The Quanta Podcast Audio Edition: How Much Energy Does It Take To Think?
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Jan 8, 2026 Explore the fascinating balance of energy in our brains, which consume about 20% of our body's energy even at rest. Insightful research reveals that effortful thinking only slightly boosts energy use. Background processes dominate, keeping our neural systems running efficiently. The discussion connects evolutionary energy constraints to cognitive fatigue, illustrating how our brains prioritize prediction over reaction. Dive into the evolutionary trade-offs that shaped our brain's complexity and functionality.
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Brain Energy Mostly Fuels Maintenance
- The brain uses nearly as much energy at rest as during focused tasks, with active cognition adding only ~5% more consumption.
- Most energy supports baseline maintenance like membrane potentials and homeostatic regulation rather than conscious thought.
Brain's Disproportionate Energy Demand
- The human brain consumes
20% of the body's energy despite being ~2% of body weight, and infants use even more (50%). - ATP from glucose powers neuronal signaling delivered via an extensive cerebral capillary network.
Membrane Potentials Drive Baseline Cost
- Maintaining membrane potentials accounts for at least half of the brain's total energy budget and supports readiness to fire.
- Active task-related rises in neuronal firing explain the modest extra ~5% energy demand.