Mai tai ehp laser

Imaging of calcium transients was performed using a B-Scope two-photon microscope (Thorlabs, Inc, UK) controlled by ScanImage 4.1 software (http://scanimage.org). Excitation light was emitted by a Mai-Tai eHP laser (SpectraPhysics, UK; 70 fs pulse width, 80 MHz repetition rate) tuned to 930 nm. The beam was directed into a Conoptics modulator (laser power, as measured under the objective, was 15–30 mW) and scanned through an 8 kHz resonant scanner in the x-plane and a galvanometric scanning mirror in the y-plane. The resonant scanner was used in bidirectional mode, at a resolution of 512 × 512 pixels, allowing us to acquire frames at a rate of ~ 30 Hz for our most common zoom. A 16X/0.80W LWD immersion objective (Nikon, UK) was used, and emitted photons were guided through a 525/50 filter onto GaAsP photomultipliers (Hamamatsu Photonics, Japan). Neuronal fields were between 200 × 200 μm and 300 × 300 μm in size. Neuronal activity was imaged in ferrets at 176 ± 26.83 μm (median ± s.d.) below the cortical surface, corresponding to layer 2 (Dahmen et al., 2008 (link)). In mice, imaging was performed at 216 ± 34.21 μm below the pial surface, corresponding to layer 2/3 in this species (Anderson et al., 2009 (link)).