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

32

THE PHYSICAL BRAIN

Nuclei of the Brain 33

Action selection

The basal ganglia have an

important role in filtering out the

noise of competing commands

coming from the cortex and

elsewhere in the forebrain.

This process is called action

selection, and it occurs entirely

subconsciously through a series

of pathways through the basal

ganglia. Generally, these pathways

block or inhibit a specific action

by having the thalamus loop the

signal back to the start point.

However, when the pathway

is silent, the action goes ahead.

Basal ganglia loops

The route of the pathway depends on the

source of the inputs from the cortex or

elsewhere in the forebrain. There are three

main pathways, and each one is able to

inhibit or select an action. The motor loop

connects to the main movement control

center, the prefrontal loop carries input from

executive regions of the brain, while the

limbic loop is governed by emotional stimuli.

SOURCE INPUT

POINTENTRY

EXIT

POINT

THALAMUS

REGION

MOTOR LOOP PREFRONTAL LOOP LIMBIC LOOP

WHAT NUCLEI ARE

LOCATED IN THE

BRAIN STEM?

The Brain Stem Pituitary Gland

the 12 pairs of cranial nuclei.

They provide motor and

sensory function to the

tongue, larynx, facial

muscles, and more.

Motor, premotor,

somatosensory

cortex

Caudate

nucleus

REGIONS OF THE BASAL GANGLIA

NUCLEUS FUNCTION

Putamen

Globus

pallidus

Subthalamic

nucleus

Amygdala

Substantia

nigra

A motor processing center that involves procedural

learning of movement patterns and conscious

inhibition of reflex actions.

A motor control center, associated with complex

learned procedures such as driving, typing,

or playing a musical instrument.

A voluntary motor control center that manages

movements at a subconscious level. When damaged,

it can create involuntary tremors.

Although its precise function is not clear, this

structure is thought to be linked to selecting a specific

movement and inhibiting any competing options.

May play a part in integrating activity between

basal ganglia and limbic system, thereby considered

by some to be part of the basal ganglia.

Plays a role in reward and movement. Symptoms

of Parkinson’s disease (see p.201) are associated

with the death of dopamine neurons found here.

Dorsolateral

prefrontal cortex

Amygdala,

hippocampus,

temporal cortex

Lateral globus

pallidus, internal

segment

Globus pallidus;

pars reticulata in

substantia nigra

Ventral pallidum

Ventral lateral and

ventral anterior

nuclei

Mediodorsal and

ventral anterior

nuclei

Mediodorsal

nucleus

Putamen Anterior caudate Ventral striatum

THE BRAIN HAS

MORE THAN 30 SETS

OF NUCLEI, MO S TLY

PAIRED LEFT AND RIGHT

US_032-033_Nuclei_of_the_brain.indd 33 20/09/2019 12:32