Motor Patterns During Walking on a Slippery Walkway

Friction and gravity represent two basic physical constraints of terrestrial locomotion that affect both motor patterns and the biomechanics of bipedal gait. To provide insights into the spatiotemporal organization of the motor output in connection with ground contact forces, we studied adaptation of human gait to steady low-friction conditions. Subjects walked along a slippery walkway (7 m long; friction coefficient ≃ 0.06) or a normal, nonslippery floor at a natural speed. We recorded gait kinematics, ground reaction forces, and bilateral electromyographic (EMG) activity of 16 leg and trunk muscles and we mapped the recorded EMG patterns onto the spinal cord in approximate rostrocaudal locations of the motoneuron (MN) pools to characterize the spatiotemporal organization of the motor output. The results revealed several idiosyncratic features of walking on the slippery surface. The step length, cycle duration, and horizontal shear forces were significantly smaller, the head orientation tended to be stabilized in space, whereas arm movements, trunk rotations, and lateral trunk inclinations considerably increased and foot motion and gait kinematics resembled those of a nonplantigrade gait. Furthermore, walking on the slippery surface required stabilization of the hip and of the center-of-body mass in the frontal plane, which significantly improved with practice. Motor patterns were characterized by an enhanced (roughly twofold) level of MN activity, substantial decoupling of anatomical synergists, and the absence of systematic displacements of the center of MN activity in the lumbosacral enlargement. Overall, the results show that when subjects are confronted with unsteady surface conditions, like the slippery floor, they adopt a gait mode that tends to keep the COM centered over the supporting limbs and to increase limb stiffness. We suggest that this behavior may represent a distinct gait mode that is particularly suited to uncertain surface conditions in general.

Download Full-text

Kinematics in Newly Walking Toddlers Does Not Depend Upon Postural Stability

Journal of Neurophysiology ◽

10.1152/jn.00088.2005 ◽

2005 ◽

Vol 94 (1) ◽

pp. 754-763 ◽

Cited By ~ 53

Author(s):

Yuri P. Ivanenko ◽

Nadia Dominici ◽

Germana Cappellini ◽

Francesco Lacquaniti

Keyword(s):

Postural Stability ◽

Balance Control ◽

Vertical Movement ◽

The Body ◽

Emg Activity ◽

Older Children ◽

Motor Patterns ◽

Gait Kinematics ◽

Locomotor Strategy ◽

Stepping In Place

When a toddler starts to walk without support, gait kinematics and electromyographic (EMG) activity differ from those of older children and the body displays considerable oscillations due to poor equilibrium. Postural instability clearly affects motor patterns in adults, but does instability explain why toddlers walk with a different gait? Here we addressed this question by comparing kinematics and EMGs in toddlers performing their first independent steps with or without hand or trunk support. Hand support significantly improved postural stability and some general gait parameters, reducing percent of falls, step width, lateral hip deviations and trunk oscillations. However, the kinematic and EMG patterns were unaffected by increased postural stability. In particular, the co-variance of the angular motion of the lower limb segments, the pattern of bilateral coordination of the vertical movement of the two hip joints, high variability of the foot path, the elliptic or single peak trajectory of the foot in the swing phase, and characteristic EMG bursts at foot contact remained idiosyncratic of toddler locomotion. Instead the toddler pattern shared fundamental features with adult stepping in place, suggesting that toddlers implement a mixed locomotor strategy, combining forward progression with elements of stepping in place. Furthermore, gait kinematics remained basically unchanged until the occurrence of the first unsupported steps and rapidly matured thereafter. We conclude that idiosyncratic features in newly walking toddlers do not simply result from undeveloped balance control but may represent an innate kinematic template of stepping.

