The Interference Between Standing Postural Control And Spatial Working Memory Updating Under Dual-task Condition:A Functional Near-infrared Spectral Imaging Study

Background: Previous evidence suggests that postural control processing may be more related to spatial working memory(SWM)than to nonspatial working memory(NWM).Methodological discrepancies between spatial and nonspatial cognitive tasks have made direct comparisons between the two systems difficult.Methods: Eighteen right-handed volunteers with normal or corrected-to-normal vision and normal body mass index participated in the study(data from one female participant were discarded due to an excessively low correct percentage(<80%)in the cognitive tasks).Data from the remaining 17 subjects were included in the final analyses.To explore the neural mechanisms of SWM and NWM relative to that of postural control,participants were subjected a cognitive-posture dual-task(DT)paradigm,consisting of a 3-back letter working memory(WM)task,using physically identical stimulus with spatial and nonspatial components memorised in different session,and a standing balance task.The subjects underwent functional near-infrared spectral imaging(f NIRS)during task performance,wherein oxygenated hemoglobin concentration([Hb O])was measured in frontal and parietal regions.Participants' reactions of WM task were recorded and postural stability was measured by tracking ground reaction forces during tandem standing.The time series data of the COP trajectory was recorded and calculated as metrics of postural control.Results: First,participants that were completing the SWM task while standing had significantly lower discernment than those completing the SWM task while sitting.Posture had no effect on NWM task discernment.Second,performance in the postural control task,as reflected by whole path length and mean speed of COP,tended to be hindered during DT-SWM blocks relative to that in the standing postural control task.Finally,f NIRS data showed that when the participants completed the standing-SWM task,[Hb O] in the frontal-parietal network of the left hemisphere trended lower compared to that observed during the sitting-SWM task.No posture-associated differences in [Hb O] were observed in NWM-related areas during NWM task performance.Conclusions: Behavioral and f NIRS data demonstrated that standing postural control had a selective interaction with SWM.Specifically,standing postural control reduced SWM discrimination and SWM-related brain activity(frontal-parietal network),but not NWM discrimination or NWM-related brain activity.And only SWM reduced the stability of standing postural control.These results suggest that postural control may share more cognitive resources with SWM than with NWM.