Discussion
bipolar bihemspheric, bipolar bihemispheric tDCS
EVENTS
The purpose of this study was to assess the impact of tDCS on the training induced improvement and retention of laparoscopic surgical skill. Two commonly used tasks were assessed, a bead transfer, and a threading task. Participants in both the sham and stimulation groups significantly improved their performance on both tasks following a training protocol that involved 5 sessions each 20 min in duration (10 min per task). While no significant difference in the level of improvement on the threading task between participants in the sham and stimulation groups was found, we did find that those participants who received bipolar bihemispheric tDCS applied over the hand regions of M1 improved both their time and kinematic based performance metrics on the bead transfer task to a greater extent than those who trained whilst receiving a sham stimulation. Furthermore, this enhanced improvement observed among the stimulation group was maintained 5 days later at the retention test. We discuss these findings within the context of training induced sensory-motor skill improvements, the effect of tDCS on the enhancement of motor skill and the future implications of enhancing surgical skill through neuromodulation techniques on the medical profession.In this study, novice surgical participants in both stimulation conditions significantly reduced the time required to complete the bead transfer task and this reduction was maintained at the retention test 5 days following completion of the Post test. However, the group receiving neurostimulation demonstrated a 5% improvement in time to completion compared to the sham group. This 5% equates to a 30 s faster time to complete the bead transfer task compared to the sham group at the retention time point. This finding corroborates the work by Cox and colleaguesOn the threading task both groups significantly improved over the course of training from pre to post/retention but there was no significant effect of neurostimulation. The stim group did, on average however, complete the task 17 s quicker than the sham group. Turning to the findings for implements distance travelled, participants in both stimulation conditions significantly reduced the distance their implements travelled to complete the bead transfer task after 5 days of training. Moreover, while this reduction was maintained at the retention test 5 days after the Post test for the sham group, further improvements were observed at retention for the stim group. A smaller distance of travel by the implements would indicate a safer more efficient laparoscopic procedure. Other surgical skills research reports a decrease in error scores coupled with quicker completion times (seeFinally, we sought to examine the steadiness or smoothness with which participants controlled the implements during the completion of both tasks and were able to do so by measuring implement velocity and defining excessive velocity events. In the bead transfer task, main effects of implement, session, and condition were all significant, as was the interaction between session and stimulation condition. Post hoc analyses revealed that in the Retention session, the stimulation group had significantly fewer excessive velocity events compared to the sham group. After confirming no significant difference in baseline TTC performance between stimulation conditions, we showed that after controlling for variations in baseline performance, a significant main effect of neurostimulation was found where those who received tDCS were able to significantly reduce the number of excessive velocity events more than those in the sham group over the course of training (Fig. The observed improvements by the stimulation group over and above those receiving sham stimulation equate to a significant time improvement, coupled with reduced instrument travel distance and improved implement control (increase in movement smoothness observed as a reduction in EVEs). These reductions are similar to training induced improvements in other sensory-motor and digital tasksHowever, while the beads task was able to successfully demonstrate a significant positive effect of bipolar bihemspheric M1 stimulation, the threading task did not. For now, we hypothesize that it may be that the beads task is a highly repetitive highly consistent spatio-temporal task that may be more conducive to the effects of brain stimulation during training. The threading task is more complex and variable from a sensorimotor standpoint where the movement and positioning of the implements appear to differ more greatly across multiple attempts at completing the task. Previous work has shown that as task complexity increases, brain activation extends towards prefrontal, parietal and temporal areasThe findings and implications from this research may be applied to several research areas and real-world situations. For example, when learning a new task, we replicate that performance can vary considerably in novice performers