrenia. The current ERP-study compared a group of schizophrenia patients (N=22) and healthy controls (N=21) while performing a Simon task and the social Simon task, enabling the investigation of own (rERN) and others' (oERN) performance monitoring. Patients showed slower reaction times, but comparable accuracy and compatibility effects in both tasks. As expected, patients' rERN amplitudes were reduced. Importantly however, oERN amplitudes were comparable between both groups. While monitoring own performance is compromised in schizophrenia, monitoring others' performance seems intact. This divergence between internal and external performance monitoring in patients is in line with studies showing normal neurophysiological responses to negative feedback. The presently found dissociation may improve our understanding of cognitive and neural mechanisms underlying monitoring of own and others' performance and may stimulate treatment development aimed at learning from external rather than internal error information in schizophrenia.

Action-monitoring impairment in anosognosia for hemiplegia

Every movement begins with action programming, and ends with a produced effect. Anosognosia for hemiplegia (AH), involving unawareness of motor deficits after brain damage, is a striking but also poorly understood symptom in clinical neurology. It has been suggested that it may result from a combination of cognitive and sensorimotor dysfunctions, including impairments in monitoring motor action and detecting the mismatch between intention and outcome. Here we investigated the relationship between motor action awareness and monitoring of self-produced movements by using a motor imaginary task, which was performed with either the intact or the affected limb. We tested 10 right brain-damaged patients, including 5 with AH, in comparison with 5 healthy controls. In a first phase, participants were asked to either realize or imagine a movement with their right or left arm. In a subsequent recognition phase, the participants had to recall whether the movement was a realized or imagined and which arm was used. AH patients performed significantly worse relative to no-AH patients and healthy controls for the left movements. Specifically, we found that AH patients believed they had realized movements with their (paralyzed) left arm even when they failed in the left execution condition. However, they also made more errors for movements actually realized with the right hand. These findings confirm that impaired action monitoring may contribute to AHP. Furthermore, our results support the notion of an action control system integrating "feedforward" signals through a comparison process between the intention and execution of movement, but also indicate that monitoring deficits in AHP are not strictly unilateral. Combined together, dysfunction of motor comparator processes and more general monitoring deficits may add up to lead to unawareness of paralysis.

Deeper into schizotypy and motor performance: Investigating the nature of motor control in a non-psychiatric sample

Numerous studies have demonstrated that motor control deficits are characteristic of patients diagnosed with schizophrenia and those at-risk for the development of the disorder. Recent advances in the quantification of motor dysfunction have confirmed this, but these methods fail to consider an important aspect of subject performance: the qualitative nature of their psychomotor dyscontrol. We report on a novel technique used to quantify the qualitative nature of psychomotor performance and its relation to schizotypy. Control (n = 35) and schizotypic subjects (n = 47) completed a line-drawing task that yields metrics for psychomotor control and predominant frequency. Schizotypes evidenced greater psychomotor dyscontrol and lower predominant frequencies than controls. These results are interpreted as evidence of reduced visual-motor integration, self-monitoring capacity, or adherence to basic motor principles in schizotypes. The potential use of these metrics as putative endophenotypes for the liability for schizophrenia and the implications of these findings for the relationship between schizophrenia and schizotypy are discussed.

Self-attribution bias during continuous action-effect monitoring in patients with schizophrenia

The feeling of being the source and controller of one's actions and their effects in the outside world is an important aspect of our sense of self. Disturbances in this sense of agency (SoA) were observed in schizophrenia and have been linked to impairments in sensorimotor integration. We used a virtual-world action-monitoring paradigm to investigate the SoA in 20 schizophrenic patients and 18 healthy subjects. Participants continuously moved a virtual pen displayed on a computer screen using a touchpad device. The control they exceeded over the virtual pen was switched periodically between the participant and the computer. Participants were requested to monitor their actions and the effects on the virtual pen, and indicate loss or regain of control over the pen's movement by button presses. The numbers of erroneous external attribution of action effects (false negative agency judgements) and erroneous self-attribution (false positive agency judgements) were not significantly different in patients and healthy subjects. However, patients showed a significant increase in the duration of false negative agency judgements. Moreover, the number of false negative agency judgements as well as the number and the duration of false positive agency judgements were negatively correlated with the performance in cognitive tests (BACS) in the patient group only. Our findings indicate that the evaluation system to detect a mismatch between actions and their effects in the outside world is probably more rigid in schizophrenic patients, which leads to an increased self-attribution bias for action effects, as commonly found in delusions of control. The impairment in sensorimotor integration may be compensated for by stronger cognitive control.

The elusive experience of agency

I here present some doubts about whether Mandik's (2010) proposed intermediacy and recurrence constraints are necessary and sufficient for agentive experience. I also argue that in order to vindicate the conclusion that agentive experience is an exclusively perceptual phenomenon (Prinz, 2007), it is not enough to show that the predictions produced by forward models of planned motor actions are conveyed by mock sensory signals. Rather, it must also be shown that the outputs of "comparator" mechanisms that compare these predictions against actual sensory feedback are also coded in a perceptual representational format.