Inconsistent information from different modalities can be delusive for perception. This phenomenon can be observed with simultaneously presented inconsistent numbers of brief flashes and short tones. The conflict of bimodal information is reflected in double flash or fission, and flash fusion illusions, respectively. The temporal resolution of the vision system plays a fundamental role in the development of these illusions. As the parallel, dorsal and ventral pathways have different temporal resolution we presume that these pathways play different roles in the illusions. We used pathway-optimized stimuli to induce the illusions on separately driven visual streams. Our results show that both pathways support the double flash illusion, while the presence of the fusion illusion depends on the activated pathway. The dorsal pathway, which has better temporal resolution, does not support fusion, while the ventral pathway which has worse temporal resolution shows fusion strongly.
- MeSH
- Acoustic Stimulation MeSH
- Time Factors MeSH
- Illusions * MeSH
- Humans MeSH
- Young Adult MeSH
- Psychometrics MeSH
- Auditory Perception MeSH
- Photic Stimulation methods MeSH
- Signal Detection, Psychological MeSH
- Visual Perception * MeSH
- Visual Pathways physiology MeSH
- Visual Cortex physiology MeSH
- Check Tag
- Humans MeSH
- Young Adult MeSH
- Male MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
1.100 myopů (-0,25 - (-8,75) dpt) bylo rozděleno do 3 skupin (I: < -3,0 dpt, II: -3,0 - (-5,75) dpt, III: -6,0 - (-8,75) dpt) a vyšetřeno před a 1.3,6 mésicú po fotorefraktivni keratektomii (FRK) provedené na excimerovém laseru firmy Schwind. Kontrolní skupinu tvořilo 20 emetropů. Nejlépe korigovaná zraková ostrost (NKZO) byla určována na logMÚR tabulích. Kontrastová citlivost (CK) byla měřena na počítačem ovládaném zařízení. II. Predoperační hodnoty NKZO u myopů všech tří skupin byly signifikantně nižší (p < 0,001) v porovnání s kontrolní skupinou. V pooperačním průběhu byl zjištěn pokles NKZO (p < 0,05 resp. p < 0,001) u všech skupin a po celou dobu sledování. III. Signifikantně nižší hodnoty (p < 0,001) CKbyly zjištěny u myopů všech skupin v porovnání s kontrolní skupinou. Za 1 a 3 měsíce po FRK byly pozorovány jen nevýznamné změny průměrných hodnot kontrastové citlivosti (MCK), za 6 měsíssíců došlo k signifikantnímu zvýšení MCK (p < 0,05) u I. a II. skupiny.
1.100 myopes (-0,25 - (8,75) D) divided into 3 groups (I: < -3,0 D, II: -3,0 - (-5,75) D, III: - 6,0 - (-8,75) D) were examined before and 1,3,6 months after photorefractive keratectomy (PRK). As a control group 20 emmetropes were examined. Best corrected visual acuity (BCVA) was tested using logMAR charts. Contrast sensitivity (CS) was measured using a computerized system. II. Preoperative BCVA in myopes of all three groups was significantly lower (p < 0,001) compared to the control group. A significant reduction of BCVA (p < 0,05 resp. p < 0,001) in all groups at all terms after PRK was noted. III. Significantly lower values of CS (p < 0,001) were found in myopes of all groups before PRK in comparison to the control group. One and 3 months after PRK only nonsignificant changes of the mean values of contrast sensitivity (MCK) were noted. After 6 months a significant improvement of MCK (p < 0,05) in myopes of I. and II. groups was observed.
