AUTHOR=Destrebecq Virginie , Rovai Antonin , Trotta Nicola , Comet Camille , Naeije Gilles 

TITLE=Proprioceptive and tactile processing in individuals with Friedreich ataxia: an fMRI study

JOURNAL=Frontiers in Neurology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2023.1224345

DOI=10.3389/fneur.2023.1224345

ISSN=1664-2295

ABSTRACT=<sec id="sec1"><title>Objective</title><p>Friedreich ataxia (FA) neuropathology affects dorsal root ganglia, posterior columns in the spinal cord, the spinocerebellar tracts, and cerebellar dentate nuclei. The impact of the somatosensory system on ataxic symptoms remains debated. This study aims to better evaluate the contribution of somatosensory processing to ataxia clinical severity by simultaneously investigating passive movement and tactile pneumatic stimulation in individuals with FA.</p></sec><sec id="sec2"><title>Methods</title><p>Twenty patients with FA and 20 healthy participants were included. All subjects underwent two 6 min block-design functional magnetic resonance imaging (fMRI) paradigms consisting of twelve 30 s alternating blocks (10 brain volumes per block, 120 brain volumes per paradigm) of a tactile oddball paradigm and a passive movement paradigm. Spearman rank correlation tests were used for correlations between BOLD levels and ataxia severity.</p></sec><sec id="sec3"><title>Results</title><p>The passive movement paradigm led to the lower activation of primary (cSI) and secondary somatosensory cortices (cSII) in FA compared with healthy subjects (respectively 1.1 ± 0.78 vs. 0.61 ± 1.02, <italic>p</italic> = 0.04, and 0.69 ± 0.5 vs. 0.3 ± 0.41, <italic>p</italic> = 0.005). In the tactile paradigm, there was no significant difference between cSI and cSII activation levels in healthy controls and FA (respectively 0.88 ± 0.73 vs. 1.14 ± 0.99, <italic>p</italic> = 0.33, and 0.54 ± 0.37 vs. 0.55 ± 0.54, <italic>p</italic> = 0.93). Correlation analysis showed a significant correlation between cSI activation levels in the tactile paradigm and the clinical severity (R = 0.481, <italic>p</italic> = 0.032).</p></sec><sec id="sec4"><title>Interpretation</title><p>Our study captured the difference between tactile and proprioceptive impairments in FA using somatosensory fMRI paradigms. The lack of correlation between the proprioceptive paradigm and ataxia clinical parameters supports a low contribution of afferent ataxia to FA clinical severity.</p></sec>