Prefrontal cortical activation in simple and choice stepping in healthy older adults and older adults with mild-to-moderate dementia

Introduction: Older adults with dementia are two to three times more likely to fall compared to their healthy counterparts. Choice stepping (i.e., the ability to take a series of rapid and accurate steps during walking) is one of the strong determinants of fall risk in older adults. The prefrontal cortex, the center of executive control, is responsible for mediating choice stepping performance. However, the neural dynamics of prefrontal cortical involvement during different stepping tasks in older adults with mild-to-moderate dementia have never been investigated.

This study aimed to examine prefrontal cortical activation during simple and choice stepping in healthy older adults and those with mild-to-moderate dementia.

Methodology: This study was a cross-sectional study. Fifteen healthy older adults (HC) and 16 older adults with mild-to-moderate dementia (MD) who could walk 10 meters independently were recruited. The participants were instructed to perform a series of simple stepping tasks (i.e., taking steps to the same target repeatedly) and choice stepping tasks (i.e., taking steps to different targets) in a random order. Functional near-infrared spectroscopy was used to assess the hemodynamic changes in the participants’ prefrontal cortical regions during the stepping tasks. Two-way repeated analysis of covariance with task (simple stepping, choice stepping) as a within-group factor, group (HC, MD) as a between-group factor, and age and body mass index as covariates was used to compare the hemodynamic changes between the two groups.

Results: HC showed significantly greater activations in right dorsolateral prefrontal cortex (p = 0.004), right frontopolar cortex (p = 0.011), and right orbitofrontal cortex (p = 0.004) during choice stepping than simple stepping (Table 1). MD showed greater right dorsolateral prefrontal cortex activation during both simple (p = 0.009) and choice stepping (p = 0.010) than HC (Figure 1). No significant “task x group” interaction was found in any prefrontal cortical region.

Conclusions: Older adults with mild-to-moderate dementia need to activate prefrontal cortex in both simple and choice stepping. In contrast, healthy older adults need to activate prefrontal cortical regions only in choice stepping. This indicates that the neural efficiency of older adults with mild-to-moderate dementia in stepping tasks is reduced, which in turn increases the risk of falls in this population. Our findings provide valuable insights into the neurophysiological risk factors for falls in older adults with mild-to-moderate dementia, as well as evidence for improving fall risk assessment tailored to this population.