Download Full-text

Kinematics in Newly Walking Toddlers Does Not Depend Upon Postural Stability

Journal of Neurophysiology ◽

10.1152/jn.00088.2004 ◽

2005 ◽

Vol 94 (1) ◽

pp. 754-763 ◽

Cited By ~ 19

Author(s):

Yuri P. Ivanenko ◽

Nadia Dominici ◽

Germana Cappellini ◽

Francesco Lacquaniti

Keyword(s):

Postural Stability ◽

Balance Control ◽

Vertical Movement ◽

The Body ◽

Emg Activity ◽

Older Children ◽

Motor Patterns ◽

Gait Kinematics ◽

Locomotor Strategy ◽

Stepping In Place

Download Full-text

Brain stem integration of vocalization: role of the midbrain periaqueductal gray

Journal of Neurophysiology ◽

10.1152/jn.1994.72.3.1337 ◽

1994 ◽

Vol 72 (3) ◽

pp. 1337-1356 ◽

Cited By ~ 119

Author(s):

S. P. Zhang ◽

P. J. Davis ◽

R. Bandler ◽

P. Carrive

Keyword(s):

Muscle Activity ◽

Sound Production ◽

Type A ◽

Periaqueductal Gray ◽

Emg Activity ◽

Digastric Muscle ◽

Type B ◽

Motor Patterns ◽

Homocysteic Acid ◽

Lower Amplitude

1. The contribution of the midbrain periaqueductal gray (PAG) to the central regulation of vocalization was investigated by analyzing the electromyographic (EMG) changes in respiratory, laryngeal, and oral muscles evoked by microinjection of D,L-homocysteic acid (DLH) in the PAG of unanesthetized, precollicular decerebrate cats. Moderate to large (6-40 nmol) doses of DLH evoked natural-sounding vocalization as well as increases in inspiratory depth and respiratory rate. 2. Two basic types of vocalization were evoked, each associated with a distinct and characteristic pattern of respiratory, laryngeal and oral EMG changes. Type A vocalization (voiced sounds such as howl/mew/growl) was characterized by excitation of the cricothyroid (CT) and thyro-arytenoid (TA) muscles, and inhibition of the posterior crico-arytenoid (PCA) muscle, whereas type B vocalization (unvoiced hiss sounds) was characterized by excitation of the PCA and TA muscles and no significant activation of the CT muscle. In addition, stronger expiratory (external oblique, internal oblique, internal intercostal) EMG increases were associated with type A responses, and larger increases in genioglossus and digastric muscle activity were associated with type B responses. 3. Microinjections of small doses of DLH (300 pmol-3 nmol), also evoked patterned changes in muscle activity (usually without audible vocalization) that, although of lower amplitude, were identical to those evoked by injections of moderate to large DLH doses. In no such experiments (175 sites) were individual muscles activated by small dose injections of DLH into the PAG. Further, type A vocalization/muscle patterns were evoked from PAG sites caudal to those at which type B vocalization/muscle patterns were evoked. 4. Considered together these results indicate: that the PAG contains topographically separable groups of neurons that coordinate laryngeal, respiratory, and oral muscle patterns characteristic of two fundamental types of vocalization and that the underlying PAG organization takes the form of a representation of muscle patterns, rather than individual muscles. 5. The patterns of EMG activity evoked by excitation of PAG neurons were strikingly similar to previously reported patterns of EMG activity characteristic of major phonatory categories in higher species, including humans (e.g., vowel phonation, voiceless consonant phonation). These findings raise the possibility that the sound production circuitry of the PAG could well be utilized by cortical and subcortical "language structures" to coordinate basic respiratory and laryngeal motor patterns that are necessary for speech.

Download Full-text

Retracing your footsteps: developmental insights to spinal network plasticity following injury

Journal of Neurophysiology ◽

10.1152/jn.00575.2017 ◽

2018 ◽

Vol 119 (2) ◽

pp. 521-536 ◽

Cited By ~ 8

Author(s):

C. Jean-Xavier ◽

S. A. Sharples ◽

K. A. Mayr ◽

A. P. Lognon ◽

P. J. Whelan

Keyword(s):

