The novel phenomenon of inter-retinal coupling predicts cortical neurovascular responses in health and disease

It has recently been discovered that physiological crosstalk exists between human retinas. Accordingly, visual stimulation of one retina elicited a neurovascular coupling (NVC) response of the contralateral retina in about 30% of individuals. The functional significance of this feature in health and disease remains unknown. Here, we asked the question whether inter-retina crosstalk predicts the nature of neurovascular coupling in the brain. To test this hypothesis, we assessed BOLD fMRI (blood-oxygen-level-dependent functional magnetic resonance imaging signal) in healthy individuals and a disease model of neurovascular coupling, type 1 diabetes. We used three visual paradigms: a Threshold speed and Sub-maximum speed discrimination tasks, and flicker stimulation. The presence or absence of inter-retinal coupling was predictive of the time course of the cortical hemodynamic response, either during the initial or late phases. The presence of interocular coupling predicted larger BOLD responses. Diabetic patients with interocular coupling showed a very similar profile to the healthy group. In sum, we identified a direct relationship between interocular physiological coupling and cortical hemodynamic responses, suggesting that this NVC response may serve as a disease biomarker in diabetes.