- MeSH
- Contrast Sensitivity MeSH
- Adult MeSH
- Photorefractive Keratectomy MeSH
- Middle Aged MeSH
- Humans MeSH
- Myopia therapy MeSH
- Visual Acuity MeSH
- Check Tag
- Adult MeSH
- Middle Aged MeSH
- Humans MeSH
- Male MeSH
- Female MeSH
- Publication type
- Review MeSH
- Comparative Study MeSH
PURPOSE: The decrease in visual acuity under low luminance conditions is well known. Recent laboratory evidence showed that crowding under low luminance (mesopic) light levels is less robust than under photopic conditions. The present study examines whether such differences in crowding influence clinical measurements of mesopic visual acuity, including test-retest repeatability. METHODS: Twenty adult subjects with normal or corrected to normal visual acuity were recruited for the study. Monocular visual acuity was measured under photopic (228 cd/m2) and mesopic (0.164 cd/m2) luminance conditions using a letter chart, similar in principle to the ETDRS logMAR chart, presented on a computer monitor. Three rows of five letters, each row differing in size by 0.05 logMAR from largest to smallest were displayed at the center of the monitor. The level of crowding was varied by varying the separation between horizontally adjacent letters from 100% optotype size to 50, 20, and 10% optotype size. Inter-row spacing was proportional to optotype size. Observers read the letters on the middle row only. Measurements continued by reducing the size of the letters, until three or more errors on the middle row were made. Each correctly identified letter contributed 0.01 to the recorded logMAR score. All measurements were repeated for each subject on two separate days. RESULTS: Visual acuity (logMAR) was significantly better under photopic than mesopic luminance conditions with a mean difference of 0.48 logMAR. Visual acuity also decreased with decreasing letter separation (i.e. increase in crowding). However, the decrease in visual acuity for the smallest letter separation was less under the mesopic luminance condition, even after accounting for the increased size of threshold acuity letters. Test-retest repeatability for mesopic and photopic conditions was not significantly different. CONCLUSIONS: Crowding under mesopic luminance conditions has less impact on visual acuity than under photopic luminance.
- MeSH
- Contrast Sensitivity MeSH
- Adult MeSH
- Humans MeSH
- Adolescent MeSH
- Young Adult MeSH
- Reference Values MeSH
- Photic Stimulation MeSH
- Color Vision physiology MeSH
- Mesopic Vision physiology MeSH
- Visual Acuity * MeSH
- Vision Tests methods MeSH
- Check Tag
- Adult MeSH
- Humans MeSH
- Adolescent MeSH
- Young Adult MeSH
- Male MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
UNLABELLED: Single cases may lead to unexpected hypotheses in psychology. We retrospectively analyzed single case studies that suggested organizational principles along the early visual pathway, which have remained unanswered until now. FIRST CASE: In spite of the inhomogeneity of sensitivity, paradoxically the visual field on the subjective level appears to be homogeneous; constancy of brightness of supra-threshold stimuli throughout the visual field is claimed to be responsible for homogeneity; specific summation properties of retinal ganglion cells are hypothesized to guarantee this effect. SECOND CASE: With a brain-injured patient having suffered a partial visual field loss it can be shown that color induction is a retinal phenomenon; lateral inhibitory processes at the level of amacrine cells are hypothesized as neural network. Third case: In a patient having suffered a bilateral occipital lobe infarction, some functional recovery has been demonstrated; divergence and convergence of projection in the ascending neural pathway are suggested as a structural basis for recovery. Slowed down binocular rivalry discloses a sequential mechanism in the construction of a visual percept. Fourth case: The pre-wired projection of the retina to the visual cortex in spite of a severe squint of one eye is confirmed, but paradoxically some local neuroplasticity is also suggested. Fifth case: Using habituation of local sensitivity in the visual field and its resetting by interhemispheric interactions as an experimental paradigm, it is suggested that spatial attention is controlled at the midbrain level. Sixth case: Observations on residual vision or "blindsight" support the hypothesis that the visual cortex is the one and only structure responsible for visual perception on a conscious level. The unifying principle of these retrospective analyses is that subjective visual phenomena can lead to unexpected but testable hypotheses of neural processing on the structural and functional level in the early visual pathway.
- MeSH
- Humans MeSH
- Geniculate Bodies physiology MeSH
- Brain Infarction physiopathology MeSH
- Brain Injuries physiopathology MeSH
- Attention physiology MeSH
- Retina physiology MeSH
- Retrospective Studies MeSH
- Blindness physiopathology MeSH
- Photic Stimulation MeSH
- Color Perception MeSH
- Visual Fields * MeSH
- Visual Pathways physiology MeSH
- Visual Cortex physiology MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Case Reports MeSH
Úvod: Testy rovnováhy jsou běžnou součástí neurologického a otorhinolaryngologického vyšetření. Cílem této studie bylo prozkoumat vliv vertikální a horizontální vizuální stimulace na posturální reflexy měřené kraniokorpografií, za účelem podrobného ověření účinnosti kontroly rovnováhy při narušení vizuálně-vestibulární integrity. Cíl: Cílem studie bylo zjistit vliv vizuální, horizontální a vertikální optokinetické a sinusoidální stimulace na posturální reflexy. Metodologie: Testována byla skupina 40 zdravých jedinců (20 žen, 20 mužů) ve věku 18–52 bez patologické otoneurologické anamnézy nebo příznaků. Za účelem zjištění poruch rovnováhy měřených kraniokorpografií během Rombergova testu byla aplikována horizontální a vertikální optokinetická a sinusoidální stimulace. Výsledky: Zjistili jsme, že vizuální stimulace (optokinetická a sinusodiální) v horizontální rovině vyvolaly silnější posturální poruchy než vizuální stimulace ve vertikální rovině. Jak horizontální, tak vertikální optokinetická stimulace vedla k větším longitudinálním výkyvům těla. Laterální vychýlení těla bylo lépe kontrolováno během vertikální stimulace. Autoři zjistili rozdíly v posturálních reflexech v závislosti na směru jak horizontální, tak vertikální vizuální stimulace. Kontrola rovnováhy byla lepší, byla-li optokinetická stimulace směřována doleva a dolů. Zvýšená intenzita vizuální stimulace (cílová velocita) rovnováhu nezhoršovala.
