Suboptimal online control of aiming movements in virtual contexts

Sensorimotor Challenges in Minimally Invasive Surgery: A Theoretically-Oriented Review

OBJECTIVE

This review surveys the literature on sensorimotor challenges impacting performance in laparoscopic minimally invasive surgery (MIS).

BACKGROUND

Despite its well-known benefits for patients, achieving proficiency in MIS can be challenging for surgeons due to many factors including altered visual perspectives and fulcrum effects in instrument handling. Research on these and other sensorimotor challenges has been hindered by imprecise terminology and the lack of a unified theoretical framework to guide research questions in the field.

METHOD

We conducted a systematic survey of the MIS literature, focusing on studies investigating sensorimotor challenges affecting laparoscopic performance. To provide a common foundation for cross-study comparisons, we propose a standardized taxonomy that distinguishes between different experimental paradigms used in the literature. We then show how the computational motor learning perspective provides a unifying theoretical framework for the field that can facilitate progress and motivate future research along clearer, hypothesis-driven lines.

RESULTS

The survey identified diverse sensorimotor perturbations in MIS, which can be effectively categorized according to our proposed taxonomy. Studies investigating monitor-, camera-, and tool-based perturbations were systematically analyzed, elucidating their impact on surgical performance. We also show how the computational motor learning perspective provides deeper insights and potential strategies to mitigate challenges.

CONCLUSION

Sensorimotor challenges significantly impact MIS, necessitating a systematic, empirically informed approach. Our proposed taxonomy and theoretical framework shed light on the complexities involved, paving the way for more structured research and targeted training approaches to enhance surgical proficiency.

APPLICATION

Understanding the sensorimotor challenges inherent to MIS can guide the design of improved training curricula and inform the configuration of setups in the operating room to enhance surgeon performance and ultimately patient outcomes. This review offers key insights for surgeons, educators, and researchers in surgical performance and technology development.

Abstract spatial, but not body-related, visual information guides bimanual coordination

Visual spatial information is paramount in guiding bimanual coordination, but anatomical factors, too, modulate performance in bimanual tasks. Vision conveys not only abstract spatial information, but also informs about body-related aspects such as posture. Here, we asked whether, accordingly, visual information induces body-related, or merely abstract, perceptual-spatial constraints in bimanual movement guidance. Human participants made rhythmic, symmetrical and parallel, bimanual index finger movements with the hands held in the same or different orientations. Performance was more accurate for symmetrical than parallel movements in all postures, but additionally when homologous muscles were concurrently active, such as when parallel movements were performed with differently rather than identically oriented hands. Thus, both perceptual and anatomical constraints were evident. We manipulated visual feedback with a mirror between the hands, replacing the image of the right with that of the left hand and creating the visual impression of bimanual symmetry independent of the right hand’s true movement. Symmetrical mirror feedback impaired parallel, but improved symmetrical bimanual performance compared with regular hand view. Critically, these modulations were independent of hand posture and muscle homology. Thus, visual feedback appears to contribute exclusively to spatial, but not to body-related, anatomical movement coding in the guidance of bimanual coordination.

Prism adaptation in virtual and natural contexts: Evidence for a flexible adaptive process

Prism exposure when aiming at a visual target in a virtual condition (e.g., when the hand is represented by a video representation) produces no or only small adaptations (after-effects), whereas prism exposure in a natural condition produces large after-effects. Some researchers suggested that this difference may arise from distinct adaptive processes, but other studies suggested a unique process. The present study reconciled these conflicting interpretations. Forty participants were divided into two groups: One group used visual feedback of their hand (natural context), and the other group used computer-generated representational feedback (virtual context). Visual feedback during adaptation was concurrent or terminal. All participants underwent laterally displacing prism perturbation. The results showed that the after-effects were twice as large in the "natural context" than in the "virtual context". No significant differences were observed between the concurrent and terminal feedback conditions. The after-effects generalized to untested targets and workspace. These results suggest that prism adaptation in virtual and natural contexts involves the same process. The smaller after-effects in the virtual context suggest that the depth of adaptation is a function of the degree of convergence between the proprioceptive and visual information that arises from the hand.

