Locomotion

Question 1

minimal gait speed for walking is:

Answer 1

1.2 mi/hr

Question 2

How does load influence locomotion?

Answer 2

WB enhances extensor activity in stance

Question 3

Locomotion does not require:

Answer 3

sensation

Question 4

Locomotion neurology is:

Answer 4

basic neural fxn
distributed in several areas of CNS
hierarchically organized
plastic

Question 5

Describe the hierarchal organization of locomotion:

Answer 5

prefrontal (goal)
motor cortex
BG, Cb, brainstem
SC - CPG
PNS and muscle

Question 6

Describe CPG’s distribution throughout the cord:

Answer 6

in ventral and intermediate horns at every SC level

Question 7

In animal studies with SC transection, stereotyped limb mvmnts are induced by:

Answer 7

cutaneous stimulation
limb mvmnt
pharmacological agents
–> NOT dependent on afferent input but sensor input IS important

Question 8

CPG fictive locomotion is:

Answer 8

stimulation of motor neuron pool in a rhythmical pattern consistent with locomotion

Question 9

CPG fictive locomotion can be done by:

Answer 9

stimulation of higher centers

pharmacological agents

Question 10

CPG half center model is based on

Answer 10

reciprocal inhibition pools of motor neurons on both sides of the SC
flexors and extensors alternate - reverberate

Question 11

CPG half center model depends on:

Answer 11

tonic input from higher center

Question 12

CPG’s are involved in _____ and _____ coordination.

Answer 12

both intra and inter-limb

Question 13

CPG output can be modified (adaptation). Can react to:

Answer 13

1. sensory inputs
2. change in higher center input
   ex: with obstacle on treadmill, if limb is in swing will enhance flexor activity. cutaneous input can enhance EMG activity. Higher centers may change gait velocity, or stepping pattern, etc.

Question 14

In humans compares to animals, CPGs may be more dependent on:

Answer 14

supraspinal initiation (ie: require higher centers)
(we don't have the same level of evidence as we do for animals)

Question 15

What requirements do we have for fxnal walking?

Answer 15

1. Equilibrium during propulsion (vestibular and Cb)
2. basic reciprocal mvmnts (MLR, R-S, vest-sp, Cb, CPG, BG)
3. adaptation to task goals and restraints (Cb, Cx)

Question 16

What regions hold the keys for fxnal walking?

Answer 16

brainstem and SC

Question 17

What is the MLR?

Answer 17

mesencephalic locomotor region

mesencephalic = midbrain

Question 18

The MLR influences locomotion through:

Answer 18

activation of other brainstem areas

Question 19

What tracts are involved in MLR locomotor fxn?

Answer 19

reticulospinal

vestibulspinal

Question 20

Describe the fxn of the two reticulospinal tracts:

Answer 20

pontine: excite extensors (inhibit flexors)
medullary: excite flexors (inhibit extensors)
ACTIVITY DURING GAIT CYCLE OSCILLATES B/W THE TWO

Question 21

R-S output is modified by several inputs:

Answer 21

CPG
vision
vestibular
–> WALKING IS MORE ADAPTIVE TO ENVIRONMENTAL CONTEXT

Question 22

Vestibulospinal tracts fxn:

Answer 22

excites extensors during stance (against gravity)

Question 23

The MLR functions to control locomotion by:

Answer 23

activating and controlling activity of CPGs
maintaining equilibrium during locomotion
adapting limb mvmnts to external conditions
coordinating locomotionw ith other motor acts

Question 24

The sensory motor cortex is especially active in:

Answer 24

complex, novel tasks

Question 25

Cb contribution to locomotion:

