Sometimes, you can picture something so vividly in your head that it feels as though you’re actually looking at what you’re imagining. But no matter how good your imagination is, information will flow through your brain in the opposite direction compared to when you actually perceive something. That’s the conclusion of a new study, published in NeuroImage, which looked at brain activity in participants when they were either watching clips or recalling them in their heads.
“A really important problem in brain research is understanding how different parts of the brain are functionally connected. What areas are interacting? What is the direction of communication?” lead scientist Barry Van Veen said in a news-release. “We know that the brain does not function as a set of independent areas, but as a network of specialized areas that collaborate.”
For the study, scientists from the University of Wisconsin-Madison and the University of Liege examined the activity of participants’ brains using a technique called electroencephalography (EEG). This uses a series of non-invasive sensors to measure electrical activity along the scalp that results from current flowing through brain cells, or neurons.
They were interested in looking at the flow of information through the cortex, which is the outer layer of the brain. In particular, they honed in on two areas: the parietal lobe and the occipital lobe. The former is a higher-order region involved in integrating and processing sensory information, such as touch and pain, and the latter is a lower-order region associated with interpreting visual stimuli and information.
After electrodes were placed on the participants’ scalps for recordings, they were given a series of short video clips before being asked to try to replay the content in their heads from memory. Next, the researchers asked volunteers to imagine riding a magical bicycle, focusing on various details such as shapes and colors, before playing them a short video of nature scenes.
Then, using an algorithm developed by the team to deconstruct the data, the scientists were able to determine the directionality of signal flow within the cortex. They found that during mental imagery, there was an increase in the flow of information from the parietal lobe to the occipital lobe, i.e. an increase in top-down signal flow. Conversely, during perception, the direction of information flow was reversed and the signal predominantly traveled from the bottom-up.
These intriguing new findings could one day help scientists understand more about patterns of brain activity during sleep and dreaming. Another possible future direction could be to apply the same methodology to further our knowledge of how the brain uses certain networks to encode short-term memory, which the researchers hope to eventually pursue.