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==Cortical control of posture==
==Cortical control of posture==
Traditionally postural control was regarded an automatic response to sensory stimuli generated by subcortical structures such as the brainstem and spinal circuits.<ref>Sherrington, C. S. (1910). Flexion‐reflex of the limb, crossed extension‐reflex, and reflex stepping and standing. The Journal of physiology, 40(1-2), 28-121; Magnus, R. (1926). The physiology of posture: Cameron Lectures. Lancet, 211(53), 1-536</ref> Since postural responses are generated quickly, without voluntary intent and with less variability than cued, voluntary movements, cerebral cortex was not considered to be involved in postural control.<ref>Diener, H. C., Dichgans, J., Bootz, F., & Bacher, M. (1984). Early stabilization of human posture after a sudden disturbance: influence of rate and amplitude of displacement. Experimental Brain Research, 56(1), 126-134; Keck, M. E., Pijnappels, M., Schubert, M., Colombo, G., Curt, A., & Dietz, V. (1998). Stumbling reactions in man: influence of corticospinal input. Electroencephalography and Clinical Neurophysiology/Electromyography and Motor Control, 109(3), 215-223</ref> Hence cortical contribution to postural regulation is controversial and highly debatable.<ref>Jacobs, J. V., & Horak, F. B. (2007). Cortical control of postural responses. Journal of neural transmission, 114(10), 1339-1348</ref> Furthermore, it was assumed that since postural control is automatic in nature, it utilized only limited attentional resources.<ref>Anne Shumway Cook, Wollcott (2007) Motor control, 3rd edition</ref> However, current evolving evidence from numerous neurophysiological, behavioural and neuroimaging studies (as given below) suggest cortical involvement in postural control and maintenance of balance. Studies also indicate that postural control involved significant attentional resources and does require cognitive and sensory processes depending on other influencing factors.<ref>Anne Shumway Cook, Wollcott (2007) Motor control, 3rd edition</ref>
Traditionally postural control was regarded an automatic response to sensory stimuli generated by subcortical structures such as the brainstem and spinal circuits.<ref>Sherrington, C. S. (1910). Flexion‐reflex of the limb, crossed extension‐reflex, and reflex stepping and standing. The Journal of physiology, 40(1-2), 28-121; Magnus, R. (1926). The physiology of posture: Cameron Lectures. Lancet, 211(53), 1-536</ref> Since postural responses are generated quickly, without voluntary intent and with less variability than cued, voluntary movements, cerebral cortex was not considered to be involved in postural control.<ref>Diener, H. C., Dichgans, J., Bootz, F., & Bacher, M. (1984). Early stabilization of human posture after a sudden disturbance: influence of rate and amplitude of displacement. Experimental Brain Research, 56(1), 126-134; Keck, M. E., Pijnappels, M., Schubert, M., Colombo, G., Curt, A., & Dietz, V. (1998). Stumbling reactions in man: influence of corticospinal input. Electroencephalography and Clinical Neurophysiology/Electromyography and Motor Control, 109(3), 215-223</ref> However, current evolving evidence from numerous neurophysiological and neuroimaging studies (as given below) suggest cortical involvement in postural control and maintenance of balance.

=== <u>Supportive evidence</u> ===

==== Behavioral studies ====
Based on the [[central capacity theory]], behavioral studies using [[dual-task paradigm]] are instrumental in evaluating the demands of [[attention]] for various postural tasks. According to the central capacity sharing theory, there are limited attentional resources and performance of any task demands utilization of some proportion of these resources.<ref>Anne Shumway Cook, Wollcott (2007) Motor control, 3rd edition</ref> In this model, there is simultaneous processing of multiple tasks and sharing of resources or processing capacity which results in interference leading to slower processing of either of the tasks.<ref>Tombu, M., & Jolicœur, P. (2003). A central capacity sharing model of dual-task performance. Journal of Experimental Psychology: Human Perception and Performance, 29(1),3</ref>
Dual task which involves performance of primary postural task (maintenance of a specific static or dynamic posture) and a secondary task (focal task involving use of the working memory) concurrently. This can lead to two possible outcomes: allocation of attentional resources to focal task during stance leading to impaired postural stability or allocation of attentional resources to maintain postural stability leading to poor performance on the focal task. Thus, such studies suggested the attentional demands of postural tasks.<ref>Tombu, M., & Jolicœur, P. (2003). A central capacity sharing model of dual-task performance. Journal of Experimental Psychology: Human Perception and Performance, 29(1),3</ref>