Answer 25

``` timing of sequential activation fine tuning (receives copy of output from CPGs ```

Question 26

BG contribution to locomotion:

Answer 26

initiation termination timing

Question 27

What tracts are essential to locomotion?

Answer 27

tracts in anterior cord reticulospinal: flexors/extensors vestibulospinal: extensor drive * ventral sparing in SCI incr. chance of walking post SCI

Question 28

What about C-S involvement in locomotion?

Answer 28

responsible for fractionated mvmnt --> not as important for walking

Question 29

Describe the role of sensory afferents in locomotion:

Answer 29

NOT essential except for adaptation (sensory input essential for modifying CPG's in response to environmental demands)

Question 30

Which sensory afferents contribute?

Answer 30

cutaneous receptors joint receptors muscle spindle (esp. Ia) GTO (Ib)

Question 31

Describe how low threshold cutaneous input facilitate CPG's:

Answer 31

extensors in stance and flexors in swing

Question 32

Describe how Ia fibers are involved in reciprocal inhibition:

Answer 32

Ia fibers presynaptically inhibited by Ia collaterals from opposing muscle groups Fxn: decrease resistive reflexes that would impede locomotion

Question 33

Describe how phase transitions are important in locomotion:

Answer 33

Hip extension: critical in transition from stance to swing (hip flexor muscle spindles activate ipsi flex and contra ext)S Triceps Surae: stretch in late stance also facilitates transition from stance to swing

Question 34

Stretch reflexes are phasic ally modulating during walking. This means that sensitivity to stretch depends on:

Answer 34

what part of the gait cycle

Question 35

What is the role of GTO in locomotion?

Answer 35

can have bimodal response during some activities like ambulation - facilitate extensor during stance and inhibit during swing (role in motor control much more complex than originally thought)

Question 36

Afferents from muscle spindle and GTO also affect higher centered via _____ tract and provide info from periphery that modifies _____ tract output.

Answer 36

spino-Cb | reticulo-spinal

Question 37

In summary, sensory input shapes the final motor output by:

Answer 37

modifying composition of active CPG circuits and their synaptic connections allowing for adaptation

Question 38

What biomechanics factors influence locomotion?

Answer 38

gait speed environment load (WB inc. extensor activity in stance)

Question 39

What is the minimal gait speed for arm swing?

Answer 39

1.2 mi/hr

Question 40

Describe CPG coordination:

Answer 40

more than one CPG may be activated separate for UE and LE multiple for LE and/or trunk

Question 41

In asymmetrical lesions (like brown sequard hemilesion), recovery mechanisms include:

Answer 41

significant reorganization of spared pathways | no ipsilateral regeneration, but ingrowth of contralateral collaterals

Question 42

What are the training and outcome considerations re: locomotion status?

Answer 42

peripheral sparing use dependent plasticity normalizing input maximizing output

Question 43

Anterior or Poster SC more important to preserve to maximize locomotion?

Answer 43

anterior SC

Question 44

Training can improve locomotion and result in fxnal walking without:

Answer 44

any change in MMT

Question 45

Peripheral sparing includes preservation of which tracts?

Answer 45

vetibulo-spinal reticulospinal (both for CPGs)

Question 46

Which motor tract is not essential for locomotion?

Answer 46

lateral cortico-spinal

Question 47

With complete SCI, what is the purpose of locomotion training?

Answer 47

CV, pulmonary, etc

Question 48

How does AD use influence locomotion?

Answer 48

ideally the AD normalizes walking so CPGs are effective: want to maintain reciprocal arm swing, etc

Question 49

What human locomotion patterns are unique from animal studies?

Answer 49

bipedal (greater control for upright posture) more dependent of supra spinal input CPG organized differently

Question 50

What applications can help normalize afferent input for locomotion?

Answer 50

normal gait kinematics (feedback to reticulo-spinal centers and CPGs) maintain tonic locomotor drive

Question 51

Walking speed for goal of BWS training:

Answer 51

1m/sec

Question 52

Walking speed for functional walking:

Answer 52

0.8m/sec

Question 53

How does walking speed influence locomotion?

Answer 53

Faster speed means more input to locomotor centers

Question 54

What are the considerations for program development and progression:

Answer 54

``` load postural control speed endurance IND adaptation ```

Question 55

What is better, treadmill or over ground?

Answer 55

over ground for fxnal walking | over ground requires more postural adjustments, more PF, more adaptation demands, and different GFRs than treadmill

Question 56

Emphasize ____ phase components in order to active CPGs.

Answer 56

stance phase | loading (IC)