Patients with lesions of the left posterior parietal cortex commonly fail in identifying their fingers, a condition known as finger agnosia, yet are relatively unimpaired in sensation and skilled action. Such dissociations have traditionally been interpreted as evidence that structural body representations (BSR), such as the body structural description, are distinct from sensorimotor representations, such as the body schema. We investigated whether performance on tasks commonly used to assess finger agnosia is modulated by changes in hand posture. We used the ‘in between’ test in which participants estimate the number of unstimulated fingers between two touched fingers or a localization task in which participants judge which two fingers were stimulated. Across blocks, the fingers were placed in three levels of splay. Judged finger numerosity was analysed, in Exp. 1 by direct report and in Exp. 2 as the actual number of fingers between the fingers named. In both experiments, judgments were greater when non-adjacent stimulated fingers were positioned far apart compared to when they were close together or touching, whereas judgements were unaltered when adjacent fingers were stimulated. This demonstrates that BSRs are not fixed, but are modulated by the real-time physical distances between body parts.

Sensorimotor simulation theory offers potential to explain the mechanisms that underpin the ability to recognize others’ emotions. In this vein, recent models propose a key role for the somatosensory cortex (SC) in emotion recognition. In addition, recent evidence suggests that the subjective experience from the perception of a facial expression is linked with responses in the SC but not with responses in the motor cortex. Furthermore, models of sensorimotor simulation converge on the idea that somatosensory representations and visual representations are integrated. Here, we want to test whether somatosensory activity during the perception of facial expressions has a role in conscious processing of such expressions, an issue that has been ignored by previous research. To this aim we will present facial expressions in binocular rivalry, a well-suited paradigm employed in behavioral and neuroimaging studies of conscious visual perception. We expect that congruent tactile facial stimulation with the somatosensory representations of happy expressions will favor the conscious content of happy facial expressions and interfere with conscious processing of neutral expressions compared to the absence of tactile stimulation.

Contents of consciousness change over time. However, the study of dynamics in consciousness has been largely neglected. Aru and Bachmann have recently brought to the attention of scientists dealing with consciousness the relevance of making inquiries about its temporal evolution. Importantly, they also pointed out several experimental questions as guidelines for researchers interested in studying the temporal evolution of consciousness, including the phases of formation and dissolution of content. They also suggested that these two phases could be characterized by asymmetric inertia. The main objective of the present investigation was to approximate the dynamics of these two phases in the context of conscious face perception. To this aim, we tested the time course of content transitions during a binocular rivalry task using face stimuli and asked participants to map their subjective experience of transitions from one content to the other through a joystick. We then computed metrics of joystick velocity linked to content transitions as proxies of the formation and dissolution phases. We found a general phase effect such that the formation phase was slower than the dissolution phase. Furthermore, we observed an effect specific to happy facial expressions, such that their contents were slower to form and dissolve than that of neutral expressions. We further propose to include a third phase of stabilization of conscious content between formation and dissolution.

Contents of consciousness change over time. However, the study of dynamics in consciousness has been largely neglected. Aru and Bachmann have recently brought to the attention of scientists dealing with consciousness the relevance of making inquiries about its temporal evolution. Importantly, they also pointed out several experimental questions as guidelines for researchers interested in studying the temporal evolution of consciousness, including the phases of formation and dissolution of content. They also suggested that these two phases could be characterized by asymmetric inertia. The main objective of the present investigation was to implement and validate a method to approximate the dynamics of these two phases. To this aim, we tested the time course of content transitions during a binocular rivalry task using face stimuli and asked participants to map their subjective experience of transitions from one content to the other through a joystick. We then computed metrics of joystick velocity linked to content transitions as proxies of the formation and dissolution phases. We found a general phase effect such that the formation phase was slower than the dissolution phase. Furthermore, we observed an effect specific to happy facial expressions, such that their contents were slower to form and dissolve than that of neutral expressions. We further propose to include a third phase of stabilization of conscious content between formation and dissolution. To conclude, the method and the metrics we propose seem to provide a good proxy to study the temporal evolution of consciousness.

Sensorimotor simulation models propose that sensorimotor brain regions play an important role in recognizing and understanding others’ emotions. In particular, the sensorimotor re-enactment by the observer would assist the recognition and understanding of emotions. In this vein, several studies have manipulated the observer’s facial mimicry during a variety of facial expression recognition tasks providing evidence in favor of the role of facial mimicry in emotion recognition. In this theoretical context, a particularly intriguing facet has been neglected, namely whether sensorimotor simulation and facial mimicry can play a role in the conscious processing of facial expressions of emotions. In the present experiment we implemented a binocular rivalry paradigm to investigate whether facial mimicry is functionally associated with conscious processing of facial expressions and in particular in accessing awareness and/or stabilizing conscious representations of emotional expressions. On each trial, female participants were exposed to a rivalrous pair of a neutral and a happy expression of the same individual through anaglyph glasses in two conditions: in one, they could freely use their facial mimicry, in the other they had to keep a chopstick between their lips. The latter manipulation constrained the mobility of the zygomatic muscle, producing a ‘noise’ at the level of the sensorimotor simulation. Our results confirmed previous evidence of an advantage of emotional faces when compared to neutral faces. Crucially, they also confirmed the main hypothesis that facial mimicry has a role on the conscious processing of facial expressions. More specifically, this role appears to be associated with the stabilization of conscious representations of expressions rather than facilitation of conscious access, as mimicry manipulation impacted an estimate of time of facial expressions dominance rather than affecting the frequency of the initial percepts and their onset time (i.e., first button press time). Taken together, our results open a door to the future investigation of the intersection between sensorimotor simulation models and conscious perception of emotional stimuli.