How Mental Map Development Affects How We Perceive the Visual World Around Us

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The brain is widely recognized as the most powerful organ of the human body. With our brains, we reason, learn, dream, plan, and perceive the world around us. Part of perception is the development of an internal mapping system based on visual cues. A new study from The Scripps Research Institute (TSRI), published in the Proceedings of the National Academy of Sciences journal, is challenging the way scientists look at the brain’s visual system, and the results could have implications for treating sensory processor disorders like autism.

Humans are trained to view the world as we move forward. After all, we are accustomed to walking or driving forward, and going backward feels unnatural. Researchers at TSRI have discovered that moving forward might have a tremendous impact on how we perceive the world. Moving forward might actually train the brain to sense the world normally, and the order in which we see objects might affect how we perceive time.

For example, if you drive down the street and pass a street sign, your brain will take note of its position behind you. If you keep driving and pass another sign, the brain will not only register the position of it relative to the previous sign but also the distance in time between them. In other words, the key to creating mental maps in the brain is sensing the sequence of objects as they pass into and out of our field of our visual field.

Scientists at TSRI, Hollis Cline and Masaki Hiramoto, analyzed this phenomenon by using transparent tadpoles to observe how nerve fibers, or axons, developed between the retina and the brain. These tadpoles were split into two groups, and one group was shown images on a computer screen with bars of light that moved past them from front to back. This simulated the normal front-to-back movement that humans experience. The other group saw the bars in reverse order which simulated moving backwards.


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The results demonstrated that the visual map of the tadpoles developed naturally when the bars moved from front to back. The tadpoles that where shown the images in reverse order, however, extended nerve fibers to the wrong spots in the map, confirming that the brain would perceive those images as backwards. By adding the element of order, this new study flies in the face of 50 years of neuroscience. It has long been believed that the sequence of neurons firing does not matter, only that neighboring neurons fired at about the same time.

The results demonstrated that the visual map of the tadpoles developed naturally when the bars moved from front to back. The tadpoles that were shown the images in reverse order, however, extended nerve fibers to the wrong spots in the map, confirming that the brain would perceive those images as backwards.

The results demonstrated that the visual map of the tadpoles developed naturally when the bars moved from front to back (A-P motion stimulus). The tadpoles that were shown the images in reverse order (P-A motion stimulus), however, extended nerve fibers to the wrong spots in the map, confirming that the brain would perceive those images as backwards. Figure: Haricot and Cline, 2014.

There is hope that this study could broader implications. Not only could this link between time and space apply to other senses such as touch and hearing but also offer possibilities of retraining the brain for those who have strokes. Discovering more about this connection between time and spatial cues could also help those suffering from temporal and sensory processing disorders including autism.

References

Harimoto, Masaki and Hollis T. Cline.  Optic flow instructs retinotopic map formation through a spatial to temporal to spatial transformation of visual informationPNAS 2014 111 (47) E5105E5113; doi:10.1073/pnas.1416953111.

The backwards brain? Study shows how brain maps develop to help us perceive the world. http://medicalxpress.com/news/2014-11-brain-world.html

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