Abstract
BackgroundAdaptation changes in postural control and contingent negative variation (CNV) for the elderly were investigated during repeated forward floor translation.MethodsFifteen healthy elderly persons, living in the suburban area of Kanazawa City, Japan, underwent backward postural disturbance by a forward-floor translation (S2) 2 s after an auditory warning signal (S1). A set with 20 trials was repeated until a negative peak of late CNV was recognized in the 600-ms period before S2, and the last set was defined as the final set. Electroencephalograms, center of foot pressure in the anteroposterior direction (CoPap), and electromyograms of postural muscles were analyzed.ResultsCoPap displacement generated by the floor translation was significantly decreased until the twelfth trial in the first set, and mean CoPap displacement was smaller in the second and final sets than in the first set. The mean displacement was significantly smaller in the final set than the previous set. A late CNV with a negative peak was not recognized in the first and second sets. However, most subjects (13/15) showed a negative peak by the fourth set, when the late CNV started to increase negatively from about 1,000 ms after S1 and peaked at about 300 ms before S2. At about 160 ms before the CNV peak, the CoPap forward shift started. The increase in timing of the gastrocnemius activity related to the CoPap shift was significantly correlated with the CNV peak timing (r = 0.64). After S2, peak amplitudes of the anterior postural muscles were significantly decreased in the final set compared to the first set.ConclusionsIt was demonstrated that even for the elderly, with so many repetitions of postural disturbance, a late CNV with a negative peak was recognized, leading to accurate postural preparation. This suggests the improvement of frontal lobe function (e.g., anticipatory attention and motor preparation) in the elderly.
Highlights
Adaptation changes in postural control and contingent negative variation (CNV) for the elderly were investigated during repeated forward floor translation
Across 40 postural disturbances using forward floor translation, we investigated adaptation changes in dynamic postural control and CNV [12]
The onset of a transient forward floor translation was used as Response signal (S2), which was detected by an accelerometer (AG-2GB; Kyowa, Japan) fixed to the force platform
Summary
Adaptation changes in postural control and contingent negative variation (CNV) for the elderly were investigated during repeated forward floor translation. Deterioration of equilibrium function is considered to be a primary cause of falls in the elderly. In order to adapt to a postural disturbance, the anticipation of disturbance timing and preparation for the disturbance are required functions [6,7]. The main brain parts executing these functions are the frontal lobe, including the prefrontal cortex, supplementary motor area, premotor area, and primary motor area [8,9]. Studies of postural control have reported more marked training effects even in the elderly [10,11], there have been few experimental studies using electroencephalography (EEG) to directly address training effects on the frontal lobe function related to dynamic postural control in the elderly [12]
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