Biomedical subjects

U Norrsell

Publications and source records attributed to U Norrsell.

At least 19 recordsLinked to original sources

PubMed2005

Cox's chair: 'a moral and a medical mean in the treatment of maniacs'.

Two hundred years ago Joseph Cox published his book on the treatment of insanity. His novel technique was rotating the body in a specially designed chair. Initially modest and later extravagant claims were made for the therapeutic benefit of 'Cox's chair'. It was widely adopted in Europe in the first decades of the nineteenth century, but lost favour thereafter. Its benefits have proved to be scientific rather than medical because it was adopted by students of the senses to investigate vertigo; a century later it re-emerged as the Bárány chair for the clinical assessment of vestibular function. The legacy of Cox's chair, and its related treatment of swinging, are to be found in funfairs throughout the world.

Centrifugation↗

PubMed2001

Tactile directional sensibility and diabetic neuropathy.

Five different procedures used to diagnose neuropathy were compared in a "blind" study with diabetic patients. The aim was to evaluate tests of tactile directional sensibility. Three matched groups were examined, two groups with type I diabetes, either with or without suspected neuropathy, and one of healthy controls. Testing consisted of: (1) examination by a specialist in neurology, (2) electrophysiologic measurement of nerve conduction velocity and determination of cool sensitivity, and (3) determination of directional sensibility in two stages, with categorical and quantitative techniques. Abnormal test results were obtained for both groups of diabetic patients. Quantitatively measured directional sensibility had the highest sensitivity (89%) and specificity (85%) when calculated for patients who had received a diagnosis of neuropathy from the neurologist, despite one case of abnormal directional sensibility among the healthy controls. Conduction velocity testing was almost comparably sensitive (80%) and cool sensitivity, comparably specific (85%) when calculated in the same manner.

Adult↗

PubMed2001

Directional sensibility of hairy skin and postural control.

People can feel and report the direction of very small movements which cause changes in the tension of the forearm's hairy skin. This subjective sensory function may perhaps reflect more fundamental sensorimotor tasks. The hypothesis was investigated by measuring body sway and movement of six female and male volunteers who were performing the tandem-stance Romberg test with open and closed eyes. The increase in sway and movement after eye closure was reduced significantly when the subjects were allowed to use one forearm to touch a spatially fixed object from below. Three objects were used, a solid Perspex rod, an easily rotating steel ball, and a pointed metal peg whose tip was attached to the skin with a droplet of contact glue. Possible mechanical support could be excluded on basis of the objects' technical properties and the magnitudes of forearm movements. Movement of the forearm relative to an object could provide spatial information about changes of the forearm's position in space. Likewise, changes of skin tension that were caused by such movements could be useful. The Perspex rod and the steel ball might provide both types of information. However, the glued peg only caused changes of skin tension, but reduced sway and movement equally effectively. Therefore, information from tension receptors of the forearm's hairy skin underlying the accurate subjective directional sensibility also appears to participate in basic motor control.

Adult↗

PubMed2000

Magnus Gustaf Blix (1849-1904); neurophysiological, physiological, and engineering virtuoso.

This paper was written to honour the 150th anniversary of the birth of Magnus Gustaf Blix. Blix belongs to the small group of 19th century physiologic neuroscientists who still regularly are cited, on account of having presented fundamental results. He contributed to three fields: somatic sensation, and visual and muscular function. He was the first to publish evidence regarding modality specific receptors in the skin. He extended the work of Hermann von Helmholtz on the optical properties of the anterior ocular chamber of living humans, after having constructed the necessary apparatus. He also measured the heat production of contracting muscles. For this purpose he constructed the apparatus that provided a start for A. V. Hill's Nobel Prize-winning work in the field. He showed for the first time that the power of muscle contractions depended on the length/extension of the muscle fibres. He worked on the possibility of muscle powered human aviation. For this purpose he constructed a bicycle dynamometer for measuring the maximal human power output. He was the vice-chancellor of Lund university when he died from an acute disease in 1904 at the age of only 55 years.

Aviation↗

PubMed1999

Cutaneous sensory spots and the "law of specific nerve energies": history and development of ideas.

By use of suitable methods, different spots on the skin surface can be shown to be selectively sensitive to one of four sensory qualities in decreasing order of density: pain, touch, cool and warm. The presence of such spots was observed virtually simultaneously in the early 1880s by three independent investigators. Two papers on punctuate sensitivity of the skin were published in 1882 and 1883 by Magnus Blix of Uppsala University in Sweden; three papers were published in 1884 by Alfred Goldscheider, a German army doctor; and one was published in 1885 by Henry Donaldson of Johns Hopkins University in Maryland. Donaldson's findings originated from a serendipitous observation. In contrast, Blix's and Goldscheider's experiments were based on Johannes Muller's concept of "specific sense energies" and the extension of this idea to sensory qualities (the law of "specific nerve energies") by others, including Hermann von Helmholtz. The discovery of different types of sensory spots had considerable influence on other researchers of the period, including Max von Frey, but has only recently been substantiated by electrophysiological experiments.

