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  • 1
    ISSN: 1432-055X
    Keywords: Schlüsselwörter Nosokomiale Infektionen ; Intensivstationen ; NIDEP ; Bundesweite Prävalenzstudie ; Key words Nosocomial infections ; Intensive care unit ; NIDEP ; Nationwide prevalence survey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract In a large, multicenter survey in 1994, the prevalence of nosocomial infections in German hospitals was examined, predominant pathogens were identified, and possible risk factors evaluated. In this paper the results from the intensive care units (ICUs) are presented. Methods. Seventy-two representative hospitals in Germany were selected by randomisation and divided into four different groups according to their size (〈200 beds; 200–400 beds; 400–600 beds; 〉600 beds). During 10 months four especially trained doctors documented the patients clinical and laboratory data and possible endogenous and exogenous risk factors for nosocomial infections. For better evaluation, they discussed the cases with the responsible senior officers and health care workers and visited the patients. Diagnosis of nosocomial infection was based on CDC criteria. Results. In 515 patients in 89 ICUs, 78 hospital-acquired infections were documented (15.3%). The most common were pneumonia (5.9%), bronchitis (2.7%), urinary tract infections (2.4%), and septicaemia (2.2%). Possible exogenous risk factors included: peripheral venous catheters (65.6%); catheterisation of the urinary tract (64.5%); central venous catheters (60.4%); gastric tubes (38.0%); wound drainage (28.6%) and artificial ventilation (27.6%). The most frequent concomitant diseases were cardiovascular (61.9%), diabetes (20.2%), malignancies (18.8%), pre-existing infections (15.3%), and chronic respiratory disease (14.0%). The prevalence of nosocomial infections was higher in hospitals with more than 600 beds than in smaller ones (28.3% versus 12.9%, P〈0.001). Predominant pathogens were Pseudomonas aeruginosa, enterococci, Staphylococcus aureus, Candida spp., Escherichia coli, and Klebsiella spp.. Fifty per cent of the ICUs changed ventilation tubes and 66.3% changed infusion sets daily; 34.8% of patients received drugs for the prevention of stress ulcers that neutralise or decrease production of gastric acid; only 7.6% received sucralfate. Routine microbiological surveillance of tracheal aspirates and urine was done by 25.9% and 24.6% of the ICUs, respectively. Discussion. Nosocomial infections are seen far more often in ICUs than on normal wards due to the immunosuppressed state of many ICU patients and the continuous use of invasive diagnostic and therapeutic procedures. Most of these infections are of endogenous origin. Other prevalence surveys have shown results comparable to ours. Daily changing of ventilation tubes is no longer necessary, but is still routine in many hospitals. Infusion sets were also changed more often than required. The use of selective decontamination of the digestive tract for the prevention of pneumonia is still controversial; in our study it was practised in only 1.5% of the cases. The most commonly used drugs for the prevention of stress ulcers were H2-receptor blocking agents, although it has been shown that sucralfate is the better choice, as it can help prevent nosocomial pneumonia. Routine microbiological surveillance of tracheal aspirates and urine was done in 25.9% and 24.6% of the ICUs. No study so far has shown that routine cultures of tracheal secretions and urine have a preventive effect regarding infection.
