Prefrontal cortex is frequently linked to dual-task gait performance; however, its
precise role is unknown. The purpose of this thesis was to examine the role of
prefrontal cortex in the control of dual-task gait. Using transcranial direct
stimulation (tDCS) to alter prefrontal cortex activity, the influence of prefrontal
cortex on dual-task gait performance and the corticospinal system was examined
across four experiential studies using the guided activation framework of prefrontal
cortex function (Miller and Cohen, 2001).
The first study examined the role of cognitive task type and walking speed on stride
time variability and trunk range of motion during dual-task walking. Results
revealed the greatest dual-task cost on gait occurred when walking at a slow speed
whilst simultaneously performing a serial subtraction task, compared to performance
of a working memory task, providing a rationale for the use of this paradigm in later
The second study examined the effect of prefrontal tDCS on dual-task gait
performance during both normal and slow walking. Anodal tDCS reduced the dualtask
cost on both gait and cognitive task performance, and these effects were not
dependent on walking speed. These results indicating that prefrontal tDCS may alter
the allocation of cognitive control across tasks during dual-task gait, in accordance
with established models of prefrontal cortex function.
The third study examined the effect of prefrontal tDCS on corticospinal excitability
and working memory performance. Results revealed that cathodal tDCS reduced
corticospinal excitability. However, there was no effect of tDCS on working
memory performance. Because prefrontal tDCS altered the activity in remote motor
networks, these results indicated a possible mechanism by which prefrontal cortex
exerts control over gait performance. In addition, because this study failed to
replicate previous reports of working memory improvement following tDCS, these
results also suggested a degree of inter-individual variability in response to tDCS.
The final study examined the influence of walking modality and task difficulty on
the effects of prefrontal tDCS on dual-task gait performance. tDCS altered the
allocation of cognitive control during over-ground dual-task gait performance, and
these effects were mediated by task difficulty. In contrast to the second study, there
was no effect of tDCS on treadmill dual-task gait. A secondary aim of the final study
was to examine whether cognitive and walking task performance were coordinated.
Results revealed that participants articulated answers during the initial swing phase
of the gait cycle more frequently than other phases, indicating a degree of
coordination between the performance of these tasks.
Overall the finding of this thesis indicate that prefrontal cortex is involved in the
allocation of cognitive control processes during dual-task walking, in accordance
with the guided activation and flexible hub accounts of frontal cortex function
(Miller and Cohen, 2001; Cole et al., 2013). These findings may have implications
for the design and validation of strategies aimed at improving the cognitive control
|Date of Award