50 Fun Facts About Neuroscience

Roughly how many neurons does the adult human brain contain?

There are about as many non-neuronal glial cells again, and the whole organ is only about 2% of body weight.

The brain uses roughly what share of the body's energy?

More than any other organ, for something that weighs a little over a kilogram.

The electrical signals neurons fire are called what?

A neuron's sequence of them is called its spike train; some plant and pancreatic cells fire them too.

Which animals are the only ones with no neurons at all?

The ability to fire electrical signals seems to have appeared 700 to 800 million years ago; plants and fungi never evolved it.

The junction across which one neuron signals to another cell is called what?

They come in chemical and electrical varieties; the electrical kind couples cells through gap junctions.

The fatty sheath that insulates axons and speeds up conduction is called what?

The gaps between segments, the nodes of Ranvier, let the impulse jump from node to node in what is called saltatory conduction.

Which glial cells wrap axons in their insulating sheath inside the brain and spinal cord?

In the peripheral nerves the same job is done by Schwann cells; glia make up over half the volume of neural tissue.

The cerebellum takes up only about 10% of the skull's contents by volume yet holds what?

The credit goes to its vast numbers of tiny granule cells; its name is Latin for 'little brain'.

The memory-forming structure deep in the temporal lobe is named after its resemblance to which animal?

The Venetian anatomist Aranzi first compared it to a silkworm in 1587 before settling on the seahorse.

Which limbic structure, named from the Greek for 'almond', is central to processing fear?

It was first identified and named by Karl Friedrich Burdach in 1822.

The thick fibre bundle that links the two cerebral hemispheres is found only in which group of animals?

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

Broca's area, linked to speech production, sits in which lobe?

Paul Broca identified it from two patients who had lost the ability to speak after injury there.

Which lobe of the cerebrum is dedicated to vision?

The one at the front of the head handles executive functions such as planning and self-control.

Phineas Gage survived an 1848 accident in which what passed through his head?

He was setting a blasting charge near Cavendish, Vermont; the case became known as the American Crowbar Case.

Patient H.M. lost the ability to form new memories after 1953 surgery removed most of which brain structure?

Henry Molaison's operation was meant to cure his epilepsy; he became the most studied patient in memory research.

Which two rivals shared the 1906 Nobel Prize for work on the structure of the nervous system?

The Italian's silver 'black reaction' stain let the Spaniard draw the neurons that disproved the Italian's own theory of a continuous network.

Santiago Ramón y Cajal was the first person from which country to win a scientific Nobel Prize?

Hundreds of his drawings of branching brain cells are still used for teaching.

Hodgkin and Huxley worked out how nerve impulses propagate using which animal's giant axon?

Their 1952 equations won the 1963 Nobel Prize and are still the standard conductance-based model of the neuron.

Otto Loewi's Nobel-winning proof that nerves signal chemically came to him how?

He woke on Easter Saturday 1921 unable to remember it, then dreamed it again the next night and went straight to the lab to stimulate a frog's heart.

Which neurotransmitter do motor neurons release to make muscles contract?

It is also the main transmitter of the parasympathetic nervous system, which is why drugs that block it can cause paralysis.

Modern pharmacology says dopamine signals not pleasure itself but what?

It flags how desirable or aversive an outcome is, pushing behaviour toward or away from it; it is made from L-DOPA in the brain and kidneys.

About 90% of the body's serotonin is made where?

Enterochromaffin cells in the gastrointestinal tract use it to regulate intestinal movement; only 1-2% is in the central nervous system.

Botulinum toxin causes flaccid paralysis by blocking neurotransmitter release where?

In heavily diluted form the same mechanism smooths wrinkles and treats migraine as Botox.

Tetrodotoxin takes its name from the order of fish that includes which species?

Blue-ringed octopuses and rough-skinned newts carry it too, and it is actually made by symbiotic bacteria.

The blood-brain barrier is formed mainly by which type of cell lining the brain's capillaries?

Astrocyte end-feet and pericytes complete the seal, which lets oxygen and hormones through but blocks most pathogens and antibodies.

Roughly how much cerebrospinal fluid does the human body produce each day?

