Johari Karim, Behroozmand Roozbeh
Speech Neuroscience Lab., Department of Communication Sciences and Disorders, University of South Carolina, 915 Greene Street, Columbia, SC 29208, United States.
Speech Neuroscience Lab., Department of Communication Sciences and Disorders, University of South Carolina, 915 Greene Street, Columbia, SC 29208, United States.
Behav Brain Res. 2018 Jul 16;347:281-291. doi: 10.1016/j.bbr.2018.03.028. Epub 2018 Mar 22.
Skilled motor actions are mediated by neural mechanisms that incorporate sensory feedback for driving or suppressing movement with remarkable temporal precision. The predictive coding model proposes that the brain performs this function by establishing an internal representation of timing to accelerate movement response time. However, it is unclear whether different neural mechanisms are involved in temporal processing of movement initiation and cessation. The present study examined how temporal information is encoded for initiation and cessation of speech and hand movement. Event-related potentials (ERPs) were recorded while young healthy subjects performed speech and hand movement initiation and cessation in response to temporally predictable and unpredictable visual stimuli. We found that predictable stimuli elicited faster movement in both speech and hand modalities, with shorter reaction times associated with movement cessation compared with initiation. Analysis of ERPs revealed that premotor neural activities were significantly attenuated before speech initiation and hand movement initiation and cessation for temporally predictable vs. unpredictable conditions, but an opposite pattern was observed for speech cessation. In addition, we observed that the premotor ERPs were significantly modulated during speech initiation vs. cessation, but no such effect was found during hand movement. Finally, we found that the premotor ERPs were strongly correlated with motor reaction time during movement initiation and cessation for speech and hand modalities only in response to temporally predictable stimuli. These findings indicate that premotor ERPs reflect a temporal predictive code for planning of movement initiation and cessation and highlight functional dissociation of temporal processing mechanisms in speech and hand motor systems.
熟练的运动行为由神经机制介导，这些神经机制整合感觉反馈，以极高的时间精度驱动或抑制运动。预测编码模型提出，大脑通过建立时间的内部表征来执行此功能，以加速运动反应时间。然而，尚不清楚不同的神经机制是否参与运动起始和停止的时间处理。本研究考察了语音和手部运动的起始和停止是如何编码时间信息的。在年轻健康受试者对时间上可预测和不可预测的视觉刺激做出语音和手部运动起始及停止反应时，记录事件相关电位（ERP）。我们发现，可预测刺激在语音和手部两种模式下都引发了更快的运动，与运动起始相比，运动停止的反应时间更短。ERP分析显示，对于时间上可预测与不可预测的情况，在语音起始、手部运动起始和停止之前，运动前神经活动显著减弱，但在语音停止时观察到相反的模式。此外，我们观察到在语音起始与停止期间，运动前ERP有显著调制，但在手部运动期间未发现这种效应。最后，我们发现仅在对时间上可预测的刺激做出反应时，运动前ERP在语音和手部运动的起始和停止期间与运动反应时间密切相关。这些发现表明，运动前ERP反映了运动起始和停止计划的时间预测编码，并突出了语音和手部运动系统中时间处理机制的功能分离。
