1,721,068 research outputs found
Visual influences on balance
No full textThis paper discusses the impact of vision on balance and orientation in patients with vestibular disorders and in anxiety patients with space and motion discomfort (SMD). When the vestibular system is impaired, vision has a greater influence on standing postural control, resulting in greater sway when individuals are presented with erroneous or conflicting visual cues. Studies have shown that individuals with other motion sensitivities, such as motion sickness, also tend to rely on vision for balance and do not disregard erroneous visual cues. Recently, patients with anxiety disorders that include SMD also have been shown to have increased postural sway in conflicting visual environments, similar to patients with vestibular disorders. Thus, while specific vestibular deficits are not always directly associated with SMD, data regarding the impact of vision on balance suggest that some patients with SMD may have an underlying balance disorder
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
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
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
Attentional demands of continuously monitoring orientation using vestibular information
No full textThe aim of this series of experiments was to determine whether attention is normally required for continuously processing vestibular information concerning orientation, or is required only when orientation is disrupted (eg by vestibular dysfunction or by conflicting visual and vestibular orientation cues). In the first two studies, healthy subjects were passively oscillated, and indicated when they perceived they were passing through their starting position. There was only weak evidence for interference between performance on this ‘continuous orientation monitoring task’ and on concurrent mental tasks. However, a third study showed that when patients with vestibular imbalance carried out the continuous orientation monitoring task their performance on a concurrent mental arithmetic task was substantially impaired. This dual task interference was correlated with inaccuracy in judging orientation on the continuous orientation monitoring task, which in turn correlated with severity of recent vestibular symptomatology (assessed by questionnaire). In a fourth experiment, disorientation was induced in healthy subjects by rotating the visual field about the line of sight. Bidirectional interference was observed between monitoring orientation (assessed by accuracy in setting a rod to the perceived vertical) and performance of an arithmetic task. Dual task interference was correlated with baseline levels of disorientation induced by the visual field, as indicated by inaccuracy in judging the visual vertical. These findings suggest that monitoring orientation makes significant demands upon cortical processing resources when disorientation is induced, whether the disorientation results from deficient sensory functioning or from ambiguous perceptual information
Psychophysical and Psychological Factors Affecting Recovery from Acute Balance Disorders
Full text linkPatients with acute vestibular neuritis are traditionally investigated with caloric or rotational examination of the vestibular-ocular reflex. However, clinical outcome is poorly predicted by such vestibular reflex assessments. We hypothesised that symptomatic recovery would depend upon higher order visuo-vestibular compensatory mechanisms.
Thirty-one patients were studied in the acute and recovery phases of vestibular neuritis (median 2 days and 10 weeks, respectively). Patients underwent examination of vestibulo-ocular and vestibular-perceptual responses, at threshold and supra-threshold levels. Supra-threshold stimuli (90°/s velocity step rotations) allowed quantification of vestibulo-ocular and vestibulo-perceptual time constants. Additional measures of visual dependency (rod-and-disc task), dizziness symptom load (Vertigo Symptom Scale and Dizziness Handicap Inventory) and psychological factors (including - autonomic arousal, anxiety, depression, fear of bodily sensations) were obtained.
Vestibulo-perceptual and vestibulo-ocular thresholds were raised and asymmetric acutely and remained slightly elevated and asymmetric at recovery. Acutely, supra-threshold vestibulo-ocular time constants were shortened and asymmetric. In contrast, perceptual responses were reduced but notably symmetrical. At recovery, vestibulo-ocular supra-threshold responses remained abnormal but perceptual supra-threshold responses normalised. Visual dependency was significantly elevated above normals in both acute and recovery stages. Vertigo symptom recovery was significantly predicted by acute levels of visual dependency (p=0.002), autonomic anxiety (p=0.004). A number of measures were associated with vertigo symptoms at recovery, in addition to visual dependency (p=0.012) and autonomic anxiety (p<0.001), including - anxiety and depression (p<0.003), fear of body sensations (p=0.033), vestibular perceptual thresholds (p=0.017) and caloric canal paresis (p=0.001). Factor Analysis revealed a strong association between clinical outcome, visual dependency and psychological factors, all loading on a single component accounting for 59.15% of the variance.
The bilateral suppression of supra-threshold vestibular perception observed acutely represents a hitherto unrecognised central adaptive ‘anti-vertiginous’ mechanism. However, poor symptomatic recovery is best predicted by increased visual dependency and psychological factors. The findings show that long term recovery from unilateral vestibular deficit is mediated by central compensatory mechanisms, including multi-sensory integration and psychological processing
Are white matter abnormalities associated with “unexplained dizziness”?
Full text linkIntroduction
Although cerebral small vessel disease is a significant contributor to the development of imbalance and falls in the elderly, whether it causes dizziness is not known.
Methods
A retrospective case analysis was conducted for 122 dizzy patients referred to two neuro-otology tertiary centres in London and Pisa. Patients were divided into ‘explained’ causes of dizziness (e.g. benign positional vertigo, vestibular neuritis, orthostatic hypotension, cerebellar ataxias) and ‘unexplained’ dizziness. White matter hyperintensities (WMH) in MRI (T2 weighted and FLAIR sequences) were blindly rated according to the Fazekas scale.
Results
122 patients; 58 (mean age = 72, SD=7.95 years) in the ‘unexplained’ group and 64 (mean age=72.01, SD=8.28 years) in the ‘explained’ group were recruited. The overall frequency of lesions (Fazekas 1–3) significantly differed between groups (p=0.011). The frequency of severe lesions (Fazekas 3) was significantly higher in the ‘unexplained’ group (22%) than in the ‘explained’ group (5%; p=0.003).
Conclusion
Increased severity of WMH in cases of unexplained dizziness suggests that such abnormalities are likely contributory to the development of dizziness. WM lesions may induce dizziness either because patients perceive a degree of objective unsteadiness or by a disconnection syndrome involving vestibular or locomotor areas of the brain
Behavioural manipulations of parietal lobe function
Full text linkThe aim of this thesis was to develop a novel behavioural technique to disrupt parietal function in order to induce top-down cortical modulation of low-level brain structures, namely the brainstem mediated vestibulo- ocular reflex and the early visual cortex. The premise of the technique was based upon using stimuli that engaged overlapping neuronal networks. To this end, we employed a technique that involved concurrent vestibular activation and viewing of bistable perceptual visual stimuli or performing visualised spatial attention tasks. The thesis presents data that shows the ability of this technique to induce a handedness related cortical modulation of the vestibulo-ocular reflex and modulation of the early visual cortex. Subsequently we applied trans-cranial direct stimulation to directly disrupt parietal inter-hemispheric balance in order to induce an asymmetrical modulation of the VOR and propose a revised computational model for vestibular processing. The results from these experiments present the first behavioural demonstration that vestibular cortical processing is strongly lateralised to the non-dominant hemisphere. We propose that this technique developed and validated in this thesis can be used to further probe and investigate cognitive parietal function such as numerical cognition and human decision making.Open Acces
- …
