EXSS 380- Locomotion (pt. 2)

what are the three sources of sensory info crucial to control of locomotion?

• somatosensory

• visual input

• vestibular apparatus

what is the role of somatosensory receptors?

automatic regulation of stepping

what specific somatosensory receptors aid in the regulation of stepping?

muscle spindles in the hip flexors

what do exteroreceptors do?

adjustment of stepping for external stimuli

what big input help us make adjustments?

eyes/vision

what is the evidence for somatosensory input importance in human subjects?

hip extension produces rhythmic lower extremity movement in spinal cord injured individuals

what is the evidence of somatosensory input in cats?

• stepping in cats is initiated via treadmill movement and the rate of stepping matches the treadmill speed; increasing speed causes transition from walking to trotting to galloping

• reasoning is due to stretch of the hip flexor muscle spindles

• suggests mechanisms for transition located in spinal cord

in terms of transitions, what does increase speed of locomotion result in?

inter-limb coordination changes

what does walking typically do for limbs?

contralateral limbs out of phase

what does galloping typically do for limbs?

contralateral limbs in phase

what are the three main forms of information that visual info tells us?

• aid in regulating gait velocity

• used to identify potential obstacles and navigate around them

• visual processing

what is gait velocity?

how quickly we walk

what does doubling visual flow do?

increase stride length in 100% of participants

what do participants typically report when visual flow has been doubled?

50% will sense their force production has decreased or sense that their cadence has doubled

what do tilting walls on the treadmill result in?

participants incline the trunk in the direction of the wall tilt

what can vision identifying obstacles do for our locomotion ?

• avoidance

• changing foot placement

• increasing ground clearance

• changing direction of gait

• topping

what percentage of processing happens on even ground terrain?

10%

what percentage of processing happens on uneven ground terrain?

30%

what is not necessary for producing basic motor pattern for stepping?

supraspinal structures

what control the basic rhythmicity for stepping pattern?

neuron circuits contained entirely within spinal cord

what are spinal circuits activated by?

descending commands

what is the role of sensory input for locomotion?

spinal pattern generating circuits do not require sensory input, but are highly regulated by it; helps us adapt

how is locomotor developed?

sequentially

what demand is met first in locomotion development?

progression; stepping behavior

what goal is met second in locomotion development?

postural stability

when is postural ability usually developed?

5-6 months

what is refined over the first years of walking?

adaptability

what is observed at 16 weeks?

alternating leg movements

what development patterns to animals show?

top down

what is the specific patterns of animal development?

• fore → hindlimbs

• proximal → distal joints

• intralimb → interlimb coordination

what do we know about rats locomotor development?

rats don’t show coordinated locomotor movement until about 1 week of age, but can swim at birth

what kind of early stepping behavior do we see in humans?

• with water submergence, stepping frequency increases

• supine kicking is kinematically similar to stepping