How the Brain Works The Facts Visually Explained by DK (z-lib.org)

48

THE PHYSICAL BRAIN

The Adult Brain 49

Disrupting memories

New brain cells help store information, so boosting

neurogenesis in the brain can improve learning into

adulthood. However, it also has a role to play in

forgetting. Adding in new brain cells with new

connections disrupts existing memory circuits

by competing with them. This means there is

an optimal level of neurogenesis, which balances

learning ability with retaining older memories.

New neurons

Neurons grow from stem

cells, dividing, specializing,

and maturing into

functional brain cells.

Memory storage

Due to the creation

of new brain cells,

hippocampal memories

may degrade before

they can be stored in

the cortex. This might

explain why we are

unable to remember

our infancy.

Neurogenesis

Neurogenesis is the development of new neurons by neural stem cells

(cells that can become other cells). In a range of mammals, neurogenesis

happens in the hippocampus and olfactory areas and continues

throughout life, with new neurons being produced regularly.

The same is thought to be true in humans, although the evidence is

mixed. Neurogenesis may also play a role in learning and memory.

TYPE 1

STEM CELL

TYPE 2B

STEM CELL

TYPE 3

STEM CELL

E A R LY

IMMATURE

NEURON

L ATE

IMMATURE

NEURON

MATURE

NEURON

TYPE 2A

STEM CELL

Axons and

dendrites

develop

Mature axons

and dendrites

allow neuron

to integrate

with cell

network

NORMAL

MEMORY PATH

DISRUPTED

MEMORY PATH

HIPPOCAMPUS CORTEX

Memory forms

in hippocampus

New neurons

develop in

hippocampus

Memory

retained

long-term

Memory

poorly

retained

Consolidation

disrupted by new

neurons

Memory

consolidated and

transferred to cortex

W

OR

K

M

OR

AL

ITY

FU

TU

RE

THE VOLUME OF

WHITE MATTER

IN A PERSON’S

BRAIN PEAKS

AROUND

AGE 40

US_048-049_Adult_brain.indd 49 20/09/2019 12:32