Do you ever feel like you are actually doing, seeing, or experiencing the things in your daydreams? Perhaps the warm sand beneath your toes while you relax on the beach; the wind rushing through your hair while you drive a fancy sports car; the smooth finish of that fine wine you have been wanting to try. Even if you have never experienced these things before, your brain is recalling sensory information stored in your brain and processing it as abstract thoughts. But how does it do this?

Neuroscientists have long studied how information travels through the brain, but the complex and intricate web has spurred more questions than answers. Are there independent pathways or are there integrated conduits? What direction does information travel, and does it make a difference? While these answers are far from being decided, new evidence suggests that, when you are experiencing or perceiving something, information courses through your brain in the opposite direction as when you are imagining something.

To study brain activity during both visual input and imagination, researchers performed electroencephalography (EEG) on subjects when they were using their imagination and when they were receiving visual input. Some subjects watched short video clips before being asked to recall an image in their heads; other subjects were asked to imagine riding on a magical, flying bicycle before watching video clips. By analyzing the output of the EEG data, the study authors were able to determine the directional flow of information in the brain.

In short, during imagination, information flowed from the parietal lobe to the occipital lobe – from a high-order region that combines multiple sensory inputs to a lower-order region. During visual input, information flowed from the occipital lobe (the area that processes visual stimuli) to the parietal lobe. One hypothesis is that when the brain experiences something, the sensory stimuli get organized and stored; however, when the brain imagines something, it sorts through these stored bits of information and reorganizes them until they actually feel real.

Even if you have not experienced the exact thing that you are imagining, your brain has similar, previous experiences that are stored and ready to be recalled and formed into a new, almost-real experience.

This new information will be useful for engineers, scientists, and medical professionals because it will help build tools to evaluate just how the brain works. Understanding the anatomical and functional features of the brain will eventually assist victims of brain injury and people suffering memory impairment, as well as those involved in sleep and dream research.

References

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Dentico D, Cheung BL, Chang JY, Guokas J, Boly M, Tononi G, & Van Veen B (2014). Reversal of cortical information flow during visual imagery as compared to visual perception. NeuroImage, 100, 237-43 PMID: 24910071

Hamamé CM, Vidal JR, Ossandón T, Jerbi K, Dalal SS, Minotti L, Bertrand O, Kahane P, & Lachaux JP (2012). Reading the mind’s eye: online detection of visuo-spatial working memory and visual imagery in the inferior temporal lobe. NeuroImage, 59 (1), 872-9 PMID: 21839843

Mechelli A, Price CJ, Friston KJ, & Ishai A (2004). Where bottom-up meets top-down: neuronal interactions during perception and imagery. Cerebral cortex (New York, N.Y. : 1991), 14 (11), 1256-65 PMID: 15192010

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