Spinal Cord ◽

Neuronal Excitability ◽

Weight Bearing ◽

Rhythmic Activity ◽

Motor Output ◽

Parallel Mechanisms ◽

Sensory Afferents ◽

Motor Patterns ◽

Network Function ◽

Cord Injury

During development of the spinal cord, a precise interaction occurs between descending projections and sensory afferents, with spinal networks that lead to expression of coordinated motor output. In the rodent, during the last embryonic week, motor output first occurs as regular bursts of spontaneous activity, progressing to stochastic patterns of episodes that express bouts of coordinated rhythmic activity perinatally. Locomotor activity becomes functionally mature in the 2nd postnatal wk and is heralded by the onset of weight-bearing locomotion on the 8th and 9th postnatal day. Concomitantly, there is a maturation of intrinsic properties and key conductances mediating plateau potentials. In this review, we discuss spinal neuronal excitability, descending modulation, and afferent modulation in the developing rodent spinal cord. In the adult, plastic mechanisms are much more constrained but become more permissive following neurotrauma, such as spinal cord injury. We discuss parallel mechanisms that contribute to maturation of network function during development to mechanisms of pathological plasticity that contribute to aberrant motor patterns, such as spasticity and clonus, which emerge following central injury.

Download Full-text

Forms of Forward Quadrupedal Locomotion. II. A Comparison of Posture, Hindlimb Kinematics, and Motor Patterns for Upslope and Level Walking

Journal of Neurophysiology ◽

10.1152/jn.1998.79.4.1687 ◽

1998 ◽

Vol 79 (4) ◽

pp. 1687-1701 ◽

Cited By ~ 87

Author(s):

Patricia Carlson-Kuhta ◽

Tamara V. Trank ◽

Judith L. Smith

Keyword(s):

Stance Phase ◽

Emg Activity ◽

Similar Data ◽

Flexor Muscle ◽

Motor Patterns ◽

Quadrupedal Locomotion ◽

Hindlimb Muscles ◽

Level Walking ◽

Ankle Joints ◽

Hindlimb Kinematics

Carlson-Kuhta, Patricia, Tamara V. Trank, and Judith L. Smith. Forms of forward quadrupedal locomotion. II. A comparison of posture, hindlimb kinematics, and motor patterns for upslope and level walking. J. Neurophysiol. 79: 1687–1701, 1998. To gain insight into the neural mechanisms controlling different forms of quadrupedal walking of normal cats, data on postural orientation, hindlimb kinematics, and motor patterns of selected hindlimb muscles were assessed for four grades of upslope walking, from 25 to 100% (45° incline), and compared with similar data for level treadmill walking (0.6 m/s). Kinematic data for the hip, knee, ankle, and metatarsophalangeal joints were obtained from digitizing ciné film that was synchronized with electromyographic (EMG) records from 13 different hindlimb muscles. Cycle periods, the structure of the step cycle, and paw-contact sequences were similar at all grades and typical of lateral-sequence walking. Also, a few half-bound and transverse gallop steps were assessed from trials at the 100% grade; these steps had shorter cycle periods than the walking steps and less of the cycle (68 vs. 56%) was devoted to stance. Each cat assumed a crouched posture at the steeper grades of upslope walking and stride length decreased, whereas the overall position of the stride shifted caudally with respect to the hip joint. At the steeper grades, the range and duration of swing-related flexion increased at all joints, the stance-phase yield was absent at the knee and ankle joints, and the range of stance-phase extension at knee and ankle joints increased. Patterns of muscle activity for upslope and level walking were similar with some notable exceptions. At the steeper grades, the EMG activity of muscles with swing-related activity, such as the digit flexor muscle, the flexor digitorum longus (FDL), and the knee flexor muscle, the semitendinosus (ST), was prolonged and continued well into midswing. The EMG activity of stance-related muscles also increased in amplitude with grade, and three muscles not active during the stance phase of level walking had stance activity that increased in amplitude and duration at the steepest grades; these muscles were the ST, FDL, and extensor digitorum brevis. Overall the changes in posture, hindlimb kinematics, and the activity patterns of hindlimb muscles during upslope walking reflected the need to continually move the body mass forward and upward during stance and to ensure that the paw cleared the inclined slope during swing. The implications of these changes for the neural control of walking and expected changes in hindlimb kinetics for slope walking are discussed.

