Functional ultrasound imaging of the spreading activity following optogenetic stimulation of the rat visual cortex

Abstract

Optogenetics has revolutionized neurosciences by allowing fine control of neuronal activity. An important aspect for this control is assessing the activation and/or adjusting the stimulation, which requires imaging the entire volume of optogenetically-induced neuronal activity. An ideal technique for this aim is fUS imaging, which allows one to generate brain-wide activation maps with submesoscopic spatial resolution. However, optical stimulation of the brain with blue light might lead to non-specific activations at high irradiances. fUS imaging of optogenetic activations can be obtained at these wavelengths using lower light power (< 2mW) but it limits the depth of directly activatable neurons from the cortical surface. Our main goal was to report that we can detect specific optogenetic activations in V1 even in deep layers following stimulation at the cortical surface. Here, we show the possibility to detect deep optogenetic activations in anesthetized rats expressing the red-shifted opsin ChrimsonR in V1 using fUS imaging. We demonstrate the optogenetic specificity of these activations and their neuronal origin with electrophysiological recordings. Finally, we show that the optogenetic response initiated in V1 spreads to downstream (LGN) and upstream (V2) visual areas.

Neural correlates of blood flow measured by ultrasound

“…Functional ultrasound imaging (fUSI) is an appealing method for studying brain function because it estimates changes in the cerebral blood volume with high resolution, resolving spatial features $100 mm in size to a depth of $2 cm (Deffieux et al, 2018;Edelman and Mace ´, 2021;Mace ´et al, 2011;Rabut et al, 2020). It is thus used to study how the activity of brain regions depends on sensory stimuli, internal state, and behavior in species ranging from mice (Aydin et al, 2020;Boido et al, 2019;Brunner et al, 2020;Ferrier et al, 2020;Koekkoek et al, 2018;Mace ét al., 2018;Sans-Dublanc et al, 2021) to rats (Bergel et al, 2018(Bergel et al, , 2020Gesnik et al, 2017;Mace ´et al, 2011;Osmanski et al, 2014;Provansal et al, 2021;Rahal et al, 2020;Sieu et al, 2015;Urban et al, 2015), to marmosets (Zhang et al, 2021), ferrets (Bimbard et al, 2018), and macaques (Blaize et al, 2020;Dizeux et al, 2019). In a small animal such as the mouse, fUSI can image the whole brain, yielding measurements that may parallel those obtained in humans with functional magnetic resonance imaging (fMRI).…”

Cranial and Spinal Window Preparation for in vivo Optical Neuroimaging in Rodents and Related Experimental Techniques

“…Optical imaging approaches have been used to investigate structural and functional brain connections in rodents. For example, the optical neuroimaging methods such as two- or multi-photon excitation (2PE or MPE) imaging [ 26 - 29 ], calcium-sensitive dye imaging (calcium imaging, CaSDI) [ 30 , 31 ], voltage-sensitive dye imaging (VSDI) [ 32 - 34 ], laser speckle contrast imaging (LSCI) [ 35 - 38 ], optical intrinsic signal imaging (OISI) [ 35 , 39 - 42 ], and ultrasound imaging (USI) combined with light [ 43 , 44 ] have been widely used. These techniques enabled the investigation of vascular and cellular structures, neuronal activation, blood flow, blood pressure, and oxygen saturation.…”

“…The type of cranial and spinal window can be decided based on the region of interest (ROI) to be examined with the microscope. Here we describe various types of cranial windows such as the olfactory bulb [ 18 , 60 - 64 ], somatosensory cortex [ 34 , 35 , 65 , 66 ], visual cortex [ 31 , 44 , 67 ], hippocampus [ 68 - 70 ], cerebellum [ 71 , 72 ], medial entorhinal cortex [ 73 ], and the spinal cord chamber window (SCCW) [ 21 - 23 ]. Fig.…”

Neural correlates of blood flow measured by ultrasound

“…fUSI is appealing because it estimates changes in cerebral blood volume with high resolution, resolving spatial features in the order of ~100 μm up to a depth of ~2 cm (Macé et al ., 2011). It is thus used to study how the activity of brain regions depends on sensory stimuli, internal state, and behavior, in multiple species including mice (Aydin et al, 2020; Boido et al, 2019; Brunner et al, 2020; Ferrier et al, 2020; Koekkoek et al, 2018; Macé et al, 2018; Sans-Dublanc et al, 2021), rats (Bergel et al, 2018; Bergel et al, 2020; Gesnik et al, 2017; Macé et al ., 2011; Osmanski et al, 2014; Provansal et al, 2021; Rahal et al, 2020; Sieu et al, 2015; Urban et al, 2015), marmosets (Zhang et al, 2021), ferrets (Bimbard et al, 2018), and macaques (Blaize et al, 2020; Dizeux et al, 2019). In a small animal like a mouse, fUSI can image the whole brain, yielding measurements that may parallel those obtained in humans with functional magnetic resonance imaging (fMRI).…”