Illusory limb movements activate different brain networks than imposed limb movements: an ALE meta-analysis.

Proprioceptive information allows us to perform smooth coordinated movements by constantly updating us with knowledge of the position of our limbs in space. How this information is combined and processed to form conscious perceptions of limb position is still relatively unknown. Several functional neuroimaging studies have attempted to tease out the brain areas responsible for proprioceptive processing in the human brain. Yet there still exists some disagreement in the specific brain regions involved. In order to consolidate the current knowledge in the field, we performed a systematic review of the literature and an activation likelihood estimation (ALE) meta-analysis of functional neuroimaging studies of proprioception. We identified 12 studies that used a proprioceptive stimulus of the upper extremity for ALE analysis (n = 141 participants). Two types of stimuli (illusion of movement induced through muscle tendon vibration and passive/imposed movements) were found to be most commonly used to probe proprioceptive networks in the brain. ALE analysis of these two stimulus types revealed that both were associated with activation in the left precentral, postcentral, and anterior cingulate gyri. Interestingly, different patterns of activation were also observed between illusions of movement and imposed movement. In the left hemisphere, imposed movements resulted in activations that were more inferior in the post-central gyrus. In the right hemisphere, imposed movements resulted in two clusters of activation in the inferior aspect of the precentral gyrus and the hand area of the post-central gyrus, while illusions of movement resulted in a single cluster of activation in the inferior parietal lobule. These results suggest that illusions of movement without limb displacement may activate different brain areas compared with actual limb displacement. Careful consideration should be made in future studies when selecting a proprioceptive stimulus to probe these brain networks.

The Right Supramarginal Gyrus Is Important for Proprioception in Healthy and Stroke-Affected Participants: A Functional MRI Study.

Human proprioception is essential for motor control, yet its central processing is still debated. Previous studies of passive movements and illusory vibration have reported inconsistent activation patterns related to proprioception, particularly in high-order sensorimotor cortices. We investigated brain activation specific to proprioception, its laterality, and changes following stroke. Twelve healthy and three stroke-affected individuals with proprioceptive deficits participated. Proprioception was assessed clinically with the Wrist Position Sense Test, and participants underwent functional magnetic resonance imaging scanning. An event-related study design was used, where each proprioceptive stimulus of passive wrist movement was followed by a motor response of mirror -copying with the other wrist. Left (LWP) and right (RWP) wrist proprioception were tested separately. Laterality indices (LIs) were calculated for the main cortical regions activated during proprioception. We found proprioception-related brain activation in high-order sensorimotor cortices in healthy participants especially in the supramarginal gyrus (SMG LWP z = 4.51, RWP z = 4.24) and the dorsal premotor cortex (PMd LWP z = 4.10, RWP z = 3.93). Right hemispheric dominance was observed in the SMG (LI LWP mean 0.41, SD 0.22; RWP 0.29, SD 0.20), and to a lesser degree in the PMd (LI LWP 0.34, SD 0.17; RWP 0.13, SD 0.25). In stroke-affected participants, the main difference in proprioception-related brain activation was reduced laterality in the right SMG. Our findings indicate that the SMG and PMd play a key role in proprioception probably due to their role in spatial processing and motor control, respectively. The findings from stroke--affected individuals suggest that decreased right SMG function may be associated with decreased proprioception. We recommend that clinicians pay particular attention to the assessment and rehabilitation of proprioception following right hemispheric lesions.

Intra- and interrater reliability of the Modified Tardieu Scale for the assessment of lower limb spasticity in adults with neurologic injuries.

OBJECTIVE: To examine the intra- and interrater reliability of the Modified Tardieu Scale (MTS) for lower limb assessment of adults with chronic neurologic injuries. DESIGN: Single-center intra- and interrater reliability study. SETTING: Outpatient neurorehabilitation unit. PARTICIPANTS: Adults (N=30; mean age ± SD, 54.1±12.5y) with various chronic neurologic injuries and lower limb spasticity. INTERVENTIONS: Two experienced physiotherapists performed slow (R2) and fast (R1) passive movements for lower limb muscles half an hour apart on the same day (interrater reliability), while a third physiotherapist took goniometric measurements only. One physiotherapist repeated the assessment 1 to 3 days earlier or later (intrarater reliability). Assessors qualitatively rated the resistance to fast passive movements. MAIN OUTCOME MEASURES: Intraclass correlation coefficients (ICCs) and limits of agreement (LOA) were calculated for R1, R2, and R2-R1. Kappa coefficients were calculated for tibialis range of movement and qualitative spasticity ratings. RESULTS: Intra- and interrater R1 and R2 measurements showed moderate to high reliability for the affected hamstrings, rectus femoris, gastrocnemius, soleus (mean ICC ± SD, .79±.08), and tibialis anterior (mean κ ± SD, .58±.10). Only intrarater measurements of the affected tibialis posterior were moderately reliable (R1=.57, R2=.77). Seven of 16 spasticity angle measurements of the affected muscles were moderately reliable. LOA were mostly unacceptably wide. Qualitative spasticity ratings were moderately reliable for affected hamstrings, gastrocnemius, and tibialis muscles (mean κ ± SD, .52±.10). CONCLUSIONS: The MTS is reliable for assessing spasticity in most lower limb muscles of adults with chronic neurologic injuries. Repeated MTS measurements of spasticity are best based on R1 measurements rather than spasticity angle or qualitative ratings of spasticity. Optimally, MTS measurements should be undertaken by the same clinician.