BBC Science The Theory of (nearly) Everything 2019

THE FUNDAMENTALS OF LIFE

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5 event held in 1803 in London, for
example, Giovanni Aldini (nephew of
the pioneering anatomist Luigi
Galvani) applied electricity to George
Forster’s brain to show how it caused
the muscles of his face to twitch.
Forster didn’t know much about this

• he’d just been hanged for the murder
  of his wife and child. But for the
  audience it helped to show how
  electricity was part of the way that
  nerves communicate.
  Even as the scientific establishment
  came to recognise the brain’s
  functional significance, however,
  another mistaken dogma persisted –
  the idea that mental functions, such
  as language, are distributed uniformly
  throughout the cortex rather than
  being partly localised in specific
  brain regions.
  One historical patient played a
  particularly important role in helping
  to overturn this idea. His name was
  Louis Victor Leborgne, but he was
  nicknamed ‘Tan’, because this was
  virtually the only word he could utter.
  At autopsy, t he French neu rologist
  Paul Broca discovered that Leborgne
  had highly localised damage to a
  region in his left frontal cortex, known

today as Broca’s area, and he inferred

that the damaged region must play an

important role in speech.

Broca’s presentation of Leborgne’s

case to the Société d’Anthropologie

and the Société Anatomique in 1861

was instrumental in convincing the

academic community that language

function is particularly dependent

on the frontal lobes. The historian

Stanley Finger describes this moment

as a “key turning point in the history

of the brain sciences”. Patients like

Leborgne, wit h pa r ticula r mental or

physical def icits tied to specif ic a reas

of brain damage, have been one of the

most important sources of information

about the workings of the brain, and

this is still true today.

At the end of the 19th century, brain

science was focused once again on the

perplexing issue of how exactly nerves

ma nage to communicate wit h each

other. While the earlier realisation of

electricity’s role had helped to debunk

t he notion of a nimal spirits, it was

clear that there was more to nerve

communication. We k now today t hat

electrical current along a nerve cell

(neuron) causes it to release chemicals

across a tiny gap – a synapse – and

these chemicals, known as

neurotransmitters, are then picked

up on the other side by the receiving

neuron. In the late 1800s, however,

even the best microscopes and

staining methods were incapable of

revealing the presence of these gaps

between neurons. This led the Italian

scientist Camillo Golgi and his

contemporaries to propose that nerves

are fused together – an erroneous idea

known as the ‘reticular theory’ (from

the Latin for ‘net’).

It was the Spanish neuroscientist

Santiago Ramón y Cajal who killed

off the nerve net idea thanks to his

advances in cell staining techniques,

which made it clear that neurons are

not joined together after all.

Brain activity

In the 20th century, technology began

to play an increasingly important role

in advancing our knowledge of the

brain, pa r ticula rly by allowing

psychologists and neuroscientists

to monitor brain activity. In the

1920s, scientists sta r ted to use

electroencephalography (EEG), which

involves recording electricity emitted

by the brain through electrodes placed

425 BC

The Hippocratic treatise

On the Sacred Disease

states, contrary to the

dominant cardiocentric

view, that “from the brain

and the brain only arise our

pleasures, joys, laughter and

jests, as well as our sorrows,

pains, griefs and tears.”

C.130-210

In the 2nd century, the

philosopher Galen of

Pergamon performs the

pig demonstration (see

p74), showing that the

brain controls behaviour.

1543

Renaissance anatomist

Andreas Vesalius publishes

his landmark book On the

Fabric of the Human Body,

showing some of the

most detailed dissections

of the human brain

ever produced.

1848

Railway worker Phineas

Gage becomes one of the

most famous patients in

neuroscience after surviving

an accident in which an iron

rod passes straight through

the front of his brain,

changing his personality.

1830s

Phrenology reaches the

peak of its popularity. This

was the mistaken idea that

psychological aptitudes and

personality traits can be

discerned from the bumps

on someone’s skull.

“Previously, researchers had to make

assumptions. With EEG they could see how

different brain regions became more active”

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