Zheng, Jieyu and Meister, Markus, The unbearable slowness of being: Why do we live at 10 bits/s? Neuron, Dec. 17, 2024, doi: 10.1016/j.neuron.2024.11.008
Summary: This article is about the neural conundrum behind the slowness of human behavior. The information throughput of a human being is about 10 bits/s. In comparison, our sensory systems gather data at ?109 bits/s. The stark contrast between these numbers remains unexplained and touches on fundamental aspects of brain function: what neural substrate sets this speed limit on the pace of our existence? Why does the brain need billions of neurons to process 10 bits/s? Why can we only think about one thing at a time? The brain seems to operate in two distinct modes: the ?outer? brain handles fast high-dimensional sensory and motor signals, whereas the ?inner? brain processes the reduced few bits needed to control behavior. Plausible explanations exist for the large neuron numbers in the
From section 8 of the article:
The discrepancy between peripheral processing and central cognition suggests that the brain operates in two distinct modes: The “outer brain” is closely connected to the external world through sensory inputs and motor outputs. This is a realm of high dimensionality: many millions of sensory receptors and muscle fibers, and extremely high information rates. The “inner brain”, on the other hand, operates on a dramatically reduced data stream, filtered to the essential few bits that matter for behavior at any one moment. The challenge for the inner brain is to combine the animal’s goals with current inputs from the world and previous memories to make decisions and trigger new actions. The information rates are very low, but the processing must remain flexible because context and goals can shift at a moment’s notice. A number of interesting research questions emerge regarding the relationship between the inner and outer brain.
From Carl Zimmer's NYTimes article about this research:
Britton Sauerbrei, a neuroscientist at Case Western Reserve University who was not involved in the new study, questioned whether Dr. Meister and Ms. Zheng had fully captured the flow of information in our nervous system. They left out the unconscious signals that our bodies use to stand, walk or recover from a trip. If those were included, “you’re going to end up with a vastly higher bit rate,” he said.
But when it comes to conscious tasks and memories, Dr. Sauerbrei said, he was convinced that very little information flows through the brain. “I think their argument is pretty airtight,” he said.
Martin Wiener, a neuroscientist at George Mason University, said that the new study should prompt researchers to compare our information flow with that of other animals.
“A lot of people haven’t paid attention to other species,” Dr. Wiener said. It’s possible that some animals will get by on even slower rates of information. Or perhaps flying insects that make split-second changes to their flight patterns enjoy torrents of information flowing through their brains that we mere humans can only imagine.
