Spatial perception and vestibulomotor responses in man

A study was made on normal human subjects, using a stabilograph to investigate changes in posture produced in response to transcutaneous galvanic stimulation of the right labyrinth. Results were obtained for different head positions and under the illusion of head and trunk rotation produced by stimulating (vibrating) the gulteus maximus muscle. In the absence of illusion of movement, the direction of the vestibulomotor response was determined by the position of the head in relation to the feed: with the normal head position, the body swayed on a frontal plane, and on a sagittal plane when the heat turned through 90°. Vestibulomotor responses were sagittally oriented, as with real head turning, when illusory head and trunk turning through 90° was produced by vibration. When the illusion of head rotation (in relation to the feet) was not produced by this stimulus, the direction of the postural response was not produced by this stimulus, the direction of the postural response was determined by the real orientation of the head. It is concluded that the spatial perception system plays a major part in controlling spatially oriented vestibulomotor responses.Institute for Research into Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 18, No. 6, pp. 779–787, November–December, 1986.     

Characteristics of locomotion regulation in man

It has been found by transforming experimental kinematic data to normal coordinates with calculating of muscle force moments during walking that the locomotor movements are regulated almost discontinuously at each degree of freedom of leg, so two piece constant parameters of control are switched few times during gait cycle. Therefore musculature acts like switched elastic constraints, and energy expenditure depends on the trajectories of movements essentially less than on the kinematic conditions displayed during fixed switchings.     

Phase-dependent responses in locomotor muscles of walking man

Bilateral reflex responses in locomotor muscles were studied in normal human subjects walking on a treadmill. Reflex responses were elicited in response to a momentary resistance applied to one leg. The responses were recorded electromyographically from superficial muscles of both lower limbs: the vastus lateralis, gluteus medius and tibialis anterior. A four-channel storage oscilloscope displayed a quartet record which consisted of phases of the walking cycle and patterns of EMG activity. Resistance and response data were collected for comparison. The appearance of reflex responses was found to be conditioned. The following two observations provide the phase-dependent characteristics of those responses: muscles of the ipsilateral limb elicited responses throughout the walking cycle regardless of whether the muscles were active or silent and muscles of the contralateral limb produced responses that depended on the point at which resistance occurred during the walking cycle. Discusion follows concerning inhibition of the response that may be responsible for this phase-dependent phenomenon.     

Descending modulation of reflex reactions in spinal motoneurons produced by spinal cord injury in man

A study was made of changes in the amplitude of H-reflexes in m. gastrocnemius and the intensity of Ia inhibition in healthy subjects versus patients with midthoracic injury to the spinal cord before, during, and after voluntary tensing of the masticatory, cervical, and finger muscles. Tensing these muscles brought about facilitation of H-reflex and reduced intensity of Ia response in healthy subjects and patients with paraparesis but produced the opposite effect on paraplegics (or had no influence on reactions). This leads to a discussion of the relationship between the changes observed in reflex reactions and posttrauma damage to structure and function of the spinal cord.A. A. Bogomolets Institute, of Physiology, Academy of Sciences of the Ukrainian SSR. Kiev. Translated from Neirofiziologiya, Vol. 20, No. 1, pp. 105–113, January–February, 1988.     

Hormonal responses to analgesic nitrous oxide in man

Analgesic concentrations of nitrous oxide were administered to 6 healthy male subjects, and blood samples were assayed for prolactin, ACTH, follicle stimulating hormone, luteinising hormone, growth hormone, cortisol and thyroid hormones. Analgesic nitrous oxide (mean concentration = 48.8%) produced statistically significant elevation of prolactin and depression of cortisol whilst not producing statistically significant changes in the other hormones assayed. The increase in prolactin and decrease in cortisol levels are similar to the hormonal changes associated with administration of opioids in man. We have also confirmed the findings of other workers that cortisol levels may not always be correlated with ACTH levels.     

Vascular responses to plasma hypoosmolality in man.

To study limb vascular responses to plasma hypoosmolality in man, we infused test solutions of hypoosmolar NaCl (145 mOsm/kg) and control solutions of isosmolar NaCl (290 mOsm/kg) into the brachial arteries of 14 mornotensive and 13 essential hypertensive patients. Limb blood pressures were monitored, limb blood flow was measured by indicator-dilution, and limb vascular resistance was calculated as mmHg/ml flow/min/100 cm3 limb volume. The infusions did not significantly change systemic plasma osmolality, sodium concentration, or blood pressure. Compared to control infusions, the hypoosmolar infusions decreased limb venous plasma osmolality and serum sodium concentrations by an average of 12 mOsm/kg and 7 mEq/1, respectively. Compared to control infusions, limb venous serum concentrations of potassium, calcium, magnesium, or blood hematocrit were not altered by the hypoosmolar infusions. In response to the hypoosmolar infusions, limb resistance increased by 28% in normotensives and by 26% in hypertensives. We conclude that the acute local vascular response to a small reduction in plasma osmolality in the limb of man is a large increase in vascular resistance. We found no evidence for abnormal responses to plasma hypoosmolality in essential hypertensives.     

Visceral responses to spinal manipulation

While spinal manipulation is widely seen as a reasonable treatment option for biomechanical disorders of the spine, such as neck pain and low back pain, the use of spinal manipulation to treat non-musculoskeletal complaints remains controversial. This controversy is due in part to the perception that there is no robust neurobiological rationale to justify using a biomechanical treatment of the spine to address a disorder of visceral function. This paper therefore looks at the physiological evidence that spinal manipulation can impact visceral function. A structured search was conducted, using PubMed and the Index to Chiropractic Literature, to construct of corpus of primary data studies in healthy human subjects of the effects of spinal manipulation on visceral function. The corpus of literature is not large, and the greatest number of papers concerns cardiovascular function. Authors often attribute visceral effects of spinal manipulation to somato-autonomic reflexes. While this is not unreasonable, little attention is paid to alternative mechanisms such as somato-humoural pathways. Thus, while the literature confirms that mechanical stimulation of the spine modulates some organ functions in some cohorts, a comprehensive neurobiological rationale for this general phenomenon has yet to appear.     

Anterior spinal arteries. Origin and distribution in man

This study was designed to extend our present knowledge of the origin and distribution of anterior spinal arteries and was carried our using 31 human cadavers with arterial injections of natural latex. The conclusions reached are that there are always one or two anterior spinal arteries (right or left), which proceed from the intracranial segment of the vertebral arteries. These arteries have a descending course, with distribution into the ventral face of the medulla oblongata and the first cervical segments of the medulla spinalis. In cases where there are two anterior spinal arteries, they anastomose with each other to form the common, unpaired and median anterior spinal artery. The different observed locations of the origins of anterior spinal arteries may be systematised into three types. Each of these types has differential characteristics: bilateral origin (type I; 77.4%), unilateral origin (type II; 9.7%) and origin in an intervertebral transversal anastomosis (type III; 12.9%). We do however subdivide the bilateral origin group, according to the calibre of the arteries, into the subtypes 'balanced' (type Ia; 22.6%), 'right dominated' (type Ib; 32.2%) and 'left dominated' (type Ic; 22.6%). The collaterals of the anterior spinal arteries which distribute into the ventral face of the medulla oblongata are described.