Grant: Discovery Grants Program - Individual

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) theory 13,14 , 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.