Spatial light modulator (SLM) two-photon imaging and photostimulation. (Ai) Arbitrary pattern of desired output from SLM in the shape of letters “HHMI”. (Aii) Pattern by SLM from a single circular input beam, projected through 60× 0.9NA objective into agar block filled with Alexa 488 fluorescent dye. (Bi) Similar to (Ai), however more complex desired output pattern of output from SLM in the shape of a patch clamped neuron. This image was thresholded and binarized to create a final output template. (Bii) SLM-created pattern projected into Alexa 488-filled agar block under 40× 0.8NA objective. (Ci) Basal dendrite from a layer 5 pyramidal neuron in an acute slice of mouse neocortex. The neuron is loaded with Alexa-488 and the slice bathed in MNI-glutamate. The SLM was used to create a diffraction pattern placing beamlets adjacent to individual spines of the dendrite (red dots). Pulses of excitation light delivered simultaneously at these points using the SLM triggered uncaging of MNI-glutmate. (Cii) Whole cell patch clamp recording at cellular soma of integrated potentials created by simultaneous uncaging at the spots indicated. Each horizontal trace represents a repetition of the stimulation and reveals the uncaging potentials recorded at the soma. (Di) Similar to (C), however now in a new neuron with uncaging targeted to locations near a dendritic shaft rather than near spines. (Dii) Patch clamp recordings of multiple trials of multi-point simultaneous uncaging revealing the uncaging potentials recorded at the soma. See Nikolenko et al. (2008) for more detailed description of the methods used for these recordings.