Multi-Digit Coordination in Absence of Cutaneous Sensory Feedback During Grasping Tasks

Motor learning and adaptation to object properties and task requirements requires integration of cutaneous sensory feedback with motor commands. Joint mechanics constantly change, with individual joints or muscles compensation so performance output is the same per task. Effects of mixed cutaneous sensory feedback on multi-digit coordination is not well understood. Investigators sought to determine the influence absent cutaneous sensory feedback has on motor learning and adaptation, and how the CNS coordinates multi-digit mechanical output to adapt to manual tasks, with partially intact digital sensory feedback. 19 participants were randomly assigned for three-digit anesthesia administration (TIM- thumb, index, middle; TRL- thumb, ring, little). Experimental tasks were repeated on two visits (control and anesthesia): grasping and lifting an object, and a functional task. Under partial digital anesthesia, total maximal voluntary contraction (MVC) was lower, and decreased force production was seen in all five digits (

Temporary Nerve Block at Selected Digits Revealed Hand Motor Deficits in Grasping Tasks

Peripheral sensory feedback plays a crucial role in ensuring correct motor execution throughout hand grasp control. Previous studies utilized local anesthesia to deprive somatosensory feedback in the digits or hand, observations included sensorimotor deficits at both corticospinal and peripheral levels. However, the questions of how the disturbed and intact sensory input integrate and interact with each other to assist the motor program execution, and whether the motor coordination based on motor output variability between affected and non-affected elements (e.g., digits) becomes interfered by the local sensory deficiency, have not been answered. The current study aims to investigate the effect of peripheral deafferentation through digital nerve blocks at selective digits on motor performance and motor coordination in grasp control. Our results suggested that the absence of somatosensory information induced motor deficits in hand grasp control, as evidenced by reduced maximal force production ability in both local and non-local digits, impairment of force and moment control during object lift and hold, and attenuated motor synergies in stabilizing task performance variables, namely the tangential force and moment of force. These findings implied that individual sensory input is shared across all the digits and the disturbed signal from local sensory channel(s) has a more comprehensive impact on the process of the motor output execution in the sensorimotor integration process. Additionally, a feedback control mechanism with a sensation-based component resides in the formation process for the motor covariation structure