Kerr et al. demonstrated recall on a spatial memory task was affected negatively (increased errors) during concurrent standing balance task due to sharing of common neural resources for postural stability and cognitive processing.<ref>Kerr B, Condon SM, McDonald LA. Cognitive spatial processing and the regulation of posture. J Exp Psychol Hum Percept Perform 1985;11:617_/22</ref> Furthermore, it was also found that attentional cost increased as the challenge to maintain balance on equilibrium tasks increased. This was demonstrated by increased reaction time to auditory stimulus when subject performed standing and walking rather than sitting.<ref>Lajoie Y, Teasdale N, Bard C, Fleury M. Attentional demands for static and dynamic equilibrium. Exp Brain Res 1993;97:139_/44</ref> It has been found that postural sway increased on performance of a cognitive task concurrently with a postural task.<ref>(Pellecchia, G. L. (2003b). Postural sway increases with attentional demands of concurrent cognitive task. Gait and Posture, 18,29–34)</ref> Dual task training improved dual task performance.<ref>Pellecchia, G.L. (2005).Dual task training reduces impact of cognitive task on postural sway. Journal of motor behaviour.37-3;239-246</ref>


==== Neurophysiological studies ====
==== Neurophysiological studies ====
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==== Neuroimaging studies ====
==== Neuroimaging studies ====
Various [[functional neuroimaging]] techniques such as [[Functional near-infrared spectroscopy]], [[Functional magnetic resonance imaging]], [[Positron emission tomography]] have been used to elucidate cortical control in static and dynamic postures. Using PET, Ouchi Y et al. 1999 <ref>Ouchi, Y., Okada, H., Yoshikawa, E., Nobezawa, S., & Futatsubashi, M. (1999). Brain activation during maintenance of standing postures in humans. Brain, 122(2), 329-338</ref> evaluated mechanisms involved in bipedal standing and confirmed the pivotal contribution of [[cerebellar vermis]] in maintenance of standing posture and further suggested involvement of the visual association cortex in controlling postural equilibrium while standing. Mauloin et al. 2003 <ref>Malouin, F., Richards, C. L., Jackson, P. L., Dumas, F., & Doyon, J. (2003). Brain activations during motor imagery of locomotor‐related tasks: A PET study. Human Brain Mapping, 19(1), 47-62</ref> using PET studied motor imagery of locomotion under four conditions and confirmed supraspinal control in locomotion by demonstrating activation in the dorsal premotor cortex and precuneus bilaterally, the left dorsolateral prefrontal cortex, the left [[inferior parietal lobule]], and the right posterior cingulate cortex. There was increased engagement of higher cortical structures noted with increase in demands of locomotor tasks.
Various [[functional neuroimaging]] techniques such as [[Functional near-infrared spectroscopy]], [[Functional magnetic resonance imaging]], and [[Positron emission tomography]] have been used to elucidate cortical control in static and dynamic postures. Using PET, Ouchi Y et al. 1999 <ref>Ouchi, Y., Okada, H., Yoshikawa, E., Nobezawa, S., & Futatsubashi, M. (1999). Brain activation during maintenance of standing postures in humans. Brain, 122(2), 329-338</ref> evaluated mechanisms involved in bipedal standing and confirmed the pivotal contribution