First author Anish Mitra, PhD, and Andrew Kraft, PhD – both MD/PhD students at Washington University – and colleagues decided to approach the mystery of the ultra-slow waves using two techniques that directly measure electrical activity in mice brains. In one, they measured such activity on the cellular level. In the other, they measured electrical activity layer by layer along the outer surface of the brain. They found that the waves were no artifact: Ultra-slow waves were seen regardless of the technique, and they were not the sum of all the faster electrical activity in the brain. Instead, the researchers found that the ultra-slow waves spontaneously started in a deep layer of mice’s brains and spread in a predictable trajectory. As the waves passed through each area of the brain, they enhanced the electrical activity there. Neurons fired more enthusiastically when a wave was in the vicinity. Moreover, the ultra-slow waves persisted when the mice were put under general anesthesia, but with the direction of the waves reversed.Nothing new about the existence of slow waves in the brain. Known as long as EEG has been around. The BIG part is the triggering or polling effect (enhancing electrical activity), and the BIGGEST part is the reversal when unconscious. How do senses come in to awareness and memory? Vision and hearing are processed first in a complex series of filtering centers in the brainstem. The resulting CODED signals describing movements of colors and shapes, and movements of frequencies and intensities, are then sent out to the cortex for high level comparison to memory templates. Match the formants with intonation, phonemes, morphemes, and grammar. The results of the match are then stored in memory for use in the next comparison. The outward polling would enhance or speed the movement of coded data from brainstem out to cortex. What happens when the polling shifts into reverse? Memories and patterns from the cortex flow better toward the centers of awareness in the brainstem, where they are treated as sensory data. DREAMS. = = = = = Later thought: The radial fibers (corona radiata) of the white matter wouldh't care much about this outward-moving stimulation. They are essentially wires from the cortex to the brainstem. The passage of charge waves might help to encourage flow of ions, especially on the part of the axon inside the myelin, which is a candidate for subconscious or dreamy action. The charge waves would have their best effect on the association fibers that tie various parts of the radial fibers together permanently or temporarily, creating patterns and templates. You can imagine them being activated in sequence: If we think about polling or scanning, the waves would be similar to sonar or radar, multiplexing different types of association into a time series. With normal sonar (bat or electronic) the sender calculates location of an object by the time between sent pulse and received pulse. In this type of scan the sender would be activating the various circumferential associations in sequence, and picking up the sequential results in the radial fibers. Maybe a better analogy would be the old acoustic delay line computer memories. = = = = = I went ahead and bought the full paper. For once the paid part contains more info than the abstract. Usually you don't get extra by paying. The first thing that stands out: In the mouse, each complete scan is about 10 seconds, though the wave as observed by experimental methods is not strongly periodic. This is much slower than breathing or heartbeat or motor response time. It's suggestively close to minimal attention span, which is 7 seconds in humans. We can be trained to hold attention longer, but TV producers know how to lock in phase with the 7 second basic span.
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