Effect of automaticity induced by treadmill walking on prefrontal cortex activation and dual-task performance in older adults

Abstract

As individuals age, they may experience a decline in gait automaticity, which requires increased attentional resources for the control of gait. This age-related decline in gait automaticity has been shown to contribute to higher prefrontal cortex (PFC) activation and lower dual-task performance during dual-task walking in older adults. This study is to investigate the effect of treadmill walking on PFC activation and dual-task performance in older adults. A total of 20 older adults (mean age, 64.35 ± 2.74 years) and 20 younger adults (mean age, 30.00 ± 3.15 years) performed single- and dual-task walking in overground and treadmill conditions. A wearable functional near-infrared spectroscopy and gait analyzer were used to analyze PFC activation and dual-task performance, respectively. To determine the dual-task (gait and cognitive) performance, the dual-task cost (DTC) was calculated using the following formula: (single-task - dual-task)/single-task × 100. In both groups, dual-task treadmill walking led to reduced PFC activation and reduced DTC compared to dual-task overground walking. Furthermore, despite a higher DTC in gait variability, correct response, total response, response index and a higher error score in older adults than in younger adults during overground walking, there was no difference in treadmill walking. The difference in PFC activation between single- and dual-tasks was also observed only in overground walking. Performing dual-task walking on a treadmill compared to overground walking results in different levels of dual-task performance and PFC activity. Specifically, older adults are able to maintain similar levels of dual-task performance as younger adults while walking on a treadmill, with reduced PFC activation due to the automaticity induced by the treadmill. Therefore, older adults who exhibit low dual-task performance during overground walking may be able to improve their performance while walking on a treadmill with fewer attentional resources.

Fig 1. The order of different walking tasks in both older and younger adults.

In the older adult groups, the first subject performed treadmill walking as the initial condition, followed by the overground walking condition, whereas in younger adults, the order was reversed. In each group, the second subject’s order was reversed.

Fig 2. The arrangement of channels in PFC subregions including information on the number and location of source-detector pairs.

The numbers represent channels. Ch, channel.

Fig 3. Comparison of DTC in dual-task performance (Mean ± SE).

The values of older adults during overground walking were significantly higher than those during treadmill walking, and higher than those during overground walking in younger adults. (a) DTC in gait variability. (b) DTC in CR. (c) DTC in total response. (d) DTC in response index. (e) Error score. CR, correct response; DTC, dual-task cost; *, P < 0.05, **, P < 0.01, ***, P < 0.001.

Fig 4. Comparison of PFC activation (Mean ± SE).

The values of PFC activation during dual-task overground walking were significantly higher than those during single-task overground walking, and higher than those during dual-task treadmill walking. (a) Right DLPFC activation. (b) Left DLPF activation. (c) Right FPFC activation. (d) Left FPFC activation. (e) Right VLPFC activation. (f) Left VLPFC activation. PFC, prefrontal cortex; DLPFC, dorsolateral PFC; FPFC, frontopolar PFC; VLPFC, ventrolateral PFC; HbO₂, oxygenated hemoglobin; ST, single-task; DT, dual-task; OW, overground walking; TW, treadmill walking; *, P < 0.05, **, P < 0.01, ***, P < 0.001.