of [[cerebellar vermis]] in maintenance of standing posture and further suggested involvement of the visual association cortex in controlling postural equilibrium while standing. Mauloin et al. 2003 <ref>Malouin, F., Richards, C. L., Jackson, P. L., Dumas, F., & Doyon, J. (2003). Brain activations during motor imagery of locomotor‐related tasks: A PET study. Human Brain Mapping, 19(1), 47-62</ref> using PET studied motor imagery of locomotion under four conditions and confirmed supraspinal control in locomotion by demonstrating activation in the dorsal premotor cortex and precuneus bilaterally, the left dorsolateral prefrontal cortex, the left [[inferior parietal lobule]], and the right posterior cingulate cortex. There was increased engagement of higher cortical structures noted with increase in demands of locomotor tasks.
Using FMRI, Jahn et al. 2004 <ref>Jahn, K., Deutschländer, A., Stephan, T., Strupp, M., Wiesmann, M., & Brandt, T. (2004). Brain activation patterns during imagined stance and locomotion in functional magnetic resonance imaging. Neuroimage, 22(4), 1722-1731</ref> studied the activation pattern with three imagined conditions and found that standing was associated with activation of the thalamus, basal ganglia, and cerebellar vermis.
Using FMRI, Jahn et al. 2004 <ref>Jahn, K., Deutschländer, A., Stephan, T., Strupp, M., Wiesmann, M., & Brandt, T. (2004). Brain activation patterns during imagined stance and locomotion in functional magnetic resonance imaging. Neuroimage, 22(4), 1722-1731</ref> studied the activation pattern with three imagined conditions and found that standing was associated with activation of the thalamus, basal ganglia, and cerebellar vermis.
Using FNIRS, Mihara M et al. 2008 <ref>Mihara, M., Miyai, I., Hatakenaka, M., Kubota, K., & Sakoda, S. (2008). Role of the prefrontal cortex in human balance control. Neuroimage, 43(2), 329-336</ref> studied activation related to external perturbation and suggested prefrontal cortex to be involved in adequate allocation of visuospatial attention. Zwergal A et al. 2012 <ref>Zwergal, A., Linn, J., Xiong, G., Brandt, T., Strupp, M., & Jahn, K. (2012). Aging of human supraspinal locomotor and postural control in fMRI. Neurobiology of aging, 33(6), 1073-1084</ref> studied role of aging on activation pattern in standing and found more activation in bilateral insula, superior and middle temporal gyrus, inferior frontal gyrus, middle occipital gyrus and postcentral gyrus suggesting decreased reciprocal inhibition of these areas.
Using FNIRS, Mihara M et al. 2008 <ref>Mihara, M., Miyai, I., Hatakenaka, M., Kubota, K., & Sakoda, S. (2008). Role of the prefrontal cortex in human balance control. Neuroimage, 43(2), 329-336</ref> studied activation related to external perturbation and suggested prefrontal cortex to be involved in adequate allocation of visuospatial attention. Zwergal A et al. 2012 <ref>Zwergal, A., Linn, J., Xiong, G., Brandt, T., Strupp, M., & Jahn, K. (2012). Aging of human supraspinal locomotor and postural control in fMRI. Neurobiology of aging, 33(6), 1073-1084</ref> studied role of aging on activation pattern in standing and found more activation in bilateral insula, superior and middle temporal gyrus, inferior frontal gyrus, middle occipital gyrus and postcentral gyrus suggesting decreased reciprocal inhibition of these areas.

