Alcala, I. | Search bioRxiv

bioRxiv2026

From Functional Organization to Vascular Structure in the Primate Visual Cortex Using Ultrasound Imaging

The primary visual cortex (V1) provides an exceptional structure to assess information encoding in the cortex thanks to its highly controlled visual input. However, optical measures and electrophysiology are limited to very superficial layers while fMRI provides low spatial resolution. Taking advantages of functional ultrasound imaging (fUSi), we examined large volumes of V1 in two awake non-human primates. We showed the conservation of retinotopic maps within deep sulcal regions and across cortical layers. We then assessed the cortical point image and compared it to its vasculature distribution through ultrasound localization microscopy (ULM). We further identified the smallest vascular compartment underlying the signal. Together, these results establish fUSi, complemented by ULM, as a minimally invasive mesoscale approach for resolving functional organization of the cortex in deep sulci.

neuroscience↗

bioRxiv2021

Sonogenetic stimulation of the brain at a spatiotemporal resolution suitable for vision restoration

Remote, precisely controlled activation of the brain is a fundamental challenge in the development of brain-machine interfaces providing feasible rehabilitation strategies for neurological disorders. Low-frequency ultrasound stimulation can be used to modulate neuronal activity deep in the brain1-7, but this approach lacks spatial resolution and cellular selectivity and loads the brain with high levels of acoustic energy. The combination of the expression of ultrasound-sensitive proteins with ultrasound stimulation ( sonogenetic stimulation) can provide cellular selectivity and higher sensitivity, but such strategies have been subject to severe limitations in terms of spatiotemporal resolution in vivo8-10, precluding their use for real-life applications. We used the expression of large-conductance mechanosensitive ion channels (MscL) with high-frequency ultrasonic stimulation for a duration of milliseconds to activate neurons selectively at a relatively high spatiotemporal resolution in the rat retina ex vivo and the primary visual cortex of rodents in vivo. This spatiotemporal resolution was achieved at low energy levels associated with negligible tissue heating and far below those leading to complications in ultrasound neuromodulation6,11. We showed, in an associative learning test, that sonogenetic stimulation of the visual cortex generated light perception. Our findings demonstrate that sonogenetic stimulation is compatible with millisecond pattern presentation for visual restoration at the cortical level. They represent a step towards the precise transfer of information over large distances to the cortical and subcortical regions of the brain via an approach less invasive than that associated with current brain-machine interfaces and with a wide range of applications in neurological disorders.

neuroscience↗