[Impact of mydriatic eyedrops on distance visual acuity in patients with exudative age-related macular degeneration]. / Impact de l'instillation de collyres mydriatiques sur la mesure d'acuité visuelle de loin chez des patients présentant une DMLA exsudative.

PURPOSE: To demonstrate a decrease in distance visual acuity (VA) following instillation of mydriatic eyedrops in eyes with exudative age-related macular degeneration (AMD). MATERIALS AND METHODS: A prospective assessment in clinical practice was conducted in our ophthalmology department at the University Hospital of Tours from 7/19/2018 to 8/29/2018. Distance (ETDRS) and near (Parinaud) VA were assessed before and after instilling one drop each of tropicamide 0.5% and phenylephrine 10% in the 40 included eyes with exudative AMD. RESULTS: The mean difference in distance VA before and after pupillary dilation (PD) was 0.06 LogMAR (SD=0.14) (P<0.01), i.e. -3.05 letters read (SD=7.52) on the ETDRS chart (P=0.01). For near VA, the mean difference was 0.16 LogMAR (SD=0.16) (P<0.001), i.e. -1.58 paragraphs read (SD=1.63) on the Parinaud chart (P<0.001). DISCUSSION: The absence of a clinically significant loss in post-dilation distance VA for exudative AMD could be explained by negligible glare coming from the ETDRS chart, milder photophobia, low pre-dilation VA's and a balance between higher order optical aberrations and diffraction. The opposite result for near VA could essentially be explained by greater glare induced by the light illuminating the Parinaud chart. CONCLUSION: Our primary goal was not achieved. A study presuming the absence of a clinically significant decrease in post-dilation distance VA would be necessary to consider directly measuring post-dilation VA in eyes with exudative AMD in our daily practice.

Directional and color preference in adult zebrafish: Implications in behavioral and learning assays in neurotoxicology studies.

The zebrafish (Danio rerio) is a useful vertebrate model organism for neurological studies. While a number of behavior and learning assays are recently reported in the literature for zebrafish, many of these assays are still being refined. The initial purpose of this study was to apply a published T-maze assay for adult zebrafish that measures how quickly an organism can discriminate between different color stimuli after receiving reinforcement to measure learning in a study investigating the later life impacts of developmental Pb exposure. The original results were inconclusive as the control group showed a directional and color preference. To assess directional preference further, a three-chambered testing apparatus was constructed and rotated in several directions. The directional preference observed in males was alleviated by rotating the arms pointing west and east. In addition, color preference was investigated using all combinations of five different colors (orange, yellow, green, blue and purple). With directional preference alleviated results showed that both male and female zebrafish preferred colors of shorter wavelengths. An additional experiment tested changes in color preference due to developmental exposure to Pb in adult male zebrafish. Results revealed that Pb-exposed males gained and lost certain color preferences compared to control males and the preference for short wavelengths was decreased. Overall, these results show that consideration and pretesting should be completed before applying behavioral and learning assays involving adult zebrafish to avoid innate preferences and confounding changes in neurotoxicology studies and that developmental Pb exposure alters color preferences in adult male zebrafish.

Dopaminergic contributions to distance estimation in Parkinson's disease: a sensory-perceptual deficit?

Recent research has found that perceptual deficits exist in Parkinson's disease (PD), yet the link between perception and movement impairments is not well understood. Inaccurate estimation of distance has the potential to be an underlying cause of movement impairments. Alternatively, those with PD may not be able to perceive their own movements accurately. The main objectives of these studies were to evaluate (1) whether distance estimation is influenced by static perception compared to perception during movement in PD, (2) how visual motion processing contributes to distance estimation during movement, and (3) how dopaminergic medication contributes to these distance estimation deficits. Thirty-seven participants (19 individuals with PD, 18 age-matched healthy control (HC) participants) estimated distance to a remembered target in a total of 48 trials, in 4 randomized blocks. Estimation conditions included: (i) static perception (laser): participants pointed with a laser, (ii) active dynamic perception (walk): participants walked to the estimated position, (iii) passive dynamic perception (wheelchair): participants were pushed in a wheelchair while they gave their estimate. PD patients completed this protocol twice; once OFF and once ON dopaminergic medication. Participants with PD and HC did not differ in judgment accuracy during the static perception (laser) condition. However, those with PD had greater amounts of error compared to HC participants while estimating distance during active dynamic perception (walk). Interestingly, those with PD significantly underestimated the target position compared to healthy control participants across all conditions. Individuals with PD also demonstrated greater variability in their judgments overall. There was no significant influence of dopaminergic medication in any of the conditions. Individuals with PD demonstrated distance estimation deficits only when required to actively move through their environment. In contrast to estimations made with movement, neither static perception (laser) nor passive dynamic perceptions (wheelchair) revealed significant differences in the magnitude of error between the two groups. Thus perceptual estimation deficits appear to be amplified during movement, which may be suggestive of an underlying sensory processing deficit which leads to a problem integrating vision and self-motion information.

