  In the field of neuroscience, the importance of constructing closed-loop
experimental systems has increased in conjunction with technological advances
in measuring and controlling neural activity in live animals. This paper
provides an overview of recent technological advances in the field, focusing on
closed-loop experimental systems where multiphoton microscopy (the only method
capable of recording and controlling targeted population activity of neurons at
a single-cell resolution in vivo) works through real-time feedback.
Specifically, we present some examples of brain machine interfaces (BMIs) using
in vivo two-photon calcium imaging and discuss applications of two-photon
optogenetic stimulation and adaptive optics to real-time BMIs. We also consider
conditions for realizing future optical BMIs at the synaptic level, and their
possible roles in understanding the computational principles of the brain.