Download Full-text

Interactions Between Posture and Locomotion: Motor Patterns in Humans Walking With Bent Posture Versus Erect Posture

Journal of Neurophysiology ◽

10.1152/jn.2000.83.1.288 ◽

2000 ◽

Vol 83 (1) ◽

pp. 288-300 ◽

Cited By ~ 117

Author(s):

R. Grasso ◽

M. Zago ◽

F. Lacquaniti

Keyword(s):

Gait Cycle ◽

Emg Activity ◽

Muscle Synergies ◽

Ground Reaction Forces ◽

Motor Patterns ◽

Erect Posture ◽

Body Segments ◽

Plane Orientation ◽

Temporal Coupling ◽

Reaction Forces

Human erect locomotion is unique among living primates. Evolution selected specific biomechanical features that make human locomotion mechanically efficient. These features are matched by the motor patterns generated in the CNS. What happens when humans walk with bent postures? Are normal motor patterns of erect locomotion maintained or completely reorganized? Five healthy volunteers walked straight and forward at different speeds in three different postures (regular, knee-flexed, and knee- and trunk-flexed) while their motion, ground reaction forces, and electromyographic (EMG) activity were recorded. The three postures imply large differences in the position of the center of body mass relative to the body segments. The elevation angles of the trunk, pelvis, and lower limb segments relative to the vertical in the sagittal plane, the ground reaction forces and the rectified EMGs were analyzed over the gait cycle. The waveforms of the elevation angles along the gait cycle remained essentially unchanged irrespective of the adopted postures. The first two harmonics of these kinematic waveforms explain >95% of their variance. The phase shift but not the amplitude ratio between the first harmonic of the elevation angle waveforms of adjacent pairs was affected systematically by changes in posture. Thigh, shank, and foot angles covaried close to a plane in all conditions, but the plane orientation was systematically different in bent versus erect locomotion. This was explained by the changes in the temporal coupling among the three segments. For walking speeds >1 m s−1, the plane orientation of bent locomotion indicates a much lower mechanical efficiency relative to erect locomotion. Ground reaction forces differed prominently in bent versus erect posture displaying characteristics intermediate between those typical of walking and those of running. Mean EMG activity was greater in bent postures for all recorded muscles independent of the functional role. The waveforms of the muscle activities and muscle synergies also were affected by the adopted posture. We conclude that maintaining bent postures does not interfere either with the generation of segmental kinematic waveforms or with the planar constraint of intersegmental covariation. These characteristics are maintained at the expense of adjustments in kinetic parameters, muscle synergies and the temporal coupling among the oscillating body segments. We argue that an integrated control of gait and posture is made possible because these two motor functions share some common principles of spatial organization.

Download Full-text

Behaviour and Motor Output for an Insect Walking on a Slippery Surface: II. Backward Walking

Journal of Experimental Biology ◽

10.1242/jeb.118.1.287 ◽

1985 ◽

Vol 118 (1) ◽

pp. 287-296 ◽

Cited By ~ 3

Author(s):

D. GRAHAM ◽

S. EPSTEIN

Keyword(s):

Motor Activity ◽

Motor Pattern ◽

Motor Output ◽

Retractor Muscle ◽

Backward Walking ◽

Stick Insects ◽

Weak Activity ◽

Slippery Surface ◽

Walking Recovery ◽

Simple Phase

Coordination of the legs and the motor activity of four muscles in a middle leg were recorded in adult stick insects walking on a slippery glass surface. Backward walking was not achieved by a simple phase shift of levators and depressors. In all muscles examined, there was a considerable disturbance of motor activity during backward walking when compared with that found in forward walking. In backward walking, recovery was performed, in the middle leg, by strong fast unit activity in the retractor muscle and all muscles showed weak activity at inappropriate times. Fast motor output appeared to be superimposed on the forward walking motor pattern to produce the movements required for backward walking in this insect.

