tRNS boosts visual perceptual learning in participants with bilateral macular degeneration

Perceptual learning (PL) has shown promise in enhancing residual visual functions in patients with age-related macular degeneration (MD), however it requires prolonged training and evidence of generalization to untrained visual functions is limited. Recent studies suggest that combining transcranial random noise stimulation (tRNS) with perceptual learning produces faster and larger visual improvements in participants with normal vision. Thus, this approach might hold the key to improve PL effects in MD. To test this, we trained two groups of MD participants on a contrast detection task with (n = 5) or without (n = 7) concomitant occipital tRNS. The training consisted of a lateral masking paradigm in which the participant had to detect a central low contrast Gabor target. Transfer tasks, including contrast sensitivity, near and far visual acuity, and visual crowding, were measured at pre-, mid and post-tests. Combining tRNS and perceptual learning led to greater improvements in the trained task, evidenced by a larger increment in contrast sensitivity and reduced inhibition at the shortest target to flankers’ distance. The overall amount of transfer was similar between the two groups. These results suggest that coupling tRNS and perceptual learning has promising potential applications as a clinical rehabilitation strategy to improve vision in MD patients

Optic Flow Processing in Patients With Macular Degeneration

International audiencePURPOSE. Optic flow processing was characterized in patients with macular degeneration (MD).METHODS. Twelve patients with dense bilateral scotomas and 12 age-and gender-matched control participants performed psychophysical experiments. Stimuli were dynamic random-dot kinematograms projected on a large screen. For each component of optic flow (translational, radial, and rotational), we estimated motion coherence discrimination thresholds in our participants using an adaptive Bayesian procedure.RESULTS. Thresholds for translational, rotational, and radial patterns were comparable between patients and their matched control participants. A negative correlation was observed in patients between the time since MD diagnosis and coherence thresholds for translational patterns.CONCLUSIONS. Our results suggest that in patients with MD, selectivity to optic flow patterns is preserved

Processing of translational, radial and rotational optic flow in older adults

Abstract Aging impacts human observer’s performance in a wide range of visual tasks and notably in motion discrimination. Despite numerous studies, we still poorly understand how optic flow processing is impacted in healthy older adults. Here, we estimated motion coherence thresholds in two groups of younger (age: 18–30, n = 42) and older (70–90, n = 42) adult participants for the three components of optic flow (translational, radial and rotational patterns). Stimuli were dynamic random-dot kinematograms (RDKs) projected on a large screen. Participants had to report their perceived direction of motion (leftward versus rightward for translational, inward versus outward for radial and clockwise versus anti-clockwise for rotational patterns). Stimuli had an average speed of 7°/s (additional recordings were performed at 14°/s) and were either presented full-field or in peripheral vision. Statistical analyses showed that thresholds in older adults were similar to those measured in younger participants for translational patterns, thresholds for radial patterns were significantly increased in our slowest condition and thresholds for rotational patterns were significantly decreased. Altogether, these findings support the idea that aging does not lead to a general decline in visual perception but rather has specific effects on the processing of each optic flow component

Enhancing visual scene categorization in people with age-related macular degeneration through perceptual learning

International audienceAge-related macular degeneration (AMD) is characterized by a central vision loss causedby the destruction of macular photoreceptors. Some studies have investigated the visualabilities of AMD patients in their residual vision. Contrast sensitivity measured using sinusoidal gratings has been shown to decrease for high and low spatial frequencies both at fovea and parafovea suggesting that deficits are not confined to central vision. Other studies confirmed a deficit in processing high spatial frequencies in large photographs of scenes in comparison to normally-sighted participants. The processing of low spatial frequencies was relatively well preserved, allowing effective perception of scenes in parafoveal vision. However, the processing of spatial frequencies is impaired by low-level luminance contrast. A promising readaptation strategy for patients is to train their residual vision through perceptual learning in order to diminish their visual deficits. In this study, we investigated whether perceptual learning could improve patients’ performance in processing spatial frequencies in visual scenes. Four AMD patients participated in an intensive training (12 one-hour sessions spread over 4 weeks). They had to categorize large filtered scenes (covering the residual visualfield) as indoor or outdoor scenes. Scenes were filtered in low spatial frequencies (LSF)or in high spatial frequencies (HSF) and luminance contrast was equalized between LSF and HSF stimuli. Perceptual learning improvements were assessed by comparing performances in sessions before and after the training, using the same categorization task of LSF and HSF filtered scenes, but different stimuli. For each patient, we compared correct responses between the pre- and post-training sessions by calculating an improvement rate. This allowed us to reduce disparities among patients using the formula: ((post-training results - pretraining results)/pre-training results) * 100. Patients showed an average rate improvement of 14.74% (standard error: 6.59%) in processing HSF filtered scenes and of 8.21% (standard error: 4.22%) in processing LSF filtered scenes. Although these findings are preliminary and have to be confirmed with more patients, they suggest that perceptual learning could be an efficient tool to improve AMD patients’ scene perception in their residual vision

tRNS boosts visual perceptual learning in participants with bilateral macular degeneration

