Effects Of Optical Stimulation Research Articles

Optical Stimulation Effects on TiO2Sensor Dielectric Used in Capacitively-Coupled High-Density CMOS Microelectrode Array

The effect of optical stimulation of neural tissue is considered in capacitively coupled CMOS microelectrode arrays used for in vitro extracellular recording from neural tissue. Using a 25-nm high-k TiO2 sensor dielectric with 20% ZrO2, light-induced currents through the dielectric are found at short wavelengths within the visible and relevant spectrum for the above-mentioned purpose. Purely capacitive behavior is obtained for green light and longer wavelength, leakage-induced artifacts at shorter wavelengths are avoided by using optimized operating conditions of recording sites and entire system.

Striatal D1 medium spiny neuron activation induces dyskinesias in parkinsonian mice.

Dyskinesias are a disabling motor complication that arises with prolonged l-dopa treatment. Studies using D1 receptor drugs and genetically modified mice suggest that medium spiny neurons expressing D1 receptors play a primary role in l-dopa-induced dyskinesias. However, the specific role of these neurons in dyskinesias is not fully understood. We used optogenetics, which allows for precise modulation of select neurons in vivo, to investigate whether striatal D1-expressing medium spiny neuron activity regulates abnormal involuntary movements or dyskinesia in parkinsonian mice. D1-cre mice unilaterally lesioned with 6-hydroxydopamine received striatal injections of cre-dependent channelrhodopsin2 virus or control virus. After stable virus expression, the effect of optical stimulation on dyskinesia was tested in l-dopa-naïve and l-dopa-primed mice. Single-pulse and burst-optical stimulation of D1-expressing medium spiny neurons induced dyskinesias in l-dopa-naïve channelrhodopsin2 mice. In stably dyskinetic mice, l-dopa injection induced dyskinesia to a similar or somewhat greater extent than optical stimulation. Combined l-dopa administration and stimulation resulted in an additive increase in dyskinesias, indicating that other mechanisms also contribute. Molecular studies indicate that changes in extracellular signal-regulated kinase phosphorylation in D1-expressing medium spiny neurons are involved. Optical stimulation did not ameliorate parkinsonism in l-dopa-naïve mice. However, it improved parkinsonism in l-dopa-primed mice to a similar extent as l-dopa administration. None of the stimulation paradigms enhanced dyskinesia or modified parkinsonism in l-dopa-naïve or l-dopa-primed control virus mice. The data provide direct evidence that striatal D1-expressing medium spiny neuron stimulation is sufficient to induce dyskinesias and contributes to the regulation of motor control. © 2017 International Parkinson and Movement Disorder Society.

The effects of optical, electrical and chemical stimulation on serotonin release from median raphe and hippocampus of mice

The present study has examined several characteristics of the release of [3H]5-HT from the median raphe nucleus (MRN) and hippocampus in terms of its dependence of nerve impulse. We used electrical stimulation and the sodium channel opener veratridine, which excite all of the neuronal processes in the stimulation field, and optogenetics to selectively stimulate those terminals which express channelrhodopsin-2 (ChR2) and compared 5-HT release evoked by electrical and chemical depolarization and by light. We injected an adeno-associated virus containing DNA construct encoding ChR2 into the MRN of mice and investigated [3H]5-HT release from MRN and hippocampal slices. Serotonergic nerve terminals was locally stimulated with 473 nm light (blue laser diode) and electrically by bipolar electrode and by veratridine and transmitter release was monitored by collecting the effluent in a fraction collector. Electrical filed stimulation and veratridine resulted in a significantly increase in the efflux of 5-HT, whereas optical stimulation of ChR2 expressing nerve terminals at various frequencies (10, 20, 50, 100 Hz) elicited only a negligible increase in 5-HT release either from the hippocampus or from the MRN itself. The electrically induced release of radioactive neurotransmitter was completely inhibited by perfusion with tetrodotoxin. We have also applied the 5-HT transporter inhibitor, fluoxetine and the GABAA blocker bicuculline to relieve released 5-HT from re-uptake and any endogenous inhibition. Nevertheless, the effect of optical stimulation remained closed to the detection limit under these condition. In conclusion, whereas our method is suitable to detect [3H]5-HT efflux in response to ongoing neuronal sodium channel activity its sensitivity is too low to detect transmitter efflux evoked by focal optogenetic stimulation. The most likely reason for the failure of detection of 5-HT efflux is that ChR2 is expressed only by a small subpopulation of nerve terminals.

