It seems so easy to keep your head up. Yet this process involves one of the most complicated sensorimotor system of the human body, dr. Patrick Forbes found.
“Imagine yourself as a sleepy train passenger making the long journey home, your head creeping slowly down from upright as you drift into dreamland”, says Forbes. “Suddenly, BAM! An abrupt movement by the train jolts you awake, and just as quickly your neck instinctively returns to its vigilant state of maintaining a stable head posture.”
How does our sensorimotor system regulate such instinctive movements of the head? “It has a lot to do with the vestibular system, a series of sensory organs located just inside our ears that help us keep our balance”, says Forbes (3ME faculty). This system is more robustly connected with the neck muscles in comparison to muscles throughout the rest of our body, or so Forbes found out during his PhD research, which he defended earlier this month.
The Canadian researcher did experiments in which he applied electrical currents to healthy participants. He placed two electrodes behind the ears of his volunteers and ran a current through their heads. “Of no more than 5 milliamps”, he adds. “This is not really painful, though in a few subjects it can cause nausea.” This zapp activates neurons in the vestibular organ that make you believe that your head is moving.
When zapped in standing conditions, reflexes in leg muscles are evoked and participants automatically sway forward in an attempt to compensate for the perceived movement. If these participants are supported, and no longer need to balance, the reflex in leg muscles does not occur. Forbes’ research has demonstrated that vestibular reflexes in neck muscles are very different. When students sat with their heads supported, thereby removing the need to keep their head upright, this reflex in neck muscles still occurred. “This demonstrates a very robust and almost hard wired coupling between our vestibular organs and our neck muscles.”
Forbes, who graduated cum laude for his thesis, was also awarded a Marie Curie award which will allow him to continue working on a neck muscle project with TU Delft and University of British Columbia in Vancouver, Canada.

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