ScienceDaily has an item (here) on a paper (D. Dentico, B.L. Cheung, J. Chang, J. Guokas, M..e Boly, G. Tononi, B. Van Veen. Reversal of cortical information flow during visual imagery as compared to visual perception. NeuroImage, 2014; 100: 237) looking at EEC dynamics during thought.
The researchers examined electrical activity as subjects alternated between imagining scenes and watching video clips.
Areas of the brain are connected for various functions and these interactions change as during processing. The changes to network interactions appear as movement on the cortex. The research groups are trying to develop tools to study these changing networks: Tononi to study sleep and dreaming and Van Veen to study short-term memory.
The activity seems very directional. “During imagination, the researchers found an increase in the flow of information from the parietal lobe of the brain to the occipital lobe — from a higher-order region that combines inputs from several of the senses out to a lower-order region. In contrast, visual information taken in by the eyes tends to flow from the occipital lobe — which makes up much of the brain’s visual cortex — “up” to the parietal lobe… To zero in on a set of target circuits, the researchers asked their subjects to watch short video clips before trying to replay the action from memory in their heads. Others were asked to imagine traveling on a magic bicycle — focusing on the details of shapes, colors and textures — before watching a short video of silent nature scenes.”
The study has been used to verify their equipment, methods and calculations – could they discriminate the ‘flow’ in the two situations of imagining and perceiving. And it appears they could.
The actual directions of flow are not surprising. In perception, information starts in the primary sensory areas at the back of the brain. The information becomes more integrated as it moves forward to become objects in space, concepts and even word descriptions. On the other hand during imagining the starting points are objects, concepts and words. They must be rendered in sensory terms and so processing would be directed back towards the primary sensory areas. In both cases the end point would be a connection between sensory qualia and their high level interpretation. In perception the movement is from the qualia to the interpretation and in imagining it would be from the interpretation to the qualia.