Revision as of 17:08, 31 August 2022

Postural control refers to the maintenance of body posture in space. Central nervous system interprets the sensory inputs to produce motor output to maintain upright posture.[1]

Definition

Postural control is defined as achievement, maintenance or regulation of balance during any static posture or dynamic activity for the regulation of stability and orientation.[2] The interaction of the individual with the task and the environment develops postural control.[3] Stability refers to maintenance of the centre of mass within the base of support while orientation refers to maintenance of relationship within the body segments and between body and the environment for the task.[4] These stability and orientation challenges necessitate change in the task and environment, thereby making postural control the most essential pre requisite for most of the tasks.[5] There are two types of postural control strategies: predictive and reactive, which utilize the feed forward and feedback postural control respectively in order to maintain stability during various circumstances.[6] Feed forward postural control refers to the postural adjustments made in response to the anticipation of a voluntary or a self-generated movement that may be destabilizing in while feedback postural control refer to the postural adjustments made in reaction to sensory stimuli from the externally generated perturbation.[7] Furthermore, these strategies may involve either a fixed-support or a change-in-support response depending on the intensity of the perturbation.[8]

Systems involved in posture control

Postural control involves a complex interaction of multiple systems in order to maintain stability and orientation. Multi-components of the conceptual model of postural control include:[9]

  • Musculoskeletal components
  • Neuro muscular synergies
  • Individual sensory systems: visual, vestibular and somatosensory system
  • Sensory strategies
  • Anticipatory mechanisms
  • Adaptive mechanisms
  • Internal representations

The functional task and the environment define the precise organization of the postural systems.

Cortical control of posture

Traditionally postural control was regarded an automatic response to sensory stimuli generated by subcortical structures such as the brainstem and spinal circuits.[10] Since postural responses are generated quickly, without voluntary intent and with less variability than cued, voluntary movements, cerebral cortex was not considered to be involved in postural control.[11] However, current evolving evidence from numerous neurophysiological and neuroimaging studies (as given below) suggest cortical involvement in postural control and maintenance of balance.

Neurophysiological studies

An initial postural reaction on exposure to an external perturbations was shown to be generated by the brainstem and spinal cord in animal and human studies (short latency mono or polysynaptic spinal loop 40-65ms) [12] followed by the later part of the reaction which is modified by direct transcortical loops (long latency loops, ~132ms).[13] Cerebral cortex via cerebellum which helps in adapting by using prior experience [14] or via basal ganglia which helps generating a response based on the current context, modifies the postural response.[15]

Neuroimaging studies

Various functional neuroimaging techniques such as Functional near-infrared spectroscopy, Functional magnetic resonance imaging, and Positron emission tomography have been used to elucidate cortical control in static and dynamic postures. Using PET, Ouchi Y et al. 1999 [16] evaluated mechanisms involved in bipedal standing and confirmed the pivotal contribution of cerebellar vermis in maintenance of standing posture and further suggested involvement of the visual association cortex in controlling postural equilibrium while standing. Mauloin et al. 2003 [17] using PET studied motor imagery of locomotion under four conditions and confirmed supraspinal control in locomotion by demonstrating activation in the dorsal premotor cortex and precuneus bilaterally, the left dorsolateral prefrontal cortex, the left inferior parietal lobule, and the right posterior cingulate cortex. There was increased engagement of higher cortical structures noted with increase in demands of locomotor tasks. Using FMRI, Jahn et al. 2004 [18] studied the activation pattern with three imagined conditions and found that standing was associated with activation of the thalamus, basal ganglia, and cerebellar vermis. Using FNIRS, Mihara M et al. 2008 [19] studied activation related to external perturbation and suggested prefrontal cortex to be involved in adequate allocation of visuospatial attention. Zwergal A et al. 2012 [20] studied role of aging on activation pattern in standing and found more activation in bilateral insula, superior and middle temporal gyrus, inferior frontal gyrus, middle occipital gyrus and postcentral gyrus suggesting decreased reciprocal inhibition of these areas.