Illuminating Hippocampal Control of Fear Memory and Anxiety

Previous reports on dorsal and ventral hippocampal regulation of context learning versus anxiety have been mixed. In this issue of Neuron, a new study by Kheirbek etal. (2013) using optogenetics demonstrates that dentate gyrus granule cell activity in dorsal hippocampus encodes contextual fear learning while ventral granule cell activity regulates anxiety behavior.

In-body optical stimulation formed connective tissue vascular grafts, “biotubes,” with many capillaries and elastic fibers

The autologous biotube, developed by using in-body tissue architecture technology, is one of the most promising small-diameter vascular grafts in regenerative medicine. The walls of the biotubes obtained by a traditional silicone mold-based method were very thin, and this is still the primary obstacle while handling anastomosis, even though these biotubes have adequate pressure resistance ability. This pilot study showed the effect of optical stimulation of subcutaneous tissue formation in the body during the preparation of the biotubes. A blue light-emitting diode (LED) was embedded into a silicone rod as a mold. The biotube was prepared by placing the luminescent molds into the dorsal subcutaneous pouches of a pair of beagles (each weighing ~10kg) for 2weeks under photoirradiation. The wall thickness of the obtained biotubes was 506.9±185.7μm, which was remarkably more than that of the previous biotubes prepared by 2months of embedding similarly in beagles' subcutaneous pouches (thickness, 77.2±14.8μm). Many capillaries with smooth muscle cells were infiltrated into the wall and concentrated in the internal layer. Interestingly, the formation of elastic fibers had already started along with collagen fibers, mostly with a regular circumferential orientation. The short-term in-body optical stimulation resulted in the rapid formation of a biotube. These phenomena will allow easy surgical handling and may induce vascular maturation in histology during the acute phase after implantation.

Effects of photostimulation in natural zircon

Abstract Effects of optical stimulation were studied in unirradiated as well as in X, β and VUV irradiated natural zircon crystals. Various optical and dosimetric properties were investigated and in particular thermoluminescence (TL) and optically stimulated thermoluminescence (OSTL or PTTL), as well as optically stimulated luminescence (OSL). After X or β irradiation at RT, main TL peaks appeared in the samples at about 354, 385 K and weaker ones at about 470, 520 and near 600 K. TL could also be excited by monochromatic VUV radiation. Results show that the same traps are responsible for the TL induced by VUV as by X or β irradiation. In pre-irradiated samples, a notable OSTL was recorded below RT as well as at about 420 K. The same emission bands appeared in the XL as in various TL and OSTL peaks, indicating the same luminescence centers are involved in these emissions. OSTL stimulation spectra showed maxima at 425 and 294 nm. Prolonged illumination with these wavelengths also caused a notable decrease in the OSTL; this bleaching effect is attributed to the depletion of the carriers from the trap responsible for the phototransfer. The TL sensitivity of the main TL peaks below 400 K was ∼ 1 10 of that of TLD-100, and that of the higher temperature TL peaks was even lower by 1–2 orders of magnitude. The TL peaks below 400 K are subject to fast thermal fading at RT. The application of the OSTL method may therefore be preferable to the regular TL method in these crystals.

Analysis of microwave characteristics of photoconductive IC structures

A one-dimensional analytic solution for the microwave photoresponse of an optically modulated semiconductor channel is presented. This extends the existing treatments by including the effects of nonuniform channel cross sections and conductivity, nonuniform optical illumination, field-dependent mobilities, nonzero dielectric relaxation times, arbitrary electrical and optical excitation frequencies, and full coupled bipolar carrier transport. The solution is continuous over the full range of electric field intensities and thereby describes both the saturated and nonsaturated regimes of the photocurrent. Only the low-level generation case is considered, and trapping effects and diffusion are not included. This model allows the effects of optical stimulation in many typical IC structures to be assessed from dc up through the microwave range of frequencies.