Dual Sensorimotor Channel Theory: Implications for the Development and Neural Organization of Prehension

感知，即伸手去抓住一个物体的行为，是人类经验的核心。当我们获取食物、制造工具和创作艺术时，我们毫不费力地完成它。然而，它的神经控制非常复杂，人们对其知之甚少，这就是为什么工程师们几十年来一直在努力设计一个拥有灵巧双手的机器人，但没有成功。有证据表明，伸手和抓握是由不同的神经通路介导的不同行为。早期的理论强调视觉在组织人类活动中的作用，但最近的研究表明，躯体感觉（触觉和身体感觉）也起着重要作用。为了解释这一点，我提出了双感觉运动通道（DSC）理论13，14，该理论认为，伸手和抓握的独立神经回路起源于感觉运动皮层，并通过躯体感觉经验得到改善。随后，视觉皮层和感觉运动皮层之间的神经连接得到加强，从而使视觉系统能够利用这些预先存在的到达和抓握回路。因此，当视觉可用时，我们可以有效地将伸手和抓握整合到单个伸手抓握运动中，但是如果视觉不可用，我们可以同样有效地将它们分离，以便利用各种触觉提示。** DSC理论对伸手、抓握和视觉在人类发育过程中如何结合在一起做出了3个主要预测：1）幼儿应该产生单独的伸手和抓握运动，这些运动通过体感进行细化; 2）随着婴儿年龄的增长，体感伸手和抓握运动应该逐渐整合为视觉控制下的单一伸手抓握运动; 3）到达和抓握回路的视觉输入应该是不同的，并且应该以不同的速率成熟。为了验证这些预测，我将对0.5 ~ 36个月大的婴儿在进行伸手和抓握动作时所获得的视觉和体感反馈进行处理。逐帧视频分析和3D运动跟踪将用于测量这些感官操作对婴儿手臂和手部运动的影响。脑成像将用于确定预测的从躯体感觉到视觉引导的发育过渡是否伴随着视觉和感觉运动皮质之间的神经连接的成熟。** DSC理论提供了一个新的，更全面的解释，比过去30年来主导该领域的以视觉为中心的观点更好地解释了神经控制。通过测试DSC理论，我的研究有可能改变我们对熟练的手部动作如何在人脑中进化、发展和组织的理解。这项研究的洞察力可以重新引导我们的方法来工程机器人和假肢，以更好地反映进化，发展和神经过程，使人类能够熟练地使用手。**

Prehension, the act of reaching to grasp an object, is central to human experience. We perform it effortlessly when we acquire food, construct tools, and create art. Yet, its neural control is highly complex and poorly understood, which is why engineers have struggled for decades, unsuccessfully, to design a robot with dexterous hands.******Evidence suggests that reaching and grasping are separate acts mediated by separate neural pathways. Early theories emphasize the role of vision in organizing human prehension, but recent research suggests that somatosensation (touch and body senses) also plays a prominent role. To account for this, I have formulated the Dual Sensorimotor Channel (DSC) theory13,14, which posits that separate neural circuits for the Reach and the Grasp originate in sensorimotor cortex and are refined by somatosensory experience. Subsequent strengthening of the neural connections between the visual and sensorimotor cortices then allows the visual system to tap into these pre-existing Reach and Grasp circuits. Consequently, when vision is available we can efficiently integrate the Reach and the Grasp into a single Reach-to-Grasp movement, but if vision is not available, we can just as efficiently dissociate them in order to capitalize on various tactile cues. ******The DSC theory makes 3 major predictions about how the Reach, the Grasp, and vision are brought together during human development: 1) young infants should produce separate Reach and Grasp movements that are refined by somatosensation; 2) as infants age, somatosensory Reach and Grasp movements should gradually be integrated into a single Reach-to-Grasp movement under visual control, and; 3) visual inputs to the Reach and Grasp circuits should be different and should mature at different rates. To test these predictions, I will manipulate the visual and somatosensory feedback infants receive as they perform Reach and Grasp movements between 0.5 and 36 months of age. Frame-by-frame video analysis and 3D motion tracking will be used to measure the effect of these sensory manipulations on infant arm and hand movements. Brain imaging will be used to determine whether the predicted developmental transition from somatosensory to visual guidance of prehension is accompanied by the maturation of neural connections between the visual and sensorimotor cortices. ******The DSC theory provides a novel, more comprehensive, explanation for the neural control of prehension than the vision-centric view that has dominated the field for the past 3 decades. By testing the DSC theory, my research has the potential to transform our understanding of how skilled hand movements evolved, develop, and are organized in the human brain. Insight from this research could redirect our approach to engineering robots and prosthetic limbs to better reflect the evolutionary, developmental, and neural processes that enable skilled hand use in humans. **