The sections in this article are:


1
Neural Control of Postural Orientation and Equilibrium
1.1
Behavioral Goals

1.2
Biomechanical Principles

1.3
Postural Strategies




2
Postural Orientation
2.1
Stiffness and Tonic Muscle Activation

2.2
Controlling Postural Orientation

2.3
Internal Representation of Postural Orientation




3
Coordination of Postural Equilibrium
3.1
Triggered Reactions to External Disturbances

3.2
Anticipatory Postural Adjustments for Voluntary Movement

3.3
Modeling of Postural Coordination




4
Sensory Control of Postural Orientation and Equilibrium
4.1
Sensory Integration

4.2
Somatosensory System

4.3
Vestibular System

4.4
Visual System




5
Central Neural Control of Posture
5.1
Spinal Cord and Brainstem

5.2
Basal Ganglia

5.3
Cerebellum

5.4
Cerebral Cortex




6
Concluding Remarks

Postural Orientation and Equilibrium

In order to assess the relative contribution and the interactions of the plantar cutaneous and muscle proprioceptive feedback in controlling human erect posture, single or combined vibratory stimuli were applied to the forefoot areas and to the tendons of the tibialis anterior muscles of nine standing subjects using various vibration frequency patterns (ranging from 20 to 80 Hz). The variations in the centre of foot pressure, ankle angle and the EMG activities of the soleus and tibialis anterior muscles of each subject were recorded and analysed. Separate stimulation of the plantar forefoot zones or the tibialis anterior muscles always resulted in whole-body tilts oppositely directed backwards and forwards, respectively, the amplitude of which was proportional to the vibration frequency. EMG activity of ankle muscles also varied according to the direction of the postural responses. However, the same vibration frequency did not elicit equivalent postural responses: in the low frequency range, tactile stimulation induced stronger postural effects than proprioceptive stimulation, and the converse was the case for the higher frequency range. Under sensory conflict conditions, i.e. foot sole-flexor ankle muscle co-stimulation, the direction of the body tilts also varied according to the difference and the absolute levels of the vibration frequencies. In all cases, the resulting postural shifts always corresponded to the theoretical sum of the isolated effects observed upon vibrating each of these two sensory channels. We proposed that tactile and proprioceptive information from the foot soles and flexor ankle muscles might be co-processed following a vector addition mode to subserve the maintenance of erect stance in a complementary way.

https://physoc.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-7793.2001.0869e.x

Foot sole and ankle muscle inputs contribute jointly to human erect posture regulation.

M aintaining balance is essential to carrying out daily tasks without falling. This review will describe the impact of impaired postural control on older adults, operationalize what is meant by postural control, and outline postural control test batteries. Findings from highly quantitative, laboratorybased studies will be discussed because these data serve as the foundation of knowledge regarding aging and postural control. Most of the review will be concerned with the changes in postural control that can be expected with aging and how aging and disease affect organ-system-based models of postural control. The review will also identify how ageand disease-related organ system changes might affect training to improve postural control.

https://deepblue.lib.umich.edu/bitstream/handle/2027.42/111262/j.1532-5415.1994.tb06081.x.pdf;sequence=1

Postural control in older adults

Maintenance of postural balance requires an active sensorimotor control system. Current data are limited and sometimes conflicting regarding the influence of the proprioceptive, visual, and vestibular afferent systems on posture control in children. This study investigated the development of sensory organization according to each sensory component in relation to age and sex. A total of 140 children (70 males, 70 females; mean age 10y [SD 4y]; age range 3y 5mo-16y 2mo) and 20 adults (10 males, 10 females; mean age 30y 6mo [SD 8y 4mo]; age range 17y 2mo-49y 1mo) were examined using the Sensory Organization Test. Participants were tested in three visual conditions (eyes open, blindfolded, and sway-referenced visual enclosure) while standing on either a fixed or a sway-referenced force platform. Mean equilibrium scores for the six balance conditions showed rapid increases and maturation ceiling levels for age-related development of the sensorimotor control system. Proprioceptive function seemed to mature at 3 to 4 years of age. Visual and vestibular afferent systems reached adult level at 15 to 16 years of age, revealing differences between young males and females. Characterizing balance impairments can contribute to the diagnostic evaluation of neuromotor disorders.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8749.2006.tb01299.x

Effect of age and sex on maturation of sensory systems and balance control.

Objective To provide an overview of currently available sensorimotor assessment techniques. Data sources We drew information from an extensive review of the scientific literature conducted in the areas of proprioception, neuromuscular control, and motor control measurement. Literature searches were conducted using MEDLINE for the years 1965 to 1999 with the key words proprioception, somatosensory evoked potentials, nerve conduction testing, electromyography, muscle dynamometry, isometric, isokinetic, kinetic, kinematic, posture, equilibrium, balance, stiffness, neuromuscular, sensorimotor, and measurement. Additional sources were collected using the reference lists of identified articles. Data synthesis Sensorimotor measurement techniques are discussed with reference to the underlying physiologic mechanisms, influential factors and locations of the variable within the system, clinical research questions, limitations of the measurement technique, and directions for future research. Conclusions/recommendations The complex interactions and relationships among the individual components of the sensorimotor system make measuring and analyzing specific characteristics and functions difficult. Additionally, the specific assessment techniques used to measure a variable can influence attained results. Optimizing the application of sensorimotor research to clinical settings can, therefore, be best accomplished through the use of common nomenclature to describe underlying physiologic mechanisms and specific measurement techniques.

Sensorimotor System Measurement Techniques

Postural stabilization in altered visual, vestibular, and somatosensory conditions was investigated in humans subjected to either a fast unidirectional displacement or to a continuous sinusoidal movement of the standing support. Visual inputs were varied in four ways: (1)stroboscopic illumination, (2)stabilizing the visual surround with respect to head movements, (3)inducing apparent body movement in pitch using stripe patterns which moved continuously up or down in front of the subject, (4)eye closure. Static vestibular (and neck) input was modified by bending the head forwards or backwards, or to the right or left shoulder with the eyes closed. Somatosensory input from both feet was reduced by an ischaemic block at a level just above the ankle joints. With fast, transient, toe-up platform displacements (high-frequency test) neither the biomechanical parameters as measured by the displacement of the centre of foot pressure nor the early EMG responses of the anterior tibial and triceps surae muscles were modified by a manipulation of visual, vestibular or somatosensory feedback conditions. Sudden disturbances are obviously compensated by an early set of reflex-like muscle responses that, depending on the starting position, are stereotypically released without feedback control to save time at the expence of accuracy (emergency reaction). Continuous regulation of upright stance during sinusoidal displacement at 1 or 0.3 Hz (low-frequency test), however, clearly depends on visual, vestibular, and somatosensory feedback. Studies in patients should contain both tests, since each examines different functions of the very complex posture stabilizing network. Manipulations of sensory feedback, however, are only recommended in the low-frequency test. The experimental suppression or disturbance by disease of two of the three feedback loops invariably causes a conspicuous postural instability.

H.-C. Diener

Papers

On the role of vestibular, visual and somatosensory information for dynamic postural control in humans.