3D functional ultrasound imaging of the cerebral visual system in rodents

Abstract

3D functional imaging of the whole brain activity during visual task is a challenging task in rodents due to the complex tri-dimensional shape of involved brain regions and the fine spatial and temporal resolutions required to reveal the visual tract. By coupling functional ultrasound (fUS) imaging with a translational motorized stage and an episodic visual stimulation device, we managed to accurately map and to recover the activity of the visual cortices, the Superior Colliculus (SC) and the Lateral Geniculate Nuclei (LGN) in 3D. Cerebral Blood Volume (CBV) responses during visual stimuli were found to be highly correlated with the visual stimulus time profile in visual cortices (r=0.6), SC (r=0.7) and LGN (r=0.7). These responses were found dependent on flickering frequency and contrast, and optimal stimulus parameters for largest CBV increases were obtained. In particular, increasing the flickering frequency higher than 7 Hz revealed a decrease of visual cortices response while the SC response was preserved. Finally, cross-correlation between CBV signals exhibited significant delays (d=0.35 s +/−0.1 s) between blood volume response in SC and visual cortices in response to our visual stimulus. These results emphasize the interest of fUS imaging as a whole brain neuroimaging modality for brain vision studies in rodent models.

Acoustic biomolecules enhance hemodynamic functional ultrasound imaging of neural activity

“…2C). This protocol was designed to evoke responses in brain structures that are part of the visual system, namely the visual cortex, the superior colliculus and the lateral geniculate nucleus (LGN) (28). We selected our imaging plane to optimally capture the LGN and assess the subcortical imaging capabilities of enhanced fUS.…”

Functional ultrasound imaging of deep visual cortex in awake non-human primates

“…The solution is, when possible, to perpendicularly rotate or shift the probe within the recording chamber, to image the cortex with a different angle, allowing thereby to solve the spatial problem. A 3D reconstruction could thus be made like previously achieved with parallel imaging planes (Demené et al, 2016;Gesnik et al, 2017;Macé et al, 2018).…”

3D Functional Ultrasound Imaging of Pigeons

“…Using a stateof-the-art ultrasound research system and specialized image reconstruction algorithms (Kruizinga et al, 2012) powered by graphics processing unit (GPU) computing we realized the HDfUS acquisition scheme with a Power Doppler imaging frame rate up to several hundred Hz (corresponding to a data acquisition rate of ~3.3 GB/s continuously). This enables robust filtering of the heartbeat influence (see Supplementary Note 1 for a detailed analysis) and is at present unmatched in the field (Gesnik et al, 2017;Sieu et al, 2015). Along with the development of HDfUS, it was of major importance to establish a setup for pigeons that allows awake recordings with a robust fixation and provides ultrasound penetration of the brain tissue.…”

“…The high spatiotemporal resolution of every few seconds allows to resolve and monitor local blood volume changes due to neural activation inside specific brain areas of rodents (Macé et al, 2011). This method has been named functional ultrasound (fUS) and has led to several interesting functional studies, investigating the somatosensory (Macé et al, 2011;Osmanski et al, 2014;Tiran et al, 2017;Urban et al, 2014Urban et al, , 2015, visual (Gesnik et al, 2017) and olfactory (Osmanski et al 2014-2, Rungta et al, 2017 system of rats/mice along with discussions on functional connectivity (Osmanski et al, 2014;Urban et al, 2015), epilepsy (Macé et al, 2011;Sieu et al, 2015) and awake measurements Tiran et al, 2017;Urban et al, 2015). Very recently its applicability to brain microvasculature in human neonates was shown by revealing different sleep states and congenital cortical abnormalies (Demené et al, 2017).…”