Coordination Flashcards
What does controller do?
sets overall task and organizes feedback loops that assure stable task performance given the external conditions
So that controller doesn’t have to predict all internal and external sources of variability
what does coordination require
spatial and temporal organization and relations among elements during a movement
definition of coordination
ability to initiate, execute, and terminate a smooth, accurate, and controlled movement characterized by appropriate speed, amplitude, distance, direction, and timing
synergy
- ability of units of action (DOF) to work together to achieve some goal
- loss of selectivity (fractionation) implies a problem in coordinating the DOF which results in problems of speed, amplitude, direction, smoothness, etc
individuation/ fractioned movement
ability to selective activate a muscle, allowing isolated joint motion
impaired individuation
- abnormal coupling between related muscles
- post stroke, active shoulder flexion = active elbow flexion
within reaching tasks, what do cervical propriospinal neurons do?
- play a role in coordinating descending motor commands from motor cortical areas
- C3-C4 propriospinal system receives corticospinal, reticulospinal, and tectospinal input and afferent info from the limb that may facilitate activation of muscle synergies
neural factors of fractionation
balance of descending fascilitory and inhibitory influences on segmental spinal processes –> hyper excitable brainstem pathways
peripheral afferent processes
biomechanical factors of fractionation
- length of muscle (length-tension relationship, torque/angle = stiffness)
- moment arm influences
- relationship to gravity
behavioral factors of fractionation
- practice
- habit
influence of UE task on coordination
- pointing: all segments controlled as unit
- reaching: hand is “independently” controlled
- -sequential and subcomponents influenced by separate brain areas
- different velocity and acceleration profiles
what does the neural control of reach and grasp require?
- conscious proprioception and object recognition
- localization (where the object is in space)
conscious proprioception and object recognition for reach and grasp
- visual cortex to temporal cortex (visual stream) for conscious visual perceptual experience
- person with lesion in this stream has no consciousness of orientation or dimension of the object but can pick up the object with good dexterity
localization required for reach and grasp
- visual cortex to PPC (dorsal stream)
- action relevant information about all phases of the reaching movement (may not require consciousness)
- PPC shows both motor and sensory activity
PPC for reach and grasp
- movement planning or attention (goal and type of mvmt)
- lateral intraparietal: saccade planning
- medial intraperietal: planning of reach
- anterior intraparietal: planning of grasp
medial superior temporal cortex in reach and grasp
planning smooth pursuits
optic ataxia
- lesion to PPC
- problems reaching in correct direction
- positioning fingers or adjusting correct orientation of hand when reaching
- adjusting grasp to reflex size of object being picked up
- BUT CAN IDENTIFY AND DESCRIBE THE OBJECT
What is visual feedback when reaching for?
attainment of final accuracy
reaching across midline
- takes longer and is less accurate
* * clinical implication: understand this during exam and consider this in your progression of task complexity
Somatosensory contributions to reach
- if movement is simple and non repetitive, humans can perform reach movement with vision occluded
- complex movements or repeated movement deteriorate quickly without visual feedback
- use of position sense when reaching comes mainly from spindle Ia afferents and cutaneous afferents
what is essential for control of grip forces
cutaneous afferent input
what detects a slip during a grasp
mechanoreceptors
what occurs when fingers are anesthetized?
grip force increases
coordination between grip and load forces is lost
What occurs to grip if person has only moderately impaired sensation?
coordination is preserves
what occurs when S1 is inactivated
- uncontrolled grip and load forces and increased grip force
- S1 has slowly and rapidly adapting cells –> both respond to slipping
what likely regulates hand path direction and spatial trajectory?
vision
what facilitates terminal hand position and limb status?
proprioception
what occurs to reach and grasp when object is in motion?
visual feedback from the moving object is of critical importance to predict synchronous grip and load forces in a timely manner
(grip force is facilitated when vision is directed at object)
descending pathways for reach and grasp
Anticipatory control for grasping
pre-grasp hand shaping (under visual control)
anticipatory of characteristics of the object to be grasped
what may influence the nature of control of limb synergies?
mechanical (structurally coordinated) linkages
neural factors of incoordination
- typically attributed to function of cerebellum
- also includes motor and sensory systems and spinal cord
cerebellum function is all problems of what?
metrics and timing
musculoskeletal factors of incoordination
- generally not related to overall force generating capacity of the muscles involved
- could be problems of force variability (maintaining it)
Ataxia
loss of ability to control and coordinate movements
ataxia in speech
dysarthria
ataxia is often associated with:
- delays in initiation and execution times
- dysmetria
- dysdiadochokinesia
cerebellar incoordination
- delays in initiation
- dysmetria and intention tremor
- dysdiadochokinesia
- asynergia: errors in relative timing and amplitude of components of multisegmental movements (lack of smoothness in execution phase)
hypermetria
less abrupt against burst
prolonged agonist burst and delayed antagonist burst
hypometria
may have prolonged antagonist burst
co-contraction observed
What does cerebellar damage result in and what does that mean to PTs
extend and rate at which individuals adapt movements
- longer training duration or intensity to improve performance
cerebellum as comparator –> internal model concept describing function/dysfunction
- predicts sensory consequences of movement based on motor command
- motor behaviors relay on prediction errors –> perkinje cells
decomposition
- moving one joint at a time
- impaired multijoint coordination reflects role of cerebellum in anticipating and regulating interaction torques
Impaired adaptation
- cerebellar’s pathology reduces persons ability to adjust to novel loads through trial and error
how is adaptation measured?
- object displacement in a dropped ball catch
