Abstract
Sustained pressure stimulation of the body surface has been used in several physiotherapeutic techniques, such as reflex locomotion therapy. Clinical observations of global motor responses and subsequent motor behavioral changes after stimulation in certain sites suggest modulation of central sensorimotor control, however, the neuroanatomical correlates remain undescribed. We hypothesized that different body sites would specifically influence the sensorimotor system during the stimulation. We tested the hypothesis using functional magnetic resonance imaging (fMRI) in thirty healthy volunteers (mean age 24.2) scanned twice during intermittent manual pressure stimulation, once at the right lateral heel according to reflex locomotion therapy, and once at the right lateral ankle (control site). A flexible modeling approach with finite impulse response basis functions was employed since non-canonical hemodynamic response was expected. Subsequently, a clustering algorithm was used to separate areas with differential timecourses. Stimulation at both sites induced responses throughout the sensorimotor system that could be mostly separated into two anti-correlated subsystems with transient positive or negative signal change and rapid adaptation, although in heel stimulation, insulo-opercular cortices and pons showed sustained activation. In direct voxel-wise comparison, heel stimulation was associated with significantly higher activation levels in the contralateral primary motor cortex and decreased activation in the posterior parietal cortex. Thus, we demonstrate that the manual pressure stimulation affects multiple brain structures involved in motor control and the choice of stimulation site impacts the shape and amplitude of the blood oxygenation level-dependent response. We further discuss the relationship between the affected structures and behavioral changes after reflex locomotion therapy.
Highlights
IntroductionPlastic changes can be induced via transient peripheral afferent stimulation (Powell et al, 1999)
Neuronal plasticity is a key component in restoration of human motor function
Less extensive overlap was observed in the more posterior right postcentral gyrus and superior parietal lobule (SPL), i.e., ipsilateral to the stimulated limb. Both stimulation sites were associated with signal changes in bilateral dorsolateral sensorimotor cortex (SMC, i.e., primary somatosensory cortex (S1) and primary motor cortex (M1)) in the somatotopic representation of the upper limb and face (Long et al, 2014)
Summary
Plastic changes can be induced via transient peripheral afferent stimulation (Powell et al, 1999). Peripheral pressure stimulation has been studied less extensively (Miura et al, 2013; Chung et al, 2014, 2015; Sanz-Esteban et al, 2018) despite the fact that it serves as a major component of clinical physiotherapeutic techniques, such as the “reflex locomotion” (Vojta, 1973; Vojta and Peters, 2007; Hok et al, 2017; Jung et al, 2017). The technique, known as Vojta method, uses sustained manual pressure stimulation of specific body surface areas to gradually evoke a stereotypic pattern of tonic muscle contractions in both sides of the neck, trunk, and limbs (Vojta, 1973). There is limited knowledge of the immediate neurobiological correlates of the therapeutic stimulation and the resulting interaction between the somatosensory and motor system
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