The brain: inside the most complex system.
What do you and a London taxi driver have in common? You both use the hippocampus — a part of the brain that literally changes its size under load. Eleanor Maguire's research showed that London taxi drivers, who know 25,000 streets by heart, have a noticeably larger hippocampus than other people. The brain trains just like a muscle.
The average weight of the human brain is about 1.4 kg. That's 2% of body mass, but it consumes up to 20% of all energy. Our brain-to-body ratio is the largest of any species on the planet — and it's this, not absolute size, that determines cognitive abilities.
Ninety billion neurons is an impressive number, but it's not about the quantity of cells. Each neuron forms thousands of synaptic connections. By some estimates, the total number of synapses in the brain exceeds the number of stars in the Milky Way. The neural networks that arise from these connections are what we call thinking, memory, and personality.
The cerebral cortex is divided into four lobes — frontal, parietal, temporal, and occipital. The frontal cortex is responsible for decision-making and behavioral control. The parietal lobe handles spatial perception. The temporal lobe manages language and auditory processing. The occipital lobe processes vision. They don't work in isolation: every action, every thought is a coordinated effort of several areas working simultaneously.
The thalamus deserves special mention. It's called the "gateway to consciousness": almost all sensory information passes through it before reaching the cortex. The hypothalamus, the size of a pea, regulates body temperature, hunger, thirst, and hormonal balance. Small, but very influential.
In 2023, a team from Google and Harvard University created a three-dimensional map of a cubic millimeter of human cortex — 57,000 cells and 150 million synapses. Creating this map took years. A complete map of the entire brain is the next frontier of neuroscience.
Practice
Draw a diagram of the brain from memory and label what you remember from the lesson. This activates the hippocampus and reinforces information through the motor channel.
Homework
Find and watch a 3D visualization of neural networks (for example, on the Human Connectome Project website). Notice how complex even small fragments are — and this is only a part of what is happening in your head right now.