1. NEURAL CONTROL OF
LOCOMOTION
HETSHREE BHAVSAR
MPT IN NEUROSCIENCES

2. INTRODUCTION
Mobility:
• Ability to independently and safely move oneself from one place to
other.
• Key feature of our independence as human beings.
• Includes tasks like ability to stand up from a bed or chair, to walk or
run and to navigate through often quite complex environment.

3. INTRODUCTION
Gait:
• An extraordinary complex behavior.
• It involves the entire body and therefore requires the coordination of
many muscles and joints.

4. INTRODUCTION
Locomotion:
• Essential for survival.
• Controlling it is not an easy task.
• CNS somehow generate the locomotors pattern, generate appropriate
propulsive forces, modulate changes in the center of gravity,
coordinate multi limb trajectories, adapt to changing conditions and
changing joint positions, coordinate visual , auditory, vestibular and
peripheral afferent information and account for the viscoelastic
properties of muscle.

5. INTRODUCTION
• It must do all of this within milliseconds and usually in conjunction
with coordinating a multitude of other bodily functions and
movements.
• Neural control of human locomotion is not yet fully understood.

6. INTRODUCTION
• Human locomotion (gait cycle) is not only the cycle of the mechanical
events but also controlled by nervous system.
• As child grows up and his nervous system gets matured, locomotion
pattern also changes from reflexive gestational movements to
matured adult gait cycle (bipedal plantigrade gait pattern).

7. DEFINITION
• Locomotion is defined as a translator progression of the body as a
whole, produced by coordinated, rotatory movements of the body
segments as a result of combined and coordinated actions of neuro,
muscular and skeletal systems.

8. DEFINITION
• Locomotion is also defined as a movement of b/l lower extremity in
an alternative fashion, in such a way that transmission of the COG
takes place in the sinusoidal curve in order to maintain the stability
along with the mobility.

9. LOCOMOTION
• Three essential requirements: Progression, postural control and
adaptation.
• Progression: is ensured through a basic locomotor pattern that
produces and coordinates rhythmic patterns of muscle activation in
legs and trunk that successfully move the body in desired direction.
• It also requires the ability to initiates and terminate locomotion, as
well as to guide locomotion toward end points that are not always
visible.

10. LOCOMOTION
• Postural control: reflects the need to establish and maintain an
appropriate posture and the demand for dynamic stability of the
moving body.
• Dynamic stability involves counteracting not only the force of gravity
but also other expected and unexpected forces.
• The ability to adapt gait to meet the goals of the individual and the
demands of the environment.

11. LOCOMOTION
• Successful locomotion in challenging environments requires that gait
patterns be adapted in order to avoid obstacles, negotiate uneven
terrain and change speed and direction as needed.
• The requirements must be accomplished with strategies that are both
energy efficient and effective in minimizing stress to the locomotor
apparatus, thus ensuring the long-term structural integrity of the
system over the lifespan of the person.

12. LOCOMOTION
GAIT
STANCE SWING
SUPPORT PHASE (FORCES)
HORIZONTAL (AGAINST SUPPORT
SURFACE)(PROGRESSION)(TO MOVE THE BODY IN
DESIRED DIRECTION)
VERTICAL (POSTURAL CONTROL) (TO SUPPORT THE
BODY MASS AGAINST GRAVITY)
PROGRESSION- ADVANCEMENT OF SWING LEG
POSTURAL CONTOL- REPOSITIONING LIMB IN
PREPARATION FOR WEIGHT ACCEPTANCE
(TO AVOID TOE DRAG AND OBSTACLES IN ITS
PATH)

13. LOCOMOTION
• It is the interaction of 3 different chains:
PRIMARY SECONDARY TYPES
ARTICULAR MUSCULAR POSTURAL
NEUROLOGICAL KINETIC
MUSCULAR ARTICULAR SYNERGIST
NEUROLOGICAL MUSCLE SLINGS
MYOFASCIAL CHAINS
NEUROLOGICAL ARTICULAR PRIMITIVE REFLEXIVE
CHAINS
MUSCULAR SENSORIMOTOR SYSTEM
NEURODEVELOPMENTAL
LOCOMOTOR CHAINS

14. NEUROLOGICAL CHAINS

15. PROTECTIVE REFLEXIVE CHAIN
Two fundamental protective reflex arc, crossed extensor and
withdrawal reflex which are triggered by sensory receptors.
• Flexor withdrawal reflex:
Excessive heat or noxious stimulus.
Activation of flexor and inhibition of extensor.
Pulling of the limb away from the stimulus.