Benign and time-limited visual disturbances (flashbacks) in recent abstinent high-potency heavy cannabis smokers: a case series study.

Eight high-potency heavy cannabis smokers who fulfilled DSM-IV-TR criteria for cannabis dependence sought treatment for outpatient detoxification. During routine psychiatric interview they reported the presence of visual disturbances when intoxicated and no prior history of LSD use. They all communicated the persistence of visual disturbances after ceasing cannabis use. Seven categories of visual disturbances were described when staring at stationary and moving objects: visual distortions, distorted perception of distance, illusions of movement of stationary and moving objects, color intensification of objects,dimmed color, dimensional distortion and blending of patterns and objects. Patients reported having 2-5 different categories of flashbacks up to 3-6 months after cessation of cannabis use. The described phenomena may be interpreted as a time-limited benign side effect of high-potency cannabis use in some individuals. A combination of vulnerability and use of large amounts of high potency cannabis seem to contribute to the appearance of this condition. Conclusions from uncontrolled case series should be taken with appropriate caution.

A study investigating the acute dose-response effects of 13 mg and 17 mg Delta 9- tetrahydrocannabinol on cognitive-motor skills, subjective and autonomic measures in regular users of marijuana.

Heavy use of marijuana is claimed to damage critical skills related to short-term memory, visual scanning and attention. Motor skills and driving safety may be compromised by the acute effects of marijuana. The aim of this study was to investigate the acute effects of 13 mg and 17 mg Delta 9-tetrahydrocannabinol (THC) on skills important for coordinated movement and driving and on subjective and autonomic measures in regular users of marijuana. Fourteen regular users of marijuana were enrolled. Each subject was tested on two separate days. On each test day, subjects smoked two low-nicotine cigarettes, one with and the other without THC. Seventeen mg THC was included in the cigarette on one test day and 13 mg on the other day. The sequence of cigarette types was unknown to the subject. During smoking, heart rate and blood pressure were monitored, and the subjects performed a virtual reality maze task requiring attention and motor coordination, followed by 3 other cognitive tasks (Wisconsin Card Sorting Test (WCST), a "gambling" task and estimation of time and distance from an approaching car). After smoking a cigarette with 17 mg THC, regular marijuana users hit the walls more often on the virtual maze task than after smoking cigarettes without THC; this effect was not seen in patients after they smoked cigarettes with 13 mg THC. Performance in the WCST was affected with 17 mg THC and to a lesser extent with the use of 13 mg THC. Decision making in the gambling task was affected after smoking cigarettes with 17 mg THC, but not with 13 m THC. Smoking cigarettes with 13 and 17 mg THC increased subjective ratings of pleasure and satisfaction, drug "effect" and drug "high". These findings imply that smoking of 17 mg THC results in impairment of cognitive-motor skills that could be important for coordinated movement and driving, whereas the lower dose of 13 mg THC appears to cause less impairment of such skills in regular users of marijuana.

Effects of ethanol on kinaesthetic perception.

In normal subjects, alcohol increases handwriting size, but the mechanism is not understood. Here we show that the alcohol effect on handwriting can be explained by a selective impairment of kinaesthetic perception. Thirty volunteers (15 male, aged 18-29 years) took part in an open study. They were tested before and after a drink containing vodka intended to produce a blood alcohol concentration of about 80mg/100ml. Tests included kinaesthetic distance estimation, in which volunteers worked with preferred hand and arm behind a screen which hid their movements; visual distance estimation; and measures of handwriting and drawing. Blood alcohol concentration at 55min, based on breathalyser measurements, was 76.7mg/100ml (SD 9.8). When asked to move the hand and mark a distance of 10cm from a starting point, distances estimates increased by 7-10% (p 0.01). Similar increases were seen for writing words and drawing characters. Signatures were increased in height but not in length. Distances estimated visually were increased much less, by 3-4% (p 0.05). Tests of psychomotor performance indicated the expected effects of ethanol. These results suggest that ethanol affects writing size by reducing kinaesthetically perceived distances.

