Standard pattern-reversal visual evoked potentials (VEPs) and motion-onset VEPs (M-VEPs) were tested in 19 dyslexics and 19 normal readers aged 7-13 years in order to evaluate the feasibility of M-VEPs for the objective diagnostics of a visual subtype of dyslexia, in which a dysfunction of the magnocellular subsystem/dorsal stream of the visual pathway is suspected. The set of VEPs consisted of the pattern-reversal VEPs with check sizes of 20', two types of translational motion (with low and high contrast) and two types of radial motion (in the full field or the periphery). While the P100 peak parameters in pattern-reversal VEPs did not differ between the group of dyslexics and controls, the group of dyslexics displayed significantly longer N2 latencies in all types of M-VEPs. Abnormal N2 latencies were found in 35-56% of dyslexics in different types of M-VEPs, with translational motion with high contrast being the most sensitive stimulation. A receiver operating characteristic analysis showed that the latencies of M-VEPs displayed higher discrimination potential than M-VEPs amplitudes. The study confirms a "magnocellular pathway/dorsal stream deficit" in approximately half of dyslexics.
- MeSH
- Child MeSH
- Dyslexia physiopathology MeSH
- Humans MeSH
- Adolescent MeSH
- Sensory Thresholds physiology MeSH
- Case-Control Studies MeSH
- Motion Perception physiology MeSH
- Visual Pathways physiopathology MeSH
- Evoked Potentials, Visual physiology MeSH
- Visual Cortex physiology MeSH
- Check Tag
- Child MeSH
- Humans MeSH
- Adolescent MeSH
- Male MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Comparative Study MeSH
Changes in connectivity of the posterior node of the default mode network (DMN) were studied when switching from baseline to a cognitive task using functional magnetic resonance imaging. In all, 15 patients with mild to moderate Alzheimer's disease (AD) and 18 age-, gender-, and education-matched healthy controls (HC) participated in the study. Psychophysiological interactions analysis was used to assess the specific alterations in the DMN connectivity (deactivation-based) due to psychological effects from the complex visual scene encoding task. In HC, we observed task-induced connectivity decreases between the posterior cingulate and middle temporal and occipital visual cortices. These findings imply successful involvement of the ventral visual pathway during the visual processing in our HC cohort. In AD, involvement of the areas engaged in the ventral visual pathway was observed only in a small volume of the right middle temporal gyrus. Additional connectivity changes (decreases) in AD were present between the posterior cingulate and superior temporal gyrus when switching from baseline to task condition. These changes are probably related to both disturbed visual processing and the DMN connectivity in AD and reflect deficits and compensatory mechanisms within the large scale brain networks in this patient population. Studying the DMN connectivity using psychophysiological interactions analysis may provide a sensitive tool for exploring early changes in AD and their dynamics during the disease progression.
- MeSH
- Alzheimer Disease pathology MeSH
- Oxygen blood MeSH
- Humans MeSH
- Magnetic Resonance Imaging MeSH
- Brain Mapping * MeSH
- Brain blood supply physiopathology MeSH
- Nerve Net blood supply pathology MeSH
- Neuropsychological Tests MeSH
- Image Processing, Computer-Assisted MeSH
- Aged, 80 and over MeSH
- Aged MeSH
- Case-Control Studies MeSH
- Visual Pathways blood supply physiopathology MeSH
- Check Tag
- Humans MeSH
- Male MeSH
- Aged, 80 and over MeSH
- Aged MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
AIMS: Using fMRI, we evaluated the default mode network (DMN) and the extrastriate visual resting state network (ESV-RSN) in 14 patients with Parkinson's disease dementia (PDD) as compared with 18 patients with Parkinson's disease (PD) without dementia and 18 healthy controls (HC). METHODS: We analyzed the seed-based functional connectivity of both resting state data and deactivations during a visual complex scene-encoding task. RESULTS: Using the posterior cingulate cortex/precuneus as a seed for the DMN analysis, we observed significant decreases of connectivity in the right inferior frontal gyrus in PDD as compared to PD and HC. Using the caudate nucleus as a seed for the ESV-RSN analysis, we found significant decreases of connectivity in the left and right inferior occipital gyrus in PDD as compared to HC. CONCLUSION: Differences in functional connectivity patterns between PDD and PD/HC were observed in areas known to be engaged in stimulus-driven reorienting of attention and in visual processing.
