Authors: Battaglini, Luca | Mena, Federica | Casco, Clara
Article Type: Research Article
Abstract: Background: To study motion perception, a stimulus consisting of a field of small, moving dots is often used. Generally, some of the dots coherently move in the same direction (signal) while the rest move randomly (noise). A percept of global coherent motion (CM) results when many different local motion signals are combined. CM computation is a complex process that requires the integrity of the middle-temporal area (MT/V5) and there is evidence that increasing the number of dots presented in the stimulus makes such computation more efficient. Objective: In this study, we explored whether anodal direct current stimulation (tDCS) over MT/V5 …would increase individual performance in a CM task at a low signal-to-noise ratio (SNR, i.e. low percentage of coherent dots) and with a target consisting of a large number of moving dots (high dot numerosity, e.g. >250 dots) with respect to low dot numerosity (<60 dots), indicating that tDCS favour the integration of local motion signal into a single global percept (global motion). Method: Participants were asked to perform a CM detection task (two-interval forced-choice, 2IFC) while they received anodal, cathodal, or sham stimulation on three different days. Results: Our findings showed no effect of cathodal tDCS with respect to the sham condition. Instead, anodal tDCS improves performance, but mostly when dot numerosity is high (>400 dots) to promote efficient global motion processing. Conclusions: The present study suggests that tDCS may be used under appropriate stimulus conditions (low SNR and high dot numerosity) to boost the global motion processing efficiency, and may be useful to empower clinical protocols to treat visual deficits. Show more
Keywords: Coherent motion, global motion, tDCS, MT, dot numerosity
DOI: 10.3233/RNN-201050
Citation: Restorative Neurology and Neuroscience, vol. 38, no. 5, pp. 395-405, 2020
Authors: Barollo, Michele | Contemori, Giulio | Battaglini, Luca | Pavan, Andrea | Casco, Clara
Article Type: Research Article
Abstract: Background: Amblyopic observers present abnormal spatial interactions between a low-contrast sinusoidal target and high-contrast collinear flankers. It has been demonstrated that perceptual learning (PL) can modulate these low-level lateral interactions, resulting in improved visual acuity and contrast sensitivity. Objective: We measured the extent and duration of generalization effects to various spatial tasks (i.e., visual acuity, Vernier acuity, and foveal crowding) through PL on the target’s contrast detection. Methods: Amblyopic observers were trained on a contrast-detection task for a central target (i.e., a Gabor patch) flanked above and below by two high-contrast Gabor patches. The pre- and post-learning tasks included lateral …interactions at different target-to-flankers separations (i.e., 2, 3, 4, 8λ ) and included a range of spatial frequencies and stimulus durations as well as visual acuity, Vernier acuity, contrast-sensitivity function, and foveal crowding. Results: The results showed that perceptual training reduced the target’s contrast-detection thresholds more for the longest target-to-flanker separation (i.e., 8λ ). We also found generalization of PL to different stimuli and tasks: contrast sensitivity for both trained and untrained spatial frequencies, visual acuity for Sloan letters, and foveal crowding, and partially for Vernier acuity. Follow-ups after 5–7 months showed not only complete maintenance of PL effects on visual acuity and contrast sensitivity function but also further improvement in these tasks. Conclusion: These results suggest that PL improves facilitatory lateral interactions in amblyopic observers, which usually extend over larger separations than in typical foveal vision. The improvement in these basic visual spatial operations leads to a more efficient capability of performing spatial tasks involving high levels of visual processing, possibly due to the refinement of bottom-up and top-down networks of visual areas. Show more
Keywords: Amblyopia, perceptual learning, visual acuity, crowding, contrast sensitivity
DOI: 10.3233/RNN-170731
Citation: Restorative Neurology and Neuroscience, vol. 35, no. 5, pp. 483-496, 2017
Authors: Casco, Clara | Barollo, Michele | Contemori, Giulio | Battaglini, Luca
Article Type: Research Article
Abstract: Background: In recent years, the introduction of visual rehabilitation for patients with homonymous visual field defects has been met with both enthusiasm and caution. Despite the evidence that restitutive training results in expansion of the visual field, several concerns have been raised. Objective: We tested the effectiveness of a new rehabilitative protocol called “Neuro Restoration Training” (NRT) in reducing visual field defects and in restituting visual functions in the restored hemianopic area. Methods: Ten patients with homonymous visual field defects (lesion age >6 months) where trained in detecting low contrast Gabor patches randomly presented in the blind field, which refers …to regions of 0 dB sensitivity, and along the hemianopic boundary between absolute (0 dB) and partial blindness (>0 dB). Training included static, drifting, and flickering Gabors in different blocks. Positions along the hemianopic boundary were systematically shifted toward the blind field according to the threshold reduction during the training. Before and after the training, we assessed visual field expansion and improvement in different high-level transfer tasks (i.e., letter identification and shape recognition) performed in the hemianopic boundary and in the blind field. Results: NRT led to significant visual field enlargement (≈5 deg), as indicated by the conventional Humphrey perimetry, and two custom made evaluations of visual field expansion with eye movement control (one static and one dynamic). The restored area acquired new visual functions such as small letter recognition and perception of moving shapes. Finally, for some patients, NRT also improved detection, either aware or not, of high contrast flickering grating and recognition of geometrical shapes entirely presented within the blind field. Conclusion: These results suggest that NRT may lead to visual field enlargement and translate into untrained visual functions. Show more