    Notes: Zusammenfassung Im Auftrag des Bundesgesundheitsministeriums wurde von Januar bis Oktober 1994 eine für Deutschland repräsentative Prävalenzstudie mit insgesamt 14966 Patienten an 72 nach Größenklassen ausgewählten Kliniken mit dem Ziel durchgeführt, nosokomiale Infektionen, potentielle Risikofaktoren und Hygienemaßnahmen zu erfassen (NIDEP: Nosokomiale Infektionen in Deutschland – Erfassung und Prävention). Auf 89 Intensivstationen hatten von 515 Patienten 78 (15,3%) mindestens eine nosokomiale Infektion. Die häufigsten Infektionen waren Pneumonie (5,9%), Tracheobronchitis (2,7%), Harnwegsinfektion (2,4%) und primäre Sepsis (2,2%). Die häufigsten potentiellen endogenen Risikofaktoren für Krankenhausinfektionen waren Herz-Kreislauferkrankungen (61,9%), Diabetes mellitus (20,2%), Malignome (18,8%), vorbestehende Infektionen (15,3%) und chronische Atemwegserkrankungen (14,0%). Für die potentiell exogenen Risikofaktoren ergaben sich folgende Prävalenzen: Periphere Venenkatheter (65,6%), Harndrainagen (64,5%), zentrale Venenkatheter (60,4%), Magensonden (38,0%), Wunddrainagen (28,6%), und kontrollierte Beatmung (27,6%). 50,0% der Intensivstationen wechselten die Beatmungsschläuche und 66,3% die Infusionssysteme immer noch täglich. Bei 34,8% der Patienten wurde eine säurehemmende Streßulkusprophylaxe durchgeführt, lediglich 17,6% der Patienten erhielten Sucralfat. Die Mehrzahl der Intensivstationen führte kein routinemäßiges mikrobiologisches Monitoring durch. Einige Intensivstationen untersuchten jedoch Urin und Trachealsekret täglich. Die häufigsten Erreger nosokomialer Infektionen auf Intensivstationen waren in absteigender Reihenfolge Pseudomonas aeruginosa, Enterokokken, Staphylococcus aureus, Candida spp., Escherichia coli, Klebsiella spp.
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  • 2
    ISSN: 1432-1106
    Keywords: Key words Ménière’s disease ; Unilateral vestibular neurotomy ; Static posture ; Postural recovery ; Sensory strategies ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Vestibular inputs tonically activate the antigravitative leg muscles during normal standing in humans, and visual information and proprioceptive inputs from the legs are very sensitive sensory loops for body sway control. This study investigated the postural control in a homogeneous population of 50 unilateral vestibular-deficient patients (Ménière’s disease patients). It analyzed the postural deficits of the patients before and after surgical treatment (unilateral vestibular neurotomy) of their diseases and it focused on the visual contribution to the fine regulation of body sway. Static posturographic recordings on a stable force-plate were done with patients with eyes open (EO) and eyes closed (EC). Body sway and visual stabilization of posture were evaluated by computing sway area with and without vision and by calculating the percentage difference of sway between EC and EO conditions. Ménière’s patients were examined when asymptomatic, 1 day before unilateral vestibular neurotomy, and during the time-course of recovery (1 week, 2 weeks, 1 month, 3 months, and 1 year). Data from the patients were compared with those recorded in 26 healthy, age- and sex-matched participants. Patients before neurotomy exhibited significantly greater sway area than controls with both EO (+52%) and EC (+93%). Healthy participants and Ménière’s patients, however, displayed two different behaviors with EC. In both populations, 54% of the subjects significantly increased their body sway upon eye closure, whereas 46% exhibited no change or significantly swayed less without vision. This was statistically confirmed by the cluster analysis, which clearly split the controls and the patients into two well-identified subgroups, relying heavily on vision (visual strategy, V) or not (non-visual strategy, NV). The percentage difference of sway averaged +36.7%±10.9% and –6.2%±16.5% for the V and NV controls, respectively; +45.9%±16.8% and –4.2%±14.9% for the V and NV patients, respectively. These two distinct V and NV strategies seemed consistent over time in individual subjects. Body sway area was strongly increased in all patients with EO early after neurotomy (1 and 2 weeks) and regained preoperative values later on. In contrast, sway area as well as the percentage difference of sway were differently modified in the two subgroups of patients with EC during the early stage of recovery. The NV patients swayed more, whereas the V patients swayed less without vision. This surprising finding, indicating that patients switched strategies with respect to their preoperative behavior, was consistently observed in 45 out of the 50 Ménière’s patients during the whole postoperative