Ka Chun Siu

Effects of a secondary task on obstacle avoidance in healthy young adults

Research on attention and gait stability has suggested that the process of recovering gait stability requires attentional resources, but the effect of performing a secondary task on stability during obstacle avoidance is poorly understood. Using a dual-task paradigm, the present experiment investigated the extent to which young adults are able to respond to a secondary auditory Stroop task (requiring executive attentional network resources) concurrently with obstacle crossing during gait when compared with performing unobstructed walking or sitting (control task). Our results demonstrated that as the level of difficulty in the postural task increased, there was a significant reduction in verbal response time from congruent to incongruent conditions in the auditory Stroop task, but no differences in gait parameters, indicating that these postural tasks require attention, and that young adults use a strategy of modulating the auditory Stroop task performance while keeping stable gait performance under the dual-task situations. Our findings suggest the existence of a hierarchy of control within both postural task (obstacle avoidance requires the most information processing resources) and dual-task (with gait stability being a priority) conditions.

Attentional Mechanisms Contributing to Balance Constraints during Gait: The Effects of Balance Impairments

BACKGROUND Recent research has begun to explore the ability of older adults to perform balance tasks while simultaneously performing a secondary cognitive task; however, it has suffered from limitations regarding the mechanisms underlying the problems that cause dual-task deficits in older adults with balance impairments. Two possible attentional mechanisms (reduced general attentional capacity vs. a true dual-task performance deficit and inability to allocate attention between two tasks) contributing to balance constraints were examined. METHODS Twelve healthy elderly adults and 12 elderly adults with balance impairments (BIOA) were asked to perform obstacle avoidance while walking, either alone or simultaneously with an auditory Stroop task. Two experiments were designed to examine attentional mechanisms that may contribute to reduce performance in the dual-task situations for the BIOA. RESULTS Experiment 1 determined whether for BIOA, single vs. dual-task performance conditions led to similar effects as a single-task difficulty (congruent vs. incongruent) manipulation. Results indicated that dual-task performance reduction did not exceed that of the difficult single task, suggesting that neither older adult group showed a true dual-task performance deficit, but rather BIOA showed a reduced attentional capacity. Experiment 2 showed that BIOA also showed deficits in flexibly focusing their attention between two tasks according to instructions. CONCLUSION Our study confirmed that the ability to allocate attention between a postural task and a secondary cognitive task was impaired in BIOA; it is suggested that inability to flexibly allocate attention could be one important factor among many factors that contribute to balance constraints during gait in fallers.

Dual-task interference during obstacle clearance in healthy and balance-impaired older adults

Background and aims: To investigate dual-task interference between a concurrent cognitive task (auditory Stroop test) and obstacle avoidance in older adults with or without a history of falls. Methods: Gait performance (temporal-distance parameters, range of motion and peak velocity of the center of mass) and verbal reaction time (VRT) in the secondary auditory Stroop task were monitored in 12 healthy young adults, 12 healthy older adults and 12 balance impaired older adults (BIOA) while they sat or walked with and without an obstacle in their path. VRT was used as an indicator of attention given to the secondary Stroop task. Results: Under dual-task situations, all older participants reduced their gait velocity, taking longer strides and wider steps. BIOA significantly increased toe clearance of their trailing limb during obstacle avoidance. In all participants, cognitive attention to the Stroop task, as measured by VRT, was diminished as the level of difficulty in the activity increased; however, the effect was blunted in BIOA compared to healthy subjects. Conclusions: Performing two tasks was highly inefficient among BIOA, as their performance in the gait and secondary task were both modified under dual-task situations. It is possible that dual-task interference in BIOA may be due to the inability to shift attention between the two tasks without primarily prioritizing gait. The findings suggest that BIOA should perform one task at a time in daily activities in order to reduce the risk of falling.

Saccadic output is influenced by limb kinetics during eye-hand coordination.

In several recent studies, saccadic eye movements were found to be influenced by concurrent reaching movements. The authors investigated whether that influence originates in limb kinematic or kinetic signals. To dissociate those 2 possibilities, the authors required participants (N = 6) to generate pointing movements with a mass that either resisted or assisted limb motion. With practice, participants were able to generate pointing responses with very similar kinematics but whose kinetics varied in a systematic manner. The results showed that saccadic output was altered by the amount of force required to move the arm, consistent with an influence from limb kinetic signals. Because the interaction occurred before the pointing response began, the authors conclude that a predictive signal related to limb kinetics modulates saccadic output during tasks requiring eye-hand coordination.

Validated robotic laparoscopic surgical training in a virtual-reality environment

BackgroundA robotic virtual-reality (VR) simulator has been developed to improve robot-assisted training for laparoscopic surgery and to enhance surgical performance in laparoscopic skills. The simulated VR training environment provides an effective approach to evaluate and improve surgical performance. This study presents our findings of the VR training environment for robotic laparoscopy.MethodsEight volunteers performed two inanimate tasks in both the VR and the actual training environment. The tasks were bimanual carrying (BC) and needle passing (NP). For the BC task, the volunteers simultaneously transferred two plastic pieces in opposite directions five times consecutively. The same volunteers passed a surgical needle through six pairs of holes in the NP task. Both tasks require significant bimanual coordination that mimics actual laparoscopic skills. Data analysis included time to task completion, speed and distance traveled of the instrument tip, as well as range of motion of the subject’s wrist and elbow of the right arm. Electromyography of the right wrist flexor and extensor were also analyzed. Paired t-tests and Pearson’s r were used to explore the differences and correlations between the two environments.ResultsThere were no significant differences between the actual and the simulated VR environment with respect to the BC task, while there were significant differences in almost all dependent parameters for the NP task. Moderate to high correlations for most dependent parameters were revealed for both tasks.ConclusionsOur data shows that the VR environment adequately simulated the BC task. The significant differences found for the NP task may be attributed to an oversimplification in the VR environment. However, they do point to the need for improvements in the complexity of our VR simulation. Further research work is needed to develop effective and reliable VR environments for robotic laparoscopic training.

