Scientific American - September 2018

September 2018, ScientificAmerican.com 61

FOXP2 SRGAP2C NOTCH2NL

Mirror neuron system Language circuit

Von Economo neuron Synapse Dopamine

(cell junction)

Primary motor cortex

Premotor cortex

Premotor cortex

Primary motor cortex

Primary somatosensory cortex

Primary somatosensory cortex

Prefrontaaaalclcl clcortooex xexpansion

Prefrontal cortex

ParParParParParietietietietietalal al aassa ociation cortex

Parrietietietietaal aaassociation

corccccccc texexxxexeepansionn

Primary

visual cortex

Primary

visual cortex

TemT poral

association

cortex Cerebellum Cerebellum

Broca’s area

Striatum

Temporal

association

cortex expansion Striatum

Vocal control

Primary auditory cortex

Primary auditory cortex

Wernicke’s area

Higher-order

visual cortex

Higher-order

visual cortex

CIRCUITS

The mirror neuron

system, activated when viewing

the actions of others, has intricate

circuitry in humans ●A. Expanded

connections between two sites—

Wernicke’s and Broca’s areas—form a vital

circuit for language processing ●. A link

from the motor cortex to the brain stem

coordinates the larynx muscles, a

circuit absent in chimpanzees

and macaques ●.

REGIONAL EXPANSION
Brain areas responsible for higher cognitive functions grew disproportionately in humans
compared with the same regions in chimpanzees—among them, the prefrontal, temporal
association and parietal association cortices.

A  

A  

A  

CELLS

Von Economo neurons,

which are pivotal in social-

emotional brain circuits, are bigger in

humans ●A. RNA that carries messages

to instruc t cells to make proteins is more

ac tive in the synapses of the prefrontal cor tex

( dark area ) than it is in other primates ●.

Cells produce more of the neurotransmitter

dopamine in the striatum. Dopamine

is involved in various cogni tive

functions ●.

GENES

The variant of the

FOXP2 gene found in humans

plays a role in vocal learning ●A.

SRGAP2C, a unique duplicate of

SRGAP2 that is found only in humans,

increases the density of neural

connections ●. A human version

of a gene called NOTCH, known as

NOTCH2NL, has three copies

and aids in the production

of neurons ●.