1,720,990 research outputs found
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
Eight and a Half Syndrome with Hemiparesis and Hemihypesthesia: The Nine Syndrome?
No full text"Eight-and-a-half" syndrome is "one-and-a-half" syndrome (conjugated horizontal gaze palsy and internuclear ophthalmoplegia) plus ipsilateral fascicular cranial nerve seventh palsy. This rare condition, particularly when isolated, is caused by circumscribed lesions of the pontine tegmentum involving the abducens nucleus, the ipsilateral medial longitudinal fasciculus, and the adjacent facial colliculus. Its recognition is therefore of considerable diagnostic value. We report a 71-year-old man who presented with eight and a half syndrome associated with contralateral hemiparesis and hemihypesthesia, in which brain magnetic resonance imaging scans revealed a lacunar pontine infarction also involving the corticospinal tract and medial lemniscus. These features could widen the spectrum of pontine infarctions, configuring a possible "nine" syndrom
Neuro-Ophthalmological findings in two adult siblings with ataxiatelangiectasia– like disorder
No full text
Nonlinear analysis of saccade speed fluctuations during combined action and perception tasks
No full textBACKGROUND:
Saccades are rapid eye movements used to gather information about a scene which requires both action and perception. These are usually studied separately, so that how perception influences action is not well understood. In a dual task, where the subject looks at a target and reports a decision, subtle changes in the saccades might be caused by action-perception interactions. Studying saccades might provide insight into how brain pathways for action and for perception interact.
NEW METHOD:
We applied two complementary methods, multifractal detrended fluctuation analysis and Lempel-Ziv complexity index to eye peak speed recorded in two experiments, a pure action task and a combined action-perception task.
RESULTS:
Multifractality strength is significantly different in the two experiments, showing smaller values for dual decision task saccades compared to simple-task saccades. The normalized Lempel-Ziv complexity index behaves similarly i.e. is significantly smaller in the decision saccade task than in the simple task.
COMPARISON WITH EXISTING METHODS:
Compared to the usual statistical and linear approaches, these analyses emphasize the character of the dynamics involved in the fluctuations and offer a sensitive tool for quantitative evaluation of the multifractal features and of the complexity measure in the saccades peak speeds when different brain circuits are involved.
CONCLUSION:
Our results prove that the peak speed fluctuations have multifractal characteristics with lower magnitude for the multifractality strength and for the complexity index when two neural pathways are simultaneously activated, demonstrating the nonlinear interaction in the brain pathways for action and perception.
Copyright © 2014 Elsevier B.V. All rights reserved.
KEYWORDS:
Action–perception task; Lempel–Ziv complexity; Multifractal properties; Saccade speed pea
GABAAergic dysfunction in the olivary-cerebellar-brainstem network may cause eye oscillations and body tremor
No full textAutosomal recessive cerebellar ataxias: a diagnostic classification approach according to ocular features
Full text linkAutosomal recessive cerebellar ataxias (ARCAs) are a heterogeneous group of neurodegenerative disorders affecting primarily the cerebellum and/or its afferent tracts, often accompanied by damage of other neurological or extra-neurological systems. Due to the overlap of clinical presentation among ARCAs and the variety of hereditary, acquired, and reversible etiologies that can determine cerebellar dysfunction, the differential diagnosis is challenging, but also urgent considering the ongoing development of promising target therapies. The examination of afferent and efferent visual system may provide neurophysiological and structural information related to cerebellar dysfunction and neurodegeneration thus allowing a possible diagnostic classification approach according to ocular features. While optic coherence tomography (OCT) is applied for the parametrization of the optic nerve and macular area, the eye movements analysis relies on a wide range of eye-tracker devices and the application of machine-learning techniques. We discuss the results of clinical and eye-tracking oculomotor examination, the OCT findings and some advancing of computer science in ARCAs thus providing evidence sustaining the identification of robust eye parameters as possible markers of ARCAs. Copyright © 2024 Lopergolo, Rosini, Pretegiani, Bargagli, Serchi and Rufa
Eye movement recording and nonlinear dynamics analysis - The case of saccades
Full text linkEvidence of a chaotic behavioral trend in eye movement dynamics was examined in the case of a saccadic temporal series collected from a healthy human subject. Saccades are highvelocity eye movements of very short duration, their recording being relatively accessible, so that the resulting data series could be studied computationally for understanding the neural processing in a motor system. The aim of this study was to assess the complexity degree in the eye movement dynamics. To do this we analyzed the saccadic temporal series recorded with an infrared camera eye tracker from a healthy human subject in a special experimental arrangement which provides continuous records of eye position, both saccades (eye shifting movements) and fixations (focusing over regions of interest, with rapid, small fluctuations). The semi-quantitative approach used in this paper in studying the eye functioning from the viewpoint of non-linear dynamics was accomplished by some computational tests (power spectrum, portrait in the state space and its fractal dimension, Hurst exponent and largest Lyapunov exponent) derived from chaos theory. A high complexity dynamical trend was found. Lyapunov largest exponent test suggested bi-stability of cellular membrane resting potential during saccadic experiment
- …
