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Relationship between improvement in cognitive function by balance board training and postural control adaptability in the elderly
International Congress Series 1278 (2005) 329 – 332
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Relationship between improvement in cognitive function by balance board training and postural control adaptability in the elderly Katsuo Fujiwara*, Michie Shigeiwa, Kaoru Maeda Human Movement and Health, Graduate School of Medical Science, Kanazawa University, Japan
Abstract. We investigated the improvement in cognitive function by balance board training in the elderly with different adaptability of postural control. Subjects were 31 healthy older adults. The adaptability to the floor oscillation (60 s5) was evaluated by the changing degree of body sway. The subjects performed the equilibrium training with a balance board for 3 weeks. P300 was measured in an oddball paradigm by the finger flexion before and after the training. Target (15%) and non-target sound stimulation were, respectively, 2 and 1 kHz with 55 dB above hearing threshold and 1.5-s interval. The subjects were divided into two groups according to the adaptability to floor oscillation. High adaptability group (HA) included 18 subjects who had same adaptability as young adults and the other subjects were included in low adaptability group (LA). The numbers of improved and unimproved subjects in P300 latency or amplitude were 15 and 3 in HA, and 6 and 7 in LA, respectively. The ratio of subject numbers in HA was significantly larger than that in LA. These results suggest that the improvement in the cognitive function by the balance board training is closely related to the adaptability to floor oscillation. D 2004 Elsevier B.V. All rights reserved. Keywords: P300; Postural control adaptability; Balance board training; Reaction time
1. Introduction Balance in the elderly is remarkably low compared with young adults under the nondaily conditions, in which visual and ankle kinesthesia information do not display a real postural change [1]. In addition, it was reported that postural control adaptability to a new environmental condition declined with aging, to which a cognitive function should be related [2]. We devised a balance board, and demonstrated that a balance reaction to floor * Corresponding author. 13-1 Takara-machi, Kanazawa, 920-8640 Japan. Tel.: +81 76 265 2225; fax: +81 76 234 4219. E-mail address: [email protected] (K. Fujiwara). 0531-5131/ D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ics.2004.11.051
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inclination in the elderly was improved by using it in training [3]. It is well expected that the training may improve a cognitive function to predict a postural change accompanied by an inclination of balance board. P300 is one of the assays of a cognitive function by an electroencephalogram. It may develop in the process in which a subject reacts to target sensory stimulations that rarely appear and in the preparation process for the next sensory stimulation [4]. It was reported that P300 latency increased with aging, and the amplitude tended to decrease. We have advanced the research on anticipatory postural control by using an oscillation table. The table was oscillated at 2.5-cm amplitude and 0.5-Hz frequency for 60 s. It was clarified that postural stability was rapidly improved by five trials for young adults. It was presumed that postural control adaptability was evaluated by the change rate of postural stability during five trials. For elderly people, a large individual difference has been observed in a deterioration of the adaptability, which will be affected by decline of cognitive function. Therefore, we evaluated the postural control adaptability using the oscillation table and investigated the improvement in P300 by the balance board training in elderly subjects with different postural control adaptability. 2. Methods Subjects were 6 males and 25 females, aged 61–80 years (mean 70.4). All subjects appeared to be free of any neurological or orthopaedic impairment. The measurement of the adaptability of postural control was performed with subjects standing on an oscillation table with a force platform. The platform was used to record fluctuation in the center of foot pressure (CFP) in an anteroposterior direction. The table was oscillated sinusoidally with 0.5-Hz frequency and 2.5-cm amplitude in the anteroposterior direction. The subjects were seated on a chair during the measurement of ERP. The ERP was recorded from electrodes affixed to the scalp at Pz and referred to linked ear lobes. The signal from the electrodes was amplified (40,000) and band-pass filtered (0.5–100 Hz). The electrooculogram (EOG) was recorded from a pair of electrodes placed above and below the left eye. Trials on which either the EEG or EOG exceeded a preset threshold of 100 AV were rejected. Electromyograms were recorded using bipolar surface electrodes placed over the flexor carpi ulnaris muscle on the right side. The signals from the electrodes were amplified (2000) and band-pass filtered (1.6 Hz to 1.5 kHz). Equilibrium training was carried out with a balance board for 3 weeks. The balance board consisted of a 24.5502-cm wooden board with a 2.224.52.2-cm wooden square pillar attached in the center. The maximum inclination of the board was 58. The subjects stood on the balance board with their eyes open. Standing foot positions coincided with the following 3 points being aligned with the square pillar: the middle of the longitudinal foot arch, the thenar eminence and the distal end of the tibia. To maintain the board in a horizontal position, CFP had to be maintained in the base area of the square pillar. Training time at each position was 2 min for a total of 6 min a day. Measurement of the adaptability of postural control was carried out while standing with eyes closed and with their bare feet 10 cm apart and parallel. Quiet standing posture was maintained on an oscillation table for 10 s, after which the table was oscillated for 60 s. This task was performed five times inserting a 60-s seated rest between trials.