Thorax vibrations of a stingless bee ( Melipona seminigra). II. Dependence on sugar concentration.

Using a laser vibrometer we studied the influence of the food's sugar concentration on different parameters of the thorax vibrations produced by foragers of Melipona seminigra during trophallaxis in the nest. The concentrations tested (20-70% sugar w/w) were within the biologically relevant range. They substantially influenced different parameters of the thorax vibrations. An increase of energy gains at the food source due to an increased sugar concentration was followed by an increase of both the pulse duration and the duty cycle and by a decrease of the pause duration between two subsequent pulses. These findings further support the hypothesis that the temporal pattern of the thorax vibrations reflects the energy budget of a foraging trip rather than food source distance. Likewise, the steep increase of pulse duration variability with sugar concentration is hard to reconcile with the assumption that pulse duration conveys reliable information about food source distance when bees collect at high-quality food sources.

Landmark discrimination learning in the dog: effects of age, an antioxidant fortified food, and cognitive strategy.

The landmark discrimination learning test can be used to assess the ability to utilize allocentric spatial information to locate targets. The present experiments examined the role of various factors on performance of a landmark discrimination learning task in beagle dogs. Experiments 1 and 2 looked at the effects of age and food composition. Experiments 3 and 4 were aimed at characterizing the cognitive strategies used in performance on this task and in long-term retention. Cognitively equivalent groups of old and young dogs were placed into either a test group maintained on food enriched with a broad-spectrum of antioxidants and mitochondrial cofactors, or a control group maintained on a complete and balanced food formulated for adult dogs. Following a wash-in period, the dogs were tested on a series of problems, in which reward was obtained when the animal responded selectively to the object closest to a thin wooden block, which served as a landmark. In Experiment 1, dogs were first trained to respond to a landmark placed directly on top of coaster, landmark 0 (L0). In the next phase of testing, the landmark was moved at successively greater distances (1, 4 or 10 cm) away from the reward object. Learning varied as a function of age group, food group, and task. The young dogs learned all of the tasks more quickly than the old dogs. The aged dogs on the enriched food learned L0 significantly more rapidly than aged dogs on control food. A higher proportion of dogs on the enriched food learned the task, when the distance was increased to 1cm. Experiment 2 showed that accuracy decreased with increased distance between the reward object and landmark, and this effect was greater in old animals. Experiment 3 showed stability of performance, despite using a novel landmark, and new locations, indicating that dogs learned the landmark concept. Experiment 4 found age impaired long-term retention of the landmark task. These results indicate that allocentric spatial learning is impaired in an age-dependent manner in dogs, and that age also affects performance when the distance between the landmark and target is increased. In addition, these results both support a role of oxidative damage in the development of age-associated cognitive dysfunction and indicate that short-term administration of a food enriched with supplemental antioxidants and mitochondrial cofactors can partially reverse the deleterious effects of aging on cognition.

Effect of alcohol on visual constancy values and possible relation to driving performance.

The effects of the constancy phenomena in vision seem to be to provide information about the environment which is not solely dependent upon the characteristics of shape or size of the retinal image but which is modified by the brain to appear closer to the idealized characteristics of the real object. There is a regression away from the retinal image towards the actual object's characteristics. A plate viewed from an angle tends to look more like a disc than would be predicted from the geometry of perspective. This ability of the brain to impose conditions on perception is a high-level process which may be adversely affected by the depressive action of alcohol on the nervous system. In this case, objects such as road signs, etc. would tend to look smaller and so more distant than when sober if regression is inhibited. Drivers' reactions may be delayed if hazards are seen smaller and further away, thereby increasing the possibility of accident. This research indicates a reduction in phenomenal regression after ingestion of alcohol. There are implications for accident-rates in driving or in industry.

The effect of alcohol on the visual and ocular motor systems.

Alcohol is generally considered to be a central nervous system (CNS) depressant. This effect is progressive from higher cortical centres through to fundamental body functions. The effect of alcohol ingestion on the visual and ocular motor systems of ten healthy subjects was the basis of this study. Significant changes in the following resulted from the ingestion of 0.375 g/kg of 10% ethanol alcohol: prism measurements of deviations for near and distance, ocular movements, convergence near point, and visual acuity at six metres. No significant change was observed following testing of stereopsis or near visual acuity.

