TY - JOUR

T1 - Are there cortical somatotopic motor maps outside of the human precentral gyrus?

AU - Mitev, Deyan

AU - Koldewyn, Kami

AU - Downing, Paul

N1 - Policy prohibits open access for the accepted manuscript.

PY - 2024/12/3

Y1 - 2024/12/3

N2 - Human body movements are supported by a somatotopic map - primary motor cortex (M1) - that is found along the precentral gyrus. Recent evidence has suggested two further motor maps that span the lateral occipitotemporal cortex (LOTC) and the precuneus. Confirmation of these maps is important, as they influence our understanding of the organisation of motor behaviour, for example by revealing how visual- and motor-related activity interact. However, evidence for these recently proposed maps is limited. We analysed an open fMRI dataset of 62 participants who moved performed twelve different body part movements. We analysed the magnitude of responses evoked by movements with novel quantitative indices that test for map- like organisation. We found strong evidence for bilateral somatotopic maps in precentral and postcentral gyri. In LOTC, we found much weaker responses to movement, and little evidence of somatotopy. In the precuneus, we found only limited evidence for somatotopy. We also adopted a background connectivity approach to examine correlations between M1, LOTC and the precuneus in the residual time-series data. This revealed a ventral-posterior / dorsal-anterior distinction in the connectivity between precuneus and M1, favouring the head and arms, respectively. Posterior right hemisphere LOTC showed some evidence of preferential connectivity to arm-selective regions of M1. Overall, our results do not support the existence of a somatotopic motor map in LOTC but provide some support for a coarse map in the precuneus, especially as revealed in connectivity patterns. These findings help clarify the organisation of human motor representations beyond the precentral gyrus.

AB - Human body movements are supported by a somatotopic map - primary motor cortex (M1) - that is found along the precentral gyrus. Recent evidence has suggested two further motor maps that span the lateral occipitotemporal cortex (LOTC) and the precuneus. Confirmation of these maps is important, as they influence our understanding of the organisation of motor behaviour, for example by revealing how visual- and motor-related activity interact. However, evidence for these recently proposed maps is limited. We analysed an open fMRI dataset of 62 participants who moved performed twelve different body part movements. We analysed the magnitude of responses evoked by movements with novel quantitative indices that test for map- like organisation. We found strong evidence for bilateral somatotopic maps in precentral and postcentral gyri. In LOTC, we found much weaker responses to movement, and little evidence of somatotopy. In the precuneus, we found only limited evidence for somatotopy. We also adopted a background connectivity approach to examine correlations between M1, LOTC and the precuneus in the residual time-series data. This revealed a ventral-posterior / dorsal-anterior distinction in the connectivity between precuneus and M1, favouring the head and arms, respectively. Posterior right hemisphere LOTC showed some evidence of preferential connectivity to arm-selective regions of M1. Overall, our results do not support the existence of a somatotopic motor map in LOTC but provide some support for a coarse map in the precuneus, especially as revealed in connectivity patterns. These findings help clarify the organisation of human motor representations beyond the precentral gyrus.

U2 - 10.1152/jn.00160.2024

DO - 10.1152/jn.00160.2024

M3 - Article

JO - Journal of Neurophysiology

JF - Journal of Neurophysiology

SN - 0022-3077

ER -