Volz Lukas J, Eickhoff Simon B, Pool Eva-Maria, Fink Gereon R, Grefkes Christian
Department of Neurology, University of Cologne, Germany; Department of Psychological and Brain Sciences, University of California, Santa Barbara, USA; Neuromodulation & Neurorehabilitation, Max Planck Institute for Neurological Research, Cologne, Germany.
Institute of Neuroscience and Medicine (INM-1, INM-3), Juelich Research Centre, Germany; Institute for Clinical Neuroscience and Medical Psychology, Heinrich-Heine University, Düsseldorf, Germany.
Neuroimage. 2015 Oct 1;119:44-53. doi: 10.1016/j.neuroimage.2015.05.101. Epub 2015 Jun 18.
Voluntary movements depend on a well-regulated interplay between the primary motor cortex (M1) and premotor areas. While to date the neural underpinnings of hand movements are relatively well understood, we only have rather limited knowledge on the cortical control of lower-limb movements. Given that our hands and feet have different roles for activities of daily living, with hand movements being more frequently used in a lateralized fashion, we hypothesized that such behavioral differences also impact onto network dynamics underlying upper and lower limb movements. We, therefore, used functional magnetic resonance imaging (fMRI) and dynamic causal modeling (DCM) to investigate differences in effective connectivity underlying isolated movements of the hands or feet in 16 healthy subjects. The connectivity analyses revealed that both movements of the hand and feet were accompanied by strong facilitatory coupling of the respective contralateral M1 representations with premotor areas of both hemispheres. However, excitatory influences were significantly lower for movements of the feet compared to hand movements. During hand movements, the M1(hand) representation ipsilateral to the movement was strongly inhibited by premotor regions and the contralateral M1 homologue. In contrast, interhemispheric inhibition was absent between the M1(foot) representations during foot movements. Furthermore, M1(foot) ipsilateral to the moving foot exerted promoting influences onto contralateral M1(foot). In conclusion, the generally stronger and more lateralized coupling pattern associated with hand movements suggests distinct fine-tuning of cortical control to underlie voluntary movements with the upper compared to the lower limb.
自主运动依赖于初级运动皮层（M1）和运动前区之间良好调节的相互作用。虽然迄今为止手部运动的神经基础相对较为清楚，但我们对下肢运动的皮层控制了解有限。鉴于我们的手和脚在日常生活活动中具有不同的作用，手部运动更频繁地以偏侧化方式使用，我们推测这种行为差异也会影响上下肢运动背后的网络动力学。因此，我们使用功能磁共振成像（fMRI）和动态因果模型（DCM）来研究16名健康受试者手部或足部孤立运动背后有效连接的差异。连接性分析表明，手部和足部的运动都伴随着各自对侧M1表征与双侧运动前区的强烈促进性耦合。然而，与手部运动相比，足部运动的兴奋性影响明显较低。在手部运动期间，运动同侧的M1（手）表征受到运动前区和对侧M1同源物的强烈抑制。相比之下，在足部运动期间，M1（足）表征之间不存在半球间抑制。此外，运动足同侧的M1（足）对对侧M1（足）施加促进性影响。总之，与手部运动相关的通常更强且更偏侧化的耦合模式表明皮层控制存在明显的微调，以支持上肢与下肢的自主运动。