Introduction: Tests of balance are routine elements of neurological and otolaryngological examination. What follows is a general study of the effectiveness of balance control when visual-vestibular integrity is disturbed, conducted by means of ascertaining the influence of vertical and horizontal visual stimulation on postural reflexes as measured by craniocorpography. Goal: The purpose of the study was to observe the effect of visual, horizontal and vertical optokinetic and sinusoidal stimulation on postural reflexes. Material and method: A group of 40 healthy subjects (20 female, 20 male) aged 18–52 with no pathological otoneurologial history or signs was tested. Horizontal and vertical optokinetic and sinusoidal stimulation was administered in order to observe balance disturbances, as measured by craniocorpography in the course of a R omberg test. Results: It was revealed that visual stimulation (optokinetic and sinusoidal) in the horizontal plane induced stronger postural disturbances than visual stimulation in the vertical plane. Both horizontal and vertical optokinetic stimulation resulted in high longitudinal body sway. Lateral body displacement was better controlled during vertical visual disturbances. The authors observed that the differences in postural reflexes were dependent on the direction of both horizontal and vertical visual stimulation. Balance control was better when the optokinetic incitement was directed to the left and downward. Increased intensity of visual stimulus (target velocity) did not worsen balance.
- Keywords
- kraniokorpografie, vizuální stimulace, otolity,
- MeSH
- Anthropometry MeSH
- Human Experimentation MeSH
- Kinesiology, Applied MeSH
- Humans MeSH
- Otolithic Membrane MeSH
- Vision Disorders complications MeSH
- Posture physiology MeSH
- Postural Balance physiology MeSH
- Rehabilitation MeSH
- Statistics as Topic MeSH
- Photic Stimulation methods instrumentation MeSH
- Investigative Techniques MeSH
- Visual Perception physiology MeSH
- Check Tag
- Humans MeSH
Cíle: Stanovit hodnotu náklonu subjektivní vizuální vertikály (SVV) u zdravých dobrovolníků a u pacientů s periferním vestibulárním syndromem pomocí speciálně upraveného kbelíku (SVV bucket test). Zhodnotit interindividuální opakovatelnost vyšetření u pacientů otoneurologické poradny. Metodika: Srovnáním výsledků měření lékaře a sestry u 153 pacientů otoneurologické poradny jsme hodnotili interindividuální reprodukovatelnost této metody. Dále byly porovnány výsledky 38 zdravých dobrovolníků a 42 pacientů s periferní vestibulární lézí. Výsledky: Zjistili jsme dobrou reprodukovatelnost vyšetření. Průměrná výchylka SVV u zdravých dobrovolníků byla většinou do 1°, nepřesáhla 2°. Při vyšetření pacientů s periferní vestibulární lézí byly zjištěny statisticky signifikantně větší výchylky subjektivní vizuální vertikály než u zdravých dobrovolníků (p <0,001). Výchylka se u pacientů v čase snižovala. Závěr: Vyšetření subjektivní vizuální vertikály pomocí upraveného kbelíku je levné, rychlé a reprodukovatelné. U zdravých osob nepřesahuje výchylka SVV 2°. U pacientů s akutní jednostrannou vestibulopatií je ve většině případů vyšší, ukazuje stranu léze, výchylka se snižuje v čase.