Download Full-text

Effects on Muscle Activity From Microstimuli Applied to Somatosensory and Motor Cortex During Voluntary Movement in the Monkey

Journal of Neurophysiology ◽

10.1152/jn.1997.77.5.2446 ◽

1997 ◽

Vol 77 (5) ◽

pp. 2446-2465 ◽

Cited By ~ 40

Author(s):

Gail L. Widener ◽

Paul D. Cheney

Keyword(s):

Motor Cortex ◽

Muscle Activity ◽

Voluntary Movement ◽

Primary Motor Cortex ◽

Large Fraction ◽

Single Pulse ◽

Motor Output ◽

Emg Activity ◽

Spike Triggered Averaging ◽

Area 3A

Widener, Gail L. and Paul D. Cheney. Effects on muscle activity from microstimuli applied to somatosensory and motor cortex during voluntary movement in the monkey. J. Neurophysiol. 77: 2446–2465, 1997. It is well known that electrical stimulation of primary somatosensory cortex (SI) evokes movements that resemble those evoked from primary motor cortex. These findings have led to the concept that SI may possess motor capabilities paralleling those of motor cortex and speculation that SI could function as a robust relay mediating motor responses from central and peripheral inputs. The purpose of this study was to rigorously examine the motor output capabilities of SI areas with the use of the techniques of spike- and stimulus-triggered averaging of electromyographic (EMG) activity in awake monkeys. Unit recordings were obtained from primary motor cortex and SI areas 3a, 3b, 1, and 2 in three rhesus monkeys. Spike-triggered averaging was used to assess the output linkage between individual cells and motoneurons of the recorded muscles. Cells in motor cortex producing postspike facilitation (PSpF) in spike-triggered averages of rectified EMG activity were designated corticomotoneuronal (CM) cells. Motor output efficacy was also assessed by applying stimuli through the microelectrode and computing stimulus-triggered averages of rectified EMG activity. One hundred seventy-one sites in motor cortex and 68 sites in SI were characterized functionally and tested for motor output effects on muscle activity. The incidence, character, and magnitude of motor output effects from SI areas were in sharp contrast to effects from CM cell sites in primary motor cortex. Of 68 SI cells tested with spike-triggered averaging, only one area 3a cell produced significant PSpF in spike-triggered averages of EMG activity. In comparison, 20 of 171 (12%) motor cortex cells tested produced significant postspike effects. Single-pulse intracortical microstimulation produced effects at all CM cell sites in motor cortex but at only 14% of SI sites. The large fraction of SI effects that was inhibitory represented yet another marked difference between CM cell sites in motor cortex and SI sites (25% vs 93%). The fact that motor output effects from SI were frequently absent or very weak and predominantly inhibitory emphasizes the differing motor capabilities of SI compared with primary motor cortex.

Download Full-text

Motor Patterns and Kinematics During Backward Walking in the Pacific Giant Salamander: Evidence for Novel Motor Output

Journal of Neurophysiology ◽

10.1152/jn.1997.78.6.3047 ◽

1997 ◽

Vol 78 (6) ◽

pp. 3047-3060 ◽

Cited By ~ 28

Author(s):

Miriam A. Ashley-Ross ◽

George V. Lauder

Keyword(s):

