Basal Ganglia, Cerebellum and Movement

CBA 571 Structure of the Human Body(Chapter 10, Lundy-Ekman, emphasis on pp 190-215)

Gib Willett, P.T., M.S., O.C.S., C.S.C.S.Associate Professor, UNMC P.T. Education

Objectives:

Explain the movement related functions of the basal ganglia and cerebellum.

Identify the basal ganglia and cerebellum in diagrams and on models.

Describe the neural pathways between these areas and the cerebrum which influence movement.

Describe most likely symptoms resultant from damage to a given region or pathway presented in this module.

Introduction

B.G. and cerebellum contain large collections of nuclei that modify movement on an ongoing basis

The motor cortex sends information to both areas and both respond back to cortex through the thalamus (gatekeeper to cortex)

Introduction

B.G. motor related signals to the motor cortex are inhibitory

Cerebellar motor related signals to the motor cortex are excitatory

Balance of these systems allows for smooth, coordinated movement

Basal Ganglia

What does ganglia usually refer to? Collection of cell bodies outside the CNS

What are the Basal Ganglia (B.G.)? B.G. are actually a collection of ganglia deep to

the white matter of the cerebral cortex Components of the B.G. include:

Caudate Putamen Globus pallidus Subthalamic nucleus Substantia nigria There are more, but focus will be on the above

five due to their involvement with movement

Lentiform nucleus

Basal Ganglia Location

Basal Ganglia Location

Ventricles Thalamus B.G. component: Caudate nucleus B.G. component: PutamenWhere are the Globus Pallidus,

Subthalamic Nucleus and Substantia Nigra?

Basal Ganglia: Location

Frontal plane section of cerebrum

Basal Ganglia

Sequence movement Regulate muscle tone and force Two basal ganglia pathways influence

movement Promotion of certain movement patterns

(synergies) Inhibition of certain movement patterns

(synergies) Lesions of the basal ganglia result in

disturbances of muscle tone and dyskinesias Hyperkinesia Hypokinesia

Basal Ganglia: Specifics

Caudate & Putamen receive majority of input from cortex (L-E only refers to the putamen) Doorway into basal

ganglia Reciprocally

interconnected with the substantia nigra

Basal Ganglia: Specifics

Substantia nigra Pars compacta

(SNpc)- receives input and sends information back

Produces dopamine which is critical for normal movement

See Parkinson’s Disease in L-E

Pars reticularis (SNpr)- receives input and sends it out to control head and eye movements

Basal Ganglia: Specifics

Globus pallidus Most output from putamen

goes to globus pallidus but not all…….(see figure 10-4, p223 in L-E for a more detailed diagram)

Both interna (not shown in L-E) and externa communicate with the subthalamic nucleus

Interna sends major inhibitory output from B.G. to cortex via thalamus

Interna also has output to midbrain to assist in postural control (see L-E diagram)

Cerebellum

“Little brain” – outer cortex, inner white matter, deep nuclei

Coordinates movement: compares what you wanted to do (cortex), to what happens (proprioceptive feedback), and corrects the movement if needed.

Works ipsilaterally (cerebrum entirely contralateral)

Dorsal viewX-section showing cortex and deep nuclei

Ventral view

Cerebellum

Cerebellum

Summarized by 3’s 3 highways leading in and out “peduncles”

Superior – connects to midbrain Middle – connects to pons Inferior – connects to medulla oblongata

3 lobes – anterior, posterior and flocculonodular

3 broad classes of human movements controlled for by the cerebellum (see L-E)

Equilibrium – vestibulocerebellum Gross limb movements – spinocerebellum Fine distal movements - cerebrocerebellum

Cerebellum

3 input tracts Spinocerebellar -

proprioceptive feedback

Climbing fibers - feedback from ascending tracts via medulla

Pontine fibers - feedback from cerebral cortex

These fibers must cross then enter cerebellum

Cerebellum – “fun facts”

High density of neurons in cerebellar cortex results in cerebellum accounting for 1/10 of total brain volume but contains more than 50% of CNS neurons

Involved in motor learning process Once cerebellum receives intent to move

message, it provides information on movement direction, timing and force

Ballistic movements – too fast for feedback so predictions are made and modified via cerebellum based on experience (circuts change with repetition of an activity)

Cerebellar Lesions

Primarily coordination, proprioception and equilibrium related difficulties

Signs of cerebellar problems are manifested ipsilateral to the side of the lesion

Signs of cerebellar lesions include: Hypotonia – flabby muscles, often pendulous

reflexes Dysmetria – past pointing, missing the mark Dysdiadochokinesis – inability to make rapidly

alternating movements

Cerebellar Lesions

Signs of cerebellar lesions continued: Dysynergia - decomposition of movement

ie. complex movements performed as a series of successive simple movements

Intention tremor – occurs with movement Ataxia – stumbling gait

Alcohol abuse depresses cerebellar circuts (includes dysarthria)

Nystagmus – slow component towards the side of the lesion

Conclusion

Basal Ganglia – basically sequences movement and regulates muscle tone and force

Cerebellum – basically compares actual motor output to the intended movement and adjusts the motor output as necessary to meet movement expectations

Conclusion