References

  1. ^ Massion, J. (1994). Postural control system. Current Opinion in Neurobiology, 4(6), 877-887
  2. ^ Pollock AS1, Durward BR, Rowe PJ, Paul JP (2000). “What is balance?” Clinical rehabilitation 14(4):402-6; Anne Shumway Cook, Wollcott (2007) Motor control, 3rd edition
  3. ^ Anne Shumway Cook, Wollcott (2007) Motor control, 3rd edition
  4. ^ Anne Shumway Cook, Wollcott (2007) Motor control, 3rd edition
  5. ^ Anne Shumway Cook, Wollcott (2007) Motor control, 3rd edition
  6. ^ Pollock AS1, Durward BR, Rowe PJ, Paul JP (2000). “What is balance?” Clinical rehabilitation 14(4):402-6; Anne Shumway Cook, Wollcott (2007) Motor control, 3rd edition
  7. ^ Anne Shumway Cook, Wollcott (2007) Motor control, 3rd edition
  8. ^ Pollock AS1, Durward BR, Rowe PJ, Paul JP (2000). “What is balance?” Clinical rehabilitation 14(4):402-6
  9. ^ Anne Shumway Cook, Wollcott (2007) Motor control, 3rd edition
  10. ^ Sherrington, C. S. (1910). Flexion‐reflex of the limb, crossed extension‐reflex, and reflex stepping and standing. The Journal of physiology, 40(1-2), 28-121; Magnus, R. (1926). The physiology of posture: Cameron Lectures. Lancet, 211(53), 1-536
  11. ^ Diener, H. C., Dichgans, J., Bootz, F., & Bacher, M. (1984). Early stabilization of human posture after a sudden disturbance: influence of rate and amplitude of displacement. Experimental Brain Research, 56(1), 126-134; Keck, M. E., Pijnappels, M., Schubert, M., Colombo, G., Curt, A., & Dietz, V. (1998). Stumbling reactions in man: influence of corticospinal input. Electroencephalography and Clinical Neurophysiology/Electromyography and Motor Control, 109(3), 215-223
  12. ^ Bove, M., Nardone, A., & Schieppati, M. (2003). Effects of leg muscle tendon vibration on group Ia and group II reflex responses to stance perturbation in humans. J Physiol, 550(Pt 2), 617-630. doi:10.1113/jphysiol.2003.043331
  13. ^ Ackermann, H., Diener, H. C., & Dichgans, J. (1987). Changes in sensorimotor functions after spinal lesions evaluated in terms of long-latency reflexes. J Neurol Neurosurg Psychiatry, 50(12), 1647-1654; Jacobs, J. V., & Horak, F. B. (2007). Cortical control of postural responses. Journal of neural transmission, 114(10), 1339-1348
  14. ^ Graydon, F. X., Friston, K. J., Thomas, C. G., Brooks, V. B., & Menon, R. S. (2005). Learning-related fMRI activation associated with a rotational visuo-motor transformation. Brain Res Cogn Brain Res, 22(3), 373-383. doi:10.1016/j.cogbrainres.2004.09.007
  15. ^ Jacobs, J. V., & Horak, F. B. (2007). Cortical control of postural responses. Journal of neural transmission, 114(10), 1339-1348
  16. ^ Ouchi, Y., Okada, H., Yoshikawa, E., Nobezawa, S., & Futatsubashi, M. (1999). Brain activation during maintenance of standing postures in humans. Brain, 122(2), 329-338
  17. ^ Malouin, F., Richards, C. L., Jackson, P. L., Dumas, F., & Doyon, J. (2003). Brain activations during motor imagery of locomotor‐related tasks: A PET study. Human Brain Mapping, 19(1), 47-62
  18. ^ Jahn, K., Deutschländer, A., Stephan, T., Strupp, M., Wiesmann, M., & Brandt, T. (2004). Brain activation patterns during imagined stance and locomotion in functional magnetic resonance imaging. Neuroimage, 22(4), 1722-1731
  19. ^ Mihara, M., Miyai, I., Hatakenaka, M., Kubota, K., & Sakoda, S. (2008). Role of the prefrontal cortex in human balance control. Neuroimage, 43(2), 329-336
  20. ^ Zwergal, A., Linn, J., Xiong, G., Brandt, T., Strupp, M., & Jahn, K. (2012). Aging of human supraspinal locomotor and postural control in fMRI. Neurobiology of aging, 33(6), 1073-1084
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