Overview
This lecture explores the myth that humans use only 10% of their brains and explains the true energetic demands and efficiency strategies of the human brain.
The 10% Brain Myth
- The myth claims we use only 10% of our brains, with the rest being unused potential.
- Two-thirds of the public and nearly half of science teachers believe this myth.
- The myth originated partly from William James, who meant to challenge, not limit, our mental effort.
- Early scientists misjudged the function of "silent" brain areas because damage didn't cause visible deficits.
Brain Function and Evolution
- Frontal and parietal lobes, once thought "silent," are essential for reasoning, planning, and adapting.
- Humans have more neurons packed densely in the brain than any other species.
- Human brains weigh 1.5 kg but consume 20% of adult daily glucose; much higher in children and infants.
- Cooking food allowed humans to support brains with 86 billion neurons, freeing time and energy.
Energy Consumption and Neural Activity
- The brain uses much of its energy maintaining electrical charges across neuron membranes.
- Brain consumes about 3.4 x 10^21 ATP molecules per minute.
- Most energy is used to keep neurons ready, not to transmit signals.
Efficiency and Sparse Coding
- Only 1%–16% of neurons are active at a time for optimal energy efficiency.
- Sparse coding minimizes energy use but maximizes information capacity.
- If too many neurons were inactive, evolution would have eliminated them.
Consciousness and Multitasking
- Most brain activity happens unconsciously to save energy.
- Attempting to multitask reduces the quality of performance due to energy limitations.
Key Terms & Definitions
- Frontal Lobes — brain regions involved in reasoning, planning, and decision making.
- Parietal Lobe — area important for integration and executive functions.
- Sparse Coding — strategy where only a small subset of neurons fire at once to optimize energy use.
- ATP — adenosine triphosphate, the cell’s energy molecule.
- Resting Potential — the electrical charge difference across a neuron's membrane at rest.
Action Items / Next Steps
- Review and debunk the 10% brain usage myth.
- Consider energy efficiency when studying brain function.
- Avoid multitasking to maximize cognitive performance.