Adaptation changes in dynamic postural control and contingent negative variation during repeated transient forward translation in the elderly

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.

Cortical activity during walking and balance tasks in older adults and in people with Parkinson’s disease: A structured review

“…Dual-task standing further increased PFC and temporal cortex activity in older adults [53]. Balance under perturbation (floor translation) increased cortical activity compared to normal standing in older adults [60, 63], but activation reduced over time with further perturbation exposure [60].…”

Timings of attentional switching to perturbation and postural preparation during transient forward or backward floor translation

“…EMG waveforms from − 300 ms to + 500 ms with respect to the burst onset were averaged separately for each direction in each task. Averaged waveforms were smoothed using a 40-Hz low-pass filter; then, a peak was identified [ 5 , 8 , 23 ]. The peak amplitude from baseline and the peak time with respect to burst onset were measured.…”

“…Averaged waveforms of EEG at Cz were 4-Hz low-pass filtered. The maximal negative potential identified from 1400 ms after S1 to S2 was defined as the CNV peak [ 23 ], and latency relative to S2 and amplitude from the baseline were calculated as CNV peak time and amplitude, respectively. The P3 component was observed only in the choice-reaction task, and its amplitude was the largest in the parietal area (Fig.…”

“…In most EMG and CoPap waveforms, changes for postural preparation were observed in the early period of S1–S2. Thus, changes in EMG and CoPap as postural preparation were analyzed for the 1400 ms period after S1 when the late CNV peak was not present [ 23 ]. For CoPap, forward or backward shift was defined as CoPap deviation more than 2 SD above or below the mean CoPap amplitude in the 300-ms period before S1 (base period).…”

Postural control and contingent negative variation during transient floor translation while standing with the ankle fixed

“…When S1 was a simple warning and S2 was an imperative stimulus of finger response or arm movement, the negative potential of late CNV seemed to gradually increase until S2 onset [ 21 , 25 ]. On the other hand, when S2 was a transient floor translation, the negative potential seemed to increase at a relatively early stage of the S1–S2 period [ 16 , 26 ]. When the response to S2 was determined by S1 or trial was considerably repeated, the negative potential of early CNV was small [ 27 , 28 ].…”