Basal Ganglia & Thalamus Lecture Notes

Flashcards covering the anatomical structures, nuclei, and functions of the Basal Ganglia and Thalamus based on the Week $$5$$, Lecture $$9$$ transcript.

Basal Ganglia

A group of subcortical nuclei involved in motor control, motor learning, executive function, behaviors, and emotion.

Basal Nuclei

Striatum: Caudate nucleus, Nucleus accumbens, Putamen

Globus Pallidus: Lateral (external), Medial (internal)

Subthalamic nuclei: Substantia nigra: Compact Reticular

Striatum

A composite structure of the basal ganglia consisting of the caudate nucleus, nucleus accumbens, and putamen.

Lentiform Nucleus

A lens-shaped structure formed by the putamen and the globus pallidus (both internal and external segments).

Internal Capsule

A large afferent and efferent white matter tract that relays information to and from the thalamus; it separates the caudate nucleus from the lentiform nucleus.

Nucleus Accumbens

A structure located where the head of the caudate and putamen meet, involved in motivation, reward, and behavioral reinforcement, integrates motivation with motor action

Caudate Nucleus

A long, tadpole-shaped structure that wraps around the thalamus; it is associated with motor function (role in Parkinson’s and Huntington’s disease), procedural learning, and inhibitory control.

• Other functions: Associative learning, Planned (cognitive) behaviors, emotional reward system

Subthalamic Nucleus

A diencephalic structure that uses the excitatory neurotransmitter glutamate and is frequently targeted by deep brain stimulating DBS treat Parkinson’s disease.

*subthalamic cells are inactive bc of constant inhibition by cells of the GPe; If this inhibition is removed, as it is in

Parkinson’s disease, subthalamic neurons have a high level of activity resulting in motor dysfunction, known as

disinhibition

Substantia Nigra

A midbrain nucleus named "black substance" due to neuromelanin in dopamine neurons; it is divided into the pars compacta and pars reticulata

Substantia Nigra Pars Compacta (SNc)

The dorsal part of the substantia nigra containing densely packed, pigmented dopaminergic neurons that serve as input to the basal ganglia.

Substantia Nigra Pars Reticulata (SNr)

The ventral part of the substantia nigra containing loosely packed GABAergic neurons that serve as the output from the basal ganglia.

Nigrostriatal Pathway

The connection between dopamine neurons of the SNc and the striatum; its degeneration leads to the motor deficits of Parkinson’s Disease.

Diencephalon

The caudal part of the forebrain consisting of the thalamus, hypothalamus, subthalamus, and epithalamus.

Thalamus

A structure making up 80% of the diencephalon that act as the biggest sensory and motor "relay hub" and gateway to the cerebral cortex, regulates consciousness, sleep, and alertness,

sensory processing: thalamic nuclei organize & amplify or decrease incoming signals

Internal Medullary Laminae

Y-shaped myelinated fibers that divide the thalamus into four main nuclei groups: medial, anterior, lateral, and posterior.

Interthalamic Adhesion

A band of gray matter connecting the medial surfaces of the two thalamic hemispheres across the third ventricle.

Reticular Nucleus (Thalamus)

A sheath that wraps around the thalamus; it is the only thalamic nucleus that does not project to the cortex, instead modulating signals within the thalamus itself.

Intralaminar Nuclei

Nuclei located within the internal medullary laminae, including the centromedian nucleus, involved in maintaining alertness and directing attention.

They receive input from the reticular formation in the brainstem and project to the striatum and cortex

• involved in maintain alertness, and directing attention to salient sensory events.

Ventroposterolateral Nucleus (VPL)

responsible for relaying somatic sensation for the contralateral body.

Ventroposteromedial Nucleus (VPM)

relaying somatic sensation for the contralateral face and taste.

Lateral Geniculate Nucleus (LGN)

responsible for relaying visual information.

Medial Geniculate Nucleus (MGN)

responsible for relaying auditory (hearing) information.

Mediodorsal Nucleus (MD)

A thalamic nucleus involved in motivation, drive, emotion, and the relay of olfaction (smell).

Pulvinar Nucleus

A thalamic nucleus involved in visual processing.

Ventroanterior (VA) Nucleus

A thalamic motor nucleus involved in the initiation and planning of movement.

putamen

regulate movements and influence various types of learning

globus pallidus

involved in the regulation of voluntary movements

Medial (GPi; internal, smallest), Lateral (GPe; external, largest)

skeletomotor loop

Controls facial, limb, and trunk musculature

oculomotor loop

Controls saccadic eye movements

prefrontal loop

Controls cognition and executive behavioral functions/planning

limbic loop

Mediates motivational regulation of behavior and emotions

direct pathway

produces wanted movement. When a movement is desired, a signal to initiate the movement is sent from the cortex to the BG, which frees the thalamus from the inhibitory effects of the BG and allows movement to occur

indirect pathway

prevents unwanted movements. Involves the subthalamic nucleus, leads to the increased suppression of unwanted movements. It is thought that a balance between activity in these two pathways may facilitate smooth movement

hypothalamus

an integral part of the endocrine system; Links the nervous system to the body’s hormone system via the

pituitary gland

subthalamic nucleus

receives afferent connections from the substantia nigra and striatum

Regulates skeletal muscle movements

epithalamus

connects the limbic system to other parts of the brain

• Involved in secretion of melatonin by the pineal gland that regulate circadian rhythms/sleep wake cycle

• Regulation of motor pathways and emotions

lateral posterior (LP)

involved in visual processing

Ventrolateral (VL)

involved in modulation and coordination of movement

Anterior (A)

involved in memory storage and emotion

lateral dorsal (LD)

invloved in emotion and memory storage