Using vision to move through an area by foot, rather than crawling, uses a unique region of the brain’s cortex – which could help to explain developmental milestones in children as they learn to interact with and navigate their environments.
The occipital place area (OPA) part of the cortex is used when walking, but fails to activate during other modes of moving, new research found.
Navigating through a physical environment – anything from a small room to a city – requires the brain to process several classes of information. Each class of information is processed in its own region of the brain’s cortex, which then work together to support navigation behaviour, such as walking.
Loss of any one of these regions can affect how or whether someone can successfully navigate.
Two main areas of the cortex are activated as people navigate through an environment: the OPA and the retrosplenial complex (RSC).
The RSC supports map-based navigation, which involves finding our way from a specific place to some distant, out-of-sight place.
By contrast, the research indicates the OPA supports visually-guided navigation, which involves finding our way through near environment, avoiding boundaries and obstacles.
“We asked ourselves, does the OPA come on early but just mature slowly?,” Dr Daniel Dilks, of Emory University, Atlanta, said. “Or does crawling use an entirely different system?
“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.
“Based on our study, we think OPA is specifically tied to mature, efficient walking.”
While most adults and older children primarily navigate environments by walking, we retain the ability to crawl as we did in infancy. If OPA just matured slowly, then it should be activated by both modes of movement, Dr Dilks reasoned.
To test this, the research team recorded videos from the perspective of someone walking through an environment, and then similar videos from the perspective of someone crawling through that same environment.
They also patched together scrambled shots of the videos and took videos from a flying-over-the-environment perspective, to include a mode of navigation not accessible to humans.
When viewing videos, our brains often activate as if we were performing the activity ourselves – a sympathetic response that made Dr 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 were viewing each video and imagining themselves moving through the environment.
When the participants viewed the walking video, the region of the brain corresponding to the OPA was activated. But when they viewed the other videos – crawling, flying, or scrambled, OPA was not activated. In contrast, the RSC was activated when viewing all the videos, suggesting that only OPA is specific for walking, as opposed to other modes of visual navigation.
In addition, several other brain areas were activated when the participants viewed the crawling videos, suggesting additional regions that may be involved in navigation early in life.
The study was funded by the National Eye Institute (NEI), part of the National Institutes of Health.
