Neuromodulation Through Multisensory Stimulation for Visual Field Deficits in the Subacute Stage of Disease

Condition(s) studied

Investigational drug(s) / intervention(s)

tDCS: Anodal or sham tDCS (see "Arms") is applied during the execution of an audio-visual training.

Audio-visual training: 90 min/day x 10 days. Participants are seated in front of a 2 m × 2 m training board, at a distance of 1.2 m, in a dimly lit room. The board features 48 red light-emitting diodes (LED, diameter 1 cm, luminance 90 cd m2), distributed in six horizontal rows (eight lights per row). Forty-eight piezoelectric loudspeakers (0.4 W, 8Ω) are located above each light, producing a white-noise (80 dB, duration 100 ms). Spatio-temporally congruent, cross-modal, audio-visual stimuli are presented at one out of 48 possible positions on the board. Participants are instructed to look at the fixation point - at the center of the apparatus - and to move their eyes to detect the presence of the visual stimulus (duration=100 ms) by pressing right button of a wireless mouse.

Study summary

Homonymous visual field defects (HVFDs) after acquired brain injuries affect daily life by impairing reading, navigation, and social activities, often impacting anxiety and depression. Spontaneous recovery is rare. Rehabilitation approaches include restorative treatments, which aim to expand the visual field through the stimulation of the so-called transition zone, and compensatory strategies, such as audio-visual training (AVT), which combines eye movement exercises with synchronized visual and auditory cues to train oculomotor scanning and overcome the visual field loss. Combining AVT with non-invasive brain stimulation, such as transcranial direct current stimulation (tDCS), may enhance recovery by promoting brain plasticity. Early evidence suggests that tDCS applied to the lesioned visual cortex during AVT can speed and stabilize improvements, potentially also restoring parts of the visual field. However, most studies on AVT have focused on chronic patients, whereas several clinical trials and international guidelines indicate that early treatment of HVFDs in the subacute phase can optimally exploit the window of maximal neural plasticity and prevent secondary degenerative processes, thereby maximizing visual recovery.

In the present randomized clinical trial, we assess the efficacy of a multisensory audio-visual training (AVT) combined with tDCS in patients with subacute HVFDs after stroke (\<3 months post-lesion). Participants are randomly assigned to two groups: AVT combined with real anodal tDCS applied to the lesioned occipital cortex (Group 1), or AVT combined with sham tDCS (Group 2).

The AVT requires participants to orient their gaze toward spatio-temporally congruent, cross-modal audio-visual stimuli (starting from a central fixation) and press a button as quickly as possible upon detecting the visual target. All stimuli are presented on 2mx2m panel embedded with 40 LEDs and loudspeakers (Diana, Casati, Melzi, Marzoli, et al., 2024). The training will be administered for 90 minutes daily over 10 consecutive days.

All participants underwent a neuro-ophthalmological evaluation and neuropsychological assessment of visuospatial functions before the beginning of the training (t0), at the end of the training (t1), at 2 months (t2) and after 1 year (t3).

Eligibility

Primary outcome measure(s)

• Change from baseline in Humphrey Visual Field perimetry — At baseline (at the beginning of the treatment), at the end of the treatment, at 2- and 12-month follow-ups
  Mean Deviation (MD) values of both eyes will be averaged and used for the analyses. Negative values will reflect a deviation from the expected performance in the participant's age group, hence a visual field defect.

Trial sites (1)

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