Neuroanatomy Modulation of Motor Function

Which system in the cerebral cortex is primarily responsible for controlling voluntary movement?

upper motor neuron

What two major brain structures regulate and fine-tune the output of the UMN system

The basal ganglia and the cerebellum.

What is the role of the basal ganglia in motor control?

It helps initiate and suppress movements, regulating motor output for smooth, purposeful activity.

What is the role of the cerebellum in motor control?

It coordinates movements, maintains balance, and ensures motor learning and precision.

What is the role of the cerebral cortex in movement control?

It produces and sequences movements, integrates sensory and motor signals, and enables precise, complex voluntary movements.

What is the function of the basal ganglia in movement control?

It provides the platform for purposeful behavior, encoding decisions to move, direction, amplitude, and the motor expression of emotions.

Which aspects of movement are mainly encoded by the basal ganglia?

Decision to move

Direction of movement

Amplitude of movement

Motor expression of emotions

What happens when there is excessive output from the basal ganglia?

There is abnormal slowing of movements (e.g., bradykinesia as seen in Parkinson’s disease).

What happens when there is reduced output from the basal ganglia?

Abnormal, involuntary movements occur during periods of rest (e.g., chorea in Huntington’s disease).

Large masses of gray matter deep within the cerebral hemispheres surrounding the ventricles and thalamus

Basal ganglia

Which structures sit lateral to the thalamus?

Caudate, Putamen, Globus pallidus (internal and external)

Which basal ganglia structure is located in the rostral midbrain?

Substantia nigra

Which basal ganglia structure is located inferior to the thalamus?

Subthalamic nucleus

Where is the head of the caudate nucleus located?

In the floor of the lateral ventricle

Describe the shape and course of the caudate nucleus.

Its body arches over the thalamus in a C shape and tapers off in the roof of the inferior horn of the lateral ventricle

Which basal ganglia structure is the most lateral?

Putamen

What is the embryological relationship between the putamen and caudate nucleus?

They are embryologically connected

What is the collective name for the caudate nucleus and putamen, and why are they called this?

Striatum – named for the striped appearance of fibers connecting the two

Why are the caudate and putamen called the input nuclei of the basal ganglia?

Because they receive excitatory input from the motor cortex

Where is the globus pallidus located in relation to other brain structures?

Medial to the putamen and lateral to the thalamus

What are the two parts of the globus pallidus?

External (GPe) and Internal (GPi)

Which part of the globus pallidus serves as the output nucleus of the basal ganglia?

GPi (internal segment)

What type of signals does the GPi send to the thalamus?

Inhibitory signals

Where in the rostral midbrain are dopaminergic neurons located?

Within the cerebral peduncle

To which structures do the dopaminergic neurons of the rostral midbrain project?

The striatum (caudate and putamen) and the subthalamic nucleus

What neurotransmitter is released by these neurons in the rostral midbrain?

Dopamine

What is the net effect of dopamine on movement?

It facilitates movement

From which structures does the subthalamic nucleus receive input?

Substantia nigra and external globus pallidus (GPe)

What type of inhibition is the subthalamic nucleus normally under?

Tonic inhibition

What happens when the subthalamic nucleus is released from inhibition?

Its output becomes excitatory to the GPi

Where is the nucleus accumbens located?

In the anterior and inferior part of the striatum where the head of the caudate and putamen are continuous

What type of input does the nucleus accumbens receive?

Dopamine input

What systems is the nucleus accumbens an integral part of?

The limbic system and reward circuitry

In what condition is the nucleus accumbens implicated

Addiction

Which cortical areas send input to the striatum (caudate and putamen)?

Motor, sensory, association, and limbic areas of the cortex

Which function is primarily associated with the putamen?

Motor functions

Which function is primarily associated with the caudate nucleus?

Cognitive and emotional aspects of movement

What is an important source of dopamine input to the basal ganglia?

The substantia nigra

What does input from the substantia nigra to the striatum enable?

It enables the basal ganglia to integrate information from different areas of the CNS

What does integration of input by the basal ganglia allow it to determine?

Direction of movement

Decision to move

Amplitude of movement

Motor expression of emotions

Outputs from the basal ganglia is to the thalamus from the

golbus pallidus internal (GPi)

output keeps the thalamus

inhibited

the motor portion of the thalamus is under constant

inhibition

what are the two pathways in basal ganglia circuit

excitatory and inhibitory pathway

what projection increases motor activity

Dopaminergic nigrostriatal projection

what projection decreases motor activity

Cholinergic striatal projections

What type of input does the cortex send to the striatal neurons in the caudate nucleus and putamen?

Excitatory input

What is another name for the caudate nucleus and putamen?

Neostriatum

From which areas does the striatum receive input?

Most of the cortex and many thalamic nuclei

Besides the striatum, which structure also receives projections from a subset of the same cortical and thalamic regions?

Subthalamic nucleus (STN)

Which basal ganglia structure projects within the basal ganglia?

Globus pallidus external segment (GPe)

Which structures project to targets in the brainstem and thalamus?

Globus pallidus internal segment (GPi) and substantia nigra pars reticulata (SNr)

To where does the globus pallidus interna (GPi) project inhibitory fibers?

Ventrolateral (VL) thalamus

What type of fibers does the ventrolateral thalamus send to the motor cortex?

Excitatory fibers

Summarize the pathway from GPi to motor cortex

GPi —inhibitory→ VL Thalamus —excitatory→ Motor Cortex

What is the sequence of the direct pathway of the basal ganglia?

Cortex —excitatory→ Neostriatum —inhibitory→ GPi —inhibitory→ VL Thalamus —excitatory→ Motor Cortex

How does the direct pathway promote movement?

It inhibits the GPi, which releases inhibition from the VL thalamus, allowing it to excite the motor cortex

What is the overall effect of the direct pathway on the motor cortex?

It stimulates the motor cortex

What is the purpose of the intermediate steps in the indirect pathway?

To stimulate the Globus Pallidus Interna (GPi).

What type of fibers does the striatum send to the Globus Pallidus externa (GPe) in the indirect pathway?

Inhibitory fibers.

What type of fibers does the GPe send to the Subthalamic nucleus (STN)?

Inhibitory fibers.

What type of fibers does the Subthalamic nucleus (STN) send to the GPi?

Excitatory fibers.

Summarize the sequence of the indirect pathway.

Cortex —excitatory→ Neostriatum —inhibitory→ GPe —inhibitory→ STN —excitatory→ GPi —inhibitory→ VL Thalamus —excitatory→ Motor Cortex.

What is the overall effect of the indirect pathway on the motor cortex?

It inhibits the motor cortex.

What is the function of the direct pathway?

It facilitates target-oriented and efficient behavior.

What is the function of the indirect pathway?

It suppresses superfluous behaviors that are not related to the targeted behavior.

What is the combined effect of the direct and indirect pathways?

They streamline behavioral output.

How does dopamine from the substantia nigra influence the basal ganglia pathways?

It influences both the direct and indirect pathways.

What is the net effect of dopamine signaling in the basal ganglia?

To increase cortical activity (dopamine = movement).

Basal nuclei impairments causes what kind of disturbances

impaired initiation of movement

bradykinesia

increased muscle tone

loss of dopamine inputs into neostriatum

hypokinetic

Basal nuclei impairments cause what kind of disturbances

excessive motor activity

involuntary movements

decreased muscle tone

increased disinhibition of thalamus

hyperkinetic

Loss of dopaminergic neurons in the substantia nigra causes this common disease

parkinson’s disease

Degeneration of striatum and significant loss of GABA causes this common disease

huntingtins diseases

slow, writing movements of extremities

athetosis

sustained contractions of the limb, axial or cranial voluntary muscles resulting in abnormal postures and repetitive, twisting movements

dystonia

Violent, ballistic movements of the limbs contralateral to lesions, usually caused by a discrete and localized stroke of the subthalamic nucleus (STN).

hemiballism

Involuntary movements of the tongue and face, usually caused by antipsychotic drugs that block dopamine transmission or by depletion of GABA in the neostriatum.

tardive dyskinesia

Motor and vocal tics, brief sudden involuntary movements, and vocal expressions; thought to be associated with caudate dysfunction

tourettes syndrome

what is the major blood supply of the basal ganglia

MCA

Where do the majority of spinal cord inputs to the cerebellum go?

To the anterior lobe

Which cerebellar lobe receives major inputs from the cortex and makes up the bulk of the cerebellum?

Posterior lobe.

Which cerebellar lobe is considered the most primitive and receives major inputs from the vestibular system?

Flocculonodular lobe.

what are the three lobes of the cerebellum

anterior

posterior

flocconodular

What does the inferior cerebellar peduncle (ICP) connect, and where does it enter the cerebellum?

It connects the medulla to the cerebellum and enters on the inferior aspect.

What does the middle cerebellar peduncle (MCP) connect to, and how does it enter the cerebellum?

It connects to the lateral aspect of the pons and enters the cerebellum from a lateral trajectory.

What is the major source of input from the pons to the cerebellum?

The middle cerebellar peduncle (MCP).

From where does the superior cerebellar peduncle (SCP) emerge, and where does it enter?

It emerges from the superior and medial aspects of the cerebellum and enters the upper pons/midbrain.

What is the major output pathway from the cerebellum?

The superior cerebellar peduncle (SCP).

In the cerebellum, which body parts are represented more midline?

The trunk.

In the cerebellum, which body parts are represented more laterally?

the extremities and head.

Which parts of the cerebellum make up the spinocerebellum?

The anterior lobe, vermal, and paravermal areas.

Which parts of the cerebellum make up the cerebrocerebellum, and what is notable about its size?

The rest of the posterior lobe; it is the largest division.

Which parts of the cerebellum make up the vestibulocerebellum?

The flocculonodular lobe.

What type of information do vestibular inputs provide to the cerebellum?

Information about the position of the head and body in space.

How do vestibular inputs help during locomotion?

They help orient eye movements.

To which cerebellar region do vestibular afferents project, and through which peduncle?

They project to the flocculonodular lobe through the inferior cerebellar peduncle (ICP).

From which receptors do these cerebellar afferents originate?

Muscle spindles and Golgi tendon organs (GTOs).

Which tracts carry proprioceptive information through the inferior cerebellar peduncle (ICP)?

The posterior spinocerebellar and cuneocerebellar tracts.

Which tracts carry proprioceptive information through the superior cerebellar peduncle (SCP)?

The anterior and rostral spinocerebellar tracts.

Where do these proprioceptive afferents terminate in the cerebellum?

In the anterior lobe (for limbs) and vermis (for trunk).