Our brains are able to do some wonderful things. Yet, there are several processes which, while sophisticated enough, are mainly thought of as common and basic. For example: The reflex that allows us to keep our eyes centered on one point while our heads are moving about. This reflex is called the Vestibular-Ocular Reflex (or VOR), and that we share it with most vertebrates.
For a long time, scientists have thought that this reflex is controlled within the lower brainstem as a low-level process with little sophistication. Now, researchers from in the Imperial College in London are challenging this notion, suggesting this reflex is controlled by higher-level functions, for example those that determine handedness. These studies has led to a paper which has been published within the Journal of Neuroscience.
To better understand where this VOR process takes place, Qadeer Arshad and the colleagues sat volunteers on spinning chairs and showed them a number of optical illusions. These motorized chairs spun in a speed of 1 rotation every 4 seconds. Because these subjects were spinning, researchers measured just how long it took their eyes to sit in the spinning.
The subjects were then shown a number of bistable visual phenomena. These images are optical illusions which seem to switch between 2 different images, such as the duck which also appears to be the duck or even the candlestick that also looks like two people facing each other. Scientists believe a higher-level portion of the mental abilities are responsible for detecting these images and making sense of them. Therefore, Arshad and team weren’t expecting to find any link between VOR and this high-level process.
These researchers were surprised, then, once the volunteers had difficulty focusing their gaze on these images as they were spinning. The direction which these subjects were looking relied on their handedness, too. Right handed volunteers followed a rightward rotation, and vice versa.
“This is actually the first time that anything of the kind has been confirmed. Until recently, the Vestibular-Ocular Reflex was considered a low-level reflex, not really approaching higher-order brain function. Now it would appear that this primitive reflex was specialized into the cortex, negligence the brain which governs our sense of direction,” explained Arshad in a statement detailing his latest work.
Arshad said this study may be used to realise why people sometimes get dizzy solely by visual stimuli, for example flickering lights or crowded aisles inside a supermarket.
Professor Adolfo Bronstein, co-author from the paper, says that this research could help doctors understand why some patients experience constant dizziness.
“Most causes of dizziness begin with an body or vestibular disorder however this initial phase tends to settle very rapidly. In certain patients, however, dizziness turns into a problematic long term problem as well as their dizziness becomes visually induced. The experimental set-up we used would be ideally suited to help us understand how visual stimuli can lead to long-term dizziness. Actually, we have already carried out research at Imperial around using complex visual stimuli to treat patients with long-term dizziness,” explained Bronstein.