Knee Joint ◽

Stance Phase ◽

Swing Phase ◽

The Body ◽

Motor Output ◽

Motor Patterns ◽

Backward Walking ◽

The Pacific ◽

Forward Locomotion ◽

Pacific Giant Salamander

Ashley-Ross, Miriam A. and George V. Lauder. Motor patterns and kinematics during backward walking in the Pacific Giant Salamander: evidence for novel motor output. J. Neurophysiol. 78: 3047–3060, 1997. Kinematic and motor patterns during forward and backward walking in the salamander Dicamptodon tenebrosus were compared to determine whether the differences seen in mammals also apply to a lower vertebrate with sprawling posture and to measure the flexibility of motor output by tetrapod central pattern generators. During treadmill locomotion, electromyograms (EMGs) were recorded from hindlimb muscles of Dicamptodon while simultaneous high-speed video records documented movement of the body, thigh, and crus and allowed EMGs to be synchronized to limb movements. In forward locomotion, the trunk was lifted above the treadmill surface. The pelvic girdle and trunk underwent smooth side-to-side oscillations throughout the stride. At the beginning of the stance phase, the femur was protracted and the knee joint extended. The knee joint initially flexed in early stance and then extended as the foot pushed off in late stance, reaching maximum extension just before foot lift-off. The femur retracted steadily throughout the stance. In the swing phase, the femur rapidly protracted, and the leg was brought forward in an “overhand crawl” motion. In backward walking, the body frequently remained in contact with the treadmill surface. The pelvic girdle, trunk, and femur remained relatively still during stance phase, and most motion occurred at the knee joint. The knee joint extended throughout most of stance, as the body moved back, away from the stationary foot. The knee flexed during swing. Four of five angles showed significantly smaller ranges in backward than in forward walking. EMGs of forward walking showed that ventral muscles were coactive, beginning activity just before foot touchdown and ceasing during the middle of stance phase. Dorsal muscles were active primarily during swing. Backward locomotion showed a different pattern; all muscles except one showed primary activity during the swing phase. This pattern of muscle synergy in backward walking never was seen in forward locomotion. Also, several muscles demonstrated lower burst rectified integrated areas (RIA) or durations during backward locomotion. Multivariate statistical analysis of EMG onset and RIA completely separated forward and backward walking along the first principal component, based on higher RIAs, longer durations of muscle activity, and greater synergy between ventral muscles during early stance in forward walking. Backward walking in Dicamptodon uses a novel motor pattern not seen during forward walking in salamanders or during any other locomotor activity in previously studied tetrapods. The central neuronal mechanisms mediating locomotion in this primitive tetrapod are thus capable of considerable plasticity.

Download Full-text

Cross-validated models of the relationships between neck muscle electromyography and three-dimensional head kinematics during gaze behavior

Journal of Neurophysiology ◽

10.1152/jn.00315.2011 ◽

2012 ◽

Vol 107 (2) ◽

pp. 573-590 ◽

Cited By ~ 5

Author(s):

Farshad Farshadmanesh ◽

Patrick Byrne ◽

Gerald P. Keith ◽

Hongying Wang ◽

Brian D. Corneil ◽

...

Keyword(s):

Three Dimensional ◽

Head Movements ◽

Polynomial Model ◽

Emg Activity ◽

Head Orientation ◽

Gaze Behavior ◽

Data Set ◽

Head Kinematics ◽

Musculoskeletal Anatomy ◽

Horizontal Head

The object of this study was to model the relationship between neck electromyography (EMG) and three-dimensional (3-D) head kinematics during gaze behavior. In two monkeys, we recorded 3-D gaze, head orientation, and bilateral EMG activity in the sternocleidomastoid, splenius capitis, complexus, biventer cervicis, rectus capitis posterior major, and occipital capitis inferior muscles. Head-unrestrained animals fixated and made gaze saccades between targets within a 60° × 60° grid. We performed a stepwise regression in which polynomial model terms were retained/rejected based on their tendency to increase/decrease a cross-validation-based measure of model generalizability. This revealed several results that could not have been predicted from knowledge of musculoskeletal anatomy. During head holding, EMG activity in most muscles was related to horizontal head orientation, whereas fewer muscles correlated to vertical head orientation and none to small random variations in head torsion. A fourth-order polynomial model, with horizontal head orientation as the only independent variable, generalized nearly as well as higher order models. For head movements, we added time-varying linear and nonlinear perturbations in velocity and acceleration to the previously derived static (head holding) models. The static models still explained most of the EMG variance, but the additional motion terms, which included horizontal, vertical, and torsional contributions, significantly improved the results. Several coordinate systems were used for both static and dynamic analyses, with Fick coordinates showing a marginal (nonsignificant) advantage. Thus, during gaze fixations, recruitment within the neck muscles from which we recorded contributed primarily to position-dependent horizontal orientation terms in our data set, with more complex multidimensional contributions emerging during the head movements that accompany gaze shifts. These are crucial components of the late neuromuscular transformations in a complete model of 3-D head-neck system and should help constrain the study of premotor signals for head control during gaze behaviors.

Download Full-text