Anastasopoulou Ioanna, Cheyne Douglas O, Johnson Blake W
Hospital for Sick Children Research Institute, Toronto, Ontario, Canada.
Department of Speech-Language Pathology, University of Toronto, Toronto, Ontario, Canada.
J Neurophysiol. 2025 Jul 1;134(1):229-236. doi: 10.1152/jn.00546.2024. Epub 2025 Jun 16.
Many decades after Penfield's (Penfield W, Boldrey E. Brain 60: 389-443, 1937) classic depiction of the motor homunculus, it remains unclear how spatially contiguous and interconnected representations within human sensorimotor cortex might separate their activities to achieve the directed and precise control of distinct body regions evident in activities as different as typing and speaking. One long-standing but relatively neglected explanation draws from models of simple physical systems (like swinging pendulums) to posit that small differences in the oscillatory properties of neuronal populations (termed "frequency detuning") can result in highly effective segregation of their activities and outputs. We tested this hypothesis by comparing the peak frequencies of beta-band (13-30 Hz) motor rhythms measured in a magnetoencephalographic neuroimaging study of finger and speech movements in a group of healthy adults and a group of typically developing children. Our results confirm a peak frequency task difference (speech movement vs. hand movement) of about 1.5 Hz in the beta motor rhythms of both left and right hemispheres in adults. A comparable task difference was obtained in children for the left but not for the right hemisphere. These results provide novel support for the role of frequency detuning in the functional organization of the brain and suggest that this mechanism should play a more prominent role in current models of bodily representations and their development within the sensorimotor cortex. This work is the first evidence for frequency detuning of an intrinsic motor rhythm in spatially contiguous regions of primary motor cortex associated with hand and speech movements, supporting a mechanism of functional segregation that has been largely overlooked by current models of motor cortex organization. Our results from children further provide the first evidence for frequency detuning in the developing brain, indicating an early-developing mechanism with later refinements of hemispheric control.
在彭菲尔德（Penfield W, Boldrey E. Brain 60: 389 - 443, 1937）对运动小人的经典描绘之后的数十年里，人类感觉运动皮层内空间上相邻且相互连接的表征如何分离其活动，以实现对不同身体区域的定向和精确控制，这在诸如打字和说话等不同活动中表现得很明显，仍然不清楚。一种长期存在但相对被忽视的解释借鉴了简单物理系统（如摆动的钟摆）的模型，假定神经元群体振荡特性的微小差异（称为“频率失谐”）可导致其活动和输出的高效分离。我们通过比较一组健康成年人和一组发育正常儿童在脑磁图神经成像研究中手指和言语运动时测量的β波段（13 - 30赫兹）运动节律的峰值频率，对这一假设进行了测试。我们的结果证实，成年人左右半球的β运动节律中，言语运动与手部运动的峰值频率任务差异约为1.5赫兹。儿童在左半球获得了类似的任务差异，但右半球没有。这些结果为频率失谐在大脑功能组织中的作用提供了新的支持，并表明这种机制在当前关于身体表征及其在感觉运动皮层内发育的模型中应发挥更突出的作用。这项工作是与手部和言语运动相关的初级运动皮层空间相邻区域内在运动节律频率失谐的首个证据，支持了一种功能分离机制，而这种机制在当前运动皮层组织模型中很大程度上被忽视了。我们对儿童的研究结果进一步提供了发育中大脑频率失谐的首个证据，表明这是一种早期发育的机制，并在后期对半球控制进行细化。
