1,721,004 research outputs found
Loss of large diameter spindle afferent fibres is not detrimental to the control of body sway during upright stance: evidence from neuropathy.
No full textFifteen patients with Charcot-Marie-Tooth type 1A (CMT1A) disease and 46 normal controls were studied.
In the patients, leg muscle strength, touch-pressure, vibration and joint position sense were reduced; lower limb tendon reflexes were absent in 12 or markedly decreased. Motor and sensory conduction velocity (CV) of leg nerves was either reduced or not measurable. The Neurological Disability Score and the Neuropathy Score were obtained from clinical and electrophysiological examination, respectively. Tilt of a supporting platform elicited short- (SLR) and medium-latency (MLR) responses to stretch in the foot muscle flexor digitorum brevis (FDB) in controls. In the patients, the former response was absent and the latter delayed. These findings are in keeping with the known loss of largediameter myelinated fibres, with relative sparing of the smaller fibres. The MLR delay was fully accounted for by the slowed CV of the motor fibres. The MLR afferent time was similar to that in normal subjects. Body sway area (SA) during quiet stance was recorded with eyes open or closed, and with feet apart or together. Under all postural and visual conditions, SA was within normal range in the less severely affected patients, but was moderately increased in the patients with a more severe neuropathy score. Across all patients, no correlation was found between SA and muscle force, motor CV, touch pressure, vibration and joint position sense, considered either separately or as an aggregate. We suggest that: (1) functional integrity of the largest afferent fibres is not necessary for appropriate equilibrium control during quiet stance and (2) any unsteadiness is related to additional functional alterations in smaller fibres, most likely group II spindle afferent fibres
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The shortening reaction of forearm muscles: the influence of central set.
No full textObjective: The EMG of the forearm muscles shortened by an imposed wrist joint displacement has been studied at different levels and distribution of background muscle activity and with different instructions to the subjects, in order to test the hypothesis that the recorded
EMG response (shortening reaction, ShoRe) could be deliberate in origin.
Methods: Ten normal subjects were examined. A torque motor induced 508 wrist extension or ̄exion at 5008/s. The subjects were relaxed or exerted a 10% maximal voluntary contraction. They were instructed either not to intervene, or to oppose the displacement, or else to assist
it. Several trials were repeated at different initial angles.
Results: We found a short-latency re ̄ex (SR) in the stretched muscle, be it ̄exor or extensor, and a later inconstant ShoRe in the antagonist. ShoRe latency was compatible with that of a reaction time (RT), and was not in ̄uenced by the initial wrist angle. When subjects
assisted the movement, the EMG burst in the shortening muscle was in every respect a RT; when they opposed the movement, the ShoRe disappeared. There was a strict temporal relationship between SR duration and ShoRe latency.
Conclusions:We suggest that the brain would deliberately trigger the ShoRe on recognizing the displacement direction. The occurrence of such activity in the shortened muscle makes the SR to abruptly stop. The temporal relationship between the duration of the SR and onset of
the ShoRe can be an expression of the inhibition on the SR burst by the cortical drive to the antagonist muscle being shortened, possibly through the action of spinal inhibitory interneurones. The ShoRe would complete the movement momentarily braked by the SR and redistribute the muscle tone across antagonists, appropriate for the new muscle length
Loss of large-diameter spindle afferent fibres is not detrimental to the control of body sway during upright stance: evidence from neuropathy
No full textFifteen patients with Charcot-Marie-Tooth type 1A (CMT1A) disease and 46 normal
controls were studied. In the patients, leg muscle strength, touch-pressure,
vibration and joint position sense were reduced; lower limb tendon reflexes were
absent in 12 or markedly decreased. Motor and sensory conduction velocity (CV) of
leg nerves was either reduced or not measurable. The Neurological Disability
Score and the Neuropathy Score were obtained from clinical and
electrophysiological examination, respectively. Tilt of a supporting platform
elicited short- (SLR) and medium-latency (MLR) responses to stretch in the foot
muscle flexor digitorum brevis (FDB) in controls. In the patients, the former
response was absent and the latter delayed. These findings are in keeping with
the known loss of large-diameter myelinated fibres, with relative sparing of the
smaller fibres. The MLR delay was fully accounted for by the slowed CV of the
motor fibres. The MLR afferent time was similar to that in normal subjects. Body
sway area (SA) during quiet stance was recorded with eyes open or closed, and
with feet apart or together. Under all postural and visual conditions, SA was
within normal range in the less severely affected patients, but was moderately
increased in the patients with a more severe neuropathy score. Across all
patients, no correlation was found between SA and muscle force, motor CV, touch
pressure, vibration and joint position sense, considered either separately or as
an aggregate. We suggest that: (1) functional integrity of the largest afferent
fibres is not necessary for appropriate equilibrium control during quiet stance
and (2) any unsteadiness is related to additional functional alterations in
smaller fibres, most likely group II spindle afferent fibres
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Concurrent changes in shortening reaction latency and reaction time of forearm muscles in post-stroke patients.
No full textThe objective was to confirm the hypothesis that
shortening reaction (ShoRe), normally occurring on
forcibly shortening a muscle, is depressed or delayed in
post-stroke patients. Eight post-stroke patients and ten agematched
normal subjects had a 50° wrist extension or flexion
induced by a torque-motor in the affected and the nonaffected
upper limb. Patients were instructed either not to
intervene or to assist displacement (reaction-time condition,
RT). Frequency of occurrence and latency of stretch
reflex (SR) and ShoRe, and RTs were measured from the
electromyograms (EMG) of wrist flexor (FCR) and extensor
(ECR) muscles. SR had higher than normal frequency
in both muscles. ShoRe disappeared in ECR on the affected
side but had normal frequency in FCR of both sides.
ShoRe latency was prolonged in FCR and ECR, in both
affected and unaffected sides. RTs were prolonged in both
FCR and ECR, in both affected and unaffected sides.
Across all patients, RTs and ShoRe latencies in the FCR
were correlated. Neither RTs nor ShoRe latencies were correlated
to Ashworth score. RTs were inversely correlated to
Medical Research Council scores. The decreased and
delayed ShoRe in post-stroke patients supports a role for
the cortico-spinal pathway in its production or modulation.
Monitoring of ShoRe can give insight into the recovery of
the descending control of spinal reflexes
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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