Only about 125 mL is present at any one time; the rest is continually absorbed, cushioning the brain in the meantime.

The glymphatic system, which flushes waste from the brain, works hardest during what?

The extracellular space expands during deep sleep, which may be part of why sleep feels restorative.

Mirror neurons were first recorded in the premotor cortex of which animal, by Rizzolatti's team in Parma?

They fire both when the animal acts and when it watches another do the same thing; their function in humans is still debated.

Which husband-and-wife team discovered grid cells in the brain in 2005?

They shared the 2014 Nobel Prize with John O'Keefe, who had found hippocampal place cells decades earlier.

Place cells fire when an animal is in a particular spot; collectively they are thought to form what?

They are pyramidal neurons in the memory-forming region of the temporal lobe, and they can suddenly 'remap' when the environment changes.

How many neurons does the roundworm C. elegans, the first organism with a complete wiring diagram, have?

The transparent millimetre-long worm was also the first multicellular organism to have its whole genome sequenced.

Optogenetics lets researchers switch specific neurons on and off using what?

The neurons are engineered to express light-sensitive ion channels; the technique has partially restored vision in a blind patient.

EEG electrodes are placed on the scalp according to which standard layout?

The signals mainly reflect postsynaptic potentials of pyramidal neurons; alpha waves run at 8 to 13 Hz.

Prosopagnosia is the inability to recognise what?

The developmental form affects about 2 to 2.5% of people, and the fusiform gyrus is the region usually implicated.

Split-brain syndrome results from cutting which structure, usually as a last resort for epilepsy?

One patient reportedly pulled his trousers up with one hand and down with the other, each hemisphere with its own intention.

The cortical homunculus, a distorted 'little man' mapping the body onto the brain, is linked to which neurosurgeon?

He mapped it by stimulating the cortex of awake patients, who reported sensations, memories and even déjà vu.

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

An elephant's is just over 5 kg and a human's about 1.3 kg; size alone tracks intelligence poorly.

Neuroplasticity was once thought to occur only during what stage of life?

Later 20th-century research showed the adult brain keeps rewiring, though the developing brain is more plastic.

The neocortex is made up of how many layers of neurons?

The evolutionarily older allocortex has only three or four.

The most important output neurons of the cerebellar cortex are named after which Czech anatomist?

Each receives thousands of weak inputs from granule-cell parallel fibres plus one extremely strong climbing fibre.

Otto Loewi shared his 1936 Nobel Prize with which lifelong friend?

The two met in 1902 in Ernest Starling's laboratory at University College London.

Eric Kandel called understanding learning, memory and consciousness the "epic challenge" of which field?

Neuroscience draws on physiology, molecular biology, psychology, physics, computer science and mathematics to attempt it.

Which Greek thinker from Croton first argued that the brain is the seat of sensation and thought?

Aristotle later argued the heart was the centre of intelligence and the brain merely cooled it, a view that held until Galen's observations of gladiators.

According to Herodotus, Egyptian embalmers drew the brain out through which part of the body?

The heart was believed to be the seat of intelligence, so the brain was routinely discarded during mummification from the late Middle Kingdom on.

Which German anatomist mapped the cerebral cortex into 52 numbered areas in 1909?

Brodmann areas, based on cell structure, are still used as anatomical reference points in modern neuroimaging.

Which sea slug did Eric Kandel use to study the biochemistry of learning and memory from 1966?

Its large, identifiable neurons made the changes underlying memory storage tractable to study.

Where was the first freestanding neuroscience department founded in 1964?

James L. McGaugh founded it; Stephen Kuffler's Department of Neurobiology at Harvard Medical School followed in 1966.

In which year was the Society for Neuroscience, the field's largest professional body, founded?

By 2010 it had grown to more than 40,000 members from 83 countries, with an annual meeting held in a different American city each year.

In which year was the US BRAIN Initiative announced?

The International Brain Initiative followed in 2017, linking national programmes across four continents.

What is the name of the worldwide neuroscience competition for high-school students?

It is one of several outreach efforts by neuroscientists, alongside primers such as the Society for Neuroscience's Brain Facts.