Henry Head’s lifelong studies of cutaneous sensation

2020 ◽  
pp. 096777202094055
Author(s):  
Michael Swash

In 1900 research on cutaneous sensation was defined by histological techniques defining sensory receptors in skin, leading to undetermined conceptual problems when considered in relation to Brown-Séquard’s startling finding that there were two qualitatively different afferent pathways in the spinal cord. Four modalities were considered to function as the determinants of sensory input. In 1903 Rivers and Head carried out the first interventional study of human cutaneous sensation, and analysed the return of sensation following section and immediate suture of the dorsal cutaneous branch of Head’s left radial nerve. This resulted in the revolutionary idea summarised in his description of protopathic and epicritic sensory systems in peripheral sensory nerve. Although this concept was at best seen as controversial and even ridiculed by some of his many contemporaneous critics, more recently this concept has proven a fundamentally important stimulus to understanding the physiology of cutaneous sensation. His writings show him to have been capable of deeply instructive thought, based on his clinical experience and his admiration of Hughlings Jackson’s teaching concerning the hierarchical organisation of brain function. First and foremost a clinician neuroscientist, his ideas were ahead of their time and not understood.

1996 ◽  
Vol 199 (3) ◽  
pp. 613-625
Author(s):  
T Jellema ◽  
W Heitler

The metathoracic fast extensor tibiae (FETi) motor neurone of locusts is unusual amongst insect motor neurones because it makes output connections within the central nervous system as well as in the periphery. It makes excitatory chemical synaptic connections to most if not all of the antagonist flexor tibiae motor neurones. The gain of the FETi-flexor connection is dependent on the peripheral conditions at the time of the FETi spike. This dependency has two aspects. First, sensory input resulting from the extensor muscle contraction can sum with the central excitatory postsynaptic potential (EPSP) to augment its falling phase if the tibia is restrained in the flexed position (initiating a tension-dependent reflex) or is free to extend (initiating a movement-dependent resistance reflex). This effect is thus due to simple postsynaptic summation of the central EPSP with peripheral sensory input. Second, the static tibial position at the time of the FETi spike can change the amplitude of the central EPSP, in the absence of any extensor muscle contraction. The EPSP can be up to 30 % greater in amplitude if FETi spikes with the tibia held flexed rather than extended. The primary sense organ mediating this effect is the femoral chordotonal organ. Evidence is presented suggesting that the mechanism underlying this change in gain may be specifically localised to the FETi-flexor connection, rather than being due to general position-dependent sensory feedback summing with the EPSP. The change in the amplitude of the central EPSP is probably not caused by general postsynaptic summation with tonic sensory input, since a diminution in the amplitude of the central EPSP caused by tibial extension is often accompanied by overall tonic excitation of the flexor motor neurone. Small but significant changes in the peak amplitude of the FETi spike have a positive correlation with changes in the EPSP amplitude, suggesting a likely presynaptic component to the mechanism of gain control. The change in amplitude of the EPSP can alter its effectiveness in producing flexor motor output and, thus, has functional significance. The change serves to augment the effectiveness of the FETi-flexor connection when the tibia is fully flexed, and thus to increase its adaptive advantage during the co-contraction preceding a jump or kick, and to reduce the effectiveness of the connection when the tibia is partially or fully extended, and thus to reduce its potentially maladaptive consequences during voluntary extension movements such as thrusting.


F1000Research ◽  
2017 ◽  
Vol 6 ◽  
pp. 921 ◽  
Author(s):  
Norman R. Saunders ◽  
Katarzyna M. Dziegielewska ◽  
Sophie C. Whish ◽  
Lyn A. Hinds ◽  
Benjamin J. Wheaton ◽  
...  

Background: Most animal studies of spinal cord injury are conducted in quadrupeds, usually rodents. It is unclear to what extent functional results from such studies can be translated to bipedal species such as humans because bipedal and quadrupedal locomotion involve very different patterns of spinal control of muscle coordination. Bipedalism requires upright trunk stability and coordinated postural muscle control; it has been suggested that peripheral sensory input is less important in humans than quadrupeds for recovery of locomotion following spinal injury. Methods: We used an Australian macropod marsupial, the tammar wallaby (Macropus eugenii), because tammars exhibit an upright trunk posture, human-like alternating hindlimb movement when swimming and bipedal over-ground locomotion. Regulation of their muscle movements is more similar to humans than quadrupeds. At different postnatal (P) days (P7–60) tammars received a complete mid-thoracic spinal cord transection. Morphological repair, as well as functional use of hind limbs, was studied up to the time of their pouch exit. Results: Growth of axons across the lesion restored supraspinal innervation in animals injured up to 3 weeks of age but not in animals injured after 6 weeks of age. At initial pouch exit (P180), the young injured at P7-21 were able to hop on their hind limbs similar to age-matched controls and to swim albeit with a different stroke. Those animals injured at P40-45 appeared to be incapable of normal use of hind limbs even while still in the pouch. Conclusions: Data indicate that the characteristic over-ground locomotion of tammars provides a model in which regrowth of supraspinal connections across the site of injury can be studied in a bipedal animal. Forelimb weight-bearing motion and peripheral sensory input appear not to compensate for lack of hindlimb control, as occurs in quadrupeds. Tammars may be a more appropriate model for studies of therapeutic interventions relevant to humans.


Author(s):  
Sándor Magony ◽  
Szabolcs Nyiraty ◽  
Bettina Tóth ◽  
Fruzsina Pesei ◽  
Andrea Orosz ◽  
...  

PLoS ONE ◽  
2017 ◽  
Vol 12 (10) ◽  
pp. e0187354 ◽  
Author(s):  
Mollie A. Heffner ◽  
Damian C. Genetos ◽  
Blaine A. Christiansen

Microsurgery ◽  
2001 ◽  
Vol 21 (7) ◽  
pp. 306-316 ◽  
Author(s):  
Guda C.M. Heijke ◽  
Pieter J. Klopper ◽  
Bob Baljet ◽  
Ilona B.M. van Doorn

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