Using vision to efficiently navigate through an area on foot uses a unique area of the cerebral cortex, according to a small study funded by the National Eye Institute (NEI). The area, called the occipital locus area (OPA), fails to activate during other locomotion modes, such as crawling. This finding may help explain developmental milestones as infants learn to interact with and navigate their nearby environments. The study was published in the journal cerebral cortex NEI is part of the National Institutes of Health.
Navigating through a physical environment—anything from a small room to a city—requires the brain to process several categories of information. Each category of information is processed in its own region of the cerebral cortex, which then works together to support navigational behaviour, such as walking. Missing any of these areas can affect how or whether a person can navigate successfully.
Two major regions of the cortex are activated as subjects navigate through an environment: the OPA and the retrograde splenic complex (RSC). Daniel Dilks, Ph.D., Emory University, Atlanta, finds that each of these areas supports a different type of mobility. RSC supports map-based navigation, which involves finding our way from a specific place to a remote, out-of-sight location (for example, finding our way from your home to your favorite restaurant). By contrast, OPA is believed to support visually-guided navigation, which involves finding our way through the nearby environment, avoiding boundaries and obstacles (for example, navigating through your kitchen without bumping into things).
However, his theory was controversial, in part because OPA did not appear to support visually guided navigation until about age 8. However, children are somehow managing to get around their homes and schools long before that time – even from early ages, when they’re crawling instead of walking.
“We asked ourselves, does OPA come early but mature slowly?” Dilks said. Or does crawling use a completely different system?
While most adults and older children navigate environments primarily by walking, we retain the ability to crawl as we did in childhood. If the OPA has matured slowly, it should be activated by both modes of motion, Dilks says. So, he and students Christopher Jones and Joshua Byland set out to find out if OPA would become active in adults when crawling.
To test this, the scientists recorded videos from the perspective of a person walking in an environment, and then similar videos from the perspective of a person crawling in the same environment. They also corrected random shots from the videos (mixed) and captured videos from the perspective of flying over the environment, to include a navigation mode not accessible to humans.
When watching videos, our brains often activate as if we were doing the activity ourselves—an empathic response that made the Dilks experiment possible. Using functional magnetic resonance imaging (fMRI), the researchers were able to monitor the activation of brain regions in 15 adult study participants as they watched each video and imagined themselves moving through the environment.
When the participants watched the walking video, the brain region corresponding to the OPA was activated. But when they watched the other videos—crawling, flying, or scrambling—the OPA wasn’t activated. In contrast, RSC was activated when viewing all videos, indicating that only OPA is for walking, in contrast to other visual navigation modes.
In addition, several other brain regions were activated when the participants watched the crawling videos, suggesting additional regions that may be involved in locomotion earlier in life.
“Not only does this study suggest that a very different brain system manages navigation in early versus late childhood, but it suggests that each of these parts of the navigation system comes at different stages of development,” Dilks said. “Based on our study, we believe that OPA is specifically associated with mature and efficient gait.”
The study was funded by the National Eye Institute (R01 EY29724).
video: https://youtu.be/g32ZGAHNHJo