Objectives: To determine the tilt of subjective visual vertical (SVV) in healthy volunteers and in patients with peripheral vestibular syndrome by SVV bucket test. Evaluate the interindividual repeatability of the examination in patients of otoneurological clinic. Methodology: The results of SVV bucket test of 38 healthy volunteers and 42 patients with peripheral vestibulopathy were compared. We evaluated the interrater variability of the method by comparing the results of measurements of a doctor and a nurse in 153 patients of otoneurological clinic. Results: The average SVV in healthy volunteers was mostly less than 1°, not more than 2°. Significantly greater tilt of subjective visual verticals was observed in patients with peripheral vestibular lesion (p < 0.001). The tilt decreased over time. We found a good interindividual reproducibility of the examination. Conclusion: Examination of subjective visual vertical by the SVV bucket method is inexpensive, fast and repeatable. In healthy subjects, the tilt of SVV does not exceed 2°. It is higher in most patients with acute unilateral vestibulopathy, shows the side of the lesion, and decreases over time.
Reports of visual functional impairment in spinocerebellar ataxia type 2 (SCA2) have been studied previously using pattern reversal visually evoked potentials (VEPs) with contradictory results. To provide additional evidence to this area, visual functions were studied using VEPs and event-related potentials (ERPs) in a group of ten patients with genetically verified SCA2. The electrophysiological examination included pattern reversal and motion-onset VEPs as well as visually driven oddball ERPs with an evaluation of a target and a pre-attentive response. In six patients, we found abnormal visual/cognitive processing that differed from normal values in latency, but not in the amplitude of the dominant VEP/ERP peaks. Among the VEPs/ERPs used, the motion-onset VEPs exhibited the highest sensitivity and showed a strong Spearman correlation to SCA2 duration (from r = 0.82 to r = 0.90, p < 0.001) and clinical state assessed by Brief Ataxia Rating Scale (from r = 0.71 (p = 0.022) to r = 0.80 (p < 0.001)). None of the VEP/ERP latencies showed a correlation to the triplet repeats of the SCA2 gene. In three patients, we did not find any visual/cognitive pathology, and one subject showed only a single subtle prolongation of the VEP peak. The observed visual/cognitive deficit was related to the subjects' clinical state and the illness duration, but no relationship to the genetic marker of SCA2 was found. From the VEP/ERP types used, the motion-onset VEPs seems to be the most promising candidate for clinical state monitoring rather than a tool for early diagnostic use.
- MeSH
- DNA genetics MeSH
- Adult MeSH
- Electroencephalography MeSH
- Electrophysiological Phenomena MeSH
- Evoked Potentials physiology MeSH
- Middle Aged MeSH
- Humans MeSH
- Young Adult MeSH
- Neurologic Examination MeSH
- Signal Processing, Computer-Assisted MeSH
- Pattern Recognition, Visual physiology MeSH
- Aged MeSH
- Spinocerebellar Ataxias genetics physiopathology psychology MeSH
- Aging physiology MeSH
- Photic Stimulation MeSH
- Trinucleotide Repeats MeSH
- Age of Onset MeSH
- Visual Perception physiology MeSH
- Evoked Potentials, Visual physiology MeSH
- Visual Cortex physiopathology MeSH
- Check Tag
- Adult MeSH
- Middle Aged MeSH
- Humans MeSH
- Young Adult MeSH
- Male MeSH
- Aged MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Visual evoked potentials to motion-onset stimulation (M-VEPs) gradually attenuate in amplitude during examination. The observed decline in averaged responses can be caused by decreases in single response magnitudes and/or increased variability in a response delays, that is, latency jittering. To illuminate the origins of the suppression of M-VEPs during stimuli repetition, we used correlation technique to estimate an upper bound of possible latency jittering of single sweeps and we evaluated the effect of its correction on the amplitudes of three M-VEP dominant peaks P1, N2 and P3. During prolonged visual motion stimulation, the variability of corrective latency shifts in the occipital region increased (r = 0.35: 0.44) and the number of single responses corresponding to the average curve declined in occipital and parietal derivations (r = -0.48: -0.62). While the P1 peak amplitude did not exhibit any time-specific behaviour, the N2 amplitude exhibited a significant decay of 29.4% that was partially reduced to 16.6% in the central occipital derivation by the latency jitter and non-correspondence corrections. The strongest attenuation (32.7%) was observed in the P3 amplitude and was less sensitive to the corrections, dropping only to 27.9%. The main part of the response suppression to repeated motion stimulation was caused by amplitude drop and represents non-stationary process that likely correspond to a fatigue model. The rise of variability in latency jitter correction and the reduction in single responses correlated with the M-VEP were significant factors associated with prolonged motion stimulation. The relation of these parameters to a hypothetical veridical response is ambiguous and can be caused by a time shift of the response or by a change of signal-to-noise ratio. Using selective averaging and latency jitter correction, the effect of response suppression was partially removed.
