The Brain and Mind Institute, University of Western Ontario , London, Ontario , Canada.
Institute of Cognitive Neuroscience, University College London , London , United Kingdom.
J Neurophysiol. 2019 Feb 1;121(2):418-426. doi: 10.1152/jn.00439.2018. Epub 2018 Dec 5.
Hand and finger movements are mostly controlled through crossed corticospinal projections from the contralateral hemisphere. During unimanual movements, activity in the contralateral hemisphere is increased while the ipsilateral hemisphere is suppressed below resting baseline. Despite this suppression, unimanual movements can be decoded from ipsilateral activity alone. This indicates that ipsilateral activity patterns represent parameters of ongoing movement, but the origin and functional relevance of these representations is unclear. In this study, we asked whether ipsilateral representations are caused by active movement or whether they are driven by sensory input. Participants alternated between performing single finger presses and having fingers passively stimulated while we recorded brain activity using high-field (7T) functional imaging. We contrasted active and passive finger representations in sensorimotor areas of ipsilateral and contralateral hemispheres. Finger representations in the contralateral hemisphere were equally strong under passive and active conditions, highlighting the importance of sensory information in feedback control. In contrast, ipsilateral finger representations in the sensorimotor cortex were stronger during active presses. Furthermore, the spatial distribution of finger representations differed between hemispheres: the contralateral hemisphere showed the strongest finger representations in Brodmann areas 3a and 3b, whereas the ipsilateral hemisphere exhibited stronger representations in premotor and parietal areas. Altogether, our results suggest that finger representations in the two hemispheres have different origins: contralateral representations are driven by both active movement and sensory stimulation, whereas ipsilateral representations are mainly engaged during active movement. NEW & NOTEWORTHY Movements of the human body are mostly controlled by contralateral cortical regions. The function of ipsilateral activity during movements remains elusive. Using high-field neuroimaging, we investigated how human contralateral and ipsilateral hemispheres represent active and passive finger presses. We found that representations in contralateral sensorimotor cortex are equally strong during both conditions. Ipsilateral representations were mostly present during active movement, suggesting that sensorimotor areas do not receive direct sensory input from the ipsilateral hand.
手和手指的运动主要通过来自对侧大脑半球的交叉皮质脊髓投射来控制。在单手运动中，对侧大脑半球的活动增加，而同侧大脑半球的活动被抑制在静息基线以下。尽管有这种抑制，单手运动仍然可以仅从同侧活动中解码。这表明同侧活动模式代表了正在进行的运动的参数，但这些代表的起源和功能相关性尚不清楚。在这项研究中，我们想知道同侧代表是由主动运动引起的，还是由感觉输入驱动的。参与者在进行单指按压和手指被动刺激之间交替，同时我们使用高磁场（7T）功能成像记录大脑活动。我们在对侧和同侧半球的感觉运动区域对比了主动和被动手指代表。在被动和主动条件下，对侧半球的手指代表同样强烈，突出了感觉信息在反馈控制中的重要性。相比之下，感觉运动皮层中的同侧手指代表在主动按压时更强。此外，手指代表在半球之间的空间分布也不同：对侧半球在布罗德曼区 3a 和 3b 显示最强的手指代表，而同侧半球在运动前区和顶叶区显示更强的代表。总的来说，我们的结果表明，两个半球的手指代表具有不同的起源：对侧代表既由主动运动又由感觉刺激驱动，而同侧代表主要在主动运动时参与。