Evidence of multiple coordinate representations during generalization of motor learning

Several studies have suggested that the motor system takes advantage of a coordinate system when learning a novel sensorimotor environment. Such investigations, however, have not distinguished between initial preferences of a coordinate system versus possible changes due to learning. Here, we present experimental methods that specifically entertain the possibility of multiple coordinate systems during generalization. Subjects trained with their right arm on a viscous force field. We evaluated their performances for both arms in an untrained workspace before and after training using three fields, each representing extrapolation with a candidate coordinate system. Surprisingly, our results showed evidence of improvement (pre to post) in all fields for both limbs. These findings are consistent with the hypothesis of multiple, simultaneous coordinate systems involved in generalization. We also investigated how feedback might affect the results and found in several cases that performance was better for visual displays that were aligned with the limb (in first person) versus non-aligned.

When adaptive control fails: Slow recovery of reduced rapid online control during reaching under reversed vision

Previous studies have shown that short-term exposure to mirror-reversed visual feedback suppresses rapid online control (ROC) of arm movements in response to a sudden target displacement. Here we tested if the reduced ROC under reversed vision can be observed for natural reaches without target perturbations, i.e. without corrective movements that are driven by visual input perturbation. Second, we ask if such ROC reduction generalizes to movement phases without visual feedback of the hand. Subjects were instructed to perform simple reach movements towards a stationary target position either under normal or physically reversed vision of the hand during the late movement phase. We quantified time-resolved ROC via a coefficient of determination of the reach trajectories over the full course of the movement. As for other measures in previous studies, we found that our perturbation-independent ROC was reduced within a few trials after exposure to reversed visual feedback. The reduced ROC was restricted to late movement phases, and was not observed in early movement phases. We further asked if subjects would be able to re-gain ROC with prolonged exposure to the reversed visual input. ROC gradually and incompletely increased over the course of 400 exposure trials, affecting both early and late movement phases. Our results show that under reversed vision ROC is reduced even for perturbation-independent natural reaches aiming at stationary targets.

Is visual-based, online control of manual-aiming movements disturbed when adapting to new movement dynamics?

Previous research has shown that for goal-directed movements, online visual feedback is not necessary for the adaptation of movement planning to novel movement dynamics. In the present study, we wanted to put this proposition to a stringent test and determine whether the usually dominant role of online visual feedback in movement control is diminished when goal-directed movements are performed in a condition that modifies limb dynamics. Participants performed a video-aiming task while the center of mass of their forearm was experimentally displaced by a 1.5-kg mass attached laterally to its longitudinal axis. A cursor representing the position of the participant's hand was either visible or not visible during the acquisition phase. Then, in a transfer test, the participants performed the task without online visual feedback and either with or without the lateral mass. During the acquisition phase, the participants adapted to the new movement dynamics imposed by the added mass regardless of whether online visual feedback was available. An important new finding of the present study was the observation that the role usually played by online visual feedback in refining movement planning and ensuring control of the initial portion of goal-directed movements was suppressed during adaptation to novel movement dynamics. This resulted in an increase in the role played by visual feedback late in the movement to ensure endpoint accuracy.

Simultaneous coordinate representations are influenced by visual feedback in a motor learning task

It has been widely accepted that the CNS develops a representation (model) of the environment, but what is not entirely clear is the coordinate reference frame used. We explored how visual feedback influenced the coordinate frame in which the CNS stores and recalls these memories of learned skills in a reaching-generalization task. Four groups of subjects trained to perform reaching movements in a perturbing force field, two with aligned (first person) visual feedback and two with non-aligned (vertical screen). After 170 trials of practice, we asked subjects to extrapolate (generalize) what they learned to a new part of the workspace in novel force environments (endpoint-based versus joint-based extrapolated force fields). Regardless of the test condition, all subjects improved their ability to generalize skills to the new workspace. There was evidence that the extrapolation of their learned skills was based on both object-centered and joint-based coordinates. Consistent with previous studies, subjects performed significantly better in joint-extrapolated force field, but only if the visual feedback was vertical. Subjects performed equivalently in both force fields with aligned (first person) feedback. These findings suggest that the type of visual feedback biases the way subjects perform, and that learning results can be significantly influenced by feedback.