Optical sensory and motor mapping of mouse dorsal cortex

Throughout species, including mice and humans, we all have to make decisions to fulfill our fundamentals needs: eat, drink, explore, communicate, reproduce... To make those decisions, we have to collect informations from the surrounding world and to process them with our nervous system. The neocortex is the most distinctive feature of the brain as it is the substrate of high cognitive functions. One commonly used model to study the brain is the mouse. Mice can be genetically modified to express fluorescent reporters, or optogenetic actuators in their neurons. The questions I ask in this thesis are where and when specific sensory information is processed in the mouse cortex, and where and when these signals are integrated to generate to a motor command. First, I developed a protocol to get reliable sensory maps from wide-field optical intrinsic signal imaging. Mice undergo a surgical procedure to get a relatively transparent view of the left dorsal cortex. Then I sequentially repetitively stimulated different parts of the body of anesthetized mice to map the cortical sensory representation of each stimulated organ. I also successfully imaged optogenetically evoked responses by combining optogenetic experiment with wide-field optical intrinsic signal imaging. Second, I found the coordinates of the tongue/jaw primary sensory cortex tjS1 and of the tongue/jaw primary motor cortex tjM1. While I was mechanically stimulating tongue and jaw in anesthetized Thy1-GCaMP6f mice, I imaged the calcium signals evoked in the left cortical hemisphere with a wide-field fluorescence macroscope. Third, I recorded cortical activity of behaving mice performing a 2-whisker discrimination task with the wide-field calcium imaging technique. There was a large difference between hit and miss trials. The amplitude of the responses in S1, S2, M1 and M2 were decreasing over the days of training. The earliest difference between hit and miss response occurred in S1 and S2 after 100 ms. Then the signals converged toward M2 where the amplitude of the response was amplified to lead to a lick command. Finally, I optogenetically stimulated the cortex of awake mice and I measured the evoked whisker movements to obtain whisker motor maps. I found that almost the entire cortex can evoke whisker movement. The earliest evoked movement occurred when S1 was stimulated, the contralateral whisker had a prolonged retraction. Then the ipsilateral whisker started large rhythmic protractions. When M1 was stimulated, it triggered the most protracted whisker movement of rhythmic protractions. The largest oscillating protraction was observed when the parietal association area (PtA) was stimulated. These data suggest that neuronal information needed to perform even simple tasks requires distributed cortical areas to process sensory inputs, like passive whisker deflection or optogenetic stimulation, and in return generate motor outputs, like licking or whisking. Future experiments must investigate the complex neuronal circuits connecting specific cell- types in various cortical regions using wide-field calcium imaging and combine it with optogenetic manipulations of this network at specific times and brain regions

Review of patient-specific simulations of transcatheter aortic valve implantation

International audienceTranscatheter Aortic Valve Implantation (TAVI) accounts for one of the most promising new cardiovascular procedures. This minimally invasive technique is still at its early stage and is constantly developing thanks to imaging techniques, computer science, biomechanics and technologies of prosthesis and delivery tools. As a result, patient-specific simulation can find an exciting playground in TAVI. It canexpress its potential by providing the clinicians with powerful decision support, offering great assistance in their workflow. Through a review of the current scientific field, we try to identify the challenges and future evolutions of patient-specific simulation for TAVI. This review article is an attempt to summarize and coordinate data scattered across the literature about patient-specific biomechanical simulation for TAVI

Diffuse laser illumination for Maxwellian view Doppler holography of the retina

We describe the advantages of diffuse illumination in laser holography for ophthalmology. The presence of a diffusing element introduces an angular diversity of the optical radiation and reduces its spatial coherence, which spreads out the energy distribution of the illumination beam in the focal plane of the eyepiece. The field of view of digitally computed retinal images can easily be increased as the eyepiece can be moved closer to the cornea to obtain a Maxwellian view of the retina without compromising ocular safety. Compliance with American and European safety standards for ophthalmic devices is more easily obtained by preventing the presence of a laser hot spot observed in front of the cornea in the absence of a scattering element. Diffuse laser illumination does not introduce any adverse effects on digitally computed laser Doppler images.Comment: 9 page

Perpendicular switching of a single ferromagnetic layer induced by in-plane current injection

International audienceModern computing technology is based on writing, storing and retrieving information encoded as magnetic bits. Although the giant magnetoresistance effect has improved the electrical read out of memory elements, magnetic writing remains the object of major research efforts. Despite several reports of methods to reverse the polarity of nanosized magnets by means of local electric fields and currents, the simple reversal of a high-coercivity, single-layer ferromagnet remains a challenge. Materials with large coercivity and perpendicular magnetic anisotropy represent the mainstay of data storage media, owing to their ability to retain a stable magnetization state over long periods of time and their amenability to miniaturization. However, the same anisotropy properties that make a material attractive for storage also make it hard to write to. Here we demonstrate switching of a perpendicularly magnetized cobalt dot driven by in-plane current injection at room temperature. Our device is composed of a thin cobalt layer with strong perpendicular anisotropy and Rashba interaction induced by asymmetric platinum and AlOx interface layers. The effective switching field is orthogonal to the direction of the magnetization and to the Rashba field. The symmetry of the switching field is consistent with the spin accumulation induced by the Rashba interaction and the spin-dependent mobility observed in non-magnetic semiconductors as well as with the torque induced by the spin Hall effect in the platinum layer. Our measurements indicate that the switching efficiency increases with the magnetic anisotropy of the cobalt layer and the oxidation of the aluminium layer, which is uppermost, suggesting that the Rashba interaction has a key role in the reversal mechanism. To prove the potential of in-plane current switching for spintronic applications, we construct a reprogrammable magnetic switch that can be integrated into non-volatile memory and logic architectures. This device is simple, scalable and compatible with present-day magnetic recording technolog