16. PROTECTIVE REFLEXIVE CHAIN
• Crossed extensor reflex:
Cutaneous noxious stimuli.
Flexor activation on the same side and extensor activation on the c/l
side.
Pushing the noxious stimuli away from the c/l limb.

17. SENSORIMOTOR CHAINS
• Linked neurologically through afferent and efferent systems in
controlling feedback and feed forward mechanisms.
• Provides both local and lobal dynamic stabilization of the joints
through muscle activity.
• Reflexive stabilization: on contraction of one muscle the other muscle
has to relax to provide stability of that particular joint.(reciprocal
inhibition)

18. SENSORIMOTOR CHAIN
• Evidence: eg. Horal and Nashner in 1986 in their study demonstrated
that on giving perturbation on the human body in one direction say,
anterior direction the opposite side muscle contract to maintain the
balance of the body in the distal to proximal way (ankle strategy) to
maintain smaller perturbation and proximal to distal way (hip
strategy) against a larger pertubation.
• The most important stabilizing sensorimotor chain in human body is
the pelvic chain, consisting of the TrA, multifidus, diaphragm and the
pelvic floor. These four muscles are coactivated in the pelvis for its
stability and force transmission. Pelvic weakness has shown both
proximal and distal pathologies such as LBP, groin strains, IT band
syndromes, anterior knee pain , ACL tears , ankle sprains.

19. SENSORIMOTOR CHAIN
• The sensorimotor chain depends on proprioception. Joint dysfunction
often disrupts the dynamic stabilization of the chain.
• Evidence: eg. A study by falla et al, demonstrated delayed activation
of deep cervical flexor on upper extremity tasks in whiplash injury
patients.
• Delayed activation of middle and lower traps in patients with
shoulder impingement. Cods et al,2003.

20. SENSORIMOTOR CHAIN
• ADAPTATIONS: These adaptation takes place when dysfunction such
as pain or pathology within the sensorimotor system occurs. The
adaptation may be in the form of systemic and predictable pattern.
• Janda describes the adaptation as follows:

21. SENSORIMOTOR CHAIN
1. Horizontal adaptation: occurs when impaired function in one joint
or muscle creates reaction and adaptation in the other joint
segments. Commonly seen in spine ,eg; LBP often leads to cervical
syndromes.
Evidence: Horal et al, suggested that after 6 years of first episode of
LBP, the individual develops cervical syndromes. Muscle conform to
horizontal adaptation creating a predictable pattern. Can be either
proximal to distal or either way.

22. SENSORIMOTOR CHAIN
2. Vertical adaptation: occurs between CNS and PNS. Adapt action of
one part of the sensorimotor system leads to impairment in the
function of the entire motor system.
• May progress from PNS to CNS or either way. In stroke or CP child , it
is seen as change in motor programming that is reflected in abnormal
movement pattern.
• Demonstrated in global movement pattern or postural control.

23. NEURODEVELOPMENTAL LOCOMOTOR
PATTERN
• There are two groups of muscles in phylogenetic origin: tonic and
phasic.
1. Tonic system: older in origin, dominated, involved in repetitive and
rhythmic activities and also involves in withdrawal reflex in UE and
LE. Predominant action in flexion.
2. Phasic system: younger in origin, typically work against gravity.
Mainly for postural stabilization, predominant action is extension.

24. NEURODEVELOPMENTAL LOCOMOTOR
PATTERN
• Study of movements in infants as they mature is called as
developmental kinesiology.
• Innate reflexes seen in infants such as ATNR and STNR integrate into
the MS system and become the function of the human being. These
primitive reflexes may reoccur if any injury is seen globally in CNS.
• Tonic and phasic muscles do not function individually, rather they
work through co-activation for posture, gait and coordinated
movements.
• These co-activation occurs in particular chains to achieve the desire
movement or action to be achieved synchronously in a well balanced
way.

