Visual Deprivation Research Articles

A Preliminary Study on Effectiveness of Varying Dose of Paretic Upper Limb Training with Visual Deprivation in Poststroke Patients: A Randomised Clinical Tria

Introduction: Poststroke Upper Limb (UL) rehabilitation with visual deprivation has shown potential in enhancing motor recovery through neural plasticity. However, the optimal dosage remains unclear. Aim: To evaluate the effectiveness of varying doses of paretic UL training with visual deprivation in stroke patients. Materials and Methods: This single-centre, parallel-group, single-blinded, randomised clinical trial involved 36 stroke patients who were randomly distributed into three groups varying in treatment frequency: Group A (n=12) received two sessions per week, Group B (n=12) received three sessions per week, and Group C (n=12) received five sessions per week for four weeks. Each session lasted 40 minutes of visual deprivation training for the paretic UL. A trained physiotherapist, who was blinded to group allocation, conducted pre- and postevaluations. The Wolf Motor Function Test was the principal outcome measure. This study utilised Analysis of Variance (ANOVA) for between group comparisons and independent sample t-tests for within group pre-post comparisons, with a significance level of 5%. Results: Out of the 36 study participants, three dropouts were recorded by the completion of the study: one from Group A and two from Group B. The average age of participants was 54.75±8.06 years, and the duration of stroke was 10.08±4.35 months, with 69.4% experiencing left-sided involvement. All groups showed significant improvement. Group C exhibited the highest improvement in the Wolf Motor Function Test score, with an F value of 42.86 (p-value=0.001). Post-hoc analysis revealed a significant difference in motor score improvement in Group C, (p-value=0.001). Additionally, Group C demonstrated greater improvements in the Wolf Motor Functional Ability Score (WMFAS), with a mean improvement of 15.00±0.82 (F=158.00, p-value=0.001). Conclusion: Visual deprivation training with higher intensity (five sessions per week) was effective in improving UL motor function in poststroke patients, proving superior to lower intensity (two or three sessions per week). These results highlight the importance of frequent training. Future research with larger and more diverse stroke patient populations, as well as long-term follow-up studies, is needed to validate these findings.

Spatial mapping of activity changes across sensory areas following visual deprivation in adults.

Loss of a sensory modality triggers global adaptation across brain areas, allowing the remaining senses to guide behavior more effectively. There are specific synaptic and circuit plasticity observed across many sensory areas, which suggests potential widespread changes in activity. Here we used a cFosTRAP2 mouse line to drive tdTomato (tdT) expression in active cells to spatially map the extent of activity changes in various sensory areas in adult mice of both sexes following two modes of visual deprivation. We found that in the primary visual cortex (V1) both dark exposure (DE) and enucleation (EN) caused an initial loss of active cells followed by a partial rebound, which occurred relatively more in the superficial layers. A similar pattern was observed in the secondary visual cortex, especially in the lateral areas (V2L). The spared primary sensory cortices adapted distinctly. In the primary somatosensory barrel cortex (S1BF) there was a change in the density of active cells dependent on the duration and the mode of visual deprivation. In the primary auditory cortex (A1), there was a relative reduction in the density of active cells in the superficial layers without a significant change in the overall density. There were minimal changes in the active cell density in the secondary cortices of the spared senses and the multisensory retrosplenial cortex (RSP). Our results are consistent with cross-modal recruitment of the deprived visual cortex and compensatory plasticity in the spared primary sensory cortices that can support enhanced processing and refinement of the spared senses.Significance Statement The neural basis for improved processing of the spared senses after losing vision is largely dependent on plasticity mechanisms driven by neural activity. Using a transgenic mouse model to label active neurons in a temporally controlled manner, this study reveals the spatial pattern of widespread activity changes across brain areas following visual deprivation in adult mice. The findings suggest that the deprived visual cortex undergoes an initial reduction in activity followed by a rebound suggestive of cross-modal recruitment. Activity changes in the spared primary sensory cortices conform to compensatory plasticity, which could support improved processing of the spared senses. The results highlight the presence of large-scale plasticity in the adult brain to compensate for loss of vision.

