Differential Effects of Sustained Manual Pressure Stimulation According to Site of Action

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.

Modulation of the human sensorimotor system by afferent somatosensory input: evidence from experimental pressure stimulation and physiotherapy

“…This necessitates an adequate control condition, e.g., a comparison between similar kinds of stimulation with or without known motor consequences. Therefore, several functional imaging studies contrasted the effects of therapeutic stimulation according to Vojta 25,26 with a sham stimulation 11,12,17 . Sanz-Esteban et al 17 applied pressure stimulus to an active site at the anterior thorax 25 and reported the main effect of the stimulation site (active versus control) in the ipsilateral putamen 17 .…”

“…In our fMRI study of sustained manual pressure stimulation 12 , we compared an active lateral heel site at the right foot 26 to a nearby control lateral ankle site in 30 healthy volunteers who underwent two fMRI sessions according to a cross-over single-blinded randomised study design. To more closely match the characteristic postural conditions and prolonged manual stimulation during RLT (ref.…”

“…The mechanisms behind deactivations are not yet completely understood. Nevertheless, they should still be considered when interpreting data involving prolonged stimulation 12 .…”

“…Most frequently studied peripheral stimulation modalities include electrical nerve stimulation or vibration, which are simple to control and administer [7][8][9][10] . Natural modalities of peripheral stimulation, such as tactile, pressure or proprioceptive, have been studied less extensively 11,12 , although they represent essential elements of some clinical rehabilitation techniques and procedures [13][14][15] . Whereas noxious mechanical pressure stimulation has been employed in research of central pain processing 16 , the effects of sustained innocuous pressure have been explored to a lower extent.…”

“…Even less attention has been paid to the interaction of central somatosensory processing of pressure with the "classical" motor system, but see ref. 11,12,17 .…”