K. Fujiwara et al. / International Congress Series 1278 (2005) 329–332
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ERP (P300) was measured in an oddball paradigm executed by the finger flexion task, before and after the training. Stimulus tones were randomly presented binaurally with an interval of 1.5 s, duration of 50 ms and rise/fall times of 10 ms. The target tone was 2 kHz and the non-target tone 1 kHz, which was presented at 0.15 and 0.85 probabilities, respectively. The stimuli were tone burst. Tone level was set at 55 dB above each individual’s sensation threshold. Subjects were instructed to flex their third to fifth fingers as fast as possible when they detected the target. This task was conducted 30 times. The electrical signal of the CFP for 10–60 s from the start of oscillation was sent to a computer and mean speed of CFP (mm/s) in the anteroposterior direction was calculated. We previously reported that mean speed of CFP is influenced by height of center of mass rather than weight. Therefore, measurement value was corrected by each subject’s height according to the following formula: measurement value160/height. Adaptability was evaluated by the extent of improvement in postural steadiness, which was assessed by the distribution of mean speed of CFP in the first and fifth trials. This evaluation was based on comparison with the regression line and standard error of mean speed in young adults. The data of all young adults (N=109) were distributed within regression line ( y)F2S.E. ( y=0.38x+20.66, S.E.=12.89). The elderly data distributed within this area were evaluated as high adaptability, the other data as low adaptability (Fig. 1). The analysis time for EEG and EMG was 900 ms beginning at 180 ms prior to the auditory stimulus onset. The ERPs of each subject were the result of averaging over approximately 15 artifact-free EEG waveforms. The reaction time was defined as the EMG onset latency of flexor carpi ulnaris muscle to the target stimulation in oddball paradigm. The clear positive change by the training in latency and amplitude of P300 was defined as the difference above 0.13 S.D. The alpha level was set at pb0.05. 3. Results The number of the subjects who belonged to the high and low adaptability group (HA and LA) were 18 and 13, respectively. P300 latency shortened significantly by the training in HA, the difference between before and after the training was 10.4 (S.D. 21.1) ms. In contrast, the latency showed no significant difference by the training in LA, the difference was 9.8 (S.D. 34.2) ms. The difference between two groups was not significant. P300 amplitude tended to increase by the training in HA, the difference was 1.3 AV (S.D. 3.9). P300 amplitude tended to decrease by the training in LA, the difference was 2.0 AV (S.D. 3.6). The difference between the two groups was significant (Fig. 2). Only in LA, a
Fig. 1. Evaluation of postural control adaptability to floor oscillation.
