Restoring vision in adult amblyopia by enhancing plasticity through deletion of the transcriptional repressor REST

A Systematic Review and Meta-Analysis of Perceptual Learning and Video Game Training for Adults with Monocular Amblyopia

INTRODUCTION

Amblyopia is a neurodevelopmental disorder characterized by a reduction in best-corrected visual acuity (BCVA). This meta-analysis aimed to analyze the effectiveness of perceptual learning and video game training for adults with amblyopia.

METHODS

Following Cochrane guidelines (PROSPERO CRD42024504502), we conducted a systematic search across multiple databases. Randomized controlled trials (RCTs) on adults with amblyopia receiving behavioral therapies were included. Data on interventions, sample size, and logMAR visual acuity were extracted and analyzed using Review Manager 5.4 and Stata 17.0.

RESULTS

A total of 6439 studies were identified, with 22 meeting the inclusion criteria after screening. The meta-analysis included 422 adult patients with amblyopia across these studies. Quality assessment revealed that 78% of studies had a low risk of bias. The analysis showed a statistically significant standardized mean difference (SMD) of -0.68 in the experimental group compared with controls, indicating an improvement in visual acuity (P < 0.05). Subgroup analyses indicated that perceptual learning and video game training also resulted in visual improvement (P < 0.05). In addition, the results indicated a significant improvement in visual acuity with dichoptic training or monocular training, reaching visual acuity improvement (P < 0.05).

CONCLUSIONS

These findings indicate that targeted visual training facilitates neural plasticity, reduces interocular suppression, and reinforces neural pathways associated with visual processing. While video game-based interventions represent a viable and engaging rehabilitation strategy, a combined approach may be most effective in enhancing monocular and binocular functions. Future research should focus on refining training protocols to enhance both monocular and binocular visual function more effectively.

Homeostatic regulation of brain activity: from endogenous mechanisms to homeostatic nanomachines

After the initial concepts of the constancy of the internal milieu or homeostasis, put forward by Claude Bernard and Walter Cannon, homeostasis emerged as a mechanism to control oscillations of biologically meaningful variables within narrow physiological ranges. This is a primary need in the central nervous system that is continuously subjected to a multitude of stimuli from the internal and external environments that affect its function and structure, allowing to adapt the individual to the ever-changing daily conditions. Preserving physiological levels of activity despite disturbances that could either depress neural computation or excessively stimulate neural activity is fundamental, and failure of these homeostatic mechanisms can lead to brain diseases. In this review, we cover the role and main mechanisms of homeostatic plasticity involving the regulation of excitability and synaptic strength from the single neuron to the network level. We analyze the relationships between homeostatic and Hebbian plasticity and the conditions under which the preservation of the excitatory/inhibitory balance fails, triggering epileptogenesis and eventually epilepsy. Several therapeutic strategies to cure epilepsy have been designed to strengthen homeostasis when endogenous homeostatic plasticity mechanisms have become insufficient or ineffective to contrast hyperactivity. We describe "on demand" gene therapy strategies, including optogenetics, chemogenetics, and chemo-optogenetics, and particularly focus on new closed loop sensor-actuator strategies mimicking homeostatic plasticity that can be endogenously expressed to strengthen the homeostatic defenses against brain diseases.

Interactions between excitatory neurons and parvalbumin interneurons in V1 underlie neural mechanisms of amblyopia and visual stimulation treatment

As the main cause of visual function deficits in children and adolescents worldwide, amblyopia causes serious impairment of monocular visual acuity and stereopsis. The recovery of visual functions from amblyopia beyond the critical period is slow and incomplete due to the limited plasticity of the mature cortex; notably, visual stimulation training seems to be an effective therapeutic strategy in clinical practice. However, the precise neural basis and cellular mechanisms that underlie amblyopia and visual stimulation treatment remain to be elucidated. Using monocular deprivation in juvenile mice to model amblyopia, we employed two-photon calcium imaging and chemogenetic techniques to investigate the visual responses of individual excitatory neurons and parvalbumin (PV+) interneurons in the primary visual cortex (V1) of amblyopic mice. We demonstrate that amblyopic mice exhibit an excitation/inhibition (E/I) imbalance. Moreover, visual stimulation decreases the response of PV+ interneurons, reactivates the ocular dominance plasticity of excitatory neurons, and promotes vision recovery in adult amblyopic mice. Our results reveal a dynamic E/I balance between excitatory neurons and PV+ interneurons that may underlie the neural mechanisms of amblyopia during cortical development and visual stimulation-mediated functional recovery from adult amblyopia, providing evidence for therapeutic applications that rely on reactivating adult cortical plasticity.