Connectivity Analysis during Rubber Hand Illusion-A Pilot TMS-EEG Study in a Patient with SCI.

Vanessa N Frey,Raffaele Nardone,Eugen Trinka,Yvonne Höller,Patrick B Langthaler,Alexander B Kunz,Aljoscha Thomschewski,Yasuo Terao

doi:10.1155/2021/6695530

Abstract

Background Bodily self-perception is an important concept for several neurological disorders, including spinal cord injury (SCI). Changing one's bodily self-perception, e.g., via rubber hand illusion (RHI), induces alterations of bottom-up and top-down pathways and with this the connectivity between involved brain areas. We aim to examine whether (1) this process can be manipulated by changing cortical excitability, (2) connectivity between relevant brain areas differ when the RHI cannot be evoked, and (3) how this projection differs in a patient with SCI. Method We applied RHI and facilitatory theta burst stimulation (TBS) on the right primary somatosensory cortex (S1) of 18 healthy participants and one patient with incomplete, cervical SCI. During RHI, we recorded high-density electroencephalography (HD-EEG) and extracted directed and nondirected connectivity measures. Results There is no difference in connectivity between sham and real TBS or in the effectivity of RHI. We observed a higher laterality in the patient, i.e., higher connectivity of the right and lower of the left hemisphere. Besides this, connectivity patterns do not differ between healthy participants and the patient. Conclusion This connectivity pattern might represent a neuroplastic response in the attempt to overcome the functional impairment of the patient resulting in a similar overall connectivity pattern to the healthy participants, yet with a higher sensitivity towards RHI and a higher laterality. The cortico-cortical communication was not altered depending on whether the illusion was provoked or not; hence, the perceptory illusion could not be observed in the EEG analysis.

Highlights

Humans understand an object rather as a whole structure, not as the sum of its single parts [1, 2]
Neither are there significant differences between the participants in whom the rubber hand illusion (RHI) could be elicited and the ones in whom it was not (Table 1)
We investigated the effect of RHI and repetitive TMS in healthy participants and one patient with cervical spinal cord injury (SCI) on high-density electroencephalography (HD-EEG)

Summary

Introduction

Humans understand an object rather as a whole structure, not as the sum of its single parts [1, 2] This idea was rekindled in the early 20th century by German and Austrian psychologists (Kurt Koffka, Wolfgang Köhler, and Max Wertheimer) and embedded in the emerging “Gestalt Psychology.”. Changing one’s bodily self-perception, e.g., via rubber hand illusion (RHI), induces alterations of bottom-up and top-down pathways and with this the connectivity between involved brain areas. This connectivity pattern might represent a neuroplastic response in the attempt to overcome the functional impairment of the patient resulting in a similar overall connectivity pattern to the healthy participants, yet with a higher sensitivity towards RHI and a higher laterality. The cortico-cortical communication was not altered depending on whether the illusion was provoked or not; the perceptory illusion could not be observed in the EEG analysis

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Discussion

Conclusion