Mild electrical stimulation just behind the ear seems to boost our balance and makes us walk more quickly with longer strides. The finding could lead to a device that helps people with balance disorders get around more easily.
When we move, hairs in our inner ears detect changes in speed and feed this information back to the brain, helping to stabilise vision and posture, improving our balance. Shinichi Iwasaki, at the University of Tokyo, Japan, and his colleagues have found that electrical stimulation seems to enhance this, prompting people to walk faster.
To target the hair cells of volunteers, his team placed electrodes over their mastoids 鈥� a part of the skull just behind the ear. They used these to deliver electrical current that fluctuated in frequency, making it a 鈥渘oisy鈥� signal 鈥� but not in the audible sense. In previous experiments, the team had found that this kind of stimulation while standing still.
Advertisement
This time, the team asked participants to wear a portable stimulator and walk at a speed they felt comfortable with for 15 metres. In this experiment, 19 people were exposed to this kind of stimulation at a range of currents up to 1000 microamps, and with no current at all.
Longer strides
They found that stimulation at any level above 50 microamps made a person鈥檚 stride longer and faster, but they got the best results at around 300 microamps, at which point people walked 15 per cent faster on average. The participants didn鈥檛 notice the stimulation until it was more than around 420 microamps. 鈥淎bove this level, they feel a slight tingling,鈥� says Iwasaki.
To see if this could help people who have difficulty balancing, the team tested the technique on 12 volunteers with bilateral vestibulopathy 鈥� a condition in which people struggle to balance and are at risk of falling over when they walk.
Usually, these volunteers all had a shorter stride length and slower walking speed than the other participants, but this improved when they received the stimulation. The strongest effects were seen at around 700 microamps, which increased speed by an average of 12.8 per cent, helping them to walk almost as well as if they didn鈥檛 have bilateral vestibulopathy.
Iwasaki thinks stimulation might have these effects because the noisy signal triggers the body鈥檚 balance system to become more fine-tuned, enhancing signals from the inner ear balance organs. The team is developing a stimulation device they hope will one day help people with vestibulopathy in their everyday lives.
Brain Stimulation
Read more: Robot physical therapist helps people walk again after a stroke