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Fig. 2. Latency and amplitude of P300 before and after balance board training.
significant negative correlation was found between P300 amplitude before the training and its difference between before and after the training (r= 0.71). Subjects were classified based on the improvement of either latency or amplitude of P300. The numbers of improved and unimproved subjects were 15 and 3 in HA, and 6 and 7 in LA, respectively. The ratio of subject numbers in HA was significantly larger than that in LA (v 2=4.77). The reaction time after the training was significantly shorter than that before the training in both adaptability groups. 4. Discussion A significant difference was found in the improvement in P300 by the balance board training between two groups that were classified based on the adaptability to floor oscillation. Many subjects in HA showed the improvement in either latency or amplitude of P300, while not in LA. This suggests that there is a common element between postural adaptation process during the floor oscillation and training process with a balance board. The element should be the plasticity of cognitive function. It is significant to be able to predict the training effect of the equilibrium function to which the cognitive function is strongly related by the floor oscillation test for only 5 min. In the low adaptability group, P300 amplitude decreased after the balance board training in the subjects whose amplitude was larger before the training. It is necessary to note that the balance board training in the subjects who have low adaptability may invite negative effects. In contrast to the result of P300, a significant improvement was observed in reaction time without any relation to the adaptability through the training. This confirms the finding that P300 is not related to a reaction process but related to the stimulation evaluation process [5]. References [1] G.E. Stelmach, et al., Age related decline in postural control mechanisms, International Journal on Aging and Human Development 29 (3) (1989) 205 – 223. [2] F.B. Horak, C.L. Shupert, A. Mirka, Components of postural dyscontrol in the elderly: a review, Neurobiology of Aging 10 (6) (1989) 727 – 738. [3] K. Fujiwara, et al., Dynamic balance training by balance board for the elderly, in: K. Yabe, K. Kusano, H. Nakata (Eds.), Adapted physical activity: health and fitness, Springer-Verlag, Tokyo, 1994, pp. 225 – 237. [4] J. Polich, P300 in clinical applications: meaning, method, and measurement, American Journal of EEG Technology 31 (1991) 201 – 231. [5] E. Donchin, Event-related brain potentials: a tool in the study of human information processing, in: H. Begleiter (Ed.), Evoked Potentials and Behavior, vol. 2, Plenum Press, New York, 1979, pp. 13 – 88.
www.ics-elsevier.com
Relationship between improvement in cognitive function by balance board training and postural control adaptability in the elderly Katsuo Fujiwara*, Michie Shigeiwa, Kaoru Maeda Human Movement and Health, Graduate School of Medical Science, Kanazawa University, Japan
Abstract. We investigated the improvement in cognitive function by balance board training in the elderly with different adaptability of postural control. Subjects were 31 healthy older adults. The adaptability to the floor oscillation (60 s5) was evaluated by the changing degree of body sway. The subjects performed the equilibrium training with a balance board for 3 weeks. P300 was measured in an oddball paradigm by the finger flexion before and after the training. Target (15%) and non-target sound stimulation were, respectively, 2 and 1 kHz with 55 dB above hearing threshold and 1.5-s interval. The subjects were divided into two groups according to the adaptability to floor oscillation. High adaptability group (HA) included 18 subjects who had same adaptability as young adults and the other subjects were included in low adaptability group (LA). The numbers of improved and unimproved subjects in P300 latency or amplitude were 15 and 3 in HA, and 6 and 7 in LA, respectively. The ratio of subject numbers in HA was significantly larger than that in LA. These results suggest that the improvement in the cognitive function by the balance board training is closely related to the adaptability to floor oscillation. D 2004 Elsevier B.V. All rights reserved. Keywords: P300; Postural control adaptability; Balance board training; Reaction time