25. NEURODEVELOPMENTAL LOCOMOTOR
PATTERN
• Tonic and phasic chains of UE and LE:
CO-ACTIVATION CHAINS UPPER QUARTER LOWER QUARTER
FUNCTIONAL MOVEMENTS PREHENSION,GRASPING CREEPING,CRAWLING
REACHING GAIT
TONIC FLEXION PLANTARFLEXION
IR INVERSION
ADDUCTION FLEXION
PRONATION IR
ADDUCTION
PHASIC EXTENSION DORSIFLEXION
ER EVERSION
ABDUCTION EXTENSION
SUPINATION ER
ABDUCTION

26. NEURODEVELOPMENTAL LOCOMOTOR
PATTERN
• The proper balance between two chains and upper lower quarter is
demonstrated by normal gait and posture.
• This combined integration between both the chains in upper and
lower quarters, specifically co-activation of c/l UE and LE leads to
reciprocal arm and leg movements during gait.

27. DIFFERENT STRUCTURES OF
NERVOUS SYSTEM PLAYS DIFFERENT
IMPORTANT ROLE IN LOCOMOTION

29. NEURAL CONVERGENCE
• Convergence refers to multiple afferent inputs onto a single neuron or
nucleus.
• Afferent input refers to signals providing incoming information to the
target neuron (includes descending as well as peripheral sensory
input).Convergence occurs at every level of the Central Nervous
System.
• Segmentally, interneurons and motor neurons receive multiple
inputs.
• The complexity increases in supraspinal centers.

30. NEURAL CONVERGENCE
• Determining which input has greater relative influence is a difficult
task.
• The difficulty of the task is increased by the fact that the relative
influences of afferent inputs change within a situational context, the
position of the limbs, weight bearing status and anticipatory motor
set.

31. NEURAL CONVERGENCE
• Convergence is an important concept to bear in mind to understand
about the inputs and outputs of various neural structures and
attempting to summarise function based on connectivity.
• Because of the complexity introduced by the convergence, divergence
and neuromodulation, however, descriptions of neural connectivity
alone may not be able to accurately determine what initiates,
generates, and maintains locomotion.

32. CENTRAL PATTERN GENERATORS

33. CENTRAL PATTERN GENERATORS
• CPGs refer to grouping of neurons or neural circuits that can generate
co-ordinated movement autonomously.
• Reflexive movements of human fetus start at 8 week of gestation.
• It has been observed that infants with total loss of cerebral cortex
development (anencephaly) also has co-ordinated leg
movements(stepping), which indicates presence of same mechanism
at spinal level, generating the movements known as CPG.

34. CENTRAL PATTERN GENERATORS
• CPGs can generate co-ordinating movement even in absence of
afferent inputs but if afferent neurons are intact, it gives different
outputs as per requirement of speed.
• For eg. Walking , running its activity constantly changes per inputs.
• Command neurons are the neurons which pick up the preferred
sensory input for a specific phase and initiate CPGs.

35. CENTRAL PATTERN GENERATORS
• Though this is been seen in intact SC but not true for cord injury at
higher levels or loss of efferents from cortex and hence biased for
humans.
• The possible description is quadripedal locomotion requires co-
ordinated movements for all four limbs.
• Bipedal requires more of balance i.e. equilibrium.
• As equilibrium is largely a supraspinal function. Humans have got
efferent pathways more as compared to any other animal substituting
the CPGs.

36. CENTRAL PATTERN GENERATORS

37. FLEXOR REFLEX AFFERENTS
• Flexor reflex afferents (FRAs) refers to a multisensorial and
interneuronal reflex system that appears to be at least partially
responsible for the generation of locomotion. The afferents include in
this reflex pathway include mechanoreceptors, cutaneous afferents,
nociceptors, joint afferents and muscle afferents.
• Activity in one motor neuronal pool generally results in inhibition of
antagonist pools. Alternating activity between various motor neuron
pool forms the basis for the rhythmic locomotor activity.

38. PERIPHERAL RECEPTORS AND AFFERENTS

39. PERIPHERAL RECEPTORS AND AFFERENTS
• Generation of locomotion depends on sensory inputs, the most
important input is from muscle.
• For a co-ordinated smooth bipedal locomotion, constant monitoring
of muscle length and tension is required.
• This is done by muscle spindles and GTOs which are sensitive to
length/tension.

40. PERIPHERAL RECEPTORS AND AFFERENTS
• Muscle spindles is supplied by gamma motor neurons which
determines sensitivity of muscle stretch i.e. changes its sensitivity as
per requirement of movement.
• This helps in dynamic changes in muscle length during human
locomotion.
• Thus acting as a feedforward mechanism along with feedback.

