Sensory information from a slipping object elicits a rapid and automatic shoulder response

Abstract

1Humans have the remarkable ability to hold, grasp, and manipulate objects. Previous work has 2 reported rapid and coordinated reactions in hand and shoulder muscles in response to external 3 perturbations to the arm during object manipulation; however, little is known about how 4 somatosensory feedback of an object slipping in the hand influences responses of the arm. We 5 built a hand-held device to stimulate the sensation of slipping at all five fingertips. The device 6 was integrated into an exoskeleton robot that supported it against gravity. The setup allowed us 7 to decouple somatosensory stimulation in the fingers from forces applied to the arm-two 8 variables that are highly interdependent in real-world scenarios. Fourteen participants 9 performed three experiments in which we measured their arm feedback responses during slip 10 stimulation. Slip stimulations were applied horizontally, in one of two directions, and participants 11 were either instructed to follow the slip direction, or to move the arm in the opposite direction. 12Participants showed responses within ~67 ms of slip onset when following the direction of slip, 13 but significantly slower responses when instructed to move in the opposite direction. Arm 14 responses were modulated by the speed but not the distance of the slip. Finally, when slip 15 stimulation was combined with mechanical perturbations to the arm, we found that sensory 16 information from the fingertips significantly modulated the shoulder feedback response. Overall, 17 the results demonstrate the existence of a rapid feedback system that stabilizes hand-held 18 objects. 19 20 21 22 23 24 25 26 3 NEW & NOTHEWORTHY 27 28We tested whether the sensation of an object slipping from the fingers modulates shoulder 29 feedback responses. We found rapid shoulder feedback responses when participants were 30 instructed to follow the slip direction with the arm. Shoulder responses following mechanical 31 joint perturbations were also potentiated when combined with slipping. These results 32 demonstrate the existence of fast and automatic feedback responses in the arm in reaction to 33 sensory input to the fingertips that maintain grip on hand-held objects.

Mapping the Integration of Sensory Information across Fingers in Human Sensorimotor Cortex

“…Although BA 4 is traditionally viewed as a motor area, it receives substantial inputs from the somatosensory thalamus (Jones, 1975;Darian-Smith and Darian-Smith, 1993) and from various areas of S1 (Ghosh et al, 1987). Therefore, neural populations in this region may also be involved in integrating tactile inputs from the fingers, perhaps for rapid behavioral responses to object displacements (Crevecoeur et al, 2017;Hernandez-Castillo et al, 2020). Our results demonstrate that there were finger interactions in BA 4, and the strength of these interactions was comparable to those in BA 2.…”

“…Such modulation is important, as the processing requirements of somatosensory information depend on the task at hand. For example, the reaction to object slip depends not only on the direction of the slipping object (Häger-Ross et al, 1996), but also on the perceived physical properties of the object (i.e., how "object-like" the simulation is) (Ohki et al, 2002) and the behavioral goal (Hernandez-Castillo et al, 2020). We may therefore expect that, to provide support for flexible sensory-motor mapping, the way that information is integrated across fingers changes with behavioral context.…”

Mapping the integration of sensory information across fingers in human sensorimotor cortex

“…Although BA 4 is traditionally viewed as a motor area, it receives substantial inputs from the somatosensory thalamus (Jones, 1975; Darian-Smith & Darian-Smith, 1993) and from various areas of S1 (Ghosh, Brinkman, & Porter, 1987). Therefore, neural populations in this region may also be involved in integrating tactile inputs from the fingers, perhaps for rapid behavioural responses to object displacements (Crevecoeur et al, 2017; Hernandez-Castillo et al, 2020). Our results demonstrate that there were finger interactions in BA 4, and the strength of these interactions were comparable to those in BA 2.…”

“…Such modulation is important, as the processing requirements of somatosensory information depends on the task at hand. For example, the reaction to object slip depends not only on the direction of the slipping object (Häger-Ross, Cole, & Johansson, 1996), but also on the perceived physical properties of the object (i.e., how "object-like" the simulation is, Ohki, Edin, & Johansson, 2002) and the behavioural goal (Hernandez-Castillo et al, 2020). We may therefore expect that, in order to provide support for flexible sensory-motor mapping, the way that information is integrated across fingers changes with behavioral context.…”