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Discrimination Thresholds (discrimination + threshold)
Selected AbstractsMental rotation of body parts and sensory temporal discrimination in fixed dystonia,MOVEMENT DISORDERS, Issue 8 2010Petra Katschnig MD Abstract Fixed dystonia is an uncommon but severely disabling condition typically affecting young women following a minor peripheral injury. There is no evidence of any structural lesions of the central nervous system nor any clear peripheral nerve or root damage. Electrophysiological techniques such as short intracortical inhibition, cortical silent period and a plasticity inducing protocol have revealed similarities but also differences compared to classical mobile dystonia. To further explore the pathophysiology of fixed dystonia we compared mental rotation of body parts and sensory temporal discrimination in 11 patients with fixed dystonia, 11 patients with classical mobile dystonia and 10 healthy controls. In the mental rotation task subjects were presented with realistic photos of left or right hands, feet and the head of a young women with a black patch covering the left or the right eye in six different orientations. Subjects had to verbally report the laterality of the presented stimuli. To assess sensory temporal discrimination subjects were asked to discriminate whether pairs of visual, tactile (electrical), or visuo-tactile stimuli were simultaneous or sequential (temporal discrimination threshold) and in the latter case which stimulus preceded the other (temporal order judgement). In accordance with previous studies patients with mobile dystonia were abnormal in mental rotation and temporal discrimination, whereas patients with fixed dystonia were only impaired in mental rotation. Possible explanations for this deficit may include the influence of the abnormal body posture itself, a shared predisposing pathophysiology for mobile and fixed dystonia, or a body image disturbance. These findings add information to the developing pathophysiological picture of fixed dystonia. © 2010 Movement Disorder Society [source] Theoretical evaluation of magnetoreception of power-frequency fieldsBIOELECTROMAGNETICS, Issue 5 2010Jacques Vanderstraeten Abstract Several effects of power-frequency (50/60,Hz) magnetic fields (PF-MF) of weak intensity have been hypothesized in animals and humans. No valid mechanism, however, has been proposed for an interaction between PF-MF and biological tissues and living beings at intensities relevant to animal and human exposure. Here we proposed to consider PF-MF as disrupters of the natural magnetic signal. Under exposure to these fields, an oscillating field exists that results from the vectorial summation of both the PF-MF and the geomagnetic field. At a PF-MF intensity (rms) of 0.5,µT, the peak-to-peak amplitude of the axis and/or intensity variations of this resulting field exceeds the related discrimination threshold of magnetoreception (MR) in migrating animals. From our evaluation of the 50/60,Hz responsiveness of the putative mechanisms of MR, single domain particles (Kirschvink's model) appear unable to transduce that oscillating signal. On the contrary, radical pair reactions are able to, as well as interacting multidomain iron,mineral platelets and clusters of superparamagnetic particles (Fleissner/Solov'yov's model). It is, however, not yet known whether the reception of 50/60,Hz oscillations of the natural magnetic signal might be of consequence or not. Bioelectromagnetics 31:371,379, 2010. © 2010 Wiley-Liss, Inc. [source] Molding the sensory cortex: Spatial acuity improves after botulinum toxin treatment for cervical dystoniaMOVEMENT DISORDERS, Issue 16 2007Richard Walsh MB Abstract Disorganization of sensory cortical somatotopy has been described in adult onset primary torsion dystonia (AOPTD). Although botulinum toxin type A (BTX-A) acts peripherally, some studies have suggested a central effect. Our primary hypothesis was that sensory cortical reorganization occurs after BTX-A treatment of AOPTD. Twenty patients with cervical dystonia and 18 healthy age-matched control patients had spatial discrimination thresholds (SDTs) measured at baseline and monthly for 3 months. Mean baseline SDT (±SD) was 1.75 ±0.76 mm in the dystonia group, greater than the control group mean of 1.323 ± 0.45 mm (P = 0.05). Mean control group SDT did not vary significantly over time. A transient improvement of 23% from baseline (P = 0.005) occurred in the dystonia group 1 month after injection, which did not positively correlate with changes in physician and patient ratings of torticollis severity. The presumed mechanism of SDT improvement is a modulation of afferent cortical inputs from muscle spindles. © 2007 Movement Disorder Society [source] Deficits of temporal discrimination in dystonia are independent from the spatial distance between the loci of tactile stimulationMOVEMENT DISORDERS, Issue 2 2002Michele Tinazzi MD Abstract To assess whether spatial variables influence deficits of temporal somesthetic