Hidden functional derangement of somatosensory cortices in Alzheimer's Disease

Very little evidence supported somatosensory disfunctions in AD patients, leading to the hypothesis that this function seems to be spared in AD. Nevertheless, the paper by Wiesman et al , published in this issue of EBioMedicine, has examined somatosensory function in amnestic MCI and mild AD patients. For the first time, the authors took into account attention and processing speed abilities as potential confounding factors in the evaluation of somatosensory dysfunction in AD spectrum. Through the use of MEG, this work highlighted a robust pattern of stronger somatosensory gating in AD patients: however, this alteration in functional somatosensory processing in primary sensory cortices is masked by variability in cognitive decline across individuals. In particular, variability in attention and processing speed abilities, whose deficits are both well documented in patients with AD, masks the detection of changes in somatosensory neural functions. Consequently, the detection of these somatosensory alterations led the authors to suggest considering cognitive variability in future studies regarding not only primary sensory function but also other less explored systems, for example visual and auditory processing. This could help to better understand the nuanced effects of AD.