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Tag Archives: Therapeutics
Sensory information is typically represented in distributed patterns of activity across large populations of neurons. Therefore, many emerging neuro-photonic applications, such as optogenetic retinal prostheses require systems capable of delivering intense, parallel and dynamic light patterns. Such a system will ideally allow photo-control with single-cell selectivity of large neural populations expressing optogenetic probes, rather than nonspecific flashed illumination of the whole population (as provided by many current optogenetic light delivery systems). In a recent Nature Communications report, Reutsky-Gefen, Shoham and colleagues demonstrate holographic optogenetic control of retinal neural activity which is shown to provide rapid cellular-resolution, massively parallel excitation across macroscopic (millimeter-scale) coverage areas. The study illustrates that diffractive wavefront shaping (holographic) tools offer a powerful modality for dynamic patterned photo-stimulation as they naturally combine the high intensity, efficiency and resolution that are characteristic of sequential laser deflectors (like acousto-optical deflectors) with the simultaneous scan-less parallel illumination of multiple locations of microdisplay array projectors, but without their respective limitations. Holographic tools were previously shown to allow structured excitation of dendritic arbors and neurons using neurotransmitter photolysis, as well as two-photon optogenetic stimulation of proximal neurons in brain slices.
The study’s main goal was to develop a prosthetic system that would … Continue reading
Unlike electrical stimulation, optogenetics allows neuronal manipulation with great cell-type specificity, with light directly affecting only those cells expressing opsins. In a recent report in Nature Communications, Krook-Magnuson et al harnessed this specificity to stop seizures in vivo in a mouse model of temporal lobe epilepsy. Mice were implanted with electrodes to record brain activity and 200µm thick optical fibers to deliver light to the brain. A closed-loop, on-demand responsive system detected seizures in real time, allowing temporal specificity, in addition to the cell-type specificity achieved through selective opsin expression. Specifically, the authors either selectively inhibited excitatory principal cells or, alternatively, excited a subpopulation of GABAergic inhibitory neurons in the hippocampus by delivering light at the time of a seizure. Both approaches proved successful, despite the less than 5% of illuminated neurons expressing opsins in the latter approach. Light arrested ongoing electrical seizure activity and reduced the incidence of events progressing to overt behavioral seizures.
Epilepsy, a condition of recurrent, spontaneous seizures, is a prevalent disorder, with 1 out of 26 people developing epilepsy during their lifetime. Unfortunately, for over 40% of patients, seizures cannot be controlled with current treatment options. Temporal lobe epilepsy, the most common form of epilepsy … Continue reading