Biology subjects

Blaize, K.

Publications and source records attributed to Blaize, K..

4 recordsLinked to original sources

bioRxiv2021

In vivo optogenetic stimulation of the primate retina activates the visual cortex after long-term transfection

Over the last 15 years, optogenetics has changed fundamental research in neuroscience, and is now reaching toward therapeutic applications. Vision restoration strategies using optogenetics are now at the forefront of these new clinical opportunities. But applications to human patients suffering from retinal diseases leading to blindness rise important concerns on the long-term functional expression of optogenes and the efficient signal transmission to higher visual centers. Here we demonstrate in non-human primates, continued expression and functionality at the retina level [~]20 months after delivery of our construct. We also performed in-vivo recordings of visually evoked potentials in the primary visual cortex of anaesthetized animals. Using synaptic blockers, we isolated the in-vivo cortical activation resulting from the direct optogenetic stimulation of primate retina. In conclusion, our work indicates long-term transgene expression and transmission of the signal generated in the macaque retina to the visual cortex, two important features for future clinical applications.

neuroscience↗

bioRxiv2020

Monocular vision is intrinsically unstable: a side-effect of binocular homeostasis

It is now accepted that short-term deprivation of one eye in adults results in not only a post-deprivation strengthening of the vision in the previously deprived eye but also a deterioration in the vision of the previously non-patched eye. Such monocular deprivation of 1-2 hours induces changes that last approximately 30-90 minutes. There is some support for this neuroplastic effect being the consequence of a change in the contrast gain within the binocular circuity. What is not known is when these changes in gain are initiated. One possibility is that they are initiated only once the patch is removed. The other possibility is that they are the result of a slow build up from the moment the patch is first applied. In this study, we measure monocular contrast detection thresholds of the non-deprived eye over time during the deprivation of the other eye. We show that contrast threshold increases over time during the deprivation of the other eye. This observation suggest that the patching effect is mediated by a slow build up over the deprivation period: reducing the vision of the non-deprived eye and enhancing the vision of the deprived eye reflecting reciprocal changes in sensitivity. These results highlight a hitherto unknown feature of human vision, namely that monocular vision per se is intrinsically unstable which is a consequence of the reciprocal inhibitory circuits that homeostatically regulate binocular vision. This questions a whole corpus of studies of visual function that rely on the assumption that monocular vision is intrinsically stable.

neuroscience↗

bioRxiv2019

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

Deep regions of the brain are not easily accessible to investigation at the mesoscale level in awake animals or humans. We have recently developed functional Ultrasound (fUS) imaging fUS imaging technique to uncover deep hemodynamic functional responses. Applying fUS imaging on two awake non-human primates performing a passive fixation task, we reconstructed their retinotopic maps down to the deep calcarine and lunate sulci on visual areas (V1, V2 and V3). These maps were acquired in a single hour session with very few stimuli presentation. The spatial resolution of the technology is illustrated by mapping of Ocular Dominance (OD) columns within superficial and deep layers of the primary visual cortex. These acquisitions showed that OD selectivity is mostly present in layer IV but with evidence also in layers II/III and V. The fUS imaging technology therefore provides a new mesoscale approach to map brain activities at high spatiotemporal resolution in awake subjects within the whole depth of the cortex.

neuroscience↗

bioRxiv2018

Ultrasound functional neuroimaging reveals propagation of task-related brain activity in behaving primates

In recent decades, neuroimaging has played an invaluable role in improving the fundamental understanding of the brain. At the macro scale, neuroimaging modalities such as MRI, EEG, and MEG, exploit a wide field of view to explore the brain as a global network of interacting regions. However, this comes at the price of either limited spatiotemporal resolution or limited sensitivity. At the micro scale, electrophysiology is used to explore the dynamic aspects of neuronal activity with a very high temporal resolution. However, this modality requires a statistical averaging of several tens of single task responses. A large-scale neuroimaging modality of sufficient spatial and temporal resolution and sensitivity to study brain region activation dynamically would open new territories of possibility in neuroscience\n\nWe show that neurofunctional ultrasound imaging (fUS) is both able to assess brain activation during single cognitive tasks within superficial and deeper areas of the frontal cortex areas, and image the directional propagation of information within and between these regions. Equipped with an fUS device, two macaque rhesus monkeys were instructed before a stimulus appeared to rest (fixation) or to look towards (saccade) or away (antisaccade) from a stimulus. Our results identified an abrupt transient change in activity for all acquisitions in the supplementary eye field (SEF) when the animals were required to change a rule regarding the task cued by a stimulus. Simultaneous imaging in the anterior cingulate cortex and SEF revealed a time delay in the directional functional connectivity of 0.27 {+/-} 0.07 s and 0.9 {+/-} 0.2 s for animals S and Y, respectively. These results provide initial evidence that recording cerebral hemodynamics over large brain areas at a high spatiotemporal resolution and sensitivity with neurofunctional ultrasound can reveal instantaneous monitoring of endogenous brain signals and behavior.

animal behavior and cognition↗