period, up to 1 year. We concluded that there is a differential weighting of visual inputs for the fine regulation of posture in both healthy participants and Ménière’s patients before surgical treatment. This differential weighting was correlated neither with age or sex factors, nor with the clinical variables at our disposal in the patients. It can be accounted for by a different selection of sensory orientation references depending on the personal experience of the subjects, leading to a more or less heavy dependence on vision. The change of sensory strategy in the patients who had undergone neurotomy might reflect a reweighting of the visual and somatosensory cues controlling balance. Switching strategy by means of a new sensory selection of orientation references may be a fast adaptive response to the lesion-induced postural instability.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 40 (1980), S. 103-110 
    ISSN: 1432-1106
    Keywords: Vestibular neurectomy ; Compensation ; Vision ; Free fall ; EMG ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In previous studies a contribution of vision to vestibular-dependent muscle responses during free-fall was found in the intact monkey, and the role of remaining labyrinthine afferents in compensation of these postural reactions was studied in vestibular neurectomized monkeys. In the present investigation we have compared the role of visual motion cues in the recovery of muscle responses to fall in unilateral (U.N.) and bilateral vestibular neurectomized (B.N.) baboons. During free-fall, electromyographic (EMG) responses were recorded from splenius capitis, soleus and tibialis anterior muscles. EMG activities were recorded in two randomly presented conditions: with normal motion of the visual world (NV) and with the visual world stabilized with respect to the baboon's head (SV) until 6 weeks after surgery. In B.N. baboons, results showed that condition SV was accompanied by a very strong motor depression during the entire test period. A greater decrease was observed in the splenius and soleus muscles. In U.N. baboons, significantly depressed EMG responses were recorded in the SV condition during the first two stages of compensation only (0–2 weeks), in all tested muscles except the tibialis anterior muscle. On the other hand, these motor depressions appeared to depend upon the level of neuronal resting activity in the vestibular nuclei. It is inferred that the partial recovery of muscle responses to fall observed in B.N. baboons in the NV condition is mainly due to visual information concerning motion, which replaces to the labyrinthine afferents. In U.N. baboons, the visual motion cues would fulfil only a transitory substitution function by supplying the decrease of neuronal activity in the vestibular nuclei. Later on, full compensation would be carried out by means of the remaining labyrinth.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 65 (1987), S. 569-581 
    ISSN: 1432-1106
    Keywords: Alert cat ; Vertical linear acceleration ; Otolith system ; Vestibular nuclei ; Unit activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The aim of the present study was to investigate some aspects of the central processing of otolith information during linear motion. For this purpose, the response characteristics of 69 vestibular nuclei units to sinusoidal otolith stimulation in the vertical Z axis were analysed in the alert cat. Among this population of neurons which responded to a 0.05 Hz, 290 mm translation, 47 units (70%) displayed a firing rate modulation which followed the input frequency (H1 units). The majority of these neurons exhibited an increase in discharge rate during upward displacement, with a response phase close to the motion velocity or slightly leading downward acceleration. The acceleration related units were divided into two groups according to whether they showed clear increases or only a slight change in discharge rate when the stimulus frequency was increased. The former group was characterized by an average −16.3 dB drop in gain (from 43.9±1.8 dB, S.D. to 27.6±7 dB, S.D.) within the 0.05 Hz–0.5 Hz frequency range, while the latter group displayed an average −31.2 dB gain attenuation (from 45.1±1.1 dB, S.D. to 13.9±0 dB) within the same decade. In contrast to differences in response gain, all the units tested exhibited a relatively stable phase lead of about 20° with respect to downward peak acceleration. Conversely, units whose response was close to motion velocity in the lower frequency range (0.05 Hz–0.10 Hz) displayed a strong phase lead of about 100° when the stimulus frequency was increased (up to 0.50 Hz). These neurons were thus characterized by an acceleration