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

ABSTRACT

Background: The holistic view of the person is the essence of the physiotherapy. Knowledge of approaches 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 the Self (“Core-Self”). Objectives: (1) To analyze the somatotopic brain activation during unisensory and multisensorial Self-referential stimulus; and (2) to understand if the areas activated by multisensorial Self-referential stimulation are the ones responsible for the “Core-Self.” Methods: An exploratory functional magnetic resonance imaging (fMRI) study was performed with 10 healthy subjects, under the stimulation of the lower limbs with three Self-referential stimuli: unisensory auditory-verbal, unisensory tactile-manual, and multisensory, applying the unisensory stimuli simultaneously. Results: Unisensory stimulation elicits bilateral activations of the temporoparietal junction (TPJ), of the primary somatosensory cortex (S1), of the primary motor cortex (BA4), of the premotor cortex (BA6) and of BA44; multisensory stimulation also elicits activity in TPJ, BA4, and BA6, and when compared with unisensory stimuli, activations were found in: (1) Cortical and subcortical midline structures—BA7 (precuneus), BA9 (medial prefrontal cortex), BA30 (posterior cingulated), 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 biggest activation volume. Conclusion: This specific multisensory stimulation produces a brain activation map 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 intervention strategy that might promote the Self-reorganization.

KEYWORDS:

• Auditory-verbal Self-referential stimulation
• brain map
• lower-limb
• multisensory Self-referential stimulation
• Self-processing
• tactile-manual Self-referential stimulation

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.

Funding

This work had funding resources from the Institute of Health Sciences, Catholic University of Portugal, for the use of the fMRI equipment and team. The authors are indebted to all the subjects that participated in the study.

Notes

¹ Theory of Mind is the cognitive capacity to attribute mental states to Self and others (Premack and Woodruff 1978) and more recently (Goldman 2012).

² The theory is that many of the dimensions of cognition (language, memory, attention, and reasoning) are embodied, i.e., they are dependent and are influenced by characteristics of the body, how that body collects the information of the environment, the way the body interacts with the brain, and how the brain processes this information and raises awareness (Anderson 2003; Hauk and Tschentscher 2013).

Additional information

Funding

This work had funding resources from the Institute of Health Sciences, Catholic University of Portugal, for the use of the fMRI equipment and team. The authors are indebted to all the subjects that participated in the study.