Department of Kinesiology and Health Sciences, University of Waterloo, Waterloo, Ontario, Canada.
PLoS One. 2024 May 16;19(5):e0302989. doi: 10.1371/journal.pone.0302989. eCollection 2024.
Multiple sensorimotor loops converge in the motor cortex to create an adaptable system capable of context-specific sensorimotor control. Afferent inhibition provides a non-invasive tool to investigate the substrates by which procedural and cognitive control processes interact to shape motor corticospinal projections. Varying the transcranial magnetic stimulation properties during afferent inhibition can probe specific sensorimotor circuits that contribute to short- and long-latency periods of inhibition in response to the peripheral stimulation. The current study used short- (SAI) and long-latency (LAI) afferent inhibition to probe the influence of verbal and spatial working memory load on the specific sensorimotor circuits recruited by posterior-anterior (PA) and anterior-posterior (AP) TMS-induced current. Participants completed two sessions where SAI and LAI were assessed during the short-term maintenance of two- or six-item sets of letters (verbal) or stimulus locations (spatial). The only difference between the sessions was the direction of the induced current. PA SAI decreased as the verbal working memory load increased. In contrast, AP SAI was not modulated by verbal working memory load. Visuospatial working memory load did not affect PA or AP SAI. Neither PA LAI nor AP LAI were sensitive to verbal or spatial working memory load. The dissociation of short-latency PA and AP sensorimotor circuits and short- and long-latency PA sensorimotor circuits with increasing verbal working memory load support multiple convergent sensorimotor loops that provide distinct functional information to facilitate context-specific supraspinal control.
多个感觉运动回路在运动皮层汇聚，形成一个适应性系统，能够进行特定于上下文的感觉运动控制。传入抑制提供了一种非侵入性的工具，可以研究程序性和认知控制过程相互作用以塑造运动皮质脊髓投射的基础。在传入抑制期间改变经颅磁刺激特性可以探测特定的感觉运动回路，这些回路对短潜伏期和长潜伏期抑制对周围刺激的反应有贡献。本研究使用短潜伏期（SAI）和长潜伏期（LAI）传入抑制来探测言语和空间工作记忆负荷对前后（PA）和前后（AP）TMS 诱导电流募集的特定感觉运动回路的影响。参与者完成了两个会话，其中在两个或六个字母（言语）或刺激位置（空间）的项目集的短期保持期间评估 SAI 和 LAI。会话之间的唯一区别是诱导电流的方向。随着言语工作记忆负荷的增加，PA SAI 降低。相比之下，言语工作记忆负荷不会调节 AP SAI。视空间工作记忆负荷不会影响 PA 或 AP SAI。PA LAI 和 AP LAI 都不受言语或空间工作记忆负荷的影响。随着言语工作记忆负荷的增加，短潜伏期 PA 和 AP 感觉运动回路以及短潜伏期和长潜伏期 PA 感觉运动回路的分离支持多个汇聚的感觉运动回路，这些回路提供独特的功能信息，以促进特定于上下文的皮质上控制。
