Abstract
Generalized slowing characterizes aging and there is some evidence to suggest that this slowing already starts at midlife. This study aims to assess reaction time changes while performing a concurrent low-force and high-force motor task in young and middle-aged subjects. The high-force motor task is designed to induce muscle fatigue and thereby progressively increase the attentional demands. Twenty-five young (20–30 years, 12 males) and 16 middle-aged (35–55 years, 9 males) adults performed an auditory two-choice reaction time task (CRT) with and without a concurrent low- or high-force motor task. The CRT required subjects to respond to two different stimuli that occurred with a probability of 70 or 30%. The motor task consisted of index finger abduction, at either 10% (10%-dual-task) or 30% (30%-dual-task) of maximal voluntary force. Cognitive task performance was measured as percentage of correct responses and reaction times. Middle-aged subjects responded slower on the frequent but more accurately on the infrequent stimuli of CRT than young subjects. Both young and middle-aged subjects showed increased errors and reaction times while performing under dual-task conditions and both outcome measures increased further under fatiguing conditions. Only under 30%-dual-task demands, an age-effect on dual-task performance was present. Both single- and dual-task conditions showed that already at mid-life response preparation is seriously declined and that subjects implement different strategies to perform a CRT task.
Highlights
With increasing age cognitive performance slows down (Verhaeghen and Salthouse, 1997; Der and Deary, 2006), including cognitive processes essential for motor performance (Yordanova et al, 2004)
The difference in reaction times and number of errors between frequent and infrequent stimuli were present in all sessions with faster reactions and less errors for frequent stimuli
30%-dual-task resulted in slower responses and a trend toward more errors with time In the comparison between the 10 and 30%-dual-task, we found a trend toward an interaction effect of Task by Time for accuracy (F1,39 = 3.80, p = 0.06, η = 0.08) and a significant interaction for reaction times (F1,39 = 8.24, p = 0.01, η = 0.15)
Summary
With increasing age cognitive performance slows down (Verhaeghen and Salthouse, 1997; Der and Deary, 2006), including cognitive processes essential for motor performance (Yordanova et al, 2004). Performance of motor tasks becomes less automatic and requires increased attentional demands in older subjects (57–75 years; Heuninckx et al, 2005; Wu and Hallett, 2005; Voelcker-Rehage and Alberts, 2007). Several studies found a decline in cognitive-motor task performance with age (60–90 years; Crossley and Hiscock, 1992; Voelcker-Rehage and Alberts, 2007; Fraser et al, 2010) and a meta-analysis by Verhaeghen et al (2003) revealed that dual-task costs with aging were greater than the general age-related slowing in reaction times
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