M470l2 c2

Full-field illumination was performed using a 470 nm light-emitting diode (29 nm bandwidth LED; M470L2-C2; Thorlabs) delivered through the microscope illumination path including a custom dichroic in order to reflect the 470 nm activation wavelength. Light power densities were calculated by measuring the light transmitted through the objective using a power meter (Thorlabs PM100A with S142C sensor) and dividing by the illumination area, which was directly measured by placing an autofluorescent micrometer in the image plane and illuminating with the LED to measure the fluorescent area observed through the microscope eyepiece.

Whole-field illumination in vitro was performed using a 470 nm light emitting diode (29 nm bandwidth LED; M470L2-C2; Thorlabs) delivered through the microscope illumination path including a custom dichroic in order to reflect the 470 nm activation wavelength. Light power densities were calculated by measuring the light transmitted through the objective using a power meter (Thorlabs PM100A with S146C sensor) and dividing by the illumination area, calculated from the microscope objective field number and magnification^{66 (link)}. D-AP5 (25 µM; ab120003; Abcam) and CNQX (10 µM; C-141, Alomone) were bath applied during all culture experiments. For spatially restricted illumination of neuronal soma or neurites, a 473 nm diode laser (Bruker) was directed to the imaging plane with galvanometric mirrors, yielding a diffraction-limited spot of light that provided brief light pulses (1 ms) at each location, with 500 ms inter-pulse intervals between non-adjacent locations.