Figure 1.

Schematic of the experiment. (a) A 3D visualization of a cortical brain slice (adapted and modified from Ramón y Cajal, 1909; Courtesy of the Cajal Institute-CSIC, Madrid, Spain ©CSIC), showing the organization of the neuropile. (b) Uncorrected light is scattered as it enters the brain tissue thus broadening the focus. (c) The spatial light modulator is encoded with a corrective wavefront to compensate the aberrations introduced by the tissue, resulting in a sharp focus. In (b,c) the focus at the back of the sample is imaged by a camera. (d) The corrected focus within the sample allows for optimal photostimulation with the neuronal response recorded by the glass electrode. A representative image of the focus as viewed from the camera: (e) A broadened focus; (f) Restored focus after encoding a corrective wavefront on the laser.