Germany↗

PubMed1999

Behavioral thermosensitivity after lesions of thalamic target areas of a thermosensory spinothalamic pathway in the cat.

The ability of 17 cats to discriminate floor temperatures 2-4 degrees C below the ambient temperature was tested before and after unilateral electrolytic thalamic lesions. The lesions were made contralateral to the paws showing better performance in the temperature discrimination task. They were aimed at one or more of the three main target areas of thermoreceptive-specific lamina I spinothalamic neurons [i.e., the nucleus submedius, the dorsomedial aspect of the ventral posterior medial nucleus, and the ventral aspect of the basal ventral medial nucleus (vVMb)], following microelectrode mapping of somatosensory thalamus. The thermosensory consequences of each lesion were measured in postoperative testing, beginning 6-8 days after the final preoperative test session. A mild but definite thermosensory deficiency was found in five cats, in which the response behavior on the contralateral side was reduced below the 69% criterion level for several sessions. Histological analysis indicated that these cats differed only by the inclusion in the lesion of all or part of vVMb. Consequently this area appears to be important for cats' thermosensory behavior. Nevertheless even large lesions of virtually all of the thermoreceptive lamina I spinothalamic projection areas produced only this mild thermosensory deficit in stark contrast with the massive defect observed previously after spinal lesions of the middle of the lateral funiculus, where lamina I axons ascend. Accordingly such spinal lesions were added at the C(4) level, on the same side as the thalamic lesions, in six cats 3 mo after the thalamic surgery. These lesions caused severe contralateral defects (i.e., chance level performance). Thus the present findings are taken to indicate that contralateral ascending projections to vVMb in the thalamus participate in cats' thermosensory discrimination but that ascending projections to the brain stem must play an important role in their behavioral thermosensitivity.

Animals↗

PubMed1998

Remarkable capacity for perception of the direction of skin pull in man.

We determined the ability to appreciate the direction of a skin pull caused by a moving pin that was glued to the forearm skin. A majority of the subjects were able to tell the direction of pin movements with an excursion of 0.13 mm (>/=66% correct responses, p<0.05). Local skin anaesthesia showed that stretch sensitive receptors located over 15 mm in front and behind the pin correctly signalled the direction of these minute skin pulls. It was concluded that information about patterns of skin stretch is an important component of the somatosensory system that may contribute not only to kinaesthetic, but also to cutaneous sensations.

Adult↗

PubMed1997

Directional sensibility for quantification of tactile dysfunction.

Examination of tactile directional sensibility, i.e., the ability to tell the direction of an object's motion across the skin, has been recommended by several authors for examination of patients with somatosensory disorders. Recent findings about the physiological mechanisms underlying directional sensibility suggested possibilities to further improve the test. In the present investigation a test was constructed that allowed a semiquantification of the directional sensibility of six body areas within 20 min. Normal values were obtained by testing healthy subjects (n = 40), and the normal values were compared to those obtained in a group of patients with tactile symptoms (n = 20). Ten of the patients had abnormal sensory conduction in one or several nerves, and they also had abnormal directional sensibility. Hence, examination of directional sensibility, according to the present protocol, provides a semiquantitative test that appears to be as sensitive as electrophysiological measurement of conduction in detecting dysfunction in tactile nerves.

Adult↗

PubMed1996

Aphasia, dichotic testing and defective hearing.

Cerebral lesions causing aphasia are often found close to auditory areas. The aphasia may therefore sometimes be aggravated by hearing problems, which are concealed by communicative restrictions. Unilateral lesions of the cerebral auditory system influence the functional ear preference disclosed by dichotic tests. For that reason we have examined aphasic patients with recent, initial, unilateral brain infarctions for ear preference with regard to dichotically presented two syllable words. In a consecutive series of 114 patients who could cope with the test, 29 showed signs of an acquired left ear advantage (LEA). All were offered, and 22 accepted a full scale audiological examination including pure tone, speech and phase-audiometry. Nine of these patients showed retrocochlear or central hearing disturbances, which added to their communicative predicaments. The LEA of 11 patients lacked audiological rationales and a compensatory shift of cerebral speech-lateralization cannot be excluded.

Adolescent↗

PubMed1994

Spatial cues serving the tactile directional sensibility of the human forearm.

