Proceedings of The Physiological Society
University of Oxford (2011) Proc Physiol Soc 23, C48
Dual processing changes reactive balance in healthy adults
M. Liston1, J. H. Bergmann2, D. A. Green1, M. Pavlou1
1. Centre of Human and Aerospace Physiological Sciences, King's College London, London, United Kingdom. 2. Medical Engineering Solutions in Osteoarthritis Centre of Excellence, Imperial College London, London, United Kingdom.
It is widely accepted that attentional demands for postural control placed upon an individual vary according to the nature of the task, the age of the individual and their postural stability . Dual tasking paradigms which combine postural and cognitive tasks can assess attentional demands for posture control, as well as the interference between these tasks [2, 3]. Currently, dual tasking is investigated by providing a single cognitive task alongside a postural activity (e.g. standing, walking or stepping over an obstacle) [4, 5]. How more responsive balance activities are affected by dual tasking remains unclear. This pilot study extends dual tasking to a dual processing paradigm. A reactive balance task is combined with responsive audio tasks. Healthy adults (n=10, aged 26-61 years [mean 38.1]) with no evidence of balance impairment, hearing loss or colour blindness participated in this study. An instrumented floor with four colour coded directions (front, back, left and right) was developed to measure reactive balance. This stepping task required the subject to perform a directed step at the presentation of a colour stimulus (Fig 1). The secondary verbal or spatial cognitive tasks required the subject to press one of two buttons on a hand held number pad, in response to auditory information. The verbal task consisted of a male and female voice calling male and female names. The spatial task consisted of a verbal “left” or “right” spoken into the left or right ear. Participants had to press correct if both components corresponded (e.g. male name spoken by a male). Subjects were required to perform auditory or balance tasks separately, as well as combined. Response times for each task were used to asses cognitive processing. An ANOVA with Bonferroni post hoc was used for analysis of mean stepping response. Paired t tests were used to assess mean response times for the secondary cognitive task. Dual processing significantly increased mean step response time (F=22.511, p<0.01). Post-hoc analysis showed that the spatial task significantly increased mean step response time by 67% compared to the stepping task on its own (p<0.01). However, the verbal task did not significantly increase mean step response time (p=0.14). Dual processing significantly increased mean response time for both verbal (p<0.05) and spatial (p<0.01) secondary tasks, with spatial task response times being significantly longer than verbal response times under dual processing conditions (p<0.01). This study investigated the effect of added attentional demands by utilising a novel dual processing protocol on the timing and accuracy of stepping responses in healthy adults. Dual processing significantly increases step response times and response times for the secondary cognitive task; with concurrent processing of two spatial orientated tasks having the greatest effect.
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