related response in the higher frequency range. At the same time, an average −24.8 dB gain attenuation (from 47.7±3.4 dB to 22.9±3.7 dB) was found in the 0.05 Hz–0.5 Hz decade. The remaining 22 neurons (30%) were called H2 units since they displayed a response waveform double that of the input frequency, a response already described during sinusoidal rotation. Unit discharge reached a peak approximately in phase with maximum upward and downward velocity. Asymmetrical change in unit firing rate about the resting discharge level and different dynamic behavior of the upward and downward response components were usually found. These response characteristics suggest that the H2 patterns are centrally constructed and could result from convergence of otolith afferents having opposite polarization vectors. Other evidence suggests that these units which behave like motion-detectors can exert an influence on the neck musculature. Our results corroborate, at least in part, the findings of previous studies on the dynamic responses properties of otolith-dependent central neurons during roll tilt, or pure linear acceleration in the horizontal plane.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 37 (1979), S. 563-580 
    ISSN: 1432-1106
    Keywords: Vestibular neurectomy ; Compensation ; Muscle responses to fall ; Remaining labyrinthine afferences ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The electromyographic (EMG) responses from soleus and tibialis anterior muscles and the monosynaptic H- and T-reflex responses from soleus muscles were recorded bilaterally from conscious baboon while unexpectedly dropping it with unrestricted vision. These responses were recorded either after unilateral vestibular neurectomy (U.N. baboons) or after bilateral neurectomy performed in one stage (B.N. 1 baboons) and in two stages (B.N. 2 baboons). A positive correlation was found between modifications and development of EMG responses and reflex data. In the U.N. baboons, some differences were observed when comparing data from the H- and T-reflex methods, suggesting that recovery of normal responses to fall is achieved both by means of direct influences on α-motoneurons and via the γ-loop. In the U.N. baboons postural reactions to fall developed in three distinct periods. The first or critical stage showed asymmetrical EMG and reflex responses with increased responses from contralateral soleus muscle and decreased responses from ipsilateral soleus. Opposite effects were recorded from tibialis anterior flexor muscles. The second or acute stage which began around 4 to 7 days after surgery exhibited symmetrical, but very reduced, responses when compared to the control in soleus muscles, and symmetrical, but increased, responses from tibialis anterior muscles. This stage lasted until about the end of the second postoperative week and was followed by the third or compensatory stage during which EMG as well as reflex responses developed towards the control pattern in all tested muscles. Almost normal responses were recorded on both sides 3 weeks after surgery. Only a partial recovery was found in the B.N. 1 baboons, indicating that the contralateral remaining labyrinthine afferences constitute a necessary condition for the full compensation of postural reactions to fall in the case of unilateral vestibular neurectomy. The Bechterew's compensation was obtained in the B.N. 2 baboons. These results are discussed in relation with the general organization of the vestibulospinal pathways and with those concerning development of the postoperative activity at the vestibular nuclei level. A model of vestibular compensation achieved by means of a multisensory substitution process is suggested.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 70 (1988), S. 287-298 
    ISSN: 1432-1106
    Keywords: Alert cat ; Vertical optokinetic stimulation ; Vestibular nuclei ; OKR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Extracellular activity from vestibular nuclei neurons and vertical eye movements were recorded in the alert cat during sinusoidal optokinetic stimulation in the vertical plane at frequencies varying from 0.0125 Hz to 0.75 Hz. Among a population of 96 vestibular units located in and around Deiters' nucleus, 73 neurons (76%) displayed a firing rate modulation which followed the input at the standard parameters of visual stimulation (0.05 Hz; 10.1 deg/s or 9.1 cm/s peak to peak velocity). Two different patterns of modulation were found. In 42 cells (57%) an increase in the firing rate was observed during motion of the visual scene in the downward direction, while 31 neurons (43%) showed the opposite behavior, with an enhanced firing rate during upward movement. The phase