Visual thresholds to low-contrast pattern displacement, color contrast, and luminance contrast stimuli in Parkinson's disease

1994 ◽  
Vol 9 (5) ◽  
pp. 563-570 ◽  
Author(s):  
Bernhard A. Haug ◽  
Claudia Trenkwalder ◽  
Geoffrey B. Arden ◽  
Wolfgang H. Oertel ◽  
Walter Paulus
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Luminance Contrast ◽  
Color Contrast ◽  
Low Contrast ◽  
Contrast Pattern

Occurrence of express saccades under isoluminance and low contrast luminance conditions

1991 ◽  
Vol 7 (5) ◽  
pp. 505-510 ◽  
Author(s):  
Heike Weber ◽  
Burkhart Fischer ◽  
Michael Bach ◽  
Franz Aiple
Keyword(s):  
Human Subjects ◽  
Reaction Times ◽  
Luminance Contrast ◽  
Saccade Target ◽  
White Background ◽  
Color Contrast ◽  
Express Saccades ◽  
Low Contrast ◽  
Green Background ◽  
White Target

AbstractSaccadic reaction times (SRTs) of three human subjects were analyzed. The gap paradigm was used (i.e. fixation point offset precedes target onset) to obtain high proportions of express saccades (i.e. saccades of extremely short reaction times) in the SRT distributions. In one set of experiments, the luminance of the (red) saccade target was varied from brighter to darker than the (green) background including an isoluminance condition. Express saccades were obtained in response to pure color contrast stimuli with about the same frequency and reaction time as to stimuli with both color and luminance contrast. In a second experiment, the luminance contrast of a white target on a white background was lowered below 10%. Again the number of express saccades was not reduced. Thus, in contrast to other perceptual phenomena the visual neural mechanisms underlying the generation of express saccades are not affected by isoluminance nor low contrast luminance.

scholarly journals A robust method for the detection of small changes in relaxation parameters and free water content in the vicinity of the substantia nigra in Parkinson’s disease patients

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0247552
Author(s):  
Krzysztof Dzieciol ◽  
Elene Iordanishvili ◽  
Zaheer Abbas ◽  
Adjmal Nahimi ◽  
Michael Winterdahl ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Substantia Nigra ◽  
Water Content ◽  
Free Water ◽  
Quantitative Mri ◽  
Healthy Controls ◽  
Pathological Changes ◽  
Low Contrast ◽  
Free Water Content

Alterations in the substantia nigra are strongly associated with Parkinson’s disease. However, due to low contrast and partial volume effects present in typical MRI images, the substantia nigra is not of sufficient size to obtain a reliable segmentation for region-of-interest based analysis. To combat this problem, the approach proposed here offers a method to investigate and reveal changes in quantitative MRI parameters in the vicinity of substantia nigra without any a priori delineation. This approach uses an alternative method of statistical, voxel-based analysis of quantitative maps and was tested on 18 patients and 15 healthy controls using a well-established, quantitative free water mapping protocol. It was possible to reveal the topology and the location of pathological changes in the substantia nigra and its vicinity. Moreover, a decrease in free water content, T1 and T2* in the vicinity of substantia nigra was indicated in the Parkinson’s disease patients compared to the healthy controls. These findings reflect a disruption of grey matter and iron accumulation, which is known to lead to neurodegeneration. Consequently, the proposed method demonstrates an increased sensitivity for the detection of pathological changes—even in small regions—and can facilitate disease monitoring via quantitative MR parameters.

Low contrast stimuli enhance PERG sensitivity to the visual dysfunction in Parkinson's disease

1992 ◽  
Vol 82 (6) ◽  
pp. 453-457 ◽  
Author(s):  
A. Peppe ◽  
P. Stanzione ◽  
F. Pierelli ◽  
E. Stefano ◽  
P.A. Rizzo ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Visual Dysfunction ◽  
Low Contrast

A Variant of the Anomalous Motion Illusion Based upon Contrast and Visual Latency

Perception ◽  
10.1068/p5362 ◽  
2007 ◽  
Vol 36 (7) ◽  
pp. 1019-1035 ◽  
Author(s):  
Akiyoshi Kitaoka ◽  
Hiroshi Ashida
Keyword(s):  
Critical Factor ◽  
Luminance Contrast ◽  
High Contrast ◽  
Illusory Motion ◽  
Low Contrast ◽  
Motion In Depth ◽  
Contrast Pattern ◽  
Pulfrich Effect ◽  
Series Of Experiments ◽  
Visual Delay

We examined a variant of the anomalous motion illusion. In a series of experiments, we ascertained luminance contrast to be the critical factor. Low-contrast random dots showed longer latency than high-contrast ones, irrespective of whether they were dark or light (experiments 1–3). We conjecture that this illusion may share the same mechanism with the Hess effect, which is characterised by visual delay of a low-contrast, dark stimulus in a moving situation. Since the Hess effect is known as the monocular version of the Pulfrich effect, we examined whether illusory motion in depth could be observed if a high-contrast pattern was projected to one eye and the same pattern of low-contrast was presented to the other eye, and they were binocularly fused and swayed horizontally. Observers then reported illusory motion in depth when the low-contrast pattern was dark, but they did not when it was bright (experiment 4). Possible explanations of this inconsistency are discussed.

Evaluation of Efferent Auditory System and Hearing Quality in Parkinson's Disease: Is the Difficulty in Speech Understanding in Complex Listening Conditions Related to Neural Degeneration or Aging?

2020 ◽  
pp. 1-9
Author(s):  
Nuriye Yıldırım Gökay ◽  
Bülent Gündüz ◽  
Fatih Söke ◽  
Recep Karamert
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Auditory System ◽  
Otoacoustic Emissions ◽  
Pure Tone ◽  
Pure Tone Audiometry ◽  
Auditory Pathway ◽  
Normal Hearing ◽  
System Function ◽  
Distortion Product

Purpose The effects of neurological diseases on the auditory system have been a notable issue for investigators because the auditory pathway is closely associated with neural systems. The purposes of this study are to evaluate the efferent auditory system function and hearing quality in Parkinson's disease (PD) and to compare the findings with age-matched individuals without PD to present a perspective on aging. Method The study included 35 individuals with PD (mean age of 48.50 ± 8.00 years) and 35 normal-hearing peers (mean age of 49 ± 10 years). The following tests were administered for all participants: the first section of the Speech, Spatial and Qualities of Hearing Scale; pure-tone audiometry, speech audiometry, tympanometry, and acoustic reflexes; and distortion product otoacoustic emissions (DPOAEs) and contralateral suppression of DPOAEs. SPSS Version 25 was used for statistical analyses, and values of p < .05 were considered statistically significant. Results There were no statistically significant differences in the pure-tone audiometry thresholds and DPOAE responses between the individuals with PD and their normal-hearing peers ( p = .732). However, statistically significant differences were found between the groups in suppression levels of DPOAEs and hearing quality ( p < .05). In addition, a statistically significant and positive correlation was found between the amount of suppression at some frequencies and the Speech, Spatial and Qualities of Hearing Scale scores. Conclusions This study indicates that medial olivocochlear efferent system function and the hearing quality of individuals with PD were affected adversely due to the results of PD pathophysiology on the hearing system. For optimal intervention and follow-up, tasks related to hearing quality in daily life can also be added to therapies for PD.

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