Parkinson’s Researchers Shed Light on Brain Area Controlling Eye Movements

Swedish researchers report that the massive burden of prioritizing visual stimuli from our environment lies with the the superior colliculus area of the brain. This ancient part of the brain may provide clues regarding the mechanisms leading to Parkinson’s disease, where patients often have impaired eye movement.

The Karolinska Institute research paper, “Spatiotemporal interplay between multisensory excitation and recruited inhibition in the lamprey optic tectum,” was published in eLife.

The association between  Parkinson’s and multisensory entanglements is well-established. However, specific signaling pathways connecting neurons and motor centers are still puzzling for neuroscientists and frustrating for patients waiting for new therapeutic approaches.

In their study, which relies heavily on lead author Andreas Kardamakis’s previous work, researchers studied the concept of “multisensory integration” – the merging of different environmental messages – and how it may apply to the function of the superior colliculus.

When an event occurs that is detected by our senses, certain neurons in that part of the brain get activated, often leading to a response picked up by our muscles. But when two senses (such as vision and hearing) simultaneously report contradictory events, these neurons become less active and are less likely to respond.

The researchers, who conducted most of their experiments on lamprey fish, were able to shed light on the “neural circuit” of the optic tectum (the superior culliculus of the fish) with the muscle controlling areas of the brain stem.

The study solidifies scientific evidence that indicates there’s an area of the brain with the evolutionary safeguarded ability to refocus a person’s attention and alertness on a particular event — excluding supplementary messages from the rest of the brain.

But that concept may be considered controversial because many researchers agree that stimulus selection is also influenced by other brain regions, such as the cortex. Stimulus selection is the most important part in determining our level of  visual attention.

If scientists can figure out the factors that determine orientation perception, they will be better able to pinpoint what derails the system and causes problems with visual coordination, potentially leading to future therapeutic opportunities.

Future studies are required to determine whether the findings of the research team and the concept of “multiple, simultaneous stimuli reduces alertness” can provide causal links – genetic and environmental – between sensorimotor circuits and their mistranslated signaling in Parkinson’s and other neuromuscular diseases.