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Säisänen L, Könönen M, Niskanen E, Lakka T, Lintu N, Vanninen R, Julkunen P, Määttä S. Primary hand motor representation areas in healthy children, preadolescents, adolescents, and adults. Neuroimage 2020; 228:117702. [PMID: 33385558 DOI: 10.1016/j.neuroimage.2020.117702] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 12/16/2020] [Accepted: 12/19/2020] [Indexed: 01/28/2023] Open
Abstract
The development of the organization of the motor representation areas in children and adolescents is not well-known. This cross-sectional study aimed to provide an understanding for the development of the functional motor areas of the upper extremity muscles by studying healthy right-handed children (6-9 years, n = 10), preadolescents (10-12 years, n = 13), adolescents (15-17 years, n = 12), and adults (22-34 years, n = 12). The optimal representation site and resting motor threshold (rMT) for the abductor pollicis brevis (APB) were assessed in both hemispheres using navigated transcranial magnetic stimulation (nTMS). Motor mapping was performed at 110% of the rMT while recording the EMG of six upper limb muscles in the hand and forearm. The association between the motor map and manual dexterity (box and block test, BBT) was examined. The mapping was well-tolerated and feasible in all but the youngest participant whose rMT exceeded the maximum stimulator output. The centers-of-gravity (CoG) for individual muscles were scattered to the greatest extent in the group of preadolescents and centered and became more focused with age. In preadolescents, the CoGs in the left hemisphere were located more laterally, and they shifted medially with age. The proportion of hand compared to arm representation increased with age (p = 0.001); in the right hemisphere, this was associated with greater fine motor ability. Similarly, there was less overlap between hand and forearm muscles representations in children compared to adults (p<0.001). There was a posterior-anterior shift in the APB hotspot coordinate with age, and the APB coordinate in the left hemisphere exhibited a lateral to medial shift with age from adolescence to adulthood (p = 0.006). Our results contribute to the elucidation of the developmental course in the organization of the motor cortex and its associations with fine motor skills. It was shown that nTMS motor mapping in relaxed muscles is feasible in developmental studies in children older than seven years of age.
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Affiliation(s)
- Laura Säisänen
- Department of Clinical Neurophysiology, Kuopio University Hospital, P.O. Box 100, 70029 KYS, Kuopio, Finland; Institute of Clinical Medicine, University of Eastern Finland, Finland; Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
| | - Mervi Könönen
- Department of Clinical Neurophysiology, Kuopio University Hospital, P.O. Box 100, 70029 KYS, Kuopio, Finland; Department of Applied Physics, University of Eastern Finland, Kuopio, Finland; Department of Clinical Radiology, Kuopio University Hospital, Kuopio, Finland
| | - Eini Niskanen
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
| | - Timo Lakka
- Institute of Biomedicine, Faculty of Health Sciences, University of Eastern Finland, Finland; Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital, Kuopio, Finland
| | - Niina Lintu
- Institute of Biomedicine, Faculty of Health Sciences, University of Eastern Finland, Finland
| | - Ritva Vanninen
- Institute of Clinical Medicine, University of Eastern Finland, Finland; Department of Clinical Radiology, Kuopio University Hospital, Kuopio, Finland
| | - Petro Julkunen
- Department of Clinical Neurophysiology, Kuopio University Hospital, P.O. Box 100, 70029 KYS, Kuopio, Finland; Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
| | - Sara Määttä
- Department of Clinical Neurophysiology, Kuopio University Hospital, P.O. Box 100, 70029 KYS, Kuopio, Finland
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