1. Tactile directional sensibility is considered to rely on the parallel processing of direction-contingent sensory data that depend on skin stretching caused by friction, and spatial cues that vary with time. A temperature-controlled airstream stimulus that prevented the activation of stretch receptors was used to investigate directional sensibility for the skin of the forearm. 2. The dependence on contact load and distance of movement was determined for normal subjects with a two-alternative forced-choice method. Testing was performed under two conditions, elbow bent or straight. Bracing the skin by straightening the arm did not alter the accuracy of the directional sensibility, in contrast to previous findings with stimuli that caused friction. 3. The accuracy of directional sensibility was correlated linearly to the logarithm of the distance of movement of the air jet. No correlation was found between accuracy and contact load, unlike findings with stimuli that cause friction. 4. Measurements were made with different subjects to determine the threshold distance at constant load. On average, subjects were able to distinguish direction with movements of < or = 8 mm. This acuity is sharper than has been reported with static stimuli. There was no correlation between subjects' threshold distances for judging direction and spatial acuity measured with absolute point localization. 5. The ability to distinguish direction was poor for the airstream stimulus compared with stimuli causing frictional contact with hairy skin. Nevertheless, the present findings are consistent with the suggestion that cutaneous spatial acuity is better for dynamic than for static stimuli.

Adult↗

PubMed1993

A system of unmyelinated afferents for innocuous mechanoreception in the human skin.

It is generally held that tactile mechanisms in the human skin are served by fast-conducting myelinated nerve fibres, whereas touch-sensitive afferents with unmyelinated axons are lacking in man, in contrast to other mammals. In the present study we found evidence that sensitive mechanoreceptive afferents with unmyelinated fibres are quite common and widespread in the hairy skin of human subjects. Their biological role remains an enigma which might attract more attention now that their existence in man has been demonstrated.

Afferent Pathways↗

PubMed1993

Observations on human tactile directional sensibility.

1. The ability to tell the direction of a motion across the skin deserve attention for being an easily observed function which provides a sensitive test for disturbances of the peripheral and central nervous systems. The mode of operation, on the other hand, of this tactile directional sensibility is still uncertain. 2. The dependence of directional sensibility on the contact load and distance of movement of a blunt metal tip, has now been determined for the skin of the forearm of normal subjects with the two-alternative forced-choice method. The testing was done under two conditions: elbow bent or straight. Straightening of the arm always reduced the accuracy of the directional sensibility. It also caused measurable changes of cutaneous mechanical properties, which presumably decreased the reliability of afferent information about lateral distension. 3. The average accuracy of the directional sensibility was found to be correlated linearly to the logarithm of the contact load, and straightening of the arm decreased the accuracy for each load by corresponding amounts. Similar relationships were found between the accuracy and the distance of movement. 4. Straightening of the arm did not cause any significant average reduction of the contact threshold for point stimulation of the same receptive field. A consistently lowered contact sensitivity, however, was observed for some of the subjects, which may have contributed to the reduction of the directional sensibility in these cases. 5. Correct directional estimations of the movement of the metal tip were obtained for a distance which was a fifth of the shortest distance for a corresponding estimation of the movement of a frictionless stimulus. The findings thus indicated that the friction between a moving object and the underlying skin, which can be mediated via stretch-sensitive cutaneous receptors, is critical for the determination of its direction of motion. 6. The present observations and previous observations by various authors are suggested to indicate that typical tactile directional sensibility depends on parallel processing of direction-selective data, and spatial data expressed as a function of time.

Adult↗

PubMed1992

Human, tactile, directional sensibility and its peripheral origins.

Tactile directional sensibility is probably functionally important and deserves attention as it is known to be sensitive to many different disturbances of the somatosensory system. Therefore, the ability of healthy adults to determine the direction of motion of a light tactile stimulus travelling proximally or distally along a straight line on depilated, hairy skin of the forearm was examined with two-alternative, forced-choice technique. The aim was to investigate the relative importance of different types of afferent information which may be used for this purpose. A test was started with the moving stimulus covering a distance of no less than 2.5 mm, which was subsequently increased until the subject could report the direction of motion reliably. Afterwards, the distance was decreased until the subject could no longer do so. Three different stimulation conditions were used and for a point stimulator touching the skin it was found that the necessary distance decreased to 2.5 mm after a moderate increase of the vertical contact load. No such decrease was found when a frictionless air-stream point stimulator was used instead. The distances which had to be covered by the point stimulator touching the skin increased to values which were comparable to those obtained with the air-stream stimulator after the lateral extensibility of the skin had been diminished. This was achieved by attaching a surgical sticky plaster around the stimulated skin area. The present findings consequently indicated that optimal, tactile, directional sensitivity depends on peripheral afferent messages which signal the direction of lateral stretching of the skin.

Adult↗

PubMed1990

The somatosensory intercollicular nucleus of the cat's mesencephalon.

