A method for visually guided whole-cell recordings in brain slices exhibiting spontaneous rhythmic activity.

In vitro brain slice electrophysiology is a powerful method to investigate the network and cellular bases of brain function. Ideally, slices should be able to spontaneously express the ensemble rhythms that characterize the intact brain, but this is only rarely the case in the submerged configuration required for visualization of cells. In contrast, the interface configuration often preserves in vivo-like activity but does not allow optically guided whole-cell recording. Here we present a chamber design that, when used with a heated air objective, offers the experimenter the benefits of both visualization and the interface environment. The chamber is based on the design of the traditional Oslo-style interface chamber but modified to fit an upright microscope. Spontaneous slow (0.1-1 Hz) oscillations could be recorded extracellularly from slices of the rat somatosensory cortex with similar success, duration and frequency as the traditional interface chamber. Slow oscillations could also be readily recorded in the whole-cell configuration from visually selected pyramidal neurons. In hippocampal slices spontaneous gamma oscillations (20-80 Hz) were observed both extracellularly and in whole-cell recordings. The design presented here may be useful to the in vitro study of a range of brain circuits where the combination of visualization and spontaneous patterned network activity is desired.