Hand and foot overestimation in visually impaired human adults

Previous research has shown that visual impairment results in reduced audio, tactile and proprioceptive ability. One hypothesis is that these issues arise from inaccurate body representations. Few studies have investigated metric body representations in a visually impaired population. We designed an ecologically valid behavioural task in which visually impaired adults haptically explored various sized gloves or shoes. They were asked to indicate if they perceived each clothing item as bigger than the size of their hand or foot. In the post-hoc analyses we fit psychometric curves to the data to extract the point of subjective equality. We then compared the results to age/sex matched controls. We hypothesized the blind participants body representations should be more distorted. Because previous research has shown that females are more likely to overestimate body size, we predicted sex differences in the sighted participants. However, because blind adults have no exposure to visual ideals of body size, we predicted that there would be no sex differences. Our results showed thatblind participants overestimated their hands and feetto a similar degree. Sighted controls overestimated their hands significantly more than their feet. Taken together, our results partially support our hypothesis and suggest that visual deprivation, even for short periods result in hand size overestimation.

Construct Validity of a Wearable Inertial Measurement Unit (IMU) in Measuring Postural Sway and the Effect of Visual Deprivation in Healthy Older Adults.

Inertial Motor sensors (IMUs) are valid instruments for measuring postural sway but their ability to detect changes derived from visual deprivation in healthy older adults requires further investigations. We examined the validity and relationship of IMU sensor-derived postural sway measures compared to force plates for different eye conditions in healthy older adults (32 females, 33 males). We compared the relationship of the center of mass and center of pressure (CoM and CoP)-derived total length, root means square (RMS) distance, mean velocity, and 95% confidence interval ellipse area (95% CI ellipse area). In addition, we examined the relationship of the IMU sensor in discriminating between open- (EO) and closed-eye (EC) conditions compared to the force plate. A significant effect of the instruments and eye conditions was found for almost all the variables. Overall, EO and EC variables within (force plate r, from 0.38 to 0.78; IMU sensor r, from 0.36 to 0.69) as well as between (r from 0.50 to 0.88) instruments were moderately to strongly correlated. The EC:EO ratios of RMS distance and 95% CI ellipse area were not different between instruments, while there were significant differences between total length (p = 0.973) and mean velocity (p = 0.703). The ratios' correlation coefficients between instruments ranged from moderate (r = 0.65) to strong (r = 0.87). The IMU sensor offers an affordable, valid alternative to a force plate for objective, postural sway assessment.

Pressure center behavior and plantar pressure distribution in patients undergoing total knee atropasty surgery

Objectives The study aimed to analyze the center of pressure behavior in individuals undergoing total knee arthroplasty (TKA), using a plantar pressure platform as an assessment tool. Methods Seventeen participants, with an average age of 71.23 years, diagnosed with knee osteoarthritis and undergoing TKA for the first time, were included. Inclusion criteria required participants to have no neurological dysfunctions, prior use of lower limb prostheses, or deformities on the plantar surfaces. The experimental protocol involved data collection on center of pressure behavior, arch index, and pain using the Visual Analog Scale, both with eyes open and closed. Results Revealed significant differences in anteroposterior center of pressure behavior (COPAP) and center of pressure area between moments with eyes open and closed. There were statistically significant variations in COPAP, indicating an influence of visual condition on postural stability. Other variables, such as arch index, average displacement speed, and percentage of pressure on the feet, did not show significant differences. Conclusion The visual condition, especially the difference between eyes open and closed, impacts the center of pressure behavior in patients undergoing TKA. The decrease in the center of pressure area with closed eyes suggests an adaptive response of the neuromuscular system to visual deprivation. This study emphasizes the importance of considering visual factors in the assessment of balance in pre-TKA patients, providing valuable insights for physiotherapeutic interventions and preoperative guidance.

Touch to text: Spatiotemporal evolution of braille letter representations in blind readers.

Visual deprivation does not silence the visual cortex, which is responsive to auditory, tactile, and other nonvisual tasks in blind persons. However, the underlying functional dynamics of the neural networks mediating such crossmodal responses remain unclear. Here, using braille reading as a model framework to investigate these networks, we presented sighted (N=13) and blind (N=12) readers with individual visual print and tactile braille alphabetic letters, respectively, during MEG recording. Using time-resolved multivariate pattern analysis and representational similarity analysis, we traced the alphabetic letter processing cascade in both groups of participants. We found that letter representations unfolded more slowly in blind than in sighted brains, with decoding peak latencies ∼200 ms later in braille readers. Focusing on the blind group, we found that the format of neural letter representations transformed within the first 500 ms after stimulus onset from a low-level structure consistent with peripheral nerve afferent coding to high-level format reflecting pairwise letter embeddings in a text corpus. The spatiotemporal dynamics of the transformation suggest that the processing cascade proceeds from a starting point in somatosensory cortex to early visual cortex and then to inferotemporal cortex. Together our results give insight into the neural mechanisms underlying braille reading in blind persons and the dynamics of functional reorganization in sensory deprivation.

Diffusion Optics Technology (DOT): A Myopia Control Spectacle Lens Based on Contrast Theory.