41. PERIPHERAL RECEPTORS AND AFFERENTS
• GTOs are contraction sensitive mechanoreceptors innervated by Ib
fibers.
• GTOs constantly alters the force output of different muscles as per
requirement, as in stance phase flexors are inhibited.

42. BRAINSTEM

43. BRAINSTEM
• Brainstem has got FOUR important locomotor region:
1. Mesencephalic locomotor region:
Receives afferents from BG, limbic system and sensorimotor cortex and
connects to spinal circuitry via reticulospinal tract. It is important for
relay b/w cortical limbic drive and CPGs.
2. Pontine locomotor regions:
Present just below MLR, may extend till upper cervical spinal cord.
These regions are responsible for postural tone and changes firing
within MLR.

44. BRAINSTEM
3. Subthalamic locomotor regions:
Necessary for modulation of locomotion pattern. Studies have been
done mainly on animals, which shows loss of ability to avoid obstacles
in absence of this region.
4. Reticular formation region:
Network of circuit, located at brainstem from midbrain to medulla.
Function- temporal and spatial co-ordination of movement.

45. CEREBELLUM

46. CEREBELLUM
• Important function for smooth execution of voluntary movements.
• Some regions of cerebellar cortex are active before movement and
preset the body for indented movement.
• The cerebellum receives somatopically organized inputs from cerebral
cortex, brainstem nuclei such as vestibular nuclei.
• Also from dorsoventral spinothalamic tracts both tracts gives this
similar information.

47. BASAL GANGLIA

48. BASAL GANGLIA
• Functions: play an important role in initiation and termination of
movement.
• Processes sensory stimuli and determine which stimuli will be used by
the CNS to impact movement.
• It not only integrate sensory information, but also attach situational
or emotional significance to it.

49. CEREBRAL CORTEX

50. CEREBRAL CORTEX
• Functions: motor planning, visuomotor co-ordination, cognitive
aspects of motor control.
• Cortical neurons often are activated before movement onset and
typically fire phasically during locomotion.
• For eg. Equilibrium, bipedal gait, anticipatory muscle action and
bodily responses need higher organization are done by cerebral
cortex.

51. CEREBRAL CORTEX
• Cerebral cortex makes a motor planning by integrating sensory
information from neurons within functionally action cortical cells.
• By long loops trans cortical reflex pathways it can modulate and
shape, simple spinal reflexes.
• This shaping is vitally important for anticipatory reactions.

52. CONTROL MECHANISM FOR GAIT
• Much of the research on locomotion control is done in animals,
relating it to experiments examining it in humans.
PATTERN GENERATORS FOR GAIT:
• It took almost 3 decades in research to understand the role of
nervous system control of the basic rhythmic movements underlying
locomotion.
• CPGs within spinal cord play an important role in the production of
these movement.

53. CONTROL MECHANISM FOR GAIT
• First experiment: (late 1800s Sherrington and molt)
• Served the SC of animals to eliminate the influence of higher brain centers.
• Found that the hind limbs continued to exhibit alternating movements.
• Second experiment: (in monkeys)
• Cut the sensory nerve roots on one side of the SC.
• Eliminating sensory inputs contributing to stepping on one side of the
body.
• Found that monkeys did not use the limbs that had undergone de-
afferentation during walking.
LOCOMOTION REQUIRES SENSORY INPUT

54. CONTROL MECHANISM FOR GAIT
• Created a model of locomotor control that states that the control of
locomotion to a set of reflex chains, with the output from one phase
of the step cycle acting as a sensory stimulus to reflex activate the
next phase.
• Graham brown (1911) showed opposite result.
• Making b/l sensory root lesions in animals whose SC has been
transected (spinalized animals), he could see rhythmic walking
movements.
• Why different results????

55. CONTROL MECHANISM FOR GAIT
• Taub and berman (1968):
• Result supporting graham brown
• When one limb has no sensation, and the sound limb is giving
appropriate input.
• The animal prefers not to use the limb which has no sensation.
• When they constrained the sound limb, the animal started using the
limb undergone deafferentation.
• Approach used in CIMT.

