Scientific American Sep 2018

(Jeff_L) #1
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 ●.
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