[O-KS-09-1] Effects of an auditory stimulus on postural control during choice stepping reactions in the elderly
キーワード：Postural control, External stimulus, Stepping reactions
【Purpose】
Falls among the elderly have serious consequences, in terms of injury and mortality. Impaired performance in reactive and volitional stepping has been recognized as a risk factor for falls. We have recently revealed that poor postural adjustments, caused by visual and auditory interferences, delay a step response time to external sensory stimuli（i.e., time from stimulus onset to foot-lift）in young adults（Watanabe, et al., 2015）. The purpose of this study was to investigate the effects of those interferences on postural control during stepping reactions among the elderly.
【Methods】
Healthy young and elderly participants stood on two force plates and stepped forward in response to a visual imperative stimulus（VS）presented on a PC monitor. For the VS, we used a choice reaction time task and the Simon task, which consisted of congruent（location and direction of an arrow is same）and incongruent（location and direction of an arrow is different）conditions. We also presented an auditory stimulus（AS）（80dB）in 50% of the trials. Temporal parameters of the stepping reaction and inappropriate postural adjustment rate were examined.
【Results】
AS reduced the reaction time, regardless of the task and conditions in both groups. The inappropriate postural adjustment rate was increased only in the incongruent condition for the young while it was increased in all the conditions for the elderly. The complete stepping error rate was also higher in the elderly.
【Discussion】
AS likely facilitated the automatic response toward the VS location in the young whereas it was detrimental for the elderly since it induced inappropriate postural adjustment even when VS location and direction matched. The young subjects might have also been able to associate the AS with locational information of the VS. The current results could be useful for the fall prevention programs.
Falls among the elderly have serious consequences, in terms of injury and mortality. Impaired performance in reactive and volitional stepping has been recognized as a risk factor for falls. We have recently revealed that poor postural adjustments, caused by visual and auditory interferences, delay a step response time to external sensory stimuli（i.e., time from stimulus onset to foot-lift）in young adults（Watanabe, et al., 2015）. The purpose of this study was to investigate the effects of those interferences on postural control during stepping reactions among the elderly.
【Methods】
Healthy young and elderly participants stood on two force plates and stepped forward in response to a visual imperative stimulus（VS）presented on a PC monitor. For the VS, we used a choice reaction time task and the Simon task, which consisted of congruent（location and direction of an arrow is same）and incongruent（location and direction of an arrow is different）conditions. We also presented an auditory stimulus（AS）（80dB）in 50% of the trials. Temporal parameters of the stepping reaction and inappropriate postural adjustment rate were examined.
【Results】
AS reduced the reaction time, regardless of the task and conditions in both groups. The inappropriate postural adjustment rate was increased only in the incongruent condition for the young while it was increased in all the conditions for the elderly. The complete stepping error rate was also higher in the elderly.
【Discussion】
AS likely facilitated the automatic response toward the VS location in the young whereas it was detrimental for the elderly since it induced inappropriate postural adjustment even when VS location and direction matched. The young subjects might have also been able to associate the AS with locational information of the VS. The current results could be useful for the fall prevention programs.