Perry S¹, Zhu FF², Bridges SM¹, Masters RSW³ LEUNG WK⁴

Faculty of Education, the University of Hong Kong, Hong Kong SAR, China, ²Faculty of Education, Department of Surgery, and Institute of Human Performance, the University of Hong Kong, Hong Kong SAR, China, ³Te Oranga School of Human Development and Movement Studies, University of Waikato, New Zealand, ⁴Faculty of Dentistry, the University of Hong Kong, Hong Kong SAR, China.

 Background:

Reinvestment is a term attributed to the disruption of psychomotor skills due to conscious engagement in explicit knowledge. The presence of stressors such as pressure, fatigue and distraction can disrupt the process from motor automaticity in individuals with a propensity to reinvest, causing skill breakdown.¹ Individuals with a high propensity to reinvest can be detected in a verified questionnaire: the Movement Specific Reinvestment Scale. (MSRS)

Little is understood regarding reinvestment at the cerebral cortex level. It is believed high reinvestors are more conscious of their movement control and as a result they are heavily reliant on the working memory, housed in the dorsolateral prefrontal cortex (DLPFC). Increased demands on this area of the brain could be reflected in greater changes in oxyhaemoglobin concentration in the blood flowing to the region from resting baseline to task condition. With the utilisation of Functional Near Infra-Red Spectroscopy (fNIRS) we aim to investigate the hypothesis that in a simulated dental task, high reinvestors will have greater changes in oxyhaemoglobin concentration in the DLPFC. 

Materials and Methods:

A group of 60 fourth year dental students completed the MSRS.  Students from the top and bottom quartiles of the results were invited to take part in the fNIRS study. A total of 22 students volunteered: 12 low and 10 high reinvestors. The students were then asked to carry out 4 tasks on a dental haptic virtual reality simulator, 2 standard tasks and 2 tasks aiming to induce reinvestment. During the tasks the participants wore an 18 Channel fNIRS device centred over the left and right DLPFC. Prior to each task the participants were asked to ‘rest’ for 45 seconds to record a baseline sample. This allowed the changes in oxyhaemoglobin concentration from rest to the 5-minute task to be calculated. Paired t-tests were carried out within each group to determine active channels during the four tasks. In addition t-tests were used to determine changes in levels of oxyhaemoglobin concentration from rest to task between the high and low reinvestor groups.

Results

Of the 22 participants, nine had a higher level of oxyhaemoglobin concentration in DLPFC during the rest period than that during the task and this group will be analysed separately. Of the remaining 13 participants there were six high reinvestors and seven low reinvestors. Adjusted paired t-test results (FDR correction) showed that the reinvestment tasks activated more channels in the high reinvestment group with higher numbers of active channels evident. The difference between groups in changes in level of oxyhaemoglobin concentration from rest and task was only significantly higher for one channel of the easier of the two tasks, (channel 14: t(12)=-4.3, p=0.001, significant with FDR correction) positioned on the anterior medial position of the right DLPFC. The high reinvestors were found to have greater changes in oxyhaemoglobin concentration in this region. Notably, a trend was evident that the high reinvestors had greater changes in oxyhaemoglobin in general, and in particular to the right hemisphere of the DLPFC for the easier of the two tasks.

Conclusion

This is the first insight to functional brain (cerebral cortex) activation patterns in relation to the reinvestment theory to our knowledge. The initial findings from this pilot study provide support for the hypothesis that high reinvestors rely heavily on the working memory when compared to low reinvestors. This study indicates there are differences in changes in levels of oxyhaemoglobin concentration from rest baseline to task conditions to the DLPFC during dental tasks, with greater changes associated with reinvestment conditions and also high reinvestors. High reinvestors also appeared to utilise the right DLPFC more so than the left, possibly reflecting ‘effort’ literature.² In addition, the results indicating task demands could be used to inform curriculum design regarding levels of mental effort required to carry out different types of haptic simulator task.

1.         Maxwell JP, Masters RS, Poolton JM. Performance breakdown in sport: the roles of reinvestment and verbal knowledge. Res Q Exerc Sport 2006;77(2):271-6.

2.         Posner MI, Rothbart MK. Research on attention networks as a model for the integration of psychological science. Annu Rev Psychol 2007;58:1-23.