of the neuronal responses was close (± 45°) to the velocity peaks (+90°: downward and -90°: upward) of visual scene motion for 65 among the 73 neurons. Mean values of phase was-6.1 ± 19.5° (SD) and -3.2 ± 15.5° (SD) with respect to the +90° and -90° velocity peaks, respectively. In the frequency range 0.0125–0.75 Hz, the phase of the neuronal responses remained almost stable, with only a slight lag which reaches -22° at the 0.25 Hz visual stimulation. The firing rate modulation was found to be predominant at low frequencies (0.0125 Hz–0.25 Hz), with three distinct peaks of modulation occurring either at 0.025 Hz, 0.10 Hz or 0.25 Hz, depending on the recorded cells. Above 0.5 Hz, the cell modulation was very poorly developed or even absent. A gain attenuation was observed in all units, which was more important in cells showing a peak of modulation at 0.025 Hz as compared with the others (-20.7 dB vs -9.6 dB, respectively, in the 0.025 Hz–0.25 Hz decade). The gain of the optokinetic reflex (OKR) progressively decreased from mean values of 0.78 ± 0.15 to 0.05 ± 0.06 in the 0.025 Hz–0.5 Hz frequency range. A close correlation was observed between the OKR slow phase velocity and the modulation of the neuronal responses in the two cell populations with maximal modulations at 0.10 Hz or 0.25 Hz. No correlations were noticed in the third population characterized by a peak of modulation at 0.025 Hz. In all units, the phase of eye movement velocity and of neuronal responses were both related to the velocity of the visual surround motion. These correlations were also found when varying the amplitude of the visual stimulation at a fixed frequency. Saturation was observed in the unit responses at velocities above 68.5°/s. When considering both the gain attenuation in the frequency range and the correlation between firing rate modulation and OKR slow phase velocity, two rather different cell populations can be distinguished: one with neurons peaking at 0.025 Hz (strong gain attenuation; no correlation with OKR velocity) and one with neurons peaking at 0.10 Hz or 0.25 Hz (slight gain attenuation; correlation with OKR velocity). This study points to the influence of visual motion cues on vestibular nuclei unit activity in the low-frequency range. A velocity coding of visual — surround motion in the vertical plane is performed by vestibular neurons. Our results in the alert cat suggest that both retinal (retinal slip) and extraretinal (proprioceptive afferences from eye muscles, efference copy) inputs can be involved in this visually induced modulation of vestibular nuclei neurons.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 70 (1988), S. 299-309 
    ISSN: 1432-1106
    Keywords: Alert cat ; Vertical linear acceleration ; Visual and otolith systems ; Vestibular nuclei
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the present study we have investigated in the awake cat the response dynamics of vestibular nuclei neurons to visual or/and otolith stimulation elicited by vertical linear motion. Of the 53 units tested during sinusoidal motion at 0.05 Hz (9.1 cm/ s), 1 (1.9%) was responsive to the otolith input only, 13 (24.5%) were influenced by the visual input only and 23 (43.4%) responded to both modalities. Neurons were excited either during upward or downward animal or visual surround movement. Most units displayed a firing rate modulation very close to motion velocity. All the neurons receiving convergent visual and otolith inputs (0.05 Hz, 9.1 cm/s) exhibited synergistic patterns of response. Motion velocity coding was improved in terms of inputoutput phase relationship and response sensitivity when visual and otolith signals were combined. Depending on the units, visual-otolith interactions in single neurons could follow a linear or a nonlinear mode of summation. The dynamic characteristics of visual-otolith interactions were examined in the 0.05 Hz–0.50 Hz frequency bandwidth. Visual signals seemed to predominate over otolith signals at low stimulus frequencies (up to 0.25 Hz), while the contrary was found in the higher frequency range of movement (above 0.25 Hz). The effects of visual stabilization (VS: suppression of visual motion cues) was observed in a small sample of units. As a rule, VS induced a reduction in the amplitude of unit response as compared to visual + otolith stimulation, the lower the motion frequency, the more pronounced the attenuation. VS also decreased the amplitude of the otolith-dependent component of response. The possible modes of visual-vestibular interactions in single cells are discussed. The present study supports the hypothesis that visual and vestibular motion cues are weighted according to their internal relevance.
