![]() ![]() It is the same with the brain: the higher the cognitive function, the higher the metabolic rate, the greater the blood flow and the larger the arteries that supply the blood. ![]() The greater a computer’s capacity, the more power it needs to stay running – and the bigger its electrical supply cables need to be. In this regard, we can view the brain as a rather energy-expensive supercomputer. This changes remarkably little, whether a person is awake, asleep, exercising or solving tricky maths problems. ![]() The human brain requires about 10 mL of blood every second. Because blood supplies essential oxygen to the brain, it’s closely related to synaptic energy use. To understand how much energy the brains of our ancestors used, we focused on the rate of blood flow to the brain. Human intelligence: why are we the smartest primates? Some 70% of that energy is used by the synapses to produce neurochemicals that transfer information between neurons. Although it occupies only 2% of the body, the brain uses about 20% of the energy of a resting person. The human brain contains more than 80 billion neurons and up to 1,000 trillion synapses. The synapses are the sites of information processing, much like the transistor switches of a computer. Information processing in the brain involves nerve cells (neurons) and the connections between them (synapses). Other studies of mammals in general indicate the brain’s metabolic rate – how much energy it needs to run – is nearly proportional to its size. This is not an unreasonable assumption for living primates, the number of nerve cells in the brain is almost proportional to the brain’s volume. Researchers have often assumed increases in intelligence in human ancestors (hominins) occurred as brains grew larger. ![]()
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