50 Fun Facts About The Human Brain

Roughly how many neurons does the human brain contain?

There are about as many non-neuronal cells again, mostly glia; the cerebellum alone holds most of the neurons.

About what share of the body's energy does the brain consume?

That is more than any other organ, from roughly 2% of body weight; it also takes about a quarter of the body's glucose.

The adult human brain weighs on average about how much?

Men's brains average about 1370 g and women's about 1200 g, with wide individual variation.

What everyday food is the living brain's consistency compared to?

That softness is why the brain floats in cerebrospinal fluid inside the skull rather than resting on bone.

Which three main parts make up the human brain?

The cerebrum is by far the largest; the brainstem links it to the spinal cord and the cerebellum sits behind.

The four lobes of each hemisphere are named after what?

Frontal, parietal, temporal and occipital all share names with the bones of the skull above them.

Which lobe of the brain is dedicated to vision?

It sits at the back of the head and holds most of the visual cortex; the frontal lobe handles planning and self-control.

Which is the largest lobe of the vertebrate brain?

The frontal lobe is also the most forward lobe, and the one Phineas Gage's tamping iron passed through in 1848.

What is the name of the largest bundle of fibres connecting the two hemispheres?

It is the brain's largest white-matter structure, about 10 cm long with 200–300 million axons.

Roughly how many axonal projections run through the main bridge between the hemispheres?

It is about 10 centimetres long; severing it was once used to treat severe epilepsy.

How thick is the cerebral cortex, the brain's folded outer layer of grey matter?

Its deep folds pack far more surface area into the skull; the neocortex has six layers of neurons.

How many neuronal layers does the neocortex have?

The older allocortex, which includes the hippocampus, makes do with three or four.

The cortex is mapped into about fifty functional regions named after which anatomist?

Korbinian Brodmann's areas look distinctly different under the microscope; Area 17 is the primary visual cortex.

About what fraction of total brain volume is white matter?

White matter is mostly myelinated axons, the insulated wiring beneath the grey-matter cortex.

What does the brainstem consist of?

The medulla holds the centres for heart rate, breathing and blood pressure.

Which part of the brainstem contains the centres controlling heart rate, breathing and blood pressure?

It is the lowest part of the brainstem, continuous with the spinal cord.

The name of the structure behind the brainstem means what in Latin?

The cerebellum occupies about 10% of brain volume yet contains more neurons than the rest of the brain combined.

Which brain region holds more neurons than all the rest of the brain combined, in only 10% of its volume?

Its tiny granule cells account for the numbers; damage produces problems with balance, posture and fine movement.

Which structure is named from the Greek for 'seahorse' because of its curved shape?

Venetian anatomist Julius Caesar Aranzi first likened it to a silkworm in 1587 before settling on the seahorse.

Which structure consolidates short-term memories into long-term ones and supports spatial navigation?

It is one of the first regions damaged in Alzheimer's disease, which is why memory loss is an early symptom.

Which almond-shaped structure in the temporal lobe is central to processing fear?

Its name comes from the Greek for almond; there is one in each hemisphere.

Which structure links the nervous system to the endocrine system via the pituitary gland?

About the size of an almond, it also regulates body temperature, hunger, thirst, sleep and circadian rhythms.

Which small organ produces melatonin and was called 'the principal seat of the soul' by Descartes?

Melatonin is derived from serotonin and tracks the day–night cycle; the gland is named for its pine-cone shape.

What are the three membranes covering the brain and spinal cord collectively called?

From the outside in they are the tough dura mater, the arachnoid mater and the delicate pia mater.

Which of the three membranes around the brain is the tough outermost layer?

Cerebrospinal fluid sits in the subarachnoid space between the arachnoid and the pia.

How many interconnected ventricles produce and circulate cerebrospinal fluid inside the brain?

About 500 ml of fluid is made each day, though only around 125 ml is present at any one time.

Suspended in cerebrospinal fluid, a 1,400-gram brain has an effective weight of about how much?

That buoyancy is what stops the soft brain from crushing itself against the skull.

Paul Ehrlich's injected dyes famously stained every organ in his test animals except which one?

Ehrlich was studying staining for microscopy; the barrier is a selective layer of endothelial cells.

The blood–brain barrier remains permeable to which of these?

It passes water, oxygen, carbon dioxide and most fat-soluble substances, which is why anaesthetics work.

Which vessels supply blood to the front of the brain?

The vertebral arteries feed the back; a loss of blood supply is a stroke.

Language functions sit in the left hemisphere in what share of right-handers?

Among left-handers the figure is only about 60%; Broca's and Wernicke's areas are the classic examples.

Which frontal-lobe region, usually on the left, is linked to speech production?

Pierre Paul Broca identified it after studying two patients with impaired speech; damage causes expressive aphasia.

What word for the brain's supportive cells comes from the Greek for 'glue'?

They were once thought to be mere glue holding neurons together; they make up over half the volume of neural tissue.

Which glial cells form myelin in the central nervous system?

Each sends out foot processes to wrap several axons; in the peripheral nerves, Schwann cells do the job.

What are the electrical signals fired by neurons called?

Neurons have the usual cell parts plus an axon and dendrites; a motor neuron's axon can run over a metre to the toes.

How long can the longest axon of a human motor neuron be?

It reaches from the base of the spine to the toes.

Which Spanish anatomist established the neuron as the nervous system's basic unit, sharing the 1906 Nobel?

He refined Golgi's silver stain to draw individual neurons, and was the first Spaniard to win a scientific Nobel.

Who introduced the word 'synapse' in 1897?

He coined it for Michael Foster's Textbook of Physiology; synapses can be chemical or electrical.

Who recorded the first human EEG, in 1924?

The German psychiatrist named the first rhythm he saw the alpha wave (8–13 Hz).

What frequency range defines an alpha wave on an EEG?

Beta waves run 13–30 Hz; the slow delta waves dominate deep sleep.

In 1848, what was driven through Phineas Gage's head, destroying much of his left frontal lobe?

The Vermont railroad foreman lived another 12 years, and his changed behaviour made him a landmark case in neuroscience.

What was Phineas Gage's job when his accident happened in Vermont?

He was tamping explosive into a rock hole south of Cavendish when the charge went off.

Patient H.M. could not form new memories after 1953 surgery removed most of which structures?

The operation was meant to cure his epilepsy; his working and procedural memory stayed intact.

Which Portuguese neurologist won a 1949 Nobel Prize for developing the lobotomy?

Walter Freeman later championed a version performed with an ice pick; the award remains controversial.

Which 19th-century pseudoscience tried to map personality onto regions of the skull and cortex?

Modern imaging such as fMRI and EEG replaced bumps on the head as a way to localise function.

Which extinct human relatives had brains larger than modern Homo sapiens?

They died out about 40,000 years ago; size alone does not track intelligence.

Which animal has the largest brain of any species, at about 8 kg?

That is roughly six times the weight of a human brain.

A concussion is also known medically as what?

It temporarily affects brain function; repeated concussions are linked to longer-term problems.

By how much does the brain's energy use rise during a focused mental task, according to Raichle's lab?

The finding helped reveal the 'default mode network', which stays busy when we are resting.

What is the term for the brain's ability to reorganise itself through growth and new connections?

It underlies learning and recovery after injury.