discrimination in dystonic patients, 10 patients with idiopathic dystonia and 12 healthy controls were tested with pairs of non-noxious electrical stimuli separated by different time intervals. Stimuli were delivered: (1) to the pad of the index finger (same-point condition), (2) to the pad and to the base of the index finger (same-finger condition), and (3) to the pad of the index and ring fingers (different-finger condition). Subjects were asked to report whether they perceived single or double stimuli in the first condition and synchronous or asynchronous stimuli in the second and third conditions. Somesthetic temporal discrimination thresholds (STDTs) were obtained by computing the shortest time interval at which stimuli, applied to the left or the right hand, were perceived as separate in the first condition or asynchronous in the second and third conditions. STDTs were significantly higher in dystonic patients than controls in all three conditions. In both dystonia patients and controls, STDTs resulted highest in conditions whereby stimuli were maximally separated in space. Results extend current knowledge of deficits of somesthetic temporal discrimination in dystonia by showing that temporal deficits are not influenced by spatial variables. © 2002 Movement Disorder Society. [source] Perceived blur in amblyopiaOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 6 2002A. J. Simmers Purpose:, It is well documented that visual acuity and contrast sensitivity in amblyopia are attenuated at high spatial frequencies: this would predict that amblyopes should perceive objects as blurred because they lack high spatial frequency information necessary to adequately represent sharp edges. In a series of experiments, we explored the representation of blur in amblyopia with blur discrimination and blur matching tasks. Methods:, Monocular blur discrimination thresholds were measured in a spatial 2-Alternative Force Choice procedure. The luminance profiles of the blurred edge were cumulative Gaussians with the standard deviation of the reference blurred edge being fixed at 1.88, 3.75, 7.5, 15, 30, or 60 min arc. Observers were required to discriminate which edge (right or left) appeared to be the less blurred. Observers also interocularly matched edges which were identical to those employed in the blur discrimination tasks, with the exception that they were viewed dichoptically at all times. Results:, Blur discriminination thresholds were elevated in both the amblyopic and fellow fixing eye but were within the normal range for interocular matching thresholds. Our results suggest that blur is veridically represented in the amblyopic visual system. Conclusions:, The surprising result here is that all amblyopes, even those with the most severe visual loss, veridically matched all blurred edges, including the sharpest ones. This implies that amblyopes are able to represent levels of blur that are defined by spatial structure beyond their resolution limit. These results also raise interesting questions about the mechanism by which blur is represented in the visual system. [source] Laryngeal sensory deficits in patients with chronic cough and paradoxical vocal fold movement disorder,THE LARYNGOSCOPE, Issue 8 2010Thomas Murry PhD Abstract Objectives/Hypothesis: Although the diagnostic accuracy of paradoxical vocal fold movement disorder and chronic cough has improved, the underlying pathophysiology remains relatively unknown. We hypothesize that one potential etiological factor in these patients is an aberrant laryngeal sensory response and sought to determine if respiratory retraining in addition to antireflux therapy alters this aberrant response. Study Design: Retrospective, outcomes. Methods: Sixteen patients who had been on at least 3 months of twice-daily proton pump inhibitors with no subjective improvement in their primary complaint of cough, self-reported symptoms of gastroesophageal and laryngopharyngeal reflux, and concurrent paradoxical vocal fold movement (PVFM) were included in the current study. In addition to continuing twice daily pharmacological therapy, subjects underwent a course of respiratory retraining. Outcome measures including the Reflux Symptom Index (RSI), transnasal flexible laryngoscopy, and laryngopharyngeal sensory discrimination thresholds were obtained prior to and following a course of respiratory retraining. Results: Mean bilateral laryngeal sensory response improved significantly after combined respiratory retraining and aggressive proton pump inhibitor therapy (P = .01). In addition, mean RSI score decreased significantly following treatment (P = .02). Specifically, 13 of 16 patients experienced improved sensory response, corresponding with patient reports of improved PVFM symptoms following treatment. Conclusions: Aberrant laryngeal sensation was identified in patients with PVFM and chronic cough. This response, however, normalized following a limited course of respiratory retraining, corresponding with improved patient symptoms. Laryngoscope, 2010 [source] | ||||||||||