- MeSH
- Adaptation, Ocular physiology MeSH
- Adult MeSH
- Middle Aged MeSH
- Humans MeSH
- Young Adult MeSH
- Pattern Recognition, Visual physiology MeSH
- Motion Perception physiology MeSH
- Evoked Potentials, Visual physiology MeSH
- Visual Cortex physiology MeSH
- Check Tag
- Adult MeSH
- Middle Aged MeSH
- Humans MeSH
- Young Adult MeSH
- Male MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Autoři referují o výsledcích retrospektivní studie 25 pacientů s první atakou neuritidy optiku sledované na Oční klinice LF UK a FN v Hradci Králové. V naší studii jsme se zaměřili na zrakovou ostrost a zorné pole. U všech nemocných bylo zjištěno poškození obou zrakových funkcí. Zraková ostrost byla snížena v rozmezí 0,8 až pohyb před okem. Centrální skotom byl pozorován u12 pacientů,u ostatních se vyskytovaly jiné poruchy zorného pole. U 24 nemocných došlo k plné úpravě zrakových funkcí v průběhu 6 měsíců. Všichni pacienti byli podrobně vyšetřeni pro potvrzení či vyloučení roztroušené sklerózy mozkomíšní (RSM). U pacientů bez známek RSM (15 pacientů) byli 3 z nich léčeni steroidy (dva dostávali pulsy methylprednisolonu i.v. a jeden perorální léčbu prednisonem na jiném pracovišti), ostatním byly ordinovány vitaminy. U pacientů s prokázanou RSM byla zahájena léčba tohoto onemocnění na Neurologické klinice LF a FN UK v Hradci Králové.
The authors present results of retrospective study of 25 patients with the first attack of acute optic neuritis followed at the Department of Ophthalmology, University Hospital Hradec Králové. Visual functions were deteriorated in all patients. Visual acuity was in range between 0.8 to hand movement. Central scotoma was present in 12 patients, other visual field patterns were seen in 13 patients. Complete recovery of visual functionswas observed in 24 patients during the six months. Patients were examined for signs of multiple sclerosis (MS). In the group without MS (15 patients) were three treated with steroids (2 received intravenous methylprednisolone and 1 oral prednison before referral to us), vitamins were administered to the others. The patients with provedMSwere managed at the Department of Neurology, University Hospital, Hradec Králové.
- MeSH
- Adult MeSH
- Immunoglobulin G blood MeSH
- Middle Aged MeSH
- Humans MeSH
- Neurologic Examination MeSH
- Multiple Sclerosis etiology MeSH
- Optic Neuritis diagnosis etiology drug therapy MeSH
- Visual Acuity MeSH
- Visual Fields MeSH
- Evoked Potentials, Visual MeSH
- Check Tag
- Adult MeSH
- Middle Aged MeSH
- Humans MeSH
- Male MeSH
- Female MeSH
- Publication type
- Review MeSH
OBJECTIVE: To identify intracerebral sites activated after correct motor response during cognitive task and to assess associations of this activity with mental processes. METHODS: Intracerebral EEG was recorded from 205 sites of frontal, temporal and parietal lobes in 18 epileptic patients, who responded by button pressing together with mental counting to target stimuli in visual oddball task. RESULTS: Post-movement event-related potentials (ERPs) with mean latency 295 ± 184 ms after movement were found in all subjects in 64% of sites investigated. Generators were consistently observed in mesiotemporal structures, anterior midcingulate, prefrontal, and temporal cortices. Task-variant nonspecific and target specific post-movement ERPs were identified, displaying no significant differences in distribution among generating structures. Both after correct and incorrect performances the post-performance ERPs were observed in frontal and temporal cortices with latency sensitive to error commission in several frontal regions. CONCLUSION: Mesiotemporal structures and regions in anterior midcingulate, prefrontal and temporal cortices seem to represent integral parts of network activated after correct motor response in visual oddball task with mental counting. Our results imply equivalent involvement of these structures in task-variant nonspecific and target specific processes, and suggest existence of common nodes for correct and incorrect responses. SIGNIFICANCE: Our results contribute to better understanding of neural mechanisms underlying goal-directed behavior.
- MeSH
- Adult MeSH
- Electroencephalography methods MeSH
- Middle Aged MeSH
- Humans MeSH
- Young Adult MeSH
- Brain physiology MeSH
- Movement physiology MeSH
- Psychomotor Performance physiology MeSH
- Photic Stimulation methods MeSH
- Evoked Potentials, Visual physiology MeSH
- Check Tag
- Adult MeSH
- Middle Aged MeSH
- Humans MeSH
- Young Adult MeSH
- Male MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
