Dc2200

For these experiments, we used slices prepared from animals that expressed Channelrhodopsin 2 in PV-FS interneurons. These animals were obtained by crossing Pvalb^tm1(cre)Arbr mice with Ai32(RCL-ChR2(H134R)/EYFP) mice. In cortical slices from these animals the PV expressing neurons (which express EYFP and Channelrhodopsin 2) were identified under fluorescence epi illumination. To depolarize these neurons up to the action potential firing we used pulses of blue light (470 nm) generated by a LED light source (SOLIS 1C-from Thorlabs, New Jersey, USA) and controlled by a high-power LED driver (DC2200 from Thorlabs, New Jersey, USA). The blue light was applied to the slice through the epi-illumination system of the microscope and the 40× water immersion objective, which resulted in the stimulation of the whole view of field of the objective. We used pulses of ~ 55% of the maximum power of the light source.

Current density-voltage (J-V) characteristics were measured using a Keithley 4200 Source-Measure unit (scan rate of 25 mV s⁻¹). An Oriel Instruments Solar Simulator with a Xenon lamp and calibrated to a silicon reference cell was used to provide AM1.5G irradiance. For determination of the LDR, a neutral white light LED driven by a function generator (Thorlabs, DC2200) was used. The LED light was attenuated using a selection of neutral density filters placed between the lamp and OPD. The photocurrent (J_ph) was calculated as the difference in response between the illuminated current density (J_L) and dark current density (J_d) at each light intensity. All the devices were tested in nitrogen atmosphere.

A white LED (MNWHL4, Thorlabs) powered by an LED driver (DC2200, Thorlabs) was used to randomly generate stray light during imaging, as shown in fig. S8. The LED driver was externally triggered by an analog output device (PCI-6711, National Instruments) installed on the computer. While raster scanning the object prepared on the microscope slide, at each pixel, the LabVIEW program generated a random number uniformly distributed between 0 and 1 to determine whether to trigger the white LED to output stray light. If the random number was less than 0.2, the LED was triggered to generate stray light; otherwise, no stray light would be generated. Therefore, approximately 20% of the pixels would be disrupted by stray light. To evaluate how robust the classical imaging and ICE were against stray light, we acquired images under different stray light optical powers. We calculated the SSIM between each image and the ground truth at zero stray light by $\text{SSIM}=4{\mathrm{\mu }}_1{\mathrm{\mu }}_2{\mathrm{\sigma }}_{12}/(({\mathrm{\mu }}_1^2+{\mathrm{\mu }}_2^2)({\mathrm{\sigma }}_1^2+{\mathrm{\sigma }}_2^2))$  , where μ_i and ${\mathrm{\sigma }}_i^2$ (i = 1 or 2) are the average and variance of each image, respectively, and σ₁₂ is the covariance of the two images (55 (link)). We used SSIM as the figure of merit because it aligns well with human visual perception, provides robust and accurate assessments, and is versatile across a wide range of applications and different reference availability situations (55 (link)).

We recorded 2-s bright-field videos (10 frames per second) of microdevice
cocultures with an inverted fluorescence microscope (Olympus X73). Optogenetic
stimulation was carried by illumination of the microdevice cultures for 500 ms
at 100% LED intensity with an optical fiber–coupled 470-nm LED light
source (Thorlabs, M470F3) controlled by a LED driver (Thorlabs, DC2200). The
light guide was positioned 1 cm above the microdevice, and the light intensity
at this distance was 0.2 mW/mm², which is sufficient to trigger
action potentials in ChR2-expressing neurons (63 (link)). Myofiber contraction velocity
was measured as area displacement between successive video frames by PIV with
the PIVlab package (30 ) within MATLAB (MathWorks) as described in (18 (link)).

Mice received photostimulation beginning on the 7th day post-PT surgery. Stroked mice were placed in an empty cage to allow for free movement with the laser cable connected to the fiber cannula. One session of stimulation consisted of three 1 min stimulations separated by 3 min rest intervals. All of the mice, including the sham-stimulated stroked mice, received daily (7 days/week) stimulations for 2 weeks post-stroke. In the ChR2 gene expression group, a 473 nm blue laser was controlled by a driver (Thorlabs, DC2200), and mice were stimulated with a laser set to 10 Hz, with 20 msec light pulses. In the NPHR gene expression group, a 594 nm yellow laser was controlled by the same driver as above, whereas mice were stimulated with direct current. The laser power operated with a range of 1.2-1.4 mW, which was measured by a power meter before implantation. Stimulations were performed in the morning between 12:00 and 13:00. Sham stimulation (SS) was conducted without turning on the laser.
The day after the final behavioral test, mice were anesthetized and then transcardially perfused with 4% paraformaldehyde. The regions of virus injection were confirmed under a fluorescence microscope. Data from mice with an absence of ChR2 or NPHR gene expression were excluded from the group.

As shown in Fig. 4a, the green and blue LED sources were equipped with the polarised optical microscope. For GL irradiation (525 nm), light from the LED source was passed inside of the microscope via a silver mirror, reaching the LC sample mounted on the hot stage (HCS402+mk2000 equipped with LN2-PACD2, INSTEC). In the case of BL irradiation (415 nm), the silver mirror was removed and shined a light on the LC sample directly. Unless otherwise noted, polarised optical microscopy and dielectric spectroscopy were performed simultaneously under this irradiation setup. Polarised optical microscopy and dielectric spectroscopy under a magnetic field were carried out using room temperature bore superconducting magnet systems (9 Tesla, Cryogenic). The measurement system is shown in Supplementary Fig. 7a, b. For Polarised optical microscopy under a magnetic field, we used a handmade hot stage (ITO glass heater); measurement temperature was controlled using a regulated DC power supply (PA18-6A, Kenwood) and monitored via a handmade temperature monitor. For dielectric spectroscopy under a magnetic field, a LED driver (DC2200, Thorlabs) and a white LED (MCWHLP1, Thorlabs) as a back-light and a camera (Powerpack, Basler) for microscopy were used.