1,720,975 research outputs found
Fast versus slow: different saccadic behavior in cerebellar ataxias
No full textSpinocerebellar ataxia type 2 (SCA2) is a genetic neurodegenerative disorder primarily characterized by involvement of the brainstem and cerebellum, basal ganglia, spinal cord, cerebral cortex, but white matter is also involved. In late-onset cerebellar ataxia (LOCA), the cerebellum is mainly involved, as demonstrated by clinical and neuroradiological findings. These neurodegenerative diseases are often associated with progressive abnormalities in eye movement control, particularly saccadic changes. We recorded saccadic eye movements in eight SCA2 patients and 10 LOCA patients. Here, we suggest that abnormalities in saccadic parameters differ in the two groups of patients according to specific anatomical substrates. The different saccadic behavior observed in these two clinically distinct degenerative cerebellar diseases offers the opportunity to simplify some general mechanisms of saccadic motor control. Like his mentor Fred Plum, John Leigh strongly encouraged younger neuroscientists to tackle neurological problems by investigating "pathological physiology." With this teaching in mind, we studied patients with rare neurometabolic and neurodegenerative diseases
EVA:Eye Tracking Stimulus Integrated Semi Automated Case Base System.
No full textIn a real world visual search is a common task depending from
sensory, perceptual and cognitive processes. Different classes
of eye movements are necessary to hold an image on the retina
during head rotation or movement of the image, and to move
the eye suddenly to a new point of interest in space. From a
functional point of view, two major classes of eye movements
are described in humans: those stabilizing gaze (optokinetic
nystagmus, oculovestibular reflex) and those moving gaze
(saccades, pursuits and vergence). Under natural conditions,
however, a mix of all kinds of eye movements permit
continuous scanning of the visual scene. The sequence of
fixations and saccades during visual exploration is an
expression of a number of cognitive processes; the use of
standardized tasks with pre-defined spatial-temporal variables
allows us to assess specific cognitive domains, such as
perception, attention, memory, preference and motivation.
Manipulating the search task can vary the demands on brain. In
turn, brain modulates visual search by selecting and limiting
the information available at various levels of processing.
The EVA software is a complete system based on a set of
stimulus and patient’s case able to stress brain functionalities in
order to assess some cognitive functions
Spike removal through multiscale wavelet and entropy analysis of ocular motor noise: a case study in patients with cerebellar disease.
No full textWavelet decomposition of ocular motor signals was investigated with a view to its use for noise analysis and filtering. Ocular motor noise may be physiological, depending on brain activities, or experimental, depending on the eye recording machine, head movements and blinks. Experimental noise, such as spikes, must be removed, preserving noise due to neuro-physiological activities. The proposed method uses wavelet multiscale decomposition to remove spikes and optimizes the procedure by means of the covariance of the eye signals. To measure the noise on eye motor control, we used the wavelet entropy. The method was tested on patients with cerebellar disorders and healthy subjects. A significant difference in wavelet entropy was observed, indicating this quantity as a valuable measure of physiological motor noise
Quantitative analysis of Horizontal Saccades in oculomotor abnormalities of Degenerative Ataxic Disorders
No full textDEVICE FOR THE ANALYSIS OF THE CENTRAL NERVOUS SYSTEM BY APPLICATION OF A COMBINATION OF STIMULI AND THE STUDY OF CORRESPONDING REACTIONS
No full textNeuro-Ophthalmological findings in two adult siblings with ataxiatelangiectasia– like disorder
No full textInfluences of data filtering on human-computer interaction by gaze-contingent display and eyetracking applications
No full textWe describe an interactive gaze-contingent display (GCD) applied to clinical applications; the system uses a simple texture hole to inhibit peripheral vision, to test and stress overt mechanisms of visual searching in normal subjects. The correct use of GCD in vision research is affected by tremor of the hole, due to system noise, nystagmus, eye blinking, calibration and subject reactivity. These issues compromise the execution of task. In order to obtain a stable GCD hole, we implemented a predictive gaze-contingent display (PGCD), fitting through dispersion of fixations and modulating a filter. The paper describes the PGCD and compare it with the common technique, providing evidence that humans fit exploration based on the characteristics of the computer system; in particular we found significant difference applying PGCD or a simple finite impulse response filter. We suggest that a correct human-computer interaction applied to neuropsychological context must be developed taking in consideration both technical point of view and human behavior. © 2010 Elsevier Ltd. All rights reserved
Photophobia and bilateral pulvinar involvement in non-alcoholic Wernicke's encephalopathy.
No full textEffect of memantine on saccadic intrusion in a case of hereditary spinocerebellar ataxia
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