Fig. 1. Proximity of imaging setup to optical chamber.

A 50mm/85mm tandem lens with a ring illuminator attached provides 540 nm illumination to the optical chamