UNDERSTANDING THE SYSTEMS MODEL OF MOTOR CONTROL AS

UNDERSTANDING THE SYSTEMS MODEL OF MOTOR CONTROL AS A BASIS FOR THE ASSESSMENT AND TREATMENT OF ADULT NEUROLOGICAL CONDITIONS.

The Central Nervous System • The CNS consists of several anatomically and functionally tightly connected systems and subsystems. • The relative importance of each system is decided by the task, the context, the state of the body and previous experiences. • CNS is not rigid and hierarchical in its function, but multidirectional and adaptable.

SYSTEMS MODEL This is a model which considers all levels and functions of the CNS and includes the context, the environment and cognition as key factors in performing and re-learning motor tasks.

Systems Theory • The systems approach was developed by Nicholai Bernstein. He recognised that you cannot understand the neural control of movement without an understanding of the characteristics of the system that is producing the movement and the external and internal forces acting upon the body.

In the Systems Theory • Control is distributed throughout many interacting systems working co-operatively • Central command is equated with the interplay between external forces and variations in the initial conditions • Different commands result in the same movement • The body is a mechanical system with many degrees of freedom which must be controlled in order to work together as a functional unit

Diagram to illustrate system theory Sensory Motor Cortex LOCOMOTION

Diagram to illustrate system theory Sensory Motor Cortex LOCOMOTION Substantia Nigra

Diagram to illustrate system theory Sensory Motor Cortex LOCOMOTION Substantia Nigra Mid-brain Loco-motor region

Diagram to illustrate system theory Sensory Motor Cortex LOCOMOTION Substantia Nigra Mid-brain Loco-motor region Nucleus Giganto-cellularis

Diagram to illustrate system theory Sensory Motor Cortex LOCOMOTION Substantia Nigra Mid-brain Loco-motor region Nucleus Giganto-cellularis CPG

Diagram to illustrate system theory Sensory Motor Cortex LOCOMOTION Substantia Nigra Cerebellum Mid-brain Loco-motor region Nucleus Giganto-cellularis CPG

Diagram to illustrate system theory Sensory Motor Cortex LOCOMOTION Substantia Nigra Cerebellum Mid-brain Loco-motor region Nucleus Giganto-cellularis CPG

Systems Control Lundy-Ekman 2002

The Integrated Function of The Nervous System in the Control of Movement OR Stuff goes in - stuff comes out, what happens in between?

Somatosensory tracts Kandel 2000 Kingsley 2000

• The dorsal column medial lemniscus system mediates information about pressure, touch, vibration and proprioception • The anterolateral system mediates information about pain and temperature • Information from different parts of the body runs separately (somatotopic organisation) – Prerequisite for knowing where a stimulus is coming from – Forms the basis of sensory maps in cerebral cortex – Makes selective modulation from one part of the body possible • Both systems are crossing • The dorsal spinocerebellar tract mediates precise information about joint position and movement (prorioceptive information) to cerebellum • Muscle spindles, GTO’S, skin receptors and joint receptors give information • Does not cross • The ventral spinocerebellar tract mediates more general sensory information and information about ongoing motor activity in the spinal cord • Crosses twice

SENSORI-MOTOR INTEGRATION • Ascending and descending systems are tightly connected anatomically and functionally. • Therefore it is inappropriate to talk about motor and sensory systems separately • It is the interaction between motor, sensory and cognitive systems that create what we can see as our activities of daily living.

• More than half of the human cerebral cortex consists of association areas, which coordinate events rising in the motor and sensory centres – These are involved in cognitive behaviour planning, thinking, feeling, perception, speech, learning, memory emotion, and skilled movements Kandel 2000 • Large parts of the descending systems modulate sensory information in the spinal cord and the brainstem • Sensory information modulates motor activity at all levels of the CNS

You never know what you’ve got ‘til its gone!

Primary motor cortex • Somatotopically arranged but multiple representations. • Groups of M 1 neurons control specific parameters of muscle contraction. • Creates the “postural set” for the desired activity. • Adapts its output in response to sensory input. • Modulates subcortical responses and sensory input.

Cerebrum summary • The more voluntary a movement is performed the higher degree of cortical processing is needed – Dexterous activities with the hands belong to the most voluntary movements – In more automatic functions, like walking, the voluntary control increases when we have to adapt to challenging environment

Sensorimotor cortex Putamen Pons Globus pallidus Cerebellum Thalamus Descending pathways Premotor cortex Thalamus Motor cortex Basal ganglia & cerebellum

Damage to Cortical Association Areas • Problem solving of complex tasks is difficult • Cannot choose the appropriate movement strategies due to inadequate interpretation of sensory information e. g. pusher syndrome • Feed-forward automatic postural adjustments can be dysfunctional due to altered body schema • Motivation is poor • Connecting emotions to activities is difficult • Learning is impaired

Cerebellum • Three main parts – Spinocerebellum – Vestibulocerebellum – Cerebrocerebellum Afferent information is filtered into the cerebellum-letting only Relevant information through (40 times more input than output!) Lundy-Ekman 2002

Kandel 2000

The Circuitry of the Cerebellum • Afferent input to the cerebellum via mossy fibres and climbing fibres. • Both send collaterals to the deep cerebellar nuclei forming an excitatory loop modulated by the inhibitory loop via Purkinje cell activity.

• When learning a motor task there is an increase in the number of complex spikes until the task is mastered. Then the number of simple spikes increases.

DEEP CEREBELLAR NUCLEI FLOCCULAR NODULAR LOBE VESTIBULAR NUCLEUS VERMIS PARAVERMIS FASTIGIAL GLOBOSE & NUCLEUS EMBOLIFORM N. RETICULAR RED NUCLEI NUCLEUS. SPINAL CORD CEREBELLAR HEMISPHERE DENTATE NUCLEUS THALAMIC NUCLEUS MOTOR CORTEX

Structure Task Flocculonodular lobe Balance, Vestibulo+ vestibular nuclei ocular reflex Deficit Nystagmus, vertigo, imbalance Vermis + fastigial nucleus Posture, locomotion, Postural deficits, gain of reflexes impaired locomotion Paravermis + interpositus nucleus Arm movements and Intention tremor, conditioned reflexes impaired reaching Hemispheres + dentate nucleus Skilled finger movements, speaking, recalibration of voluntary movements Loss of precision grip, slurred speech Lawes

Corticostriatothalamocortical loops • Motor pathway • Oculomotor pathway • Dorsolateral prefrontal pathway • Lateral orbitofrontal prefrontal pathway • Limbic pathway.

Functions of the basal ganglia • The focusing of attention necessary to connect sensory input to motor output. Paradoxical kinesis • Problem-solving Caudate-prefrontal cortex • Sequential limb movements Putamenpremotor loop • Performance of learned patterns of movements. SMA –putamen loop

In Summary, movement is…. • Defined by the Cortex • Refined by the Cerebellum • Contextualised by the Basal ganglia

In Summary • You can move one way when you move yourself • Move another way when facilitated to move by someone else • Move another way when told to move yourself