Diffusion optics Technology (DOT) myopia control spectacle lenses are based on contrast theory. This innovative theory represents a radical departure from the classical concept of visual deprivation myopia. However, traditional theories have evolved, arriving at remarkably similar solutions for myopia control as the DOT lenses. Nonetheless, contrast theory still represents a departure from mainstream theories. Here, in an effort to resolve discrepancies, we review the science behind contrast theory and compare it to more conventional blur and defocus theories. Finally, we consider the implications of the different theories for the rational design of myopia control solutions.

Quantitative structural organization of the sclera in chicks after deprivation myopia measured with second harmonic generation microscopy.

Visual deprivation causes enhanced eye growth and the development of myopia, which is associated with a change in the arrangement of collagen fibers within the sclera. A second harmonic generation (SHG) microscope has been used to image the collagen fibers of unstained scleral punches from the posterior part of chicken eyes. We aimed to analyze the fibrous scleral tissue and quantify the changes in collagen organization in relation to the extent of induced deprivation myopia. The scleral architecture was assessed with the Radon transform (RT) through the parameter called structural dispersion (SD) that provides an objective tool to quantify the level of organization of the collagen network. We found that final refraction and axial length changes were linearly correlated. However, no significant differences in scleral thickness were found for different amounts of induced myopia. In contrast, a significant correlation between SD and refraction was demonstrated, ranging from a non-organized (in the control sclerae) to a quasi-aligned distribution (with a dominant direction of the fibers, in the sclera of myopic chicks). These findings demonstrate a remodeling process of the scleral collagen associated with myopia progression that can be measured accurately combining SHG imaging microscopy and RT algorithms.

Spatial profiling of the interplay between cell type- and vision-dependent transcriptomic programs in the visual cortex.

Layer 2/3 (L2/3) glutamatergic neurons are important sites of experience-dependent plasticity and learning in the mammalian cortex. Their properties vary continuously with cortical depth and depend upon experience. Here, by applying spatial transcriptomics and different computational approaches in the mouse primary visual cortex, we show that vision regulates orthogonal gene expression programs underlying cell states and cell types. Visual deprivation not only induces an activity-dependent cell state, but also alters the composition of L2/3 cell types, which are appropriately described as a transcriptomic continuum. Our results provide insights into how experience shapes transcriptomes that may, in turn, sculpt brain wiring, function, and behavior.

Impact of transcranial Direct Current Stimulation on stereoscopic vision and retinal structure in adult amblyopic rodents.

The impact of visual deprivation on retinal structure is widely debated. Experimental models, like monocular deprivation through lid suture, provide insights into the consequences of lacking visual experience during development. This deprivation delays primary visual cortex (CV1) maturation due to improper neural connection consolidation, which remains plastic beyond the critical period. However, few studies have used Optical Coherence Tomography (OCT) to investigate structural alterations in the retina of animal models following monocular deprivation. Instead, some studies have focused on the ganglion cell layer using post-mortem histological techniques in amblyopia models induced by monocular deprivation. In this study, we used Cliff test to assess stereoscopic vision and spectral domain optical coherence tomography (SD-OCT) to evaluate retinal changes in an in vivo model of visual deprivation treated with Transcranial Direct Current Stimulation (tDCS). The depth perception test initially revealed differences between individuals with amblyopia and the control group. However, after 8 tDCS sessions, amblyopic subjects matched the control group's performance, which remained stable Additionally, significant changes were observed in retinal structures post-tDCS treatment. Specifically, the thickness of the Nerve Fiber Layer + Ganglion Cell Layer + Inner Plexiform Layer (NFL+GCL+IPL) increased significantly in amblyopic eyes (p<0.001). Moreover, significant retinal thickening, including the Nerve Fiber Layer + Ganglion Cell Layer + Inner Plexiform Layer (NFL+GCL+IPL) and the entire retina, was observed post-tDCS treatment (p<0.05), highlighting the critical role of tDCS in ameliorating amblyopia. Additionally, treated animals exhibited reduced thickness in the Inner Nuclear Layer (INL) and Outer Nuclear Layer (ONL). tDCS treatment effectively restores amblyopic individuals' stereoscopic vision, aligning their performance with controls, while impacting retinal structure, highlighting its potential in ameliorating amblyopia's visual deficits.

