Cerebral Microcirculatory Blood Flow Dynamics During Rest and a Continuous Motor Task

Abstract

Objectives: To examine the brain’s microcirculatory response over the course of a continuous 5-min elbow movement task in order to estimate its potential role in grading vaso-neural coupling compared to the macrocirculatory response.Methods: We simultaneously recorded cerebral blood flow velocity (CBFV), changes in oxygenated/deoxygenated hemoglobin concentrations ([oxHb], [deoxHb]), blood pressure (BP), and end-tidal CO2 over 5-min periods of rest and left elbow movements in 24 healthy persons (13 women and 11 men of mean age ± SD, 38 ± 11 years). A low frequency range (0.07–0.15 Hz) was used for analysis by transfer function estimates of phase and gain.Results: Elbow movement led to a small BP increase (mean BP at rest 83 mm Hg, at movement 87; p < 0.01) and a small ETCO2 decrease (at rest 44.6 mm Hg, at movement 41.7 mm Hg; p < 0.01). Further, it increased BP-[oxHb] phase from 55° (both sides) to 74° (right; p < 0.05)/69° (left; p < 0.05), and BP-[deoxHb] phase from 264° (right)/270° (left) to 288° (right; p < 0.05)/297° (left; p = 0.09). The cerebral mean transit time at 0.1 Hz of 5.6 s of rest remained unchanged by movement. Elbow movement significantly decreased BP-CBFV gain on both sides, and BP-CBFV phase only on the right side (p = 0.05).Conclusion: Elbow movement leads to an increased time delay between BP and [oxHb]/[deoxHb] while leaving the cerebral mean transit time unchanged. Phase shifting is usually the more robust parameter when using a transfer function to estimate dynamic cerebral autoregulation; phase shifting at the microcirculatory level seems to be a better marker of VNC-induced changes than phase shifting between BP and CBFV.

In silico assessment of electrophysiological neuronal recordings mediated by magnetoelectric nanoparticles

“…5b, four magnetization maps across a cortical slice corresponding to t = 27 ms, 59 ms, 91 ms, and 119 ms). Nanoparticles injected intravenously travel through vasculature at speeds of 65 ± 12 cm/s 79 , with a diffusion coefficient of 48-15 µm 2 /s for sizes ranging from 10.4 to 32.0 nm 80,81 . We evaluated the signal arising from MENPs perfused through a cortical voxel at 650 µm/ms with a series of 40,000 Monte Carlo simulations of MENPs at the four network bursts originating from random coordinates in the x-z plane (y = 0) and propagating along the y axis over a 1.0 ms period centered at network burst peaks (Fig.…”

“…The simulation time step was 100 μs and the extracellular voltage was recorded with a resolution of 5 µm and 1 ms. Nanoparticle concentration was maintained at 27.495 μg/mL. 40,000 particles were normally distributed within the x-z plane (200 µm × 200 µm), with the particle movement modeled by a diffusion coefficient 81 D = 15 µm 2 /s and a perfusion velocity79 of 650 µm/ms.Received: 27 March 2022; Accepted: 9 May 2022…”