Cortical functional architecture and local coupling between neuronal activity and the microcirculation revealed by in vivo high-resolution optical imaging of intrinsic signals.

TLDR

Small activity‑dependent changes in cortical intrinsic optical properties enable imaging of cortical functional architecture. The study introduces a higher‑resolution optical imaging system that surpasses existing techniques for mapping cortical functional architecture and monitoring local blood volume or oxygen saturation changes. The system provides sub‑millimeter spatial and millisecond temporal resolution, and the authors examined how sensory‑evoked intrinsic signals arise, including their wavelength dependence. High‑resolution imaging across 480–940 nm revealed cortical functional architecture and allowed noninvasive monitoring of sensory‑evoked blood volume and oxygen delivery changes, with 570 nm highlighting blood volume increases, 600–630 nm reflecting oxygen delivery, and oxygen delivery onset preceding blood volume rise.

Abstract

We have shown previously the existence of small, activity-dependent changes in intrinsic optical properties of cortex that are useful for optical imaging of cortical functional architecture. In this study we introduce a higher resolution optical imaging system that offers spatial and temporal resolution exceeding that achieved by most alternative imaging techniques for imaging cortical functional architecture or for monitoring local changes in cerebral blood volume or oxygen saturation. In addition, we investigated the mechanisms responsible for the activity-dependent intrinsic signals evoked by sensory stimuli, and studied their origins and wavelength dependence. These studies enabled high-resolution visualization of cortical functional architecture at wavelengths ranging from 480 to 940 nm. With the use of near-infrared illumination it was possible to image cortical functional architecture through the intact dura or even through a thinned skull. In addition, the same imaging technique proved useful for imaging and discriminating sensory-evoked, activity-dependent changes in local blood volume and oxygen saturation (oxygen delivery). Illumination at 570 nm allowed imaging of activity-dependent blood volume increases, whereas at 600-630 nm, the predominant signal probably originated from activity-dependent oxygen delivery from capillaries. The onset of oxygen delivery started prior to the blood volume increase. Thus, optical imaging based on intrinsic signals is a minimally invasive procedure for monitoring short- and long-term changes in cerebral activity.