We Are Upright-Walking Cats: Human Limbs as Sensory Antennae During Locomotion

Pearcey, Gregory E. P.; Zehr, E. Paul

doi:10.1152/physiol.00008.2019

Cited by 36 publications

(20 citation statements)

References 98 publications

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“…Somatosensory feedback from the lower limb, and in particular from the foot sole, plays an important role in controlling balance, posture, and gait (Inglis et al 2002;Pearcey and Zehr 2019). The foot sole is covered with glabrous skin and innervated by the same four classes of tactile afferents as the hand (SAI, SAII, FAI, FAII).…”

Section: Glabrous Skin Of the Foot Solementioning

confidence: 99%

Tactile innervation densities across the whole body

Corniani

Saal

2020

Journal of Neurophysiology

185

119

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The skin is our largest sensory organ and innervated by afferent fibers carrying tactile information to the spinal cord and onto the brain. The density with which different classes of tactile afferents innervate the skin is not constant but varies considerably across different body regions. However, precise estimates of innervation density are only available for some body parts, such as the hands, and estimates of the total number of tactile afferent fibers are inconsistent and incomplete. Here we reconcile different estimates and provide plausible ranges and best estimates for the number of different tactile fiber types innervating different regions of the skin, using evidence from dorsal root fiber counts, microneurography, histology, and psychophysics. We estimate that the skin across the whole body of young adults is innervated by approximately 230,000 tactile afferent fibers (plausible range: 200,000-270,000), with a subsequent decrement of 5-8% every decade due to aging. 15% of fibers innervate the palmar skin of both hands and 19% the region surrounding the face and lips. Slowly and fast-adapting fibers are split roughly evenly, but this breakdown varies with skin region. Innervation density correlates well with psychophysical spatial acuity across different body regions, and additionally, on hairy skin, with hair follicle density. Innervation density is also weakly correlated with the size of the cortical somatotopic representation, but cannot fully account for the magnification of the hands and the face.

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Section: Glabrous Skin Of the Foot Solementioning

confidence: 99%

Tactile innervation densities across the whole body

Corniani

Saal

2020

Journal of Neurophysiology

185

119

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“…Even though the importance of forelimb/hindlimb coupling may be amplified in quadrupeds, there is circumstantial evidence that suggests this phenomenon also exists in bipedal animals. Coupling of bipedal arm and leg movements has been observed in upright walking (Dietz, 2002; Zehr et al, 2009, 2016; Frigon, 2017; Pearcey and Zehr, 2019), swimming (Wannier et al, 2001), and crawling (MacLellan et al, 2013) in humans, mirroring the expected behavior of paired oscillators observed in quadrupedal locomotion.…”

Section: Propriospinal Interneurons Coordinate Forelimb and Hindlimb mentioning

confidence: 65%

Propriospinal Neurons: Essential Elements of Locomotor Control in the Intact and Possibly the Injured Spinal Cord

Laliberté

Goltash

Lalonde

et al. 2019

Front. Cell. Neurosci.

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Propriospinal interneurons (INs) communicate information over short and long distances within the spinal cord. They act to coordinate different parts of the body by linking motor circuits that control muscles across the forelimbs, trunk, and hindlimbs. Their role in coordinating locomotor circuits near and far may be invaluable to the recovery of locomotor function lost due to injury to the spinal cord where the flow of motor commands from the brain and brainstem to spinal motor circuits is disrupted. The formation and activation of circuits established by spared propriospinal INs may promote the re-emergence of locomotion. In light of progress made in animal models of spinal cord injury (SCI) and in human patients, we discuss the role of propriospinal INs in the intact spinal cord and describe recent studies investigating the assembly and/or activation of propriospinal circuits to promote recovery of locomotion following SCI.

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“…A most remarkable synthesis of the effects of cutaneous input from discrete regions of the foot during walking can be found in Pearcey and Zehr. 64 One may note that locomotion produces a continuous spatiotemporal change in the plantar pressures (and from foot dorsum when wearing shoes 65 ), thereby continuously varying the foot areas from which skin receptors are activated. 65,66 For instance, remarkable changes in the plantar pressure occur between straight and curved walking, 67 potentially informing the brain on how to adapt the body motion to the complex condition of steering while walking.…”

Section: Cutaneous Input and Gaitmentioning

confidence: 99%

Cutaneous and muscular afferents from the foot and sensory fusion processing: Physiology and pathology in neuropathies

Felicetti

Thoumie

et al. 2021

J Peripheral Nervous Sys

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The foot-sole cutaneous receptors (section 2), their function in stance control (sway minimisation, exploratory role) (2.1), and the modulation of their effects by gait pattern and intended behaviour (2.2) are reviewed. Experimental manipulations (anaesthesia, temperature) (2.3 and 2.4) have shown that information from foot sole has widespread influence on balance. Foot-sole stimulation (2.5) appears to be a promising approach for rehabilitation. Proprioceptive information (3) has a pre-eminent role in balance and gait. Reflex responses to balance perturbations are produced by both leg and foot muscle stretch (3.1) and show complex interactions with skin input at both spinal and supra-spinal levels (3.2), where sensory feedback is modulated by posture, locomotion and vision. Other muscles, notably of neck and trunk, contribute to kinaesthesia and sense of orientation in space (3.3). The effects of age-related decline of afferent input are variable under different foot-contact and visual conditions (3.4). Muscle force diminishes with age and sarcopenia, affecting intrinsic foot muscles relaying relevant feedback (3.5). In neuropathy (4), reduction in cutaneous sensation accompanies the diminished density of viable receptors (4.1). Loss of footsole input goes along with large-fibre dysfunction in intrinsic foot muscles. Diabetic patients have an elevated risk of falling, and vision and vestibular compensation strategies may be inadequate (4.2). From Charcot-Marie-Tooth 1A disease (4.3) we have become aware of the role of spindle group II fibres and of the anatomical feet conditions in balance control. Lastly (5) we touch on the effects of nerve stimulation onto cortical and spinal excitability, which may participate in plasticity processes, and on exercise interventions to reduce the impact of neuropathy.

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We Are Upright-Walking Cats: Human Limbs as Sensory Antennae During Locomotion

Cited by 36 publications

References 98 publications

Tactile innervation densities across the whole body

Tactile innervation densities across the whole body

Propriospinal Neurons: Essential Elements of Locomotor Control in the Intact and Possibly the Injured Spinal Cord

Cutaneous and muscular afferents from the foot and sensory fusion processing: Physiology and pathology in neuropathies

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