Explicit and implicit sense of agency in depersonalisation experiences.

The sense of agency, the feeling of controlling one's bodily actions and the world is altered in Depersonalisation (DP), a condition that makes people feel detached from one's self and body. To investigate the link between depersonalisation and both implicit and explicit sense of agency, an online study was conducted using the influential Intentional Binding paradigm in a sample of non-clinical DP participants. The results did not reveal significant differences between individuals with low and high occurrences of DP experiences on the implicit and explicit sense of agency. However, participants with high occurrences of DP experiences showed a more time-sensitive explicit sense of agency and greater temporal distortions for short intervals in the absence of self-initiated motion. These results suggest that there is a discrepancy between implicit and explicit sense of agency in people with high levels of depersonalisation. Altogether, these findings call for further investigations of the key role of time perception on altered sense of self and agency in both non-clinical and clinical populations, to disentangle the mechanisms associated with the explicit and implicit sense of agency.

Bodily self-perception during voluntary actions: The causal contribution of premotor cortex and cerebellum.

Voluntary actions are accompanied by the experience of controlling one's own movements (sense of agency) and the feeling that the moving body part belongs to one's self (sense of body ownership). So far, agency and body ownership have been investigated separately, leaving the neural underpinnings of the relation between the two largely unexplored. The aim of this study was to explore the causal role of two multisensory brain regions, that is the premotor cortex (PMc) and the cerebellum, in agency and body ownership concurrently on the same behavioral task, i.e., the moving Rubber Hand Illusion (mRHI). Participants watched a rubber hand while moving their hidden hand. The type of movement (active or passive) and posture of the rubber hand (congruent or incongruent) differed in three conditions (active congruent, passive congruent, active incongruent), so that agency and ownership could be elicited either separately or concurrently. Agency and ownership were measured by subjective report and proprioceptive drift. Sham and anodal transcranial direct current stimulation (tDCS) were delivered to the PMc (Experiment 1) or the cerebellum (Experiment 2) prior to the mRHI task. Independent of the site or type of tDCS, subjective reports revealed that both agency and ownership were evoked in the active congruent condition, ownership but not agency in the passive congruent condition, and agency but not ownership in the active incongruent condition. The proprioceptive drift was evoked in the active congruent and the passive congruent condition. Anodal tDCS over the PMc reduced the feeling of agency in the active congruent condition, while it enhanced proprioceptive drift when applied over the cerebellum. These findings suggest a specific causal contribution of the PMc and the cerebellum to bodily self-perception during voluntary movement, with the PMc mainly involved in awareness of action and the cerebellum in proprioceptive adaptation of body position in space.

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.

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.

Dissociating decision strategies in free-choice tasks - A mouse tracking analysis.

Everyday life offers a variety of possible actions, from which we choose one that corresponds to our intended goals. How do these goals and actions interact within the mind? One way to investigate this question is free-choice tasks, where participants freely choose the action they want to perform on any given trial. Such tasks are used in research on voluntary actions and goal-driven behavior, such as ideomotor theory. However, these tasks leave participants with a substantial amount of freedom and allow for different response strategies. Such strategies can, though being hidden in the final data, influence the results, for example by hiding the effects of manipulations of interest. To better understand participants' behavior in free-choice tasks, we used mouse tracking in an ideomotor free-choice experiment, where participants learn the connection between an action and an effect. Subsequently, they have to freely choose between actions, while the former effect is presented as a stimulus. We identified two distinct groups that applied different decision strategies. The first group made the decision at the beginning of or before the trial, irrespective of the yet to be presented effect stimulus. The second group decided within the trial and was affected by the stimulus more often. This suggests that people handle free-choice tasks differently which is expressed in heterogeneous choice patterns and response times and an underestimation of the examined effects. These differences potentially limit the reliability of inferences from free-choice experiments and should be considered in the interpretation of their results.

Goal-directed behaviors in patients with schizophrenia: Concept relevance and updated model.

Goal-directed behaviors are formulated to pursue a given objective by constructing a plan and selecting actions that lead to the intended goal, either immediately or over an extended period. This concept is important to the study of human behavior because of its involvement in the majority of complex or novel situations that an individual may encounter, regardless of the cognitive, affective, or social abilities required. In this paper, we aim to demonstrate the relevance of goal-directed behaviors to our understanding of the cognitive deficits and other symptoms associated with schizophrenia. A systematic analysis of this relation may allow us to develop integrative hypotheses regarding positive, negative, and disorganized symptoms of schizophrenia rather than consider them to be distinct issues. In this article, we review previous studies of goal-directed actions in patients with schizophrenia in order to clarify the relevant concepts and provide a theoretical basis for the integration of existing results. Based on available theoretical models and data, we propose an updated model to facilitate further investigation of schizophrenia-related impairments in goal-directed behaviors.

The kinematic signature of voluntary actions.

Research in the field of psychology and cognitive neuroscience has begun to explore the functional underpinnings of voluntary actions and how they differ from stimulus-driven actions. From these studies one can conclude that the two action modes differ with respect to their neural and behavioural correlates. So far, however, no study has investigated whether the voluntary and stimulus-driven actions also differ in terms of motor programming. We report two experiments in which participants had to perform either voluntary or stimulus-driven reach-to-grasp actions upon the same stimulus. Using kinematic methods, in Experiment 1 we obtained evidence that voluntary actions and stimulus-driven actions translate into differential movement patterns. Results for Experiments 2 suggest that selecting what to do, when to act, and whether to act are characterized by specific kinematic signatures and affect different aspects of the reach-to-grasp movement in a selective fashion. These findings add to current models of volition suggesting that voluntary action control results from an interplay of dissociable subfunctions related to specific decision components: what action execute, when to execute an action, and whether to execute any action.