Supportive evidence Cortical control of posture

1 supportive evidence

1.1 behavioral studies
1.2 neurophysiological studies
1.3 neuroimaging studies

supportive evidence
behavioral studies

based on central capacity theory, behavioral studies using dual-task paradigm instrumental in evaluating demands of attention various postural tasks. according central capacity sharing theory, there limited attentional resources , performance of task demands utilization of proportion of these resources. in model, there simultaneous processing of multiple tasks , sharing of resources or processing capacity results in interference leading slower processing of either of tasks. dual task involves performance of primary postural task (maintenance of specific static or dynamic posture) , secondary task (focal task involving use of working memory) concurrently. can lead 2 possible outcomes: allocation of attentional resources focal task during stance leading impaired postural stability or allocation of attentional resources maintain postural stability leading poor performance on focal task. thus, such studies suggested attentional demands of postural tasks.

kerr et al demonstrated recall on spatial memory task affected negatively (increased errors) during concurrent standing balance task due sharing of common neural resources postural stability , cognitive processing. furthermore, found attentional cost increased challenge maintain balance on equilibrium tasks increased. demonstrated increased reaction time auditory stimulus when subject performed standing , walking rather sitting. has been found postural sway increased on performance of cognitive task concurrently postural task. dual task training improved dual task performance.

neurophysiological studies

an initial postural reaction on exposure external perturbations shown generated brainstem , spinal cord in animal , human studies (short latency mono or polysynaptic spinal loop 40-65ms) followed later part of reaction modified direct transcortical loops (long latency loops, ~132ms). cerebral cortex via cerebellum helps in adapting using prior experience or via basal ganglia helps generating response based on current context, modifies postural response.

neuroimaging studies

various functional neuroimaging techniques such functional near-infrared spectroscopy, functional magnetic resonance imaging, positron emission tomography have been used elucidate cortical control in static , dynamic postures. using pet, ouchi y et al. 1999 evaluated mechanisms involved in bipedal standing , confirmed pivotal contribution of cerebellar vermis in maintenance of standing posture , further suggested involvement of visual association cortex in controlling postural equilibrium while standing. mauloin et al. 2003 using pet studied motor imagery of locomotion under 4 conditions , confirmed supraspinal control in locomotion demonstrating activation in dorsal premotor cortex , precuneus bilaterally, left dorsolateral prefrontal cortex, left inferior parietal lobule, , right posterior cingulate cortex. there increased engagement of higher cortical structures noted increase in demands of locomotor tasks. using fmri, jahn et al 2004 studied activation pattern 3 imagined conditions , found standing associated activation of thalamus, basal ganglia, , cerebellar vermis.

using fnirs, mihara m et al. 2008 studied activation related external perturbation , suggested prefrontal cortex involved in adequate allocation of visuospatial attention. zwergal et al. 2012 studied role of aging on activation pattern in standing , found more activation in bilateral insula, superior , middle temporal gyrus, inferior frontal gyrus, middle occipital gyrus , postcentral gyrus suggesting decreased reciprocal inhibition of these areas.