Keywords: Hemianopia, Neuro Restoration Training, visual field, training, contrast sensitivity
DOI: 10.3233/RNN-170752
Citation: Restorative Neurology and Neuroscience, vol. 36, no. 2, pp. 275-291, 2018
Authors: Maniglia, Marcello | Pavan, Andrea | Sato, Giovanni | Contemori, Giulio | Montemurro, Sonia | Battaglini, Luca | Casco, Clara
Article Type: Research Article
Abstract: Background: Macular Degeneration (MD), a visual disease that produces central vision loss, is one of the main causes of visual disability in western countries. Patients with MD are forced to use a peripheral retinal locus (PRL) as a substitute of the fovea. However, the poor sensitivity of this region renders basic everyday tasks very hard for MD patients. Objective: We investigated whether perceptual learning (PL) with lateral masking in the PRL of MD patients, improved their residual visual functions. Method: Observers were trained with two distinct contrast detection tasks: (i) a Yes/No task with no feedback (MD: N = 3; controls: N = 3), …and (ii) a temporal two-alternative forced choice task with feedback on incorrect trials (i.e., temporal-2AFC; MD: N = 4; controls: N = 3). Observers had to detect a Gabor patch (target) flanked above and below by two high contrast patches (i.e., lateral masking). Stimulus presentation was monocular with durations varying between 133 and 250 ms. Participants underwent 24– 27 training sessions in total. Results: Both PL procedures produced significant improvements in the trained task and learning transferred to visual acuity. Besides, the amount of transfer was greater for the temporal-2AFC task that induced a significant improvement of the contrast sensitivity for untrained spatial frequencies. Most importantly, follow-up tests on MD patients trained with the temporal-2AFC task showed that PL effects were retained between four and six months, suggesting long-term neural plasticity changes in the visual cortex. Conclusion: The results show for the first time that PL with a lateral masking configuration has strong, non-invasive and long lasting rehabilitative potential to improve residual vision in the PRL of patients with central vision loss. Show more
Keywords: Macular degeneration (MD), perceptual learning, neural plasticity, visual rehabilitation
DOI: 10.3233/RNN-150575
Citation: Restorative Neurology and Neuroscience, vol. 34, no. 5, pp. 697-720, 2016
Authors: Battaglini, Luca | Oletto, Carolina Maria | Contemori, Giulio | Barollo, Michele | Ciavarelli, Ambra | Casco, Clara
Article Type: Research Article
Abstract: Background: Several visual functions are impaired in patients with oculocutaneous albinism (OCA) associated to albinistic bilateral amblyopia (ABA). Objective: In this study, we aimed at exploring whether perceptual learning (PL) can improve visual functions in albinism. Method: Six patients and six normal sighted controls, were trained in a contrast detection task with lateral masking. Participants were asked to choose which of the two intervals contained a foveally presented low-contrast Gabor patch. Targets were presented between higher contrast collinear flankers with equal spatial frequency. When increasing target-to-flanker distance, lateral interactions effect normally switches from inhibition to facilitation, up to no effect. …Results: Our findings showed that before PL, only controls showed facilitation. After PL, results suggest that facilitatory lateral interactions are found both in controls as well as in albino patients. These results suggest that PL could induce higher processing efficiency at early cortical level. Moreover, PL positive effect seems to transfer to higher-level visual functions, but results were not very consistent among tasks (visual acuity, contrast sensitivity function, hyperacuity and foveal crowding). Conclusions: Although a small sample size was tested, our findings suggest a rehabilitative potential of PL in improving visual functions in albinism. Show more
Keywords: Albinism, amblyopia, oculocutaneous albinism, perceptual learning
DOI: 10.3233/RNN-201043
Citation: Restorative Neurology and Neuroscience, vol. 39, no. 1, pp. 45-59, 2021
Authors: Battaglini, Luca | Di Ponzio, Michele | Ghiani, Andrea | Mena, Federica | Santacesaria, Paola | Casco, Clara
Article Type: Research Article
Abstract: Background: Vision is the sense which we rely on the most to interact with the environment and its integrity is fundamental for the quality of our life. However, around the globe, more than 1 billion people are affected by debilitating vision deficits. Therefore, finding a way to treat (or mitigate) them successfully is necessary. Objective: This narrative review aims to examine options for innovative treatment of visual disorders (retinitis pigmentosa, macular degeneration, optic neuropathy, refractory disorders, hemianopia, amblyopia), especially with Perceptual Learning (PL) and Electrical Stimulation (ES). Methods: ES and PL can enhance visual abilities in clinical populations, inducing plastic …changes. We describe the experimental set-ups and discuss the results of studies using ES or PL or their combination in order to suggest, based on literature, which treatment is the best option for each clinical condition. Results: Positive results were obtained using ES and PL to enhance visual functions. For example, repetitive transorbital Alternating Current Stimulation (rtACS) appeared as the most effective treatment for pre-chiasmatic disorders such as optic neuropathy. A combination of transcranial Direct Current Stimulation (tDCS) and visual training seems helpful for people with hemianopia, while transcranial Random Noise Stimulation (tRNS) makes visual training more efficient in people with amblyopia and mild myopia. Conclusions: This narrative review highlights the effect of different ES montages and PL in the treatment of visual disorders. Furthermore, new options for treatment are suggested. It is noteworthy to mention that, in some cases, unclear results emerged and others need to be more deeply investigated. Show more
Keywords: Electrical stimulation, perceptual learning, plasticity, vision, treatment, visual damage
DOI: 10.3233/RNN-221261
Citation: Restorative Neurology and Neuroscience, vol. 40, no. 3, pp. 137-168, 2022