Remapping in cerebral and cerebellar cortices is not restricted by somatotopy

Abstract

Cardinali for help in data collection, and Victoria Root for helpful comments on the manuscript. We thank Opcare for help with recruitment, and our participants for taking part in these studies.When a hand is missing, the brain region that typically processes information from that hand may instead process information from other body-parts, a phenomenon termed reorganization. It is commonly thought that only body-parts whose information is processed in regions adjacent to the hand region, could take up the resources of this now deprived region. Here we demonstrate that information from the same bodyparts is processed in the hand regions of both the cerebral cortex and cerebellum. The native brain regions of these body-parts have varied relative distances from the hand region of the cerebellum compared to the cerebral cortex, and do not necessarily neighbor these hand regions. We therefore propose that proximity between brain regions cannot fully explain brain reorganization.

Brain (re)organisation following amputation: Implications for phantom limb pain

“…Since altered input is known to drive and shape brain organisation ( Recanzone et al., 1992 ; Wang et al., 1995 ), it is reasonable to expect that adapted behaviour substituting for the missing hand function can shape remapping. This is akin to recent studies in individuals with congenital hand loss, who exhibit remapping of multiple body parts, which are used for compensatory behaviours, including the feet, residual arm and lips ( Hahamy et al., 2017 ; Hahamy and Makin, 2019 ; Stoeckel et al., 2009 ) into the missing hand cortex. Considering that deprived cortex has been demonstrated to undergo network-level reorganisation in functional connectivity ( Makin et al., 2015a ), and that the connectome of the deprived cortex is wired to support hand function ( Glasser et al., 2016 ; Graziano and Aflalo, 2007 ), inputs relating to typical hand function (e.g.…”

“…Thirdly, the traditional focus on S1 remapping due to changed selectivity to particular body parts is probably incomplete, considering net activity changes might not adequetly reveal the underlying functional processing. Moreover, related research in monkeys ( Kambi et al., 2014 ) and humans ( Hahamy et al., 2019 ) indicate that sensorimotor cortical remapping might reflect changes in sub-cortical terminals (e.g. brainstem, basal ganglia) or cerebellum.…”

“…DTI tractography ( Behrens et al., 2003 )). Unlike direct brain stimulation and recordings, human neuroimaging provided opportunities to identify body and hand representation beyond S1/M1 – namely in the cerebellum ( Hahamy and Makin, 2019 ; Yeo et al., 2011 ), basal ganglia ( Zeharia et al., 2015 ), operculum and insula ( Brooks et al., 2005 ), supplementary motor cortex ( Zeharia et al., 2012 ), occipitotemporal cortex ( Orlov et al., 2010 ), parietal cortex ( Huang et al., 2012 ; Zeharia et al., 2019 ) and more. Despite these findings indicating that body representation should not be studied in S1 in isolation ( Longo et al., 2010 ), in the rest of this paper we will primarily focus on S1 body representation as identified with task-based fMRI (see Fig.…”

Organized Toe Maps in Extreme Foot Users

“…Previous studies reported lateral activity clusters in the cortical hand area, in addition to the medial foot area, in response to toe movement in individuals with bilateral congenital amelia (Stoeckel et al, 2009;Striem-Amit et al, 2018; see also Hahamy et al, 2017;Hahamy and Makin 2019) and passive toe stimulation in individuals with early childhood arm amputation (Yu et al, 2014(Yu et al, , 2006. Common to all such studies is the usage of univariate fMRI activity, where net changes in signal amplitude are averaged over a ROI.…”

“…We studied toe activity patterns in the artists' SI foot area and sensorimotor (missing) hand area. Previous studies indicate that uni-or bilateral congenital hand absence leads to remapping of inputs from the mouth and feet into the deprived hand territory (Hahamy et al, 2017;Hahamy and Makin, 2019;Stoeckel et al, 2009;Striem-Amit et al, 2018;Yu et al, 2014Yu et al, , 2006. However, it is unclear whether such remapping truly represents recruitment of this zone to support toe function or aberrant activity, e.g., due to deprivation-driven inhibition reduction (Hahamy et al, 2017).…”