Background: Studies comparing the effects of spatial and nonspatial secondary tasks on balance have produced conflicting results. However, in most of these studies the difficulty levels of the secondary tasks have not been matched. In this study, we compared the effects of carefully matched visuospatial (VS) and nonspatial (NS) secondary tasks on choice stepping reaction time (CSRT).
Methods: Forty-one older people (mean age 78.8 years) completed a CSRT test under five conditions: (i) no secondary task; (ii) an easy NS counting backward task; (iii) a difficult NS counting back task; (iv) an easy VS memory task; and (v) a difficult VS memory task. Response times and secondary task errors were measured for each condition. Participants also gave difficulty ratings for each secondary task.
Results: The difficult tasks were rated significantly more difficult than the easy tasks in both VS and NS conditions, and cognitive task errors were moderately correlated with perceived difficulty. A repeated-measure analysis of variance with planned contrasts revealed a significant effect of task type, with the VS condition slowing CSRT more than the NS condition. There was also a significant task difficulty effect with the more difficult tasks increasing CSRT.
Conclusions: The findings suggest that VS cognitive tasks affect CSRT more so than do NS tasks. The visuospatial sketchpad appears to be specifically utilized for carrying out motor tasks necessary for preserving balance. Practical implications are that tasks that require visuospatial attention and memory may adversely influence balance control in older people.