- MeSH
- Dementia complications pathology MeSH
- Adult MeSH
- Oxygen blood MeSH
- Middle Aged MeSH
- Humans MeSH
- Magnetic Resonance Imaging MeSH
- Brain Mapping MeSH
- Neuropsychological Tests MeSH
- Rest MeSH
- Parkinson Disease complications pathology MeSH
- Image Processing, Computer-Assisted MeSH
- Recognition, Psychology MeSH
- Aged, 80 and over MeSH
- Aged MeSH
- Statistics as Topic MeSH
- Photic Stimulation MeSH
- Occipital Lobe blood supply physiopathology MeSH
- Visual Pathways blood supply physiopathology MeSH
- Check Tag
- Adult MeSH
- Middle Aged MeSH
- Humans MeSH
- Male MeSH
- Aged, 80 and over MeSH
- Aged MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Spatiotemporal dynamics of event-related potentials (ERP) evoked by non-target stimuli in a visual oddball experiment and the presence of coherent oscillations in beta 2 frequency band of decomposed EEG records from peristimulus period were investigated by means of intracranial electrodes in humans. Twenty-one patients with medically intractable epilepsy participated in the study. The EEG signal was recorded using platinum electrodes implanted in several cortical and subcortical sites. Averaged 2 s EEG records were analyzed. Task-specific EEG changes were found in each patient, ERPs were derived from 92 electrodes used (96 % of possible cases). In the majority of analysed cases, ERPs were composed of several distinct components, and their duration was mostly longer than 1 s. The mean onset of the first ERP component was 158+/-132 ms after the stimulus (median 112 ms, minimum value 42 ms, maximum value 755 ms), and large variability of these onset times was found in all the investigated structures. Possible coherence between neural activities of remote brain sites was investigated by calculating running correlations between pairs of decomposed EEG records (alpha, beta 1, beta 2 frequency bands were used, total number of correlated pairs was 662 in each frequency band). The record pairs exhibiting highly correlated time segments represented 23 % of all the investigated pairs in alpha band, 7 % in beta 1 band, and 59 % in beta 2 band. In investigated 2 s record windows, such segments were distributed evenly, i.e. they were also found before the stimulus onset. In conclusion, the results have implicated the idea that a lot of recorded ERPs was more or less by-products of chance in spreading a signal within the neuronal network, and that their functional relevance was somewhat linked with the phenomenon of activity synchronization.
- MeSH
- Beta Rhythm MeSH
- Time Factors MeSH
- Adult MeSH
- Epilepsy physiopathology psychology MeSH
- Financing, Organized MeSH
- Electrodes, Implanted MeSH
- Cognition MeSH
- Cortical Synchronization MeSH
- Middle Aged MeSH
- Humans MeSH
- Brain Mapping methods instrumentation MeSH
- Cerebral Cortex physiopathology MeSH
- Nerve Net physiopathology MeSH
- Periodicity MeSH
- Photic Stimulation MeSH
- Signal Detection, Psychological MeSH
- Visual Perception MeSH
- Visual Pathways physiopathology MeSH
- Evoked Potentials, Visual MeSH
- Check Tag
- Adult MeSH
- Middle Aged MeSH
- Humans MeSH
- Male MeSH
- Female MeSH
Classically, the pupillary pathway is considered as a simple reflex arc comprising retinal ganglion cells, midbrain interneurons, oculomotor nerve and short ciliary nerves. However, there are some specialties in the construction of the pupillary pathways that have to be kept in mind when dealing with diseases involving pupillary disorders. This may help to localise lesions. Additionally, studies in patients with lesions of the retrogeniculate pathways have shown that pupillary disorders are possible even with lesions not involving the classical reflex arc. The pupil is therefore not only controlled subcortically, some components are influenced by the visual cortex. The aim of this article is to clarify various findings and terms such as relative afferent pupillary defect and pupillary hemihypokinesia.