Brief periods of visual deprivation in adults increase performance on auditory tasks

Brief periods of visual deprivation in adults increase performance on auditory tasks

Sensory correlation detection by children treated for congenital visual deprivation

Sensory correlation detection by children treated for congenital visual deprivation

Individual differences of brain plasticity in early visual deprivation

Individual differences of brain plasticity in early visual deprivation

Plastic reorganization of the topological asymmetry of hemispheric white matter networks induced by congenital visual experience deprivation

Congenital blindness offers a unique opportunity to investigate human brain plasticity. The influence of congenital visual loss on the asymmetry of the structural network remains poorly understood. To address this question, we recruited 21 participants with congenital blindness (CB) and 21 age-matched sighted controls (SCs). Employing diffusion and structural magnetic resonance imaging, we constructed hemispheric white matter (WM) networks using deterministic fiber tractography and applied graph theory methodologies to assess topological efficiency (i.e., network global efficiency, network local efficiency, and nodal local efficiency) within these networks. Statistical analyses revealed a consistent leftward asymmetry in global efficiency across both groups. However, a different pattern emerged in network local efficiency, with the CB group exhibiting a symmetric state, while the SC group showed a leftward asymmetry. Specifically, compared to the SC group, the CB group exhibited a decrease in local efficiency in the left hemisphere, which was caused by a reduction in the nodal properties of some key regions mainly distributed in the left occipital lobe. Furthermore, interhemispheric tracts connecting these key regions exhibited significant structural changes primarily in the splenium of the corpus callosum. This result confirms the initial observation that the reorganization in asymmetry of the WM network following congenital visual loss is associated with structural changes in the corpus callosum. These findings provide novel insights into the neuroplasticity and adaptability of the brain, particularly at the network level.

Visual Deprivation's Impact on Dynamic Posture Control of Trunk: A Comprehensive Sensing Information Analysis of Neurophysiological Mechanisms.

Visual information affects static postural control, but how it affects dynamic postural control still needs to be fully understood. This study investigated the effect of proprioception weighting, influenced by the presence or absence of visual information, on dynamic posture control during voluntary trunk movements. We recorded trunk movement angle and angular velocity, center of pressure (COP), electromyographic, and electroencephalography signals from 35 healthy young adults performing a standing trunk flexion-extension task under two conditions (Vision and No-Vision). A random forest analysis identified the 10 most important variables for classifying the conditions, followed by a Wilcoxon signed-rank test. The results showed lower maximum forward COP displacement and trunk flexion angle, and faster maximum flexion angular velocity in the No-Vision condition. Additionally, the alpha/beta ratio of the POz during the switch phase was higher in the No-Vision condition. These findings suggest that visual deprivation affects cognitive- and sensory-integration-related brain regions during movement phases, indicating that sensory re-weighting due to visual deprivation impacts motor control. The effects of visual deprivation on motor control may be used for evaluation and therapeutic interventions in the future.

Motion’s privilege in recognizing facial expressions following treatment for blindness

In his 1872 monograph, Charles Darwin posited that "… the habit of expressing our feelings by certain movements, though now rendered innate, had been in some manner gradually acquired."1 Nearly 150 years later, researchers are still teasing apart innate versus experience-dependent contributions to expression recognition. Indeed, studies have shown that face detection is surprisingly resilient to early visual deprivation,2,3,4,5 pointing to plasticity that extends beyond dogmatic critical periods.6,7,8 However, it remains unclear whether such resilience extends to downstream processing, such as the ability to recognize facial expressions. The extent to which innate versus experience-dependent mechanisms contribute to this ability has yet to be fully explored.9,10,11,12,13 To investigate the impact of early visual experience on facial-expression recognition, we studied children with congenital cataracts who have undergone sight-correcting treatment14,15 and tracked their longitudinal skill acquisition as they gain sight late in life. We introduce and explore two potential facilitators of late-life plasticity: the availability of newborn-like coarse visual acuity prior to treatment16 and the privileged role of motion following treatment.4,17,18 We find that early visual deprivation does not preclude partial acquisition of facial-expression recognition. While rudimentary pretreatment vision is sufficient to allow a low level of expression recognition, it does not facilitate post-treatment improvements. Additionally, only children commencing vision with high visual acuity privilege the use of dynamic cues. We conclude that skipping typical visual experience early in development and introducing high-resolution imagery late in development restricts, but does not preclude, facial-expression skill acquisition and that the representational mechanisms driving this learning differ from those that emerge during typical visual development.

Features of body balance in 12-year-old schoolchildren with visual deprivation compared to their relatively healthy peers

Purpose. The purpose of the presented scientific research was to carry out a comparative analysis of the state of functional balance of the body of 12-year-old schoolchildren with visual deprivation in accordance with their relatively healthy peers. Material &amp; Methods. The scientific study involved 23 schoolchildren aged 12 years, of which 13 were with visual deprivation and 10 were relatively healthy. The pedagogical research took place at the Educational and Rehabilitation Center “Zorozvit” in Odessa and at the Basic Educational Institution “Vypasnyansky Institution of General Secondary Education” of the Mologovo Village Council of the Bilhorod-Dnistrovsky District, Odessa Region. The follo wing methods were used in the study: theoretical (analysis and synthesis of scientific and methodological literature); pedagogical research (experiment and testing of the development of body balance using the Flamingo test), mathematical static data processing. Results. A scientific study found that among schoolchildren without visual deprivation, only 10% had a low ability to maintain body balance. In turn, 90% of schoolchildren with visual deprivation had a sufficient, satisfactory and high level of development of body balance. It should be noted that schoolchildren with visual deprivation demonstrate a low level of ability to maintain balance, which distinguishes them from their peers without visual deprivation.

Romberg's test revisited: Changes in classical and advanced sway metrics in patients with pure sensory neuropathy

ObjectivesThe Romberg test, undoubtedly a classical and well-established method in physical neurological assessment of patients with sensory ataxia, has long been suspected to be prone to several limitations. Here, we quantified upright stance before and after visual deprivation in a selected cohort of patients with pure sensory neuropathy. MethodsStatic balance was assessed in sensory neuropathy patients during quiet stance on a force platform under different visual and proprioceptive feedback conditions. Sural nerve neurography was employed to evaluate the severity of peripheral neuropathy. Conventional and advanced postural sway metrics were investigated to draw a quantitative analogy to the clinical Romberg test. ResultsPosturographic analyses showed that patients displayed Romberg and vestibular Romberg quotient values around 2, indicating an approximately twofold increase in body sway in the absence of vision. However, the diagnostic discrimination ability between patients and controls was only modest. Even less impactful were the diagnostic contributions of frequency domain and non-linear sway analyses. This was primarily attributed to the heightened body sway exhibited by patients with sensory neuropathy under 'eyes open' conditions, diminishing the contrast with the 'eyes closed' condition as assessed in the classical Romberg test. ConclusionWe conclude that the Romberg test, even in its quantitative form with the aid of an apparatus, had an unsatisfactory classification value in terms of distinguishing patients from healthy controls. Instead, it should be interpreted within the comprehensive context of the broader neurological examination and the electrodiagnosis of peripheral nerve function.

Effects of early monocular enucleation on cortical spreading depression in well-nourished and malnourished adult rats.

Sensory development is a complex process that can influence physiological and pathological factors. In laterally-eyed mammals, monocular enucleation (ME) during development and the subsequent lack of external sensory stimuli can result in permanent morphological and physiological changes. Malnutrition, especially in early life, also can cause permanent morphofunctional changes due to inadequate nutrient intake in both hemispheres. This study investigated the effects of early (postnatal day 7) ME and malnutrition during the suckling period on cortical excitability in adulthood (110-140 days of life). For this, we compared the speed propagation of cortical spreading depression in the occipital and parietal cortex of malnourished and well-nourished adult rats, previously suckled small-sized litters with three pups (L3/dam) medium-sized litters with six pups (L6/dam), and large-sized litters with twelve pups (L12/dam). The CSD velocity was augmented by the ME in the contralateral side of the removed eye in the parietal and occipital cortex. These findings suggest that visual sensory input deprivation is associated with permanent functional changes in the visual pathways, which can alter cortical excitability and lead to modifications in CSD propagation.

How does the Surgical Repair of Ptosis Impact Refractive Error?

ABSTRACT Purpose To identify a correlation between the degree of congenital ptosis and levels of refractive error, visual stimulus deprivation and anisometropic amblyopia, and any improvement with surgical intervention. Methods A prospective investigation of 30 patients aged 3 months to 8 years, with a diagnosis of unilateral or bilateral congenital ptosis. A full orthoptic assessment and cycloplegic refraction were performed and patients requiring surgical intervention for ptosis were at surgeon discretion. Results The mean age at presentation was 27.1 months. The prevalence of amblyopia ranged from 19 to 29%. There was no significant difference in the levels of astigmatism throughout the follow-up period between patients who underwent surgical intervention and who did not. There was a significant improvement in the visual acuity of the affected eye (p = .03) and both eyes open (p = .02), in patients who did not undergo surgery. This was then repeated on patients who underwent surgical intervention which showed no significant difference in the affected eye or both eyes open; p = .27, p = .32, respectively. Conclusion There is no significant change in the levels of astigmatism in both patients who underwent surgery and those who did not. Conservative management of congenital ptosis, while counterintuitive, proves not to deleteriously affect the visual potential of these patients.