Perceptual learning (PL) has shown promise in enhancing residual visual functions in patients with age-related macular degeneration (MD), however it requires prolonged training and evidence of generalization to untrained visual functions is limited. Recent studies suggest that combining transcranial random noise stimulation (tRNS) with perceptual learning produces faster and larger visual improvements in participants with normal vision. Thus, this approach might hold the key to improve PL effects in MD. To test this, we trained two groups of MD participants on a contrast detection task with (n = 5) or without (n = 7) concomitant occipital tRNS. The training consisted of a lateral masking paradigm in which the participant had to detect a central low contrast Gabor target. Transfer tasks, including contrast sensitivity, near and far visual acuity, and visual crowding, were measured at pre-, mid and post-tests. Combining tRNS and perceptual learning led to greater improvements in the trained task, evidenced by a larger increment in contrast sensitivity and reduced inhibition at the shortest target to flankers' distance. The overall amount of transfer was similar between the two groups. These results suggest that coupling tRNS and perceptual learning has promising potential applications as a clinical rehabilitation strategy to improve vision in MD patients

Perceptual learning improves motion perception in patients with age-related macular degeneration

International audienceAge-related macular degeneration (AMD) is the leading cause of blindness in people over 65 years. This disease is typically characterized by a progressive loss of central vision in both eyes which is irreversible and has a dramatic impact on the patients' quality of life. A promising readaptation strategy for patients is to train their peripheral vision, which remains functional, in order to diminish their visual impairments. Here, we explore whether perceptual learning can be used to improve the patients' ability to perceive motion, an important visual function that relies on both central and peripheral vision. Participants (4 AMD patients with an absolute scotoma in both eyes, aged between 66 and 82) performed 12 training sessions of about an hour and spread over 4 weeks. During each of these sessions, they had to report the motion direction (either upward or downward) of a translating pattern defined from dynamic random-dot kinematograms (RDKs) projected on a large screen (58.1° x 43.7°). Motion coherence discrimination thresholds were estimated using an adaptive Bayesian procedure. We calculated the improvement rate for each participant using the formula [(post-test result - pre-test result)/pre-test result]*100. This reduces the disparities between participants. All participants improved their performances with the training (mean improvement rate in post-tests: 34.8 percent +/- 12.2 percent of standard error), which suggests that perceptual learning is indeed efficient in this case. In order to determine whether these effects generalized to untrained and more complex visual motion tasks, we characterized the performances of the patients on multiple object tracking (MOT) before and after the training on translational motion. In this task, several identical moving disks were presented on the screen. Some of them (either 3/6 or 4/8) were designated as targets while the remaining served as distractors. Patients had to monitor the positions of the targets during 10s trials. Analyses showed that tracking performances were generally improved after the training (mean improvement rate in post-tests: 7.2 percent +/- 4.6 percent of standard error, 2 patients had higher scores in all the conditions while the two others had higher scores in only one condition). Although these preliminary results will have to be confirmed from measurements in a bigger cohort, they suggest that perceptual learning is an effective tool to improve motion perception in AMD patients and that the effects of training on a simple motion discrimination task might transfer to more complex tasks

Perceptual learning improves motion perception in patients with age-related macular degeneration

International audienceAge-related macular degeneration (AMD) is the leading cause of blindness in people over 65 years. This disease is typically characterized by a progressive loss of central vision in both eyes which is irreversible and has a dramatic impact on the patients' quality of life. A promising readaptation strategy for patients is to train their peripheral vision, which remains functional, in order to diminish their visual impairments. Here, we explore whether perceptual learning can be used to improve the patients' ability to perceive motion, an important visual function that relies on both central and peripheral vision. Participants (4 AMD patients with an absolute scotoma in both eyes, aged between 66 and 82) performed 12 training sessions of about an hour and spread over 4 weeks. During each of these sessions, they had to report the motion direction (either upward or downward) of a translating pattern defined from dynamic random-dot kinematograms (RDKs) projected on a large screen (58.1° x 43.7°). Motion coherence discrimination thresholds were estimated using an adaptive Bayesian procedure. We calculated the improvement rate for each participant using the formula [(post-test result - pre-test result)/pre-test result]*100. This reduces the disparities between participants. All participants improved their performances with the training (mean improvement rate in post-tests: 34.8 percent +/- 12.2 percent of standard error), which suggests that perceptual learning is indeed efficient in this case. In order to determine whether these effects generalized to untrained and more complex visual motion tasks, we characterized the performances of the patients on multiple object tracking (MOT) before and after the training on translational motion. In this task, several identical moving disks were presented on the screen. Some of them (either 3/6 or 4/8) were designated as targets while the remaining served as distractors. Patients had to monitor the positions of the targets during 10s trials. Analyses showed that tracking performances were generally improved after the training (mean improvement rate in post-tests: 7.2 percent +/- 4.6 percent of standard error, 2 patients had higher scores in all the conditions while the two others had higher scores in only one condition). Although these preliminary results will have to be confirmed from measurements in a bigger cohort, they suggest that perceptual learning is an effective tool to improve motion perception in AMD patients and that the effects of training on a simple motion discrimination task might transfer to more complex tasks