Swallowing Performance And Prefrontal Cortex Activation During Swallowing Dual Tasks In Healthy Adults

Objective:Dysphagia and cognitive impairment have been the focus and difficulty of rehabilitation research.Previous studies have shown that cognition plays an important role in swallowing,and cognitive training can improve the swallowing function while improving cognitive function.However,there are still few studies on the existence and nature of cognition in swallowing.The purpose of this study was to explore the relationship between swallowing and cognition by observing and comparing the performance of swallowing and parallel tasks during different types and loads of swallowing dual tasks in healthy adults,and applying f NIRS to monitor the changes in the activation of prefrontal cortex,so as to provide more evidence for further understanding the brain network mechanism between them.Method:Experiment 1:45 college students were recruited as subjects to perform swallowing single task（SST）,cognitive single task（CST）,motor single task（MST）,cognitive-swallowing dual task（CDT）and motor-swallowing dual task（MDT）.And obtain the swallowing indexes,cognitive scores and motor performance during the task period,and calculate the dual task cost.f NIRS was applied to reccord the average concentration changes of HbO₂ in the prefrontal cortex and the eight ROIs under different tasks.Functional connectivity was calculated between ROIs.To observe and compare the differences in prefrontal activation patterns among different tasks.Experiment 2:43 college students were recruited as subjects to perform swallowing single task（SST）,low load cognitive single task(ST_low),high load cognitive single task(ST_high),low load cognitive-swallowing dual task(DT_low)and high load motor-swallowing dual task(DT_high).And obtain the swallowing indexes,cognitive scores and motor performance during the task period,and calculate the dual task cost.f NIRS was applied to reccord the average concentration changes of HbO₂ in the prefrontal cortex and the eight ROIs under different tasks.Functional connectivity was calculated between ROIs.To observe and compare the differences in prefrontal activation patterns among different tasks.Result:Experiment 1:1.Swallowing performance results:There were no significant differences in swallowing times,swallowing volume,average volume per mouth,average volume per second and average swallowing time per time among SST,CDT and MDT tasks（P>0.05）.2.Cognitive performance results:The accuracy of CST was basically the same as CDT（P=1.000）.3.Motor performance results:Compared with MST,left-hand and right-hand finger-tapping rate of MDT decreased significantly（P=0.023,0.022）.4.Dual task costs:The swallowing cost of MDT was higher than that of CDT,but the swallowing costs caused by two parallel tasks were not significant（P>0.05）.Swallowing task significantly increased the motion cost during DT（P<0.05）.Dual task has little interference on cognitive accuracy.5.Comparison of brain activation and degree:There was no significant difference in the average HbO₂ concentration change of SST,CDT and MDT in the whole prefrontal cortex（P>0.05）,but the activation degree of SST was significantly higher than that of CDT in the left OFC（P<0.05）.6.Temporal characteristics of HbO₂:The average HbO₂ concentration change variation trend of CDT,MDT and SST in each ROIs were similar,but their peak values wre lower than that of SST.The average HbO₂ concentration change variation trend of CST and MST in each brain region showed a flat trend.7.Lateralization analysis results:Compared with SST,the prefrontal lobe mainly manifested the left-sided lateralization and the OFC mainly manifested the right-sided lateralization during MDT,the DLPFC mainly manifested the right-sided lateralization during CDT.In addition,the left-sided lateralization of VLPFC was more obvious in DT than in SST.8.Brain activity correlates with behavior performance during dual tasks:In CDT,the LVLPFC and the ROFC were significantly positively correlated with the swallowing volume and swallowing cost respectively（P<0.05）.In MDT,the RDLPFC and the LOFC were significantly positively correlated with the average volume per mouth and the swallowing cost respectively（P<0.05）,while the LVLPFC was significantly negatively correlated with the swallowing volume（P<0.05）.In addition,no significant correlation was found between cognitive and motor performance and activated ROIs（P>0.05）.9.Comparison of characteristics of brain functional connectivity:The mean value of functional connection strength of SST in prefontal cortex was significantly higher than that of CDT and MDT,and the mean values of functional connection strength of DT in multiple ROIs pairs were significantly lower than that of SST（P<0.05）.In different swallowing tasks,the activation of RDLPFC and LDLPFC were strongly correlated,and the strongly correlated ROIs pairs in the prefrontal cortex were mostly associated with the DLPFC.Experiment 2:1.Swallowing performance results:There were significant differences in swallowing volume among SST,DT_low and DT_high（P<0.05）,and the swallowing volume of DThigh was significantly lower than that of SST（P<0.05）.2.Cognitive performance results:The accuracy of DT_high was significantly lower than that of DT_low（P<0.05）.3.Dual task costs:DT_high significantly increased the swallowing cost during DT（P<0.05）.Compared with DT_low,the increase of cognitive load leads to more obvious cognitive cost,but has not significantly effect on the swallowing cost.4.Comparison of brain activation and degree:There was no significant difference between the average HbO₂ concentration change of SST,DT_low and DT_high in the prefrontal cortex（P>0.05）.In the left OFC,the average HbO₂ concentration change of SST were significantly higher than those in DT_low（P<0.05）.5.Temporal characteristics of HbO₂:DT_low and DT_high haved similar trends with the average HbO₂ concentration change variation trend of SST in each ROIs,but their peaks were lower than those of SST.Meanwhile,the peak value of DT_high was higher than that of DT_low.6.Lateralization analysis results:Compared with SST,the DLPFC mainly manifested the right-sided lateralization during DT_low,and the DLPFC and OFC mainly manifested the right-sided lateralization during DT_high.7.Brain activity correlates with behavior performance during dual tasks:In DT_low,the LVLPFC and the ROFC were significantly positively correlated with the swallowing volume and swallowing cost respectively（P<0.05）.In DT_high,the ROFC and the LDLPFC were significantly negatively correlated with the average oral volume and swallowing cost,respectively respectively（P<0.05）.In addition,no significant correlation was found between cognitive performance and activated ROIs（P>0.05）.8.Comparison of characteristics of brain functional connectivity:The mean value of functional connection strength of SST in prefontal cortex was significantly higher than that of DT_low and DT_high,and the mean values of functional connection strength of DT in multiple ROIs pairs were significantly lower than that of SST（P<0.05）.In different swallowing tasks,the activation of RDLPFC and LDLPFC were strongly correlated,and the strongly correlated ROIs pairs in the prefrontal cortex were mostly associated with the DLPFC.Conclusion:1.This study confirmed that daily swallowing activities require the participation of executive function and attention,and DLPFC and OFC play an important role in ensuring the safety and effectiveness of swallowing.2.When performing the motor-swallowing dual task,the activation level of PFC decreased to some extent,the right lateralization degree of OFC and the left lateralization degree of VLPFC increased,and the correlation of functional region in PFC decreased to maintain the swallowing performance.3.When performing the low-load cognitive-swallowing dual task,the activation level of PFC decreased to some extent,the right lateralization degree of DLPFC and the left lateralization degree of VLPFC increased,and the correlation of functional region in PFC decreased to maintain the swallowing performance.4.When performing the high-load cognitive-swallowing dual task,the activation level of PFC decreased to some extent,the right lateralization degree of DLPFC and OFC and the left lateralization degree of VLPFC increased,and the correlation of more functional region in PFC decreased to maintain the swallowing performance.5.The correlation between the swallowing performance and DLPFC,OFC and VLPFC in swallowing dual tasks of different types and different loads found in this study suggests that there may be a"swallow first"strategy in the swallowing dual task.