Voluntary Modulation of Hemodynamic Responses in Swallowing Related Motor Areas: A Near-Infrared Spectroscopy-Based Neurofeedback Study

Abstract

In the present study, we show for the first time that motor imagery of swallowing, which is defined as the mental imagination of a specific motor act without overt movements by muscular activity, can be successfully used as mental strategy in a neurofeedback training paradigm. Furthermore, we demonstrate its effects on cortical correlates of swallowing function. Therefore, N = 20 healthy young adults were trained to voluntarily increase their hemodynamic response in swallowing related brain areas as assessed with near-infrared spectroscopy (NIRS). During seven training sessions, participants received either feedback of concentration changes in oxygenated hemoglobin (oxy-Hb group, N = 10) or deoxygenated hemoglobin (deoxy-Hb group, N = 10) over the inferior frontal gyrus (IFG) during motor imagery of swallowing. Before and after the training, we assessed cortical activation patterns during motor execution and imagery of swallowing. The deoxy-Hb group was able to voluntarily increase deoxy-Hb over the IFG during imagery of swallowing. Furthermore, swallowing related cortical activation patterns were more pronounced during motor execution and imagery after the training compared to the pre-test, indicating cortical reorganization due to neurofeedback training. The oxy-Hb group could neither control oxy-Hb during neurofeedback training nor showed any cortical changes. Hence, successful modulation of deoxy-Hb over swallowing related brain areas led to cortical reorganization and might be useful for future treatments of swallowing dysfunction.

Motor imagery and swallowing: a systematic literature review

“…Considering the criteria of inclusion and exclusion, 4 articles were selected for this systematic review 6,[21][22][23] . The flowchart, which shows on detail, this process, follows the model of the Preferred Reporting Items for Systematic Reviews and Meta-Analyzes (PRISMA) For a better presentation of the results, the following variables of the selected articles were considered: author (year); country (sector); objective; subject; age; Inclusion criteria; Exclusion criteria; pathology (time, area, and side of brain injury); functional assessments; technique (imaging); strategy (motor imagery); major brain areas investigated; and results (Figures 2 and 3).…”

“…The use of motor imagery rehabilitation of swallowing shows to be a recent proposal, since the four selected articles are between the years 2014 and 2015 6,[21][22][23] . The literature clearly indicates the efficacy of MI as an adjuvant in motor rehabilitation of the upper limb in individuals with some neurological disorder [25][26][27] .…”

“…The countries which have published the research in question are different, however scholars of Austria and the Netherlands give signs that are involved in longitudinal research, improving topic [21][22][23] . In 2014 21 these researchers approached the use of MI by neuroimaging technique, checking changes in cerebral hemodynamics.…”

“…In 2014 21 these researchers approached the use of MI by neuroimaging technique, checking changes in cerebral hemodynamics. In 2015 23 , this same group deepens the methodology with neurofeedback strategies, with training modulation of brain oxygen levels during MI swallowing. In the other hand, the authors of Singapore 6 proposed to investigate the detection of swallowing MI as a proposal for rehabilitation through the MI of tongue movements (protrusion).…”

“…Moreover, it wouldn't be possible the admission of people with swallowing disorders 6,[21][22][23] . In the other hand, in the participants group with stroke, there was the requirement of dysphagia 6,22 , however with no others neurological and psychiatric disorders, with preserved capacity for understanding and communication 22 .…”