56. CONTROL MECHANISM FOR GAIT
• Forssberg et al,1977: muscle activity in spinalized cats is similar to
that seen in normal cats walking on treadmill.
• Smith et al, 1979: in addition, the spinalized cat is capable of fully
recruiting motor units within the SC when increasing gait from a walk
to a gallop.
• Graham brown proposed that there was a CPG creating the rhythmic
alternating flexor and extensor activity in spinal locomotion.

57. CONTROL MECHANISM FOR GAIT
• Principles:
• First: each of limbs is separately controlled by its own CPG.
• Second: CPGs have two groups of excitatory interneurons-the half centers-
that control the activity of flexor and extensor motor neurons.
• Third: inhibitory connections between the half centers allow only one
center to be active at a time.
• Fourth: a fatigue process, gradually reduces excitation in the active half-
center, allowing phase switch.
• Finally, inhibition of antagonist and agonist motor neurons is tightly
coupled.

58. CONTROL MECHANISM FOR GAIT
Two level CPG-model
Rhythm generator
Regulate gait speed ,
step cycle periods and
phase durations.
Pattern formation
Level of motor neuron
activity (as this has its own
independent mesencephalic
locomotor region input)

59. CONTROL MECHANISM FOR GAIT
• CPGs and descending pathways from higher centers and sensory
feedback from the periphery allow the rich variation in locomotor
patterns and adaptability to task and environmental conditions.
• CPGs – Body-weighted support treadmill training.

60. CONTROL MECHANISM FOR GAIT
• Descending influences:
• Important in the control of locomotor activity.
• Roles of higher centers are studied by transecting the brain of animals
along the neuraxis and observing the subsequent locomotor behavior.
• Mainly 3 systems:
1. Spinal
2. Decerebrate
3. Decorticate

61. CONTROL MECHANISM FOR GAIT

62. SENSORY FEEDBACK & ADAPTATION OF GAIT
• Normal locomotion requires ability to adapt gait to a wide range of
environments.
• For which sensory information is critical.
• Loss of it can truly alter the gait.
• Eg. In gait ataxia (loss of proprioception)
Equilibrium control
Reactive
Situation depending
Feedback
Anticipatory
Feed forward

63. REACTIVE STRATEGIES FOR MODIFYING GAIT
• SOMATOSENSORY SYSTEMS:
• Through a continuous rhythmic alternating contraction in muscles of
all joints of leg is seen in spinalized animals.
• But it does not declares that there is no role of sensory information.
• The movement characteristics differences can be observed and help
us to understand the role of it in the control of locomotion.

64. REACTIVE STRATEGIES FOR MODIFYING GAIT
SENSORY INFORMATIONS
Information from
limbs
Joint receptors
Muscle spindle afferents
(stretch hip flexors)
GTO afferents (Ib)
(inhibit flexors and promote
extensors)
Cutaneous
stimulation

65. REACTIVE STRATEGIES FOR MODIFYING GAIT
• Vision:
• Visual flow cues helps us determine our speed of locomotion.
• Visual flow cues also influence the alignment of the body with
reference to gravity and the environment during walking.
• Vestibular system:
• Otolith organs, saccule and utricle detect the angle of the head with
respect to gravity and the visual system.
• Vestibulo-ocular reflex- stabilizing gaze during head movement.
• Complex movements like walking; postural control- top down mode.

66. PROACTIVE STRATEGIES FOR MODIFYING GAIT
AVOIDANCE STRATEGIES (SHORT TERM) ACCOMODATION STRATEGIES (LONG TERM)
CHANGING THE PLACEMENT OF FOOT REDUCING STEP LENGTH
INCREASE GROUND CLEARANCE TO AVOID AN
OBSTACLE
SHIFTING THE PROPULSIVE FROM DISTAL TO
PROXIMAL WHEN CLIMBING STAIRS
CHANGING THE DIRECTION OF GAIT
STOPPING

67. REFERENCES
• Anne Shumway-cook , Majorie H.; Motor Control; Fourth edition.
• Das P, Mc Collum G. Invariant structure in locomotion.
Neuroscience.1988 June 1.
• Patla AE, Prentice SD, Robinson C, Neufeld. Visual control of
locomotion: strategies for changing direction and for going over
obstacles.1991 Aug 17.
• Patla AE. Understanding the roles of vision in the control of human
locomotion. Gait and Posture.1997 Feb 1.

68. THANK YOU