1. Introduction Balance in the elderly is remarkably low compared with young adults under the nondaily conditions, in which visual and ankle kinesthesia information do not display a real postural change [1]. In addition, it was reported that postural control adaptability to a new environmental condition declined with aging, to which a cognitive function should be related [2]. We devised a balance board, and demonstrated that a balance reaction to floor * Corresponding author. 13-1 Takara-machi, Kanazawa, 920-8640 Japan. Tel.: +81 76 265 2225; fax: +81 76 234 4219. E-mail address: [email protected] (K. Fujiwara). 0531-5131/ D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ics.2004.11.051
330
K. Fujiwara et al. / International Congress Series 1278 (2005) 329–332
inclination in the elderly was improved by using it in training [3]. It is well expected that the training may improve a cognitive function to predict a postural change accompanied by an inclination of balance board. P300 is one of the assays of a cognitive function by an electroencephalogram. It may develop in the process in which a subject reacts to target sensory stimulations that rarely appear and in the preparation process for the next sensory stimulation [4]. It was reported that P300 latency increased with aging, and the amplitude tended to decrease. We have advanced the research on anticipatory postural control by using an oscillation table. The table was oscillated at 2.5-cm amplitude and 0.5-Hz frequency for 60 s. It was clarified that postural stability was rapidly improved by five trials for young adults. It was presumed that postural control adaptability was evaluated by the change rate of postural stability during five trials. For elderly people, a large individual difference has been observed in a deterioration of the adaptability, which will be affected by decline of cognitive function. Therefore, we evaluated the postural control adaptability using the oscillation table and investigated the improvement in P300 by the balance board training in elderly subjects with different postural control adaptability. 2. Methods Subjects were 6 males and 25 females, aged 61–80 years (mean 70.4). All subjects appeared to be free of any neurological or orthopaedic impairment. The measurement of the adaptability of postural control was performed with subjects standing on an oscillation table with a force platform. The platform was used to record fluctuation in the center of foot pressure (CFP) in an anteroposterior direction. The table was oscillated sinusoidally with 0.5-Hz frequency and 2.5-cm amplitude in the anteroposterior direction. The subjects were seated on a chair during the measurement of ERP. The ERP was recorded from electrodes affixed to the scalp at Pz and referred to linked ear lobes. The signal from the electrodes was amplified (40,000) and band-pass filtered (0.5–100 Hz). The electrooculogram (EOG) was recorded from a pair of electrodes placed above and below the left eye. Trials on which either the EEG or EOG exceeded a preset threshold of 100 AV were rejected. Electromyograms were recorded using bipolar surface electrodes placed over the flexor carpi ulnaris muscle on the right side. The signals from the electrodes were amplified (2000) and band-pass filtered (1.6 Hz to 1.5 kHz). Equilibrium training was carried out with a balance board for 3 weeks. The balance board consisted of a 24.5502-cm wooden board with a 2.224.52.2-cm wooden square pillar attached in the center. The maximum inclination of the board was 58. The subjects stood on the balance board with their eyes open. Standing foot positions coincided with the following 3 points being aligned with the square pillar: the middle of the longitudinal foot arch, the thenar eminence and the distal end of the tibia. To maintain the board in a horizontal position, CFP had to be maintained in the base area of the square pillar. Training time at each position was 2 min for a total of 6 min a day. Measurement of the adaptability of postural control was carried out while standing with eyes closed and with their bare feet 10 cm apart and parallel. Quiet standing posture was maintained on an oscillation table for 10 s, after which the table was oscillated for 60 s. This task was performed five times inserting a 60-s seated rest between trials.