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  • 8
    ISSN: 1432-1106
    Keywords: Vision ; Vestibular system ; Monkey ; Free fall
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In a previous study the muscle responses from the lower limbs were studied in the Baboon (Papio-Papio) during sudden falls. On the other hand, recent findings concerning the role of vision in the control of posture during rapid perturbations in man have stimulated the present investigation. EMG activities were recorded from the fully conscious animal using chronic electrodes implanted in various muscles (splenius, quadriceps femoris, soleus, and tibialis anterior). For testing, the monkey was seated in a special chair suspended from an electromagnet and unexpectedly dropped 90 cm. EMG responses were recorded in three randomly presented conditions: with normal motion of visual world (N), with visual world stabilized with respect to the head (S) using a box covered inside by a black and white checkboard pattern surrounding the animal's head, and in total darkness (D). Results showed that condition S is accompanied in all tested muscles by a significant decrease in the EMG response; this effect is particularly evident in the interval 60–120 ms but may occur earlier. Condition D is in most of the cases accompanied by a less important decrease which is situated between condition N and condition S. These results are in contrast to previous conclusions of other authors which negated the role of vision in similar situations.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 65 (1987), S. 559-568 
    ISSN: 1432-1106
    Keywords: Otolith-neck reflexes ; Vertical linear acceleration ; EMG ; Alert cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Electromyographic activity of dorsal neck muscles elicited by sinusoidal vertical linear accelerations was studied in alert cats over a wide range of frequencies. Experiments were performed in headfixed cats and total darkness in order to activate selectively the otolith system. The polyunitary EMG activity was recorded from splenius capitis muscles in normal and labyrinthectomized cats during vertical translations varying from 0.05–1 Hz with a fixed 290 mm peak-to-peak amplitude. The corresponding accelerations ranged from 0.003–1.2 g. In normal cats, the results showed a bilateral and sinusoidal modulation of the EMG activity characterized by two typical EMG patterns depending on the stimulus frequency. In the low-frequency range (0.05–0.25 Hz), the neck muscles responses were composed of a second harmonic (frequency double that of the input signal: H2 responses). The H2 pattern was characterized by an increase in EMG activity during both the upward and downward parts of translation. These two components of the H2 response were closely related to the two peak velocities (+90° and −90°) of the animal motion. Only slight decreases in amplitude and shifts in phase were observed when increasing the frequency. In the higher frequency range (0.25–1 Hz), the neck muscles response was composed of a fundamental frequency corresponding to the input signal (H1 response). The H1 pattern was in phase with the peak of downward acceleration at 0.25 Hz. A phase lag (up to 45°) and a gain attenuation (16.5 dB) were observed when increasing the frequency. The two H1 and H2 EMG patterns were totally absent in bilateral vestibular neurectomized cats. In unilateral vestibular neurectomized cats, a strong drop in gain and phase advance was noted, which mainly affected the H1 pattern. The present results describe some characteristics of otolith-spinal reflexes acting on the head musculature during vertical motion. They are compared with the neuronal responses that we have recorded within the vestibular nuclei complex in the same experimental conditions. The functional role of the vertical otolithneck reflexes in stabilizing the head in space during many real-life situations is discussed.
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  • 10
    ISSN: 1432-1106
    Keywords: Key words Antagonist neck muscles ; Eye movements ; Unilateral vestibular neurectomy ; Visual substitution ; Motor strategies ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The purpose of this study was to investigate changes in neck muscle and eye movement responses during the early stages of vestibular compensation (first 3 weeks after unilateral vestibular neurectomy, UVN). Electromyographic (EMG) activity from antagonist neck extensor (splenius capitis) and flexor (longus capitis) muscles and eye movements were recorded during sinusoidal visual and/or otolith vertical linear stimulations in the 0.05–1 Hz frequency range (corresponding acceleration range 0.003–1.16 g) in the head-fixed alert cat. Preoperative EMG activity from the splenius and longus capitis muscles showed a pattern of alternate activation of the antagonist neck muscles in all the cats. After UVN, two motor strategies were observed. For three of the seven cats, the temporal activation of the individual neck muscles was the same as that recorded before UVN. For the other four cats, UVN resulted in a pattern of coactivation of the flexor and extensor neck muscles because of a phase change of the splenius capitis. In both subgroups, the response patterns of the antagonist neck muscles were consistent for each cat independently of the experimental conditions, throughout the 3 weeks of testing. Cats displaying alternate activation of antagonist neck muscles showed an enhanced gain of the visually induced neck responses, particularly in the high range of stimulus frequency, and a gain decrease in the otolith-induced neck responses at the lowest frequency (0.25 Hz) only. By contrast, for cats with neck muscle coactivation, the gain of the visually induced neck responses was basically unaffected relative to preoperative values, whereas otolith-induced neck responses were considerably decreased in the whole range of stimulation. As concerns oculomotor responses, results in the two subgroups of cats were similar. The optokinetic responses were not affected by the vestibular lesion. On the contrary, otolith-induced eye responses showed a gain reduction and a phase lead. Deficits and short-term changes after UVN of otolith- and semicircular canal-evoked collic and ocular responses are compared.
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