Cholinergic receptor blockade impairs spatial localization by use of distal cues in the rat.

Spatial localization was studied in the Morris water maze. The task required rats to escape from cool water (made opaque by milk) by finding a submerged, invisible platform located at a fixed place within the room. The start point was varied randomly, and there was no local cues to indicate the position of the platform. After training, the platform was moved. Rats subjected to central cholinergic receptor blockade with atropine sulfate were compared with normal rats and rats receiving peripheral cholinergic blockade with atropine methylnitrate. The controls for the use of search strategies, as compared with spatial mapping, were a group of blind rats and a group of rats for which the platform was moved from trial to trial. Measures of escape latency, swim distance, initial heading error, posttrial rearing on the platform, and search strategy after platform displacement revealed that the control rats and the atropine methylnitrate rats used a spatial mapping strategy to locate the platform. The atropine sulfate treated rats adopted a search strategy like that of the blind rats and the rats for which the platform was randomly moved: Their escape latency and swimming distance decreased across trials, including reversal trials, but their initial heading errors remained unchanged. The results support the idea that central cholinergic systems are important for spatial mapping, which demands the use of distal visual cues, but not for spatial localization, which requires other search strategies and possibly the use of proximal tactile, kinesthetic, and visual cues. Consistent with this idea, certain features of the atropine sulfate treated rats' behavior also suggested a novel explantation for some aspects of atropine stereotypies.

Methadone maintenance: an assessment of potential fluctuations in behavior between doses.

Thirty methadone maintenance outpatients were measured 1 and 25 hours after ingestion of methadone on auditory threshold, distance perception, simple and differential reaction time, time perception, attention span, and short-term memory. The results revealed a small but statistically significant difference between the two tests for distance perception. In addition, treatment interacted with preparatory interval on differential reaction time and with sex on attention span.

Clobazam, a 1,5-benzodiazepine, and car-driving ability.

1 The effects of clobazam, a new anxiolytic agent (a 1,5-benzodiazepine) on car-driving ability and other tests of psychomotor performance were investigated in a double-blind, cross-over study v. placebo in normal volunteers. 2 Clobazam (20 mg) or placebo was given nightly for six nights to ten volunteers and subjective ratings of sleep and subjective and objective assessments of behaviour and psychomotor performance on the morning following drug ingestion were recorded. 3 Clobazam significantly improved the subjective ratings of sleep induction and quality of induced sleep. 4 Clobazam did not significantly impair performance in a variety of psychomotor tests and car-driving ability. 5 The validity of the measures used and the relevance of the findings to real life car-driving situations are discussed.

Differential association between chronic cannabis use and brain function deficits.

To summarize, 12 objective tests that generated 16 test variables were administered to 850 male regular cannabis users and 839 nonusers. The tests were designed to assess various modalities, including speed of psychomotor performance, distance estimation, time estimation, immediate memory, and visuomotor coordination. Most of the test variables differentiated significantly between consumers and controls. At the same time, a significant second-order interaction emerged in most cases. This interaction meant that, under certain conditions that relate to the two dimensions "literacy-illiteracy" and/or "urbanism-ruralism," the superiority of controls over cannabis users became impressive, whereas under other conditions it almost disappeared. To account for this complex pattern of results, a working hypothesis was presented to the effect that "other conditions being equal, the lower the nondrug level of proficiency on tests of cognitive and psychomotor performance the smaller the size of function deficit associated with drug usage." For an empirical examination of the hypothesis, six predictions were formulated. Three predictions defined specific relationships between level of performance, on one hand, and each of three organismic variables, on the other: literacy, urbanism, and age. The remaining predictions delineated relationships to be expected between size of function deficit and the three organismic variables. All our predictions were confirmed, showing less function impairment to be contingent with cannabis usage among the illiterates, rurals, and older subjects. Level of cortical arousal was suggested as the central process associated with the three organismic variables. Because the version of our working hypothesis was formulated with reference to chronic material, the possibility of a transposition of the paradign to research on the acute effects of the drug was discussed. The suggestion was made that our working hypothesis, in either version, is capable of establishing genuine integration between reports that present conflicting results on possible function deficits contingent with cannabis consumption.