Development of Postural Control during Gait in Typically Developing Children: The Effects of Dual-task Conditions

The purpose of this study was to investigate the typical development of postural control in younger (5-6 yrs) and older (7-16 yrs) children (YTD and OTD) during two gait tasks, including level walking and obstacle-crossing, using a dual-task paradigm, and to compare the results of the childrens performance with that of healthy young adults (HYA). Our findings revealed that gait control in typical children requires attentional resources to maintain stability. Moreover, dual-task interference was less in HYA compared to YTD and OTD. Gait performance decrements in the dual-task context were greater in YTD compared to OTD, whereas cognitive performance decrements in YTD and OTD were similar. In addition, dual-tasking affected cognitive performance more in YTD when gait task difficulty was increased. Results suggest a developmental trend in attentional resources used to control gait in typical children. Postural control during gait under dual-task conditions was improved when children were more mature, as attentional resources increased with age.

The impact of environmental noise on robot-assisted laparoscopic surgical performance

BACKGROUND An operating room is a noisy environment. How noise affects performance during robotic surgery remains unknown. We investigated whether noise during training with the da Vinci surgical robot (Intuitive Surgical, Inc., Sunnyvale, CA) would affect the performance of simple operative tasks by the surgeon. METHODS Twelve medical students performed 3 inanimate operative tasks (bimanual carrying, suture tying, and mesh alignment) on the da Vinci Surgical System with or without the presence of noise. Prerecorded noise from an actual operating room was used. The kinematics of the robotic surgical instrument tips and the muscle activation patterns of the subjects were evaluated. RESULTS We found noise effects for all 3 tasks with increases in the time to task completion (23%; P=.046), the total distance traveled (8%; P=.011) of the surgical instrument tips, and the muscle activation volume (87%; P=.015) with the presence of noise. We confirmed that the mesh alignment task was the most difficult task with the greatest time to task completion and the greatest muscle activation volume, whereas the suture tying task and the bimanual carrying could be considered the intermediate and the least difficult task, respectively. The noise effects were significantly greater while performing more difficult tasks. CONCLUSION Our findings demonstrated that noise degraded robotic surgical performance; however, the impact of noise on robotic surgery will depend on the level of difficulty of the task. Subsequent research is required to identify how different types of noise, such as random or rhythmic sounds, affect the performance of operative tasks using robots such as the da Vinci.

The Effect of Music on Robot-Assisted Laparoscopic Surgical Performance

Music is often played in the operating room to increase the surgeon’s concentration and to mask noise. It could have a beneficial effect on surgical performance. Ten participants with limited experience with the da Vinci robotic surgical system were recruited to perform two surgical tasks: suture tying and mesh alignment when classical, jazz, hip-hop, and Jamaican music were presented. Kinematics of the instrument tips of the surgical robot and surface electromyography of the subjects were recorded. Results revealed that a significant music effect was found for both tasks with decreased time to task completion (P = .005) and total travel distance (P = .021) as well as reduced muscle activations ( P = .016) and increased median muscle frequency (P = .034). Subjects improved their performance significantly when they listened to either hip-hop or Jamaican music. In conclusion, music with high rhythmicity has a beneficial effect on robotic surgical performance. Musical environment may benefit surgical training and make acquisition of surgical skills more efficient.

Why does older adults' balance become less stable when walking and performing a secondary task? Examination of attentional switching abilities

Previous research using dual-task paradigms indicates balance-impaired older adults (BIOAs) are less able to flexibly shift attentional focus between a cognitive and motor task than healthy older adults (HOA). Shifting attention is a component of executive function. Task switch tests assess executive attention function. This multivariate study asked if BIOAs demonstrate greater task switching deficits than HOAs. A group of 39 HOA (65-80 years) and BIOA (65-87 years) subjects performed a visuo-spatial task switch. A sub-group of subjects performed a dual-task obstacle avoidance paradigm. All participants completed the Berg Balance Scale (BBS) and Timed Up and Go (TUG). We assessed differences by group for: (1) visuo-spatial task switch reaction times (switch/no-switch), and performance on the BBS and TUG. Our balance groups differed significantly on BBS score (p<.001) and switch reaction time (p=.032), but not the TUG. This confirmed our hypothesis that neuromuscular and executive attention function differs between these two groups. For our BIOA sub-group, gait velocity correlated negatively with performance on the switch condition (p=.036). This suggests that BIOA efficiency of attentional allocation in dual task settings should be further explored.

Training program for fundamental surgical skill in robotic laparoscopic surgery

Although the use of robotic laparoscopic surgery has increased in popularity, training protocols for gaining proficiency in robotic surgical skills are not well established. The purpose of this study was to examine a fundamental training program that provides an effective approach to evaluate and improve robotic surgical skills performance using the da Vinci™ Surgical System.