Researchers discovered that two main regions of the cortex were activated as people moved in various ways through an environment. But the occipital place area (OPA) didn’t activate during crawling, while the second region, the retrosplenial complex (RSC), did.
RSC supports map-based navigation, according to the researchers. This involves finding the way from a specific place to some distant, out-of-sight place.
Study co-author Daniel Dilks, of Emory University in Atlanta, has theorized that OPA supports visually guided navigation, such as moving through the kitchen without bumping into things.
His theory has been controversial, in part because the OPA doesn’t seem to support visually guided navigation until around age 8 and yet young kids still manage to walk through their homes before that and to crawl even earlier.
“We asked ourselves, ‘Does the OPA come on early, but just mature slowly?’” Dilks said. “Or does crawling use an entirely different system?”
If OPA just matured slowly, then it should be activated by both walking and crawling, Dilks reasoned.
To test this theory, he and his team recorded videos from the perspective of someone walking through an environment. They then made similar videos from the perspective of someone crawling through that same environment.
The researchers also patched together random shots of the videos and took videos from a flying-over-the-environment perspective, to include a mode of navigation not accessible to humans. People’s brains often activate when viewing videos in a way that it’s as if they were really doing the activity, the researchers explained.
Using functional MRI scans, the researchers were able to monitor the activation of different brain regions in 15 adults as they were viewing each video and imagining themselves moving through the environment.
When the participants viewed the walking video, the OPA region was activated. When they viewed the crawling, flying or scrambled videos, the OPA was not activated. The RSC was activated when viewing all the videos.
This suggests that only the OPA is specific to walking, the authors said.
Interestingly, several other brain areas were activated when the participants viewed the crawling videos, suggesting additional regions that may be involved in this early-life navigation.
The study, which was funded by the U.S. National Eye Institute (NEI), was published recently in the journal Cerebral Cortex.
“Not only does this study suggest that there’s a completely different brain system managing navigation in early versus late childhood, but it suggests that each of these pieces of the navigation system come on at different stages of development,” Dilks said in an NEI news release. “Based on our study, we think OPA is specifically tied to mature, efficient walking.”
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SOURCE: U.S. National Eye Institute, news release, March 15, 2023
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