Basal Ganglia Review

Basal ganglia input nuclei

Putamen, caudate, nucleus accumbens

Basal ganglia output nuclei

globus pallidus internus, substantia nigra pars reticulata

Basal ganglia associated nuclei

globus pallidus externen, subthalamic nucleus, substantia nigra pars compacta

Striatum

putamen, caudate

ventral striatum

nucleus accumbens

Direct pathway allows for

initiation of motor program

Indirect pathway will

stop or interrupt ongoing motor programs, functions as a ‘noise filter’

Acts as a pause button on baseline thalamic and brainstem inhibition

direct pathway

enhances baseline inhibition of thalamus and brainstem

indirect pathway

tonic inhibitions in basal ganglia

GPe to Subthalamic nucleus and GPi to VA/VL of thalamus

Basal ganglia loops

motor, oculomotor, executive, limbic

Motor loop cortex

M1, SMA, PMC, CMA

Motor loop thalamus

VLo, VLm, VApc,

Basal ganglia loops pallidum substantia nigra

motor, oculomotor, associative, and limbic territory of SNr/GPi

Oculomotor loop cortex

FEF, SEF

Oculomotor loop striatum

caudate nucleus

Oculomotor loop thalamus

Maple, VLcr, VApc

Executive/associative loop cortex

DLPFC, LOFC

Executive/associative loop striatum

caudate nucleus (head)

Executive/associative loop thalamus

VApc, VAmc, VLcr, MDpl

Emotion/motivation cortex

ACA, MOFC

Emotion/motivation striatum

ventral striatum (nucleus accumbens)

Emotion/motivation thalamus

VAmc, VLm, MD

Motor loop purpose

action selection, motor planning and execution, determines scale/amplitude, duration and force of postures and movements, automatic execution of motor programs, initiation/termination of motor sequences

oculomotor loop purpose

contributes to visual attention mechanisms (saccades)

Executive loop purpose

goal-directed and socially accepted behaviors, influences attentional mechanisms, decisions

limbic loop purpose

modulates reward expectancy behaviors, procedural learning

Procedural learning loop

limbic

modulates reward expectancy behaviors loop

limbic

goal-directed and socially acceptable behaviors loop

executive

influences attentional mechanisms loop

executive

Contributes to visual attention mechanisms (saccades) loop

oculomotor

Action selection, motor planning, and execution loop

motor

determines scale/amplitude, duration, and force of postures and movements loop

motor

Automatic execution of motor programs loop

motor

initiation/termination of motor sequences loop

motor

Parallel motor circuits

thalamocortical and brainstem basal ganglia circuits run simultaneously

parallel motor circuits will

link automatic movement sequences with volitional goals and selects and tunes automatic behaviors to fulfill volitional intent

Parallel motor circuit for MNs to muscles for voluntary movement

motor thalamus to lateral corticospinal and rubrospinal tracts

Parallel motor circuit for MNs to postural and girdle muscles

pedunculopontine nucleus to reticulospinal tracts

Parallel motor circuit for stepping pattern generators (walking)

midbrain locomotor region to reticulospinal tracts