As people get older, their driving skills tend to diminish. Failing eyesight and heavy medication are often blamed for this phenomenon, but there might be a neurological reason...and it could help us better understand depression and schizophrenia.
Driving requires us to be able to spot any objects coming at us on the road, which means we need to be able to see the foreground well. But as humans age, their brains shift away from that, and older people become far more adept at see large-scale movement off in the distance. It's a subtle but fundamental difference in how younger and older people see the world...and one of them makes driving far more difficult.
This shift occurs because the middle temporal visual area of our brains decreases in power as we get older, and without this area it becomes more difficult to filter out background stimuli. Researchers were able to simulate this decrease in visual area function in younger people, and the volunteers all became far more aware of larger movements in the background of their vision. But there wasn't any concurrent reduction in foreground vision, meaning the volunteers' brains had to suddenly deal with far more visual stimuli, which would make paying attention during driving much more difficult.
As the researchers point out, similar types of vision and attention problems have been seen among those with depression and schizophrenia:
"These paradoxical results mimic special population findings, particularly patients with a history of depression who exhibit better-than-normal motion perception of large patterns coupled with normal perception of small, moving stimuli."
This suggests that the parts of the brain responsible for visual processing also play a role in these conditions. Figuring out what these areas do and why they malfunction could go a long way to better treatments for depression and schizophrenia.
[via Scientific American]