Junyu Wang¹, Dorita H F Chang¹; ¹The University of Hong Kong

Sensory eye dominance (SED) is characterized by an uneven weighting of visual inputs from the two eyes by the brain. It is well-speculated that SED is driven by mechanisms at primary visual cortex (V1). Here, we compared the effects of brain stimulation in the form of continuous theta burst stimulation (cTBS) and intermittent theta burst stimulation (iTBS) over V1 (and control site, Cz) on SED. We also investigated the effects of iTBS/cTBS stimulation on an important functional outcome of binocular vision: stereoacuity. Participants were tested in three phases: Pre-stimulation tests, stimulation delivery, and post-stimulation tests. During both the pre- and post-tests, participants completed two computer-based tasks: a dichoptic global motion task to index SED and a fine depth discrimination task to index stereoacuity. Depending on the group assigned to them, participants received stimulation in the form of cTBS (40s, 600 pulses) or iTBS (190s, 600 pulses) over neuronavigated V1 (localized via phase-encoded retinotopy), or Cz. We found that iTBS resulted in a significant decrease in SED. iTBS over Cz, nor cTBS over both V1 and Cz did not change SED between the pre- and post-tests. Furthermore, stimulation in both forms and all locations did not affect stereoacuity. Our data suggest that V1 is a key locus for driving SED. We speculate that iTBS may alter SED through counteracting interocular inhibition via its posited facilitatory effects. The ability to reduce SED has potential implications for clinical interventions aimed at ameliorating visual imbalances.

Acknowledgements: This work was supported by a General Research Fund [17610022] from the University Grants Committee (Hong Kong) to D.C.