K. Fujiwara et al. / International Congress Series 1278 (2005) 329–332
331
ERP (P300) was measured in an oddball paradigm executed by the finger flexion task, before and after the training. Stimulus tones were randomly presented binaurally with an interval of 1.5 s, duration of 50 ms and rise/fall times of 10 ms. The target tone was 2 kHz and the non-target tone 1 kHz, which was presented at 0.15 and 0.85 probabilities, respectively. The stimuli were tone burst. Tone level was set at 55 dB above each individual’s sensation threshold. Subjects were instructed to flex their third to fifth fingers as fast as possible when they detected the target. This task was conducted 30 times. The electrical signal of the CFP for 10–60 s from the start of oscillation was sent to a computer and mean speed of CFP (mm/s) in the anteroposterior direction was calculated. We previously reported that mean speed of CFP is influenced by height of center of mass rather than weight. Therefore, measurement value was corrected by each subject’s height according to the following formula: measurement value160/height. Adaptability was evaluated by the extent of improvement in postural steadiness, which was assessed by the distribution of mean speed of CFP in the first and fifth trials. This evaluation was based on comparison with the regression line and standard error of mean speed in young adults. The data of all young adults (N=109) were distributed within regression line ( y)F2S.E. ( y=0.38x+20.66, S.E.=12.89). The elderly data distributed within this area were evaluated as high adaptability, the other data as low adaptability (Fig. 1). The analysis time for EEG and EMG was 900 ms beginning at 180 ms prior to the auditory stimulus onset. The ERPs of each subject were the result of averaging over approximately 15 artifact-free EEG waveforms. The reaction time was defined as the EMG onset latency of flexor carpi ulnaris muscle to the target stimulation in oddball paradigm. The clear positive change by the training in latency and amplitude of P300 was defined as the difference above 0.13 S.D. The alpha level was set at pb0.05. 3. Results The number of the subjects who belonged to the high and low adaptability group (HA and LA) were 18 and 13, respectively. P300 latency shortened significantly by the training in HA, the difference between before and after the training was 10.4 (S.D. 21.1) ms. In contrast, the latency showed no significant difference by the training in LA, the difference was 9.8 (S.D. 34.2) ms. The difference between two groups was not significant. P300 amplitude tended to increase by the training in HA, the difference was 1.3 AV (S.D. 3.9). P300 amplitude tended to decrease by the training in LA, the difference was 2.0 AV (S.D. 3.6). The difference between the two groups was significant (Fig. 2). Only in LA, a
Fig. 1. Evaluation of postural control adaptability to floor oscillation.
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K. Fujiwara et al. / International Congress Series 1278 (2005) 329–332
Fig. 2. Latency and amplitude of P300 before and after balance board training.
significant negative correlation was found between P300 amplitude before the training and its difference between before and after the training (r= 0.71). Subjects were classified based on the improvement of either latency or amplitude of P300. The numbers of improved and unimproved subjects were 15 and 3 in HA, and 6 and 7 in LA, respectively. The ratio of subject numbers in HA was significantly larger than that in LA (v 2=4.77). The reaction time after the training was significantly shorter than that before the training in both adaptability groups. 4. Discussion A significant difference was found in the improvement in P300 by the balance board training between two groups that were classified based on the adaptability to floor oscillation. Many subjects in HA showed the improvement in either latency or amplitude of P300, while not in LA. This suggests that there is a common element between postural adaptation process during the floor oscillation and training process with a balance board. The element should be the plasticity of cognitive function. It is significant to be able to predict the training effect of the equilibrium function to which the cognitive function is strongly related by the floor oscillation test for only 5 min. In the low adaptability group, P300 amplitude decreased after the balance board training in the subjects whose amplitude was larger before the training. It is necessary to note that the balance board training in the subjects who have low adaptability may invite negative effects. In contrast to the result of P300, a significant improvement was observed in reaction time without any relation to the adaptability through the training. This confirms the finding that P300 is not related to a reaction process but related to the stimulation evaluation process [5]. References [1] G.E. Stelmach, et al., Age related decline in postural control mechanisms, International Journal on Aging and Human Development 29 (3) (1989) 205 – 223. [2] F.B. Horak, C.L. Shupert, A. Mirka, Components of postural dyscontrol in the elderly: a review, Neurobiology of Aging 10 (6) (1989) 727 – 738. [3] K. Fujiwara, et al., Dynamic balance training by balance board for the elderly, in: K. Yabe, K. Kusano, H. Nakata (Eds.), Adapted physical activity: health and fitness, Springer-Verlag, Tokyo, 1994, pp. 225 – 237. [4] J. Polich, P300 in clinical applications: meaning, method, and measurement, American Journal of EEG Technology 31 (1991) 201 – 231. [5] E. Donchin, Event-related brain potentials: a tool in the study of human information processing, in: H. Begleiter (Ed.), Evoked Potentials and Behavior, vol. 2, Plenum Press, New York, 1979, pp. 13 – 88.