1. Unitary, neural activity was sampled with tungsten electrodes in the mesencephalic, intercollicular region of cats anaesthetized with chloralose. The units' stereotaxic co-ordinates were noted and they were tested for activation by adequate tactile, visual and acoustic stimuli as well as electrical nerve stimulation. The units' geometrical gradations were afterwards translated into morphological terms by means of unbiased, cytoarchitectonic identifications of those structures which had been penetrated by the electrodes. 2. The primary objectives were the conventional, somatosensory units, which had reliable, low-threshold, tactile receptive fields and could not be activated by the two other types of adequate stimulation. There were 139 such units from a total sample of 495. 3. These somatosensory units were found to occupy many of the region's structures, notably the intercollicular nucleus (INC), the nucleus of the brachium of the inferior colliculus, the stratum griseum intermedium and the stratum griseum profundum of the superior colliculus. INC was the only structure which had an exclusively somatosensory input. 4. The units of INC had tactile receptive fields varying between one and several hundred square centimetres. Convergence of afferent input from outside these fields could sometimes be demonstrated by nerve stimulation. The latencies of activation from the contralateral sciatic nerve were, on average, shorter for units of INC than for the somatosensory units of the other intercollicular structures, and INC units could also follow higher stimulation frequencies. 5. The findings support the assumption that INC may constitute a distinct mesencephalic centre for somatosensory function.

Animals↗

PubMed1989

Behavioural thermosensitivity after unilateral, partial lesions of the lateral funiculus in the cervical spinal cord of the cat.

Adult cats were tested for unilateral, behavioural thermosensitivity, before and after unilateral, surgical lesions involving part of the lateral funiculus of the cervical spinal cord. Contralateral thermosensory deficiencies were found after lesions, which involved the middle parts of the lateral funiculus. No such deficiencies were observed after lesions which were restricted to either the dorsal third, or the ventral half of the lateral funiculus. It was concluded that behaviourally important, thermosensory information is transmitted via an ascending pathway which is located ventrally in the dorsal half of the lateral funiculus.

Afferent Pathways↗

PubMed1989

Behavioural thermosensitivity after bilateral lesions of the lateral funiculi in the cervical spinal cord of the cat.

The behavioural thermosensitivity of six cats was measured before and after single stage, symmetrical, bilateral, surgical lesions of the cervical spinal cord. The lesions were aimed at an area in the most ventral parts of the dorsal halves of the lateral funiculi. Unilateral lesions of that area have previously been found to cause reproducible, although subtotal, contralateral thermosensory defects, which were attributed to interruption of the thermosensory spinothalamic pathway. The lesions of three of the present cats were found to be incomplete, and those animals showed no postoperative thermosensory deficiency. Two of the cats with complete lesions showed marked post-operative defects, especially immediately after the operations, but the third cat with a complete lesion showed no postoperative thermosensory defect at all. The differences between the last three animals have been compared to the irregularity of previous reports about thermosensitivity after spinal cord lesions in man and animals, and may depend on the testing technique, rather than differences of thermosensitivity per se.

Animals↗

PubMed1989

Orienting reactions to light tactile stimuli after single and repeated partial spinal cord lesions in the cat.

Cats which had been trained to remain quietly standing were tested for orienting responses to light tactile stimulation (ORLT) of either hindlimb before and after different single, and subsequently increased, low thoracic spinal cord lesions. The individual lesions covered one dorsal column, and/or the dorsal part of one lateral funiculus, and/or the ventral part of the lateral funiculus, and/or one entire lateral funiculus and/or one or both ventral quadrants. Normal ORLTs were produced from the first post-operative test after each of the above lesions alone, or in combination with one of the others. Acute and chronic disappearances and/or disturbances of the ORLTs were observed for one hindlimb only after lesions involving at least the dorsal column and the dorsal part of the lateral funiculus of the ipsilateral side, as well as the contralateral lateral funiculus. The amount of disturbance varied with the technique in such a way that the number of operations which had been carried out to cause the actual lesion was inversely correlated to the degree of post-operative defect. The findings showed that the severity of the tactile symptoms after spinal cord lesions may depend on the speed with which they had developed. The types of lesions causing defects indicated that cats, under normal conditions, may utilize one of the three ascending spinal pathways for orienting reactions to light tactile stimulation. In relation to the peripheral receptive fields, these pathways are the ipsilateral dorsal column and spinocervical pathways, and a pathway of the contralateral lateral funiculus. The possible spinothalamic character of the crossed pathway has yet to be established.

Afferent Pathways↗

PubMed1986

Awareness, wakefulness and arousal.

The concepts awareness, wakefulness, and arousal are compared, and some neurophysiological and neuropsychological studies of awareness are described. The different studies are suggested to show that awareness depends on neural activity of the cerebral cortex, but the relationship between cortical activity and awareness is found to be conditional. Consequently, the presence of awareness can only be established with behavioural methods.

Arousal↗