- MeSH
- Afferent Pathways physiopathology MeSH
- Optic Chiasm physiopathology MeSH
- Interneurons physiology MeSH
- Humans MeSH
- Mesencephalon physiopathology MeSH
- Oculomotor Nerve physiopathology MeSH
- Optic Nerve physiopathology MeSH
- Pupil Disorders etiology physiopathology MeSH
- Reflex, Pupillary physiology MeSH
- Retinal Ganglion Cells physiology MeSH
- Visual Field Tests MeSH
- Visual Pathways physiopathology MeSH
- Check Tag
- Humans MeSH
- Publication type
- Review MeSH
OBJECTIVE: Methamphetamine (MAP) is an indirect dopamine agonist that can temporarily increase cognitive performance. However, its long-term abuse may cause dopamine depletion and consequent cognitive and attentional impairment. The worsening of visual functions in Parkinson's disease and their improvement after levodopa administration implicates the role of dopamine in the physiology of vision. This provides the rationale for the investigation of visual functions in abstaining MAP abusers. METHODS: We investigated changes in visually evoked potentials (VEPs) to pattern-reversal and motion-onset stimuli. Such changes serve as indices of visual information processing in the primary and associative areas in a group of recently abstaining MAP abusers (5 females, 18 males, MAP abuse 5.3 +/- 2.8 years) and in 23 age- and gender-paired controls. RESULTS: We did not find differences between the groups in visual acuity. In the group of MAP abusers we observed an attenuation of the early responses around 80 ms and a prolongation of the P1 peak latency after the reversal of high spatial frequency checkerboards (10 and 20 arcmin checks). Furthermore, an attenuation of the latter positive response (170-250 ms) was observed among all the stimuli in parieto-frontal derivations for the MAP abusers. CONCLUSIONS: This is the first report suggesting a slowing and attenuation of VEP responses during visual processing in abstaining methamphetamine abusers.
- MeSH
- Adult MeSH
- Humans MeSH
- Methamphetamine adverse effects MeSH
- Young Adult MeSH
- Amphetamine-Related Disorders physiopathology MeSH
- Motion Perception physiology MeSH
- Visual Pathways physiopathology MeSH
- Evoked Potentials, Visual physiology MeSH
- Check Tag
- Adult MeSH
- Humans MeSH
- Young Adult MeSH
- Male MeSH
- Female MeSH
- Publication type
- Research Support, Non-U.S. Gov't MeSH
Five children with a history of preterm birth (mean gestational age of 27 weeks; birth weight 870-1,380 g) and perinatal post-hemorrhagic hydrocephalus were examined ophthalmologically at ages ranging from 4-11 years. An extended visual evoked potentials (VEPs) examination was simultaneously performed, using pattern-reversal, motion-onset, and cognitive visual stimuli. Although 3 of the 10 eyes displayed about normal visual acuity (> or =0.9), all of the examined eyes were abnormal for at least one variant of the tested VEPs. Pathological changes in VEPs (missing responses, shape abnormalities due to delayed VEPs maturation, prolonged peak latencies, and reduced amplitudes) were roughly proportional to both gestational age and reduction in visual acuity. A more severe pathology was found in the motion-onset VEPs (in all five subjects - nine eyes) when compared to the pattern-reversal VEPs (in four subjects - eight eyes). These observations suggest that the magnocellular system/dorsal stream of the visual pathway (which is particularly activated in response to motion stimuli) may be more frequently affected in preterm children than the parvocellular system/ventral stream (tested mostly by the standard pattern-reversal VEPs). This pilot study may encourage further testing of the combined pattern and motion-related VEPs examinations in preterm children as a way of detecting hidden cortical/cerebral visual impairment (CVI).
- MeSH
- Child MeSH
- Financing, Organized MeSH
- Gestational Age MeSH
- Humans MeSH
- Central Nervous System Diseases physiopathology MeSH
- Infant, Premature MeSH
- Infant, Low Birth Weight MeSH
- Infant, Newborn MeSH
- Pilot Projects MeSH
- Child, Preschool MeSH
- Refraction, Ocular physiology MeSH
- Visual Acuity physiology MeSH
- Visual Pathways physiopathology MeSH
- Evoked Potentials, Visual physiology MeSH
- Visual Cortex physiopathology MeSH
- Check Tag
- Child MeSH
- Humans MeSH
- Infant, Newborn MeSH
- Child, Preschool MeSH
- MeSH
- Humans MeSH
- Recovery of Function physiology MeSH
- Rehabilitation MeSH
- Scotoma rehabilitation MeSH
- Visual Field Tests utilization MeSH
- Visual Fields genetics MeSH
- Visual Pathways physiology physiopathology MeSH
- Check Tag
- Humans MeSH
- Publication type
- Evaluation Study MeSH
- MeSH
- Afferent Pathways physiology physiopathology MeSH
- Respiratory Physiological Phenomena MeSH
- Humans MeSH
- Respiratory Mechanics physiology MeSH
- Musculoskeletal Manipulations methods utilization MeSH
- Reflex, Stretch physiology MeSH
- Posture physiology MeSH
- Postural Balance physiology MeSH
- Reflex physiology MeSH
- Muscle Relaxation physiology MeSH
- Practice Guidelines as Topic MeSH
- Visual Pathways physiology physiopathology MeSH
- Check Tag
- Humans MeSH
