Have you ever wondered how we stay upright? Or have you noticed that while you nod your head your eyes shift and roll? Why do some people experience vertigo, giddiness or unsteadiness? Over the next short-while I will chat to you on Brainstorm Bites our podcast on brain health, these questions and maybe more can be answered.
When we were growing, one of the first systems to form was the balance system. In neuroscience, we call the balance system – part of the VESTIBULAR SYSTEM. The human brain is so dependent on a healthy vestibular system that not one area of the brain is dedicated to this function. In contrast, the visual system where the various aspect of what we see and the interpretation is dedicated and housed in a defined zone. The vestibular system gathers information from multiple regions.
Let's demonstrate.
You awaken from a deep sleep.
It is dark.
You are thirsty.
To resolve the thirst, you choose to fill a glass from the kitchen. The kitchen is situated along the hallway from the bedroom. Can you visualise this challenging journey! What strategies would be employed to support your balance?
A standard answer is holding and touching along the wall. TACTILE activation of somatosensory feedback.
Another answer is to become acutely aware of your movement and cautiously prowl along the hallway. PROPRIOCEPTIVE and spatial awareness from your joints and muscles is also valuable for food balance.
Finally, despite not fully dependent with the human brain is HEARING and the auditory system. Therefore, to support our balance, we utilise VISION, TACTILE, PROPRIOCEPTION and HEARING. So balance control is a cooperation of many regions and systems of the brain. Therefore good balance required good brain health.
Eyes are specialised organs for vision and ears are specialised organs for hearing; the VESTIBULAR APPARATUS which are located in the middle ear and primary senses for balance. Without getting too complicated, these apparatus very specialised nerve cells which can detect movement. The specific direction of the movement (like forward to the right) and quality (spinning vs linear) will signal to the vestibular nerve cell and carry to the brain information about this direction.
It is the collection of the information from the vestibular nerve cell to the brain that supports you upright. The actual process is quite complicated. However, if you can imagine a small spirit level. When the spirit level is off centre, an immediate adjustment is required. This adjustment could be a neck muscle – straightening the head, or even a leg muscle to shift the trunk over to the side. In fact, the brain is continuously adjusting and tuning the balance control.
The human brain is heavily dependant on visual information. As such, eye muscles are very tightly linked to the balance system. Therefore, the wired connections from balance centres will signal to the eye muscles in response to modification of the relative head positions. This hard-wired circuitry between the eye control and vestibular system is the pivotal cause of many balance problems.
A widespread balance problem, vertigo is defined as the sensation of spinning and turning. There are many causes of vertigo. However, a non-threatening and clinically familiar Vertigo is caused by a disruption to the communication between the eye control and vestibular system. Following a thorough neurological examination and special tests, some therapist would perform simple eye and head movements to stabilise this circuitry. Importantly, some forms of vertigo can be treated with appropriate therapy.
More Reading
Bayat, A., Pourbakht, A., Saki, N., Zainun, Z., Nikakhlagh, S., & Mirmomeni, G. (2012). Vestibular rehabilitation outcomes in the elderly with chronic vestibular dysfunction. Iranian Red Crescent Medical Journal, 14(11), 705–708. https://doi.org/10.5812/ircmj.3507
Boyer, F. C., Percebois-Macadré, L., Regrain, E., Lévêque, M., Taïar, R., Seidermann, L., … Chays, a. (2008). Vestibular rehabilitation therapy. Neurophysiologie Clinique = Clinical Neurophysiology, 38(6), 479–487. https://doi.org/10.1016/j.neucli.2008.09.011
Dieterich, M. (2004). Dizziness. The Neurologist, 10(3), 154–164.
Henriksson, M., Henriksson, J., & Bergenius, J. (2011). Gait initiation characteristics in elderly patients with unilateral vestibular impairment. Gait & Posture, 33(4), 661–667. https://doi.org/10.1016/j.gaitpost.2011.02.018
Herdman, S. J. (2007). Vestibular Rehabilitation. (S. J. Herdman, Ed.) (Third). Philadelphia: F.A. Davis company.
Pinter, M. M., & Brainin, M. (2012). Rehabilitation after stroke in older people. Maturitas, 71(2), 104–108. https://doi.org/10.1016/j.maturitas.2011.11.011
Whitney, S. L., Marchetti, G. F., Morris, L. O., & Sparto, P. J. (2007). The reliability and validity of the Four Square Step Test for people with balance deficits secondary to a vestibular disorder. Archives of Physical Medicine and Rehabilitation, 88(1), 99–104. https://doi.org/10.1016/j.apmr.2006.10.027
