Neural Basis of Posture Control and Gait

Question 1

what parts of the brain are used for automatic, hard wired processes in locomotion

Answer 1

basal gang
brainstem
spinal cord

Question 2

what happens if there is only spinal cord control of gait (lesion below brainstem)

Answer 2

only rudimentary form of gait
external stimulation is needed

Question 3

what happens if there is decerebrate control of gait

Answer 3

mesencephalic locomotor region critical
MLR stimulation is helpful

Question 4

what happens if there is decorticate control of gait

Answer 4

muscle tone, rhythmic stepping and initiation possible
goal directed locomotion
no external stimulation needed

Question 5

what happens if cortex is intact in terms of control of gait

Answer 5

vision is incorporated and smooth gait is adaptable to the environment

Question 6

what are some evidence for CPGs

Answer 6

various experiements: cats with severed SC still able to move, rhythmically step, adapt step cycle to clear obstacles, and go from walk to run

Question 7

what foes CPG formation control

Answer 7

controls level of motor neuron activity

Question 8

what is evidence of CPGs in humans with SCI

Answer 8

persons can elicit stepping acting with stimulation during PWB support walking

Question 9

what is evidence of CPGs in humans with regard to development

Answer 9

stepping is observed in newborns before pathways are developed

Question 10

what are some descending influences on CPGs

Answer 10

visuomotor cortex
cerebellum
basal gang
brainstem

Question 11

what is the basal gangs role in gait

Answer 11

modulation
muscle tone
gait initiation
velocity and amplitude

Question 12

what parts of the brain does complex gait use

Answer 12

PMA
SMA
Parahippocampal gyrus
putamen
thalamus

Question 13

when you walk at increasing speeds, what activates

Answer 13

more prefrontal and premotor along with brainstem

Question 14

when does visual sampling increase

Answer 14

uneven surfaces, when specific foot placement is required, hazard in path

Question 15

how can you anticipate modifications needed short term

Answer 15

change foot placement, ground clearance, direction, stop

Question 16

how can you anticipate modifications needed long term

Answer 16

shortened step length with experience (ex, walking on ice)

Question 17

describe gait on cognition in healthy young adults

Answer 17

gait isn’t very cognitively demanding in young adults

Question 18

going from simplest to most complex, list some gait behaviors

Answer 18

sit to stand
standing in tandem romberg
walking
recovery from external preturbations
obstacle avoidance during walking

Question 19

what model can explain many of our gait actions

Answer 19

passive inverted pendulum model

Question 20

how is motor programming supported in gait

Answer 20

we can walk without much attention
long rx times in complex situations
embedded neural circuitryw

Question 21

what happens when we slip

Answer 21

direction specific response
distal -> prox sequence

Question 22

what happens when we trip

Answer 22

depends on phase in gait cycle
early swing: elevating strategy
late swing: lowering strategy

Question 23

what happens when we are walking on a slippery surface

Answer 23

shorter strides, lower contact velocities, and reduced stance time

Question 24

how do we react when walking on a soft surface

Answer 24

stiffen ankle and knee to control posture and stability

Question 25

increased optic flow = ______ speed

Answer 25

increase

Question 26

what is very important during locomotion (think vestibular)

Answer 26

head stabilization - usually use VOR to stabilize vision

Question 27

describe automatic postural responses (SS systems)

Answer 27

direction specific response to platform translations
distal –> proximal activation
includes plantar vibration

Question 28

describe cutaneous info response in gait (SS system)

Answer 28

reflex modulation: includes crossed extensor reflex and stretch reflex of plantar flexors
both are phase dependent

Question 29

describe how muscle spindles work in gait (SS system)

Answer 29

stretched hip flexors reset locomotor rhythm which excites ipsi hip flexors and inhibits hip extensors

Question 30

describe how GTOs affect timing of locomotor rhythm

Answer 30

they excite their own muscle and inhibit antagonists to regulate transition from stance to swing

Question 31

if you lose the parietal cortex, what happens to gait

Answer 31

lose the ability to avoid obstacles

Question 32

what does the hippocampus do in regard to gait

Answer 32

code topographical info

Question 33

what does the MRF in the brain stem do in regard to gait

Answer 33

activates CPGs
target of MLR (initiates and adjusts)

Question 34

overall, what does the cerebellum do in regard to gait

Answer 34

fine tuning, error correction, adjustments due ot visual cues, multi-joint coordination and locomotor adaptation

Question 35

what does the medial (vermis) lobe of the cerebellum do for gait

Answer 35

integrate vestibular, visual, and SS system

Question 36

what does the intermediate lobe do in regard to gait

Answer 36

regulates gait through SS input from limb (muscle spindles and GTO) , receives proprioceptive input from dorsal column

Question 37

what does the lateral lobe do in regard to gait

Answer 37

adjust gait in novel context when vision is critical, receives info from cerebral cortex (parietal lobe) via pontine nuclei

Question 38

what is evidence of CPGs in humans with SCI

Answer 38

persons can elicit stepping acting with stimulation during PWB support walking

Question 39

what is evidence of CPGs in humans with regard to development

Answer 39

stepping is observed in newborns before pathways are developed

Question 40

when does visual sampling increase

Answer 40

uneven surfaces, when specific foot placement or hazard in path

Question 41

how can you anticipate modifications needed long term

Answer 41

shortened step length with experience