Mark van de Ruit1, Matthijs J L Perenboom2, Michael J Grey3. 1. NIHR Surgical Reconstruction and Microbiology Research Centre, School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Edgbaston B15 2TT, UK; MRC-ARUK Centre for Musculoskeletal Ageing Research, School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Edgbaston B15 2TT, UK. 2. Department of Biomechanical Engineering, Delft University of Technology, Delft, the Netherlands. 3. NIHR Surgical Reconstruction and Microbiology Research Centre, School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Edgbaston B15 2TT, UK; MRC-ARUK Centre for Musculoskeletal Ageing Research, School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Edgbaston B15 2TT, UK; Department of Neuroscience and Pharmacology, Panum Institute, University of Copenhagen, Copenhagen, Denmark. Electronic address: m.j.grey@bham.ac.uk.
Abstract
BACKGROUND: Transcranial magnetic stimulation (TMS) corticospinal excitability maps are a valuable tool to study plasticity in the corticospinal tract. Traditionally, data acquisition for a single map is time consuming, limiting the method's applicability when excitability changes quickly, such as during motor learning, and in clinical investigations where assessment time is a limiting factor. OBJECTIVE: To reduce the time needed to create a reliable map by 1) investigating the minimum interstimulus interval (ISI) at which stimuli may be delivered, and 2) investigating the minimum number of stimuli required to create a map. METHOD: Frameless stereotaxy was used to monitor coil position as the coil was moved pseudorandomly within a 6 × 6 cm square. Maps were acquired using 1-4 s ISIs in 12 participants. The minimum number of stimuli was determined by randomly extracting data and comparing the resulting map to the original data set. To confirm validity, the pseudorandom walk method was compared against a traditional mapping method. RESULTS: Reliable maps could be created with 63 stimuli recorded with a 1 s ISI. Maps created acquiring data using the pseudorandom walk method were not significantly different from maps acquired following the traditional method. CONCLUSIONS: To account for inter-participant variability, outliers, coil positioning errors and, most importantly, participant comfort during data acquisition, we recommend creating a map with 80 stimuli and a 1.5 s ISI. This makes it possible to acquire TMS maps in 2 min, making mapping a more feasible tool to study short- and long-term changes in cortical organization.
BACKGROUND: Transcranial magnetic stimulation (TMS) corticospinal excitability maps are a valuable tool to study plasticity in the corticospinal tract. Traditionally, data acquisition for a single map is time consuming, limiting the method's applicability when excitability changes quickly, such as during motor learning, and in clinical investigations where assessment time is a limiting factor. OBJECTIVE: To reduce the time needed to create a reliable map by 1) investigating the minimum interstimulus interval (ISI) at which stimuli may be delivered, and 2) investigating the minimum number of stimuli required to create a map. METHOD: Frameless stereotaxy was used to monitor coil position as the coil was moved pseudorandomly within a 6 × 6 cm square. Maps were acquired using 1-4 s ISIs in 12 participants. The minimum number of stimuli was determined by randomly extracting data and comparing the resulting map to the original data set. To confirm validity, the pseudorandom walk method was compared against a traditional mapping method. RESULTS: Reliable maps could be created with 63 stimuli recorded with a 1 s ISI. Maps created acquiring data using the pseudorandom walk method were not significantly different from maps acquired following the traditional method. CONCLUSIONS: To account for inter-participant variability, outliers, coil positioning errors and, most importantly, participant comfort during data acquisition, we recommend creating a map with 80 stimuli and a 1.5 s ISI. This makes it possible to acquire TMS maps in 2 min, making mapping a more feasible tool to study short- and long-term changes in cortical organization.
Authors: Gabriela P Tardelli; Victor H Souza; Renan H Matsuda; Marco A C Garcia; Pavel A Novikov; Maria A Nazarova; Oswaldo Baffa Journal: Brain Topogr Date: 2022-03-09 Impact factor: 4.275