Optical stimulation methods have been a staple of neuroscience research for a number of years, having been used extensively to study neuronal signaling in vitro, often at the synaptic level, and in vivo in behaving animals, although not at the cellular level.
This exciting paper out of Michael Häusser’s lab at University College London describes methods utilizing multiphoton microscopy to both optically record and optically stimulate at the cellular level in fields containing hundreds of cells that form neural circuits. A key piece of technology implemented in their instrumental configuration is the use of a spatial-light modulator to create precise patterns of light to simultaneously stimulate specific groups of cells and at the same time record their activity and the activity of neighboring cells.
In an interview the authors describe their methodology as being able to both read and write brain activity, opening up the door for experimental designs that allow conversations with the brains of behaving animals in order to unravel the mysteries of brain activity.