Modulation of Motor Function

Movement is controlled by what system in the cerebral cortex?

UMN system

movement output is controlled and regulated by

the basal ganglia and cerebellum

Platform of which purposeful behavior can be made

Basal Ganglia (nuclei)

what provides Production of movement and sequences of movements

• Organizing and integrating signals from both sensory and motor regions of the brain

• Precise, complex voluntary movements

Cerebral Cortex

Excessive output can lead to

abnormal slowing of movements

Reduced output can lead to

abnormal, involuntary movements that occur during periods of rest

Where are the Basal Ganglia?

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

the head of what is in the floor of the lateral ventricle

• Body arches over thalamus in a C shape

• Tapers off in the roof of the inferior horn of the lateral ventricle

Caudate Nucleus

what is The most lateral part of the ganglia

• Embryologically connected to the caudate nucleus

Putamen

The striatum is comprised of what?

the caudate and putamen

what is the INPUT nuclei of the Basal ganglia

striatum

what is medial to the putamen and lateral to the thalamus?

• Divided into external (Gpe) and internal (Gpi)

• Parts function differently and have distinct connections

Globus Pallidus

what is the OUTPUT nucleus of the Basal Ganglia

Gpi

what signals does the Gpi send to the thalamus

inhibitory signals

what is found in Rostral midbrain within cerebral peduncle

• Contains dopaminergic neurons that project to the striatum and the subthalamic nucleus

• Influences activity in both regions

• Net effect of dopamine – facilitates movement

Substantia Nigra

what Receives input from substantia nigra and external globus pallidus (GPe)?

Subthalamic Nucleus

Under “tonic inhibition” What is the subthalamic nucleus’ output when released from inhibition?

its output is excitatory to the GPi

what is the anterior and inferior part of the striatum where head of caudate and putamen are continuous?

Nucleus Accumbens

the Nucleus Accumbens receives what kind of input that is Integral part of limbic system and reward circuity

• Implicated in addiction

dopamine input

basal ganglia helps to form

emotional body language

in what disease does the caudate nucleus atrophy, lateral ventricle balloons

huntingtons disease

The Putamen is involved more in _____ & the Caudate is involved more in ______?

motor functions

cognitive and emotional aspects of movement

What is the Important producer of dopamine input to the BG?

the Substantia Nigra

Input to striatum enables basal ganglia to

integrate information from different areas of the CNS

Integration of input allows BG to determine

Direction of movement

• Decision to move

• Amplitude of movement

• Motor expression of emotions

Globus Pallidus Internal (GPi) keeps what inhibited?

thalamus

When the GPi is inhibited, the thalamus is released from inhibition, letting it

excite the cerebral cortex and get you moving

Motor thalamus (Mthal) encompasses thalamic nuclei that are strategically located between

motor areas of the cerebral cortex, the basal ganglia, and cerebellum

Dopaminergic nigrostriatal projection does what?

increases motor activity.

Cholinergic striatal projections do what to motor activity?

decreases motor activity

For both excitatory and inhibitory paths: Excitatory input from the cortex projects to

striatum

The striatum is split into what receptors for dopamine?

D1 or D2

both paths start in the

cortex and goes to the striatum

both paths end in same way:

1. Globus pallidus interna projects inhibitory fibers to VL thalamus.

2. VL thalamus sends excitatory fibers to the motor cortex

Inhibition of the GPi frees its inhibition from

the VL Thalamus to Promote Movement

In what pathway does the cortex excites neostriatum which inhibits GPi which inhibits VL thalamus which excites motor cortex

direct pathway

which path? Cortex (+)excites neostriatum which (-)inhibits GPe which (-)inhibits Subthalamic nucleus (STN) which (+)excites GPi which (-)inhibits VL thalamus which excites (quiets) motor cortex

Indirect Pathway

d1 receptors are

excitatory

Direct Pathway Function

Facilitate movement

Indirect Pathway Function

Suppress superfluous behavior during movement

Dopamine from substantia nigra in indirect path

suppresses the indirect path

d2 receptors are

inhibitory

Impaired initiation of movement

• Bradykinesia

• Increased muscle tone

• Loss of dopamine inputs into neostriatum

• Net effect: greater inhibition of thalamus

Hypokinetic Disturbances

Excessive motor activity

• Involuntary movements

• Decreased muscle tone

• Increased disinhibition (ie greater excitation) of thalamus

Hyperkinetic Disturbances

what is described as slow, writhing movements of extremities?

Athetosis

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

Dystonia

what presents with violent, ballistic movements of limbs contralateral to lesions; usually discrete and localized stroke of STN

Hemiballism

What involves involuntary movements of tongue and face; usually due to administration of antipsychotic drugs that block dopamine transmission or depletion of BAGA in neostriatum?

Tardive Dyskinesia

What involves motor and vocal tics; brief, sudden involuntary movements and vocal expressions; thought to be associated with caudate dysfunction?

Tourette’s syndrome