Understanding and Using the Systems Theory of Motor Control in ...

Understanding and Using theSystems Theory of Motor Control inthe Assessment and Treatment ofthe Upper ExtremityBy: Marianne Lawton, B.Sc. PTInstructor Bobath/NDT, IBITA

Voluntary Movement• is made intentionally• guided by perception (for example vision)• planned and then executed by output ofmotor commands which specify the correctsequence of muscle activation• sensory feedback can be used to optimizeperformance.

• Active Movement requiresPostural Support for BalanceControl

Arm Function• Support and Mobility• Balance and Walking• Protection• Manipulation• Sensation

Movement ControlAll areas of the brain, including visual andauditory cortices, are directly or indirectlyinvolved in motor control.Interconnectivity between cortical areas willimpact movementMore complex the movement, the morecortical networks involved.

Cortex to Spinal Pathways• Lateral Corticospinal Tract• mainly supplies the most distal muscles of the limbsand specifically for precise movements such as thehand• Completes the planning of voluntary movements andthe elaboration of motor commands for their execution• Anterior Corticospinal Tract• mainly innervates the axial (trunk) muscles• uncrossed fibres

Motor Control Pathways• Corticospinal system originates in bothmotor and sensory regions of thecerebral cortex.

Origins of Corticospinal Pathways• Areas• 4 (Primary motor cortex) 1/3 distribution to hand/face/restof body. Provides selectivity, skill and precision inmovement• 6 (Supplementary motor cortex and premotor motor cortex)adjusts the manner in which the spinal cord responds to theperipheral input• 3,1,2, (Primary somatosensory cortex)/ 5,7, (Posteriorparietal cortex) adjusts transmission of the sensorypathways including stereognosis and discriminatorysensation

Corticospinal Tracts• Directs active movement control• Allows for fine tuning of volitional movementsespecially skilled, independent finger control• Responsible of Skill and Precision in Movement byincorporating visual and auditory information.• Controls the rate and rhythm of automatic movementprograms• Directs speed & agility to voluntarymovements→performing rapid skilled movements• Not a Robust System

Motor Cortex• Divided into three reciprocallyinterconnected areas including:• Primary Motor Area• Secondary Motor Area• comprised of Supplementary Motor Area andthe Premotor Area

Motor Program Recruitment• Secondary Motor areas forms a loop with theBasal Ganglia• Primary Motor area forms a loop with thecerebellum

Primary Motor Area• First cortical area directly associatedwith motor function.• Has much more cortical space devotedto regions such as the hands and facewhere the variety and complexity ofmovements is greatest• Primary Motor Area is made up of 40%of Pyramidal Tract Fibres

Primary Motor Area continued• Receives a somatopic projection from thesomatosensory cortex• part of the input is from the muscle spindlesand is the sensory side to the stretch reflex• neurons in the motor cortex correlate with awide variety of movement parametersincluding force, velocity and direction.

Secondary Motor Area• Involved in planning movements• its neurons fire hundreds ofmilliseconds before a movement begins.• Comprised of two parts: SupplementaryMotor Area and the Premotor Area

Supplementary Motor Cortex• is crucial for performing complicated tasksinvolving both sides of the body such as twohanded activities• involved in performing complex sequences ofmovement that have been previously learned• is more active in sequential motor tasks andis internally generated.

Premotor Area• primarily concerned with planning movementsthat require sensory cues (primarily visual)• receives a large input from the posteriorparietal cortex (Brodman 5, 7)• provides sensory input for targeted areas andaction is context specific i.e. reaching forfood.

Premotor Area continued• have direct projections to the spinal cord, butnot as extensive as from the Motor Cortex.• Involved primarily in planning and initiation ofcentrally programmed motor commands.• Involved in establishment of the postural setrequired for a specific task.

Premotor Area continued• Involved in activities that require sequencingof goal directed movements; for example,typing or a remembered sequence• Less active during repetitive simplemovements such as finger tapping

Primary Somatosensory Area• Most cells fire in this area after themovement starts.• Cells respond to sensory feedbacksignals generated by movement.• Information transported via thethalamus, then to primarysomatosensory areas.

Primary Somatosensory Areacontinued…• Multiple sensory fields in eachsomatosensory area that respondsspecifically to a somatosensory input;for example, light touch muscle stretch.• Richly connected within the brain• Projects to the spinal cord, brain stemand thalamus, therefore control sensoryinput to the cerebral cortex.

Somatosensory Motor Cortex vs.Pre Motor Cortex• Both are active during learning of amotor task.• Pre motor cortex is more involved withmovements that rely on sensory inputsfrom the environment, such as visionand proprioception.

Somatosensory Motor Cortex vs.Pre Motor Cortex continued…• Somatosensory motor cortex are active inskills that require planning severalmovements ahead, particularly any tasks thatrequire temporal ordering of proximal anddistal movements.• Pre motor areas respond to changes insensory input during complex movement orduring perturbations of the movement.

Modulation of Voluntary Control• The Motor Cortex alters its output dependingon its afferent input, therefore responsive tosomatosensory information received.• Because the pyramidal tract neurons of theMotor Cortex are also active beforemovement, they appear to contribute to theestablishment of the postural set required forthe desired movement.• Allows feedback and feed forward loop.

Intentional Movement: Reaching• Movements that are made intentionally to achieve aparticular aim or reach a target• Involves several independent processes• perceptual input may evoke or guide it (for examplevisual input)• requires planning as different motor tasks can beperformed in various ways• this is called Motor Equivalence

Motor Equivalence• planning is required to organize preciselywhich set of postural adjustments should berecruited at the start and during themovements• executed by the output of motor commandswhich specify the correct timing of muscleactivation• sensory feedback during the movement finetune the execution to ensure that theperformance matches the desired goal.

Clinical Manifestations of Damageto Motor Areas• Difficult to be exact in definition since cortical areasdo not work in isolation.• Generally motor cortex damage results in:• Permanent deterioration in the ability to make fineindependent movements of the hand• Loss of contralateral hand orientating responses• Disruption of the sensory motor linkage, particularly spatialadjustments• Destruction in internal capsule – contralateral hemiplegiainitially flaccid, later spastic ; most marked in distal muscles

Clinical Manifestations of Damageto Motor Areas continued• Primary Motor Area:• muscle paresis spasticity and difficulties withmulti-joint movements on the same side of theface and the contralateral side of the body.• Loss of fractionation of movement

Clinical Manifestations of Damageto Motor Areas continued• Premotor Area:• similar in presentation as to primary• weakness tends to involve more proximal jointweakness especially hip and shoulder• motor planning skills are affected i.e. can reachfor an object but not manipulate the object• bilateral activities are affected

Clinical Manifestations of Damageto Motor Areas continued• Supplementary Motor Cortex• affect bilateral arm and hand movements but theproblems are most apparent not during visuallyguided movements but rather movements madebased on patterns or sequences• akinesis of movement where loss of planning formovement control

Clinical Manifestations of Damageto Motor Areas continued• Primary Somatosensory Area• contralateral sensory loss• possible loss of stereognosis• because limb position sense can be affected atype of sensory ataxia can occur where the patientappears uncoordinated during attempted limbmovements

Clinical Implications in Therapy• Most interesting things to the CNS issomething new and novel• Therapists should produce a stimulussignificant to the patient that relates to theirCNS at a moment in time to allow forintegration of sensory proprioceptive control• Individual differences - some respond tocognitive and some sensory- assess responseof patient