The VIBRANT (Vision Improvement through Behavioral Rehabilitation And Neuroplasticity Training) study is a prospective, double-blind, crossover design (within-subject) in participants with homonymous hemianopia-a type of visual field loss resulting from damage to the post-chiasmatic visual pathways. It aims to investigate whether transcranial random noise stimulation (tRNS) combined with perceptual learning-based training has potential for improving visual impairments.
At least 18 years of age.
Capable of providing informed consent and complying with study procedures.
Unilateral or bilateral focal brain damage causing loss of vision.
At least three months post-stroke or traumatic brain injury, or a stable brain tumor within the past year.
Severe CNS diseases or disorders unrelated to the focal lesion, which could interfere with study results.
Severe mental health challenges that could interfere with study results, or current or recent (within the past 6 months) drug or alcohol abuse or addiction as defined by DSM-5.
Vision loss resulting from ocular disease or disorder.
At least 18 years of age.
Crossover
transcranial random noise stimulation (tRNS)
DeviceStimulation location: bilateral human middle temporal complex (hMT+). Stimulation parameters: 1 mA current intensity, with a frequency range of 101-640 Hz.
Sham Stimulation
DeviceStimulation location: bilateral human middle temporal complex (hMT+). Stimulation parameters: Ramp up stimulation at 1mA with a frequency range of 101-640Hz for the first 30 seconds followed by no current for the remainder of the duration.
Perceptual learning-based training
BehavioralA motion discrimination task, judging the global direction of moving dot stimuli with two different coherence levels.
Change in Motion Discrimination Performance
Change in accuracy on a computerized motion direction discrimination task programmed in the lab. The task assesses participants' ability to discriminate the direction of the peripherally presented moving dots at two locations (one within the blind field and the other at a mirror-symmetric location in the intact visual field). Accuracy is defined as the proportion of correct responses out of the total number of trials completed.
Visual Field Change
Change in visual field function, assessed by perimetric mean deviation (PMD) measured using Humphrey perimetry. PMD is a global index representing the average deviation of visual field sensitivity compared to age-matched norms, measured in decibels (dB). More negative PMD values indicate greater visual field loss.
Visual Perception Change
Change in visual perception in the following two task: 1. Face/Object Recognition: identify whether a peripherally presented stimulus is a face or an object. 2. Motion Discrimination: discriminate the direction of the peripherally presented moving dots. Performance on both tasks will be measured at visual field locations targeted by brain stimulation and at control visual field locations not targeted by brain stimulation.
Quality of Life Change
Change in quality of life evaluated using the National Eye Institute 25 Item Visual Function Questionnaire (NEI-VFQ 25). Scores range from 0 to 100, with higher scores indicating better vision-related quality of life.
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