Unisensory and multisensory self-referential stimulation of the lower limb: an exploratory fMRI study on healthy subjects

Background: The holistic view of the person is the essence of the physiotherapy. Knowledge ofapproaches that develop the whole person promotes better patient outcomes. Multisensory Self-referential stimulation, more than a unisensory one, seems to produce a holistic experience of theSelf (“Core-Self”).Objectives: (1) To analyze the somatotopic brain activation during unisensoryand multisensorial Self-referential stimulus; and (2) to understand if the areas activated by multi-sensorial Self-referential stimulation are the ones responsible for the“Core-Self.”Methods:Anexploratory functional magnetic resonance imaging (fMRI) study was performed with 10 healthysubjects, under the stimulation of the lower limbs with three Self-referential stimuli: unisensoryauditory-verbal, unisensory tactile-manual, and multisensory, applying the unisensory stimulisimultaneously.Results: Unisensory stimulation elicits bilateral activations of the temporoparietaljunction (TPJ), of the primary somatosensory cortex (S1), of the primary motor cortex (BA4), of thepremotor cortex (BA6) and of BA44; multisensory stimulation also elicits activity in TPJ, BA4, andBA6, and when compared with unisensory stimuli, activations were found in: (1) Cortical andsubcortical midline structures—BA7 (precuneus), BA9 (medial prefrontal cortex), BA30 (posteriorcingulated), superior colliculum and posterior cerebellum; and (2) Posterior lateral cortex—TPJ,posterior BA13 (insula), BA19, and BA37. Bilateral TPJ is the one that showed the biggestactivation volume.Conclusion: This specific multisensory stimulation produces a brain activationmap in regions that are responsible for multisensory Self-processing and may represent the Core-Self. We recommend the use of this specific multisensory stimulation as a physiotherapy inter-vention strategy that might promote the Self-reorganization.