Individuals with mirror touch synaesthesia (MTS) experience touch on their own body when observing others being touched. A recent account proposes that such rare experiences could be linked to impairment in self-other representations.Here we tested participants with MTS on a battery of social cognition tests and found that compared to non-synaesthete controls, the MTS group showed impairment in imitation-inhibition but not in visual perspective taking or theory of mind. Although all of these socio-cognitive abilities rely on the control of selfother representations, they differ as to whether the self, or the other, should be preferentially represented. For imitation-inhibition, representations of the other should be inhibited and self-representations should be enhanced, whereas the opposite is true for visual perspective taking and theory of mind. These findings suggest that MTS is associated with a specific deficit in inhibiting representation of other individuals and shed light on the fractionability of processes underlying typical social cognition.

Mirror-touch synaesthesia (MTS) is a condition that leads people to experience tactile sensations on their own body when watching at someone else being touched. Recent accounts postulate that MTS is linked with atypical self-other representations. It has been suggested that this may be associated with disturbances in two main components of self-awareness: sense of agency and sense of ownership. This study investigates changes in sense of agency and sense of ownership in MTS. Using a paradigm that deliberately blurs the boundaries between the self and the other, we not only found that MTS affects sense of agency and sense of ownership, but that these aspects of self-awareness are affected differently. We suggest that alterations in sense of agency can be linked to more profound disturbances in sense of ownership in MTS, and that MTS may be characterised by underlying difficulties in self-other processing.

The study assessed whether the auditory reference provided by a music scale could improve spatial exploration of a standard musical instrument keyboard in right-brain-damaged patients with left spatial neglect. As performing music scales involves the production of predictable successive pitches, the expectation of the subsequent note may facilitate patients to explore a larger extension of space in the left affected side, during the production of music scales from right to left. Eleven right-brain-damaged stroke patients with left spatial neglect, 12 patients without neglect, and 12 age-matched healthy participants played descending scales on a music keyboard. In a counterbalanced design, the participants' exploratory performance was assessed while producing scales in three feedback conditions: With congruent sound, no-sound, or random sound feedback provided by the keyboard. The number of keys played and the timing of key press were recorded. Spatial exploration by patients with left neglect was superior with congruent sound feedback, compared to both Silence and Random sound conditions. Both the congruent and incongruent sound conditions were associated with a greater deceleration in all groups. The frame provided by the music scale improves exploration of the left side of space, contralateral to the right hemisphere, damaged in patients with left neglect. Performing a scale with congruent sounds may trigger at some extent preserved auditory and spatial multisensory representations of successive sounds, thus influencing the time course of space scanning, and ultimately resulting in a more extensive spatial exploration. These findings offer new perspectives also for the rehabilitation of the disorder.

Sense of agency (SoAg) is the feeling of control over one's actions and their effects. It can be augmented or attenuated by internal signals and by external cues. Research has shown a reduction in the SoAg in older adulthood, but the reasons behind this change remain unclear. We investigated agency processing differences that may underpin age-related changes in SoAg. Using a modified version of a vicarious agency paradigm, we tested the modulation of SoAg by manipulating external situational agency cues in younger and older adults. Our results show that the illusion of vicarious agency was less pronounced in older adults. These results were replicated in a second experiment which also showed that older adults performed significantly better in interoception and proprioception tasks. We suggest that increased reliance on internal cues may explain differences in agency processing in older adulthood.