Forward Counting Research Articles

PREFRONTAL BLOOD FLOW DURING DUAL-TASK WALKING IN ADULTS WITH AND WITHOUT MILD COGNITIVE IMPAIRMENT

Abstract Background Blood flow differences in the prefrontal cortex (PFC) during dual-task walking are thought to indicate various degrees of neural efficiency. Individuals with poorer neural resources might need higher activation to meet behavioral performance. We aim to assess PFC cerebral blood flow (CBF) among older adults with and without mild cognitive impairment (MCI) during dual-task using functional Diffuse Correlation Spectroscopy (fDCS). Methods We assessed PFC CBF with DCS during dual-task paradigm: 1)Normal Walk(NW); 2)Forward-count(FWC); 3)Backward-count(BWC); 4)Obstacle negotiation(WWO). We assessed demographics, clinical variables, physical and cognitive function in those with MCI vs normal cognition (NC). Linear mixed effects models assessed changes of CBF across the tests in the dual-task paradigm and differences between MCI and NC. Results 49 older adults (median age=78 years, 51% women, 34 MCI) were included. MCI were older, with higher frailty, polypharmacy and comorbidity. Compared to NC, MCI showed worse cognitive and physical performance scores and lower Gait Speed (GS) during NW and WWO but not during FWC and BWC. N=12 were unable to perform BWC. CBF change from NW to FWC was higher in MCI compared to NC (estimate=0.35, 95%CI [0.03, 0.67], p=0.03). CBF change from NW to BWC and WWO was not different between groups. There was no effect of age or clinical covariates. Conclusions Higher NW-FWC CBF change seems due to the cognitive load of FWC in MCI. Higher activation in MCI compared to healthier counterparts could be explained by compensatory mechanisms. Further research should focus on better understanding dual-task related neural mechanisms.

Changes in gait while backward counting in demented older adults with frontal lobe dysfunction

Background Gait disorders caused by dementia have been associated with frontal lobe dysfunction. Dual-tasking is used to explore the involvement of cortical level in gait control. It has been shown that dual-task induced gait changes that could be related to (1) the efficiency of executive function, (2) the level of difficulty involved in the walking-associated task, or (3) the articulo-motor components comprised in the walking-associated task. A better understanding of dual-task related changes in demented subjects with frontal lobe dysfunction could help us to clarify the role of the frontal lobe in motor gait control. Objective To assess and compare the effects of two mental arithmetic tasks involving similar articulo-motor components but different level of difficulty on the mean values and coefficient of variation (CV) of stride time among demented older adults with impaired executive function. Methods The mean values and coefficients of variation of stride time were measured using a GAITRite ®-System among 16 demented older adults with impaired executive function while walking with and without forward counting (FC) and backward counting (BC). Results The mean values and CV of stride time were significantly higher under both dual-task conditions than during a simple walking task ( p < 0.05). The change in CV of stride time during BC was significantly higher when compared with the change during FC ( p = 0.015), whereas the change in mean value was not significant ( p = 0.056). There was no difference between the dual-task and single task condition as far the number of enumerated figures were concerned ( p = 0.678 for FC and p = 0.069 for BC), but significantly fewer figures were enumerated while BC compared with FC ( p < 0.001). Conclusion BC provoked more changes in gait parameters than FC with major modification in gait variability related to an inappropriate focusing of attention. These findings suggest that the CV may be a suitable criterion for the assessment of gait control.