The SELF-TOUCH project has achieved its objectives for the first 24-month period including the collection of behavioural, neuroimaging (MEG and MRI) and trait schizotypy datasets in addition to several highly complementary studies arising from fruitful collaborations. The main work performed and associated results are summarised below:
1. Behavioural results have replicated previous demonstrations that self-touch is perceived as weaker than externally generated touch, but with important additional controls. Specifically, unlike the previous studies we included a control condition in which the same action was performed, that elicited an identical tactile stimulus, but a spatial separation between the action and its sensory consequence was introduced. A spatial separation condition controls for time-locked movement and touch of the active hand which is not possible when comparing only externally generated and self-generated touch conditions. Furthermore, a spatial separation control condition is also matched in the temporal predictability of the stimulus, divided attention between the two hands, and the dual-task requirement of the self-generated condition, all of which are not matched in externally generated touch conditions. The results demonstrate that self-touch is perceptually attenuated and rules out the confounds associated with the previous research.
2. The results show that neural responses in the primary somatosensory cortex are attenuated for self-generated touch compared to externally generated touch and compared to a control condition in which the same action is performed, but a spatial separation between the hands is introduced. This is the first demonstration, to our knowledge, of early neural somatosensory attenuation that cannot be explained by confounds associated with comparing only self-generated touch to externally generated touch.
3. The results also indicate that modulations of oscillations reflect the prediction of self-generated touch and that connectivity between key brain areas including the somatosensory cortex and the cerebellum may mediate predictions during self-touch.
4. Violating expectations of self-generated touch by unexpectedly omitting the stimulus results in a (prediction-related) signal over somatosensory areas following the omitted stimulus, which may directly reflect predictive signals in the brain.
These results are currently being investigated with respect to the participant's schizotypal personality traits to elucidate how individuals who are low versus high on schizotypal personality traits predict and process self-generated touch. Manuscripts are currently in preparation for a comprehensive dissemination of the findings.
In addition to the main work performed, highly complementary behavioural research was also performed by the fellow in collaborations including i) research challenging recent theoretical accounts of prediction during self-touch (Job & Kilteni, 2023), ii) research showing that the positive dimension of schizotypy is associated with reduced attenuation and precision of self-generated touch (Asimakidou, Job & Kilteni, 2022), ii) research investigating the perception of self-generated touch in healthy ageing (Timar, Job, Orban de Xivry & Kilteni (2023) and iv) research investigating the temporal tuning of somatosensory perception during self-touch.
