Altered neocortical tactile but preserved auditory early change detection responses in Friedreich ataxia

Available online 11 May 2019Objective: To study using magnetoencephalography (MEG) the spatio-temporal dynamics of neocortical responses involved in sensory processing and early change detection in Friedreich ataxia (FRDA). Methods: Tactile (TERs) and auditory (AERs) evoked responses, and early neocortical change detection responses indexed by the mismatch negativity (MMN) were recorded using tactile and auditory oddballs in sixteen FRDA patients and matched healthy subjects. Correlations between the maximal amplitude of each response, genotype and clinical parameters were investigated. Results: Evoked responses were detectable in all FRDA patients but one. In patients, TERs were delayed and reduced in amplitude, while AERs were only delayed. Only tactile MMN responses at the contralateral secondary somatosensory cortex were altered in FRDA patients. Maximal amplitudes of TERs, AERs and tactile MMN correlated with genotype, but did not correlate with clinical parameters. Conclusions: In FRDA, the amplitude of tactile MMN responses at SII cortex are reduced and correlate with the genotype, while auditory MMN responses are not altered. Significance: Somatosensory pathways and tactile early change detection are selectively impaired in FRDAThis study was financially supported by (i) the research grant ‘‘Les Voies du Savoir” from the Fonds Erasme (Brussels, Belgium) and (ii) the Fonds de la Recherche Scientifique (FRS-FNRS, Brussels, Belgium; research credit: J.0095.16.F). Gilles Naeije was supported by a research grant from the Fonds Erasme (Brussels, Belgium). Mathieu Bourguignon was supported by the program Attract of Innoviris (grant 2015-BB2B-10), by the Spanish Ministry of Economy and Competitiveness (grant PSI2016-77175-P), and by the Marie Skłodowska-Curie Action of the European Commission (grant 743562). Xavier De Tiège is Postdoctorate Clinical Master Specialist at the Fonds de la Recherche Scientifique (FRS-FNRS, Brussels, Belgium). The MEG project at the CUB Hôpital Erasme is financially supported by the Fonds Erasme (Research grant ‘‘Les Voies du Savoir”, Brussels, Belgium). The authors would like to thank Brice Marty for his help in MEG data acquisition