16 questions · Health & Medicine
On 13 September 1848 a blast in Vermont drove an iron rod more than a metre long through the head of a railway worker named Phineas Gage. He survived, was talking again within minutes and rode to the doctor sitting upright. Yet his friends said he was “no longer Gage”: the dependable foreman had become moody and erratic. For the first time, medicine suspected that even personality has a place in the brain. This organ weighs just under 1.4 kilograms but uses about 20 percent of the body’s energy. Its roughly 86 billion neurons swap chemical messengers at synapses: dopamine drives the reward system, serotonin is the target of many antidepressants. The cerebellum keeps us balanced, the brainstem runs breathing and heartbeat, the hypothalamus controls temperature, hunger and thirst, and the corpus callosum links the two hemispheres. Much of what we know comes from patients. In 1861 Paul Broca examined a man who could say only a single syllable and traced the damage to the region now called Broca’s area; a few years later Carl Wernicke described Wernicke’s area, which handles understanding speech. In 1953 a surgeon removed large parts of both hippocampi from the patient known as H. M., Henry Molaison, to ease his epilepsy. Afterwards he could no longer form new memories. Today researchers can watch the brain at work, from the EEG, which has recorded brain waves since 1924, to scans in which the amygdala lights up with fear.
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Cerebellum
It sits at the back of the head beneath the cerebrum and fine-tunes movements so that they run smoothly.
💡 Did you know? Although it makes up only about a tenth of the brain’s mass, it holds roughly four out of five of the brain’s nerve cells.
Brainstem
It links the brain to the spinal cord and is made up of the midbrain, the pons and the medulla oblongata.
💡 Did you know? Reflexes such as coughing, swallowing and sneezing are also triggered in the brainstem.
Hippocampus
It lies deep in the temporal lobe, one in each hemisphere, and also helps us find our way in space.
💡 Did you know? Its name means seahorse, because its curved shape resembles the animal.
Amygdala
This almond-shaped cluster in the temporal lobe judges whether a stimulus is threatening.
💡 Did you know? People whose amygdala is destroyed on both sides feel hardly any fear.
Hypothalamus
Weighing only a few grams, it also controls many hormones by way of the pituitary gland.
💡 Did you know? It also houses the body clock that sets our day and night rhythm.
Corpus callosum
It is made of about 200 million nerve fibres through which the left and right halves exchange information.
💡 Did you know? In severe epilepsy it used to be cut; such split-brain patients showed that each half has tasks of its own.
Broca’s area
Paul Broca described it in 1861 after examining a patient who could say only the syllable “Tan”.
💡 Did you know? That patient’s brain is still kept in Paris today.
Wernicke’s area
The German neurologist Carl Wernicke described it in 1874.
💡 Did you know? People with damage there often speak fluently but without meaning, and barely understand even simple sentences.
Neurons
A human brain contains about 86 billion of them.
💡 Did you know? A single neuron can be connected to as many as ten thousand others.
Synapse
There the electrical signal is usually translated into a chemical messenger that crosses a tiny gap.
💡 Did you know? The term was coined in 1897 by the British physiologist Charles Sherrington.
Dopamine
It is released above all when we expect a reward; in Parkinson’s disease the cells that make it die off.
💡 Did you know? Chemically, dopamine is the precursor of noradrenaline and adrenaline.
Serotonin
The drugs slow its reuptake into the nerve cell, so that it acts for longer.
💡 Did you know? Most of the body’s serotonin is made not in the brain but in the gut.
20 percent
An adult brain weighs just under 1.4 kilograms and needs a constant supply of sugar and oxygen.
💡 Did you know? Just a few minutes without oxygen can damage nerve cells for good.
Phineas Gage
The rod destroyed much of his left frontal lobe; afterwards the once level-headed foreman was seen as moody and unruly.
💡 Did you know? His skull and the iron rod are on display today in a museum at Harvard University.
Henry Molaison
To ease his severe epilepsy, a surgeon removed large parts of both his hippocampi.
💡 Did you know? His full name was made public only after his death in 2008.
EEG
Brain waves show up as traces; doctors use them to spot epilepsy and the stages of sleep.
💡 Did you know? The German psychiatrist Hans Berger recorded the first human EEG in Jena in 1924.
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