Abstract
When retinal activity is increased by exposure to dynamic visual stimuli, blood vessels dilate and the flow of blood within vessels increases to meet the oxygen and glucose demands of the neurons. This relationship is termed ‘neurovascular coupling’ and it is critical for regulating control of the human retinal vasculature. In this study, we used a recently developed technique based on a dual-beam adaptive optics scanning laser ophthalmoscope to measure changes in red blood cell velocities, vessel diameter, and flow in interconnected small parafoveal retinal vessels (< 50 µm) of nine healthy participants. A full-field flicker stimulus was presented onto the retina to induce a vascular response to neural activity. Flicker stimulation increased blood velocity, vessel diameter, and therefore flow in arterioles, capillaries, and venules in all nine subjects. ANOVA and post hoc t-test showed significant increases in velocity and flow in arterioles and venules. These measurements indicate that the mechanism of neurovascular coupling systematically affects the vascular response in small retinal vessels in order to maintain hemodynamic regulation in the retina when exposed to visual stimulation, in our case flicker. Our findings may provide insight into future investigations on the impairments of neurovascular coupling from vascular diseases such as diabetic mellitus.
Highlights
When retinal activity is increased by exposure to dynamic visual stimuli, blood vessels dilate and the flow of blood within vessels increases to meet the oxygen and glucose demands of the neurons
In the current paper we investigate the ability of this dual-beam imaging approach[29], to measure activity induced changes in red blood cell (RBC) velocity in small arterioles, venules, and capillaries (< 50 μm) as well as changes in vessel diameter, and in RBC flow using a full-field flicker stimulus under three conditions: before flicker stimulation, during flicker stimulation, and after flicker stimulation
For the duration of the full-field flicker stimulus, the average RBC velocity increased by 10% for arterioles (± 2% standard error of the mean), 15% for capillaries (± 7% standard error of the mean), and 12% for venules (± 2% standard error of the mean)
Summary
When retinal activity is increased by exposure to dynamic visual stimuli, blood vessels dilate and the flow of blood within vessels increases to meet the oxygen and glucose demands of the neurons. ANOVA and post hoc t-test showed significant increases in velocity and flow in arterioles and venules These measurements indicate that the mechanism of neurovascular coupling systematically affects the vascular response in small retinal vessels in order to maintain hemodynamic regulation in the retina when exposed to visual stimulation, in our case flicker. Second the vasculature of the retina is arranged in multiple layers[16] with relatively few connections that carry blood axially from inner to outer layers or vice versa This laminar organization of the retinal vasculature allows optical modalities to capture flow at vessel sizes down to capillaries using two-dimensional imaging, without the need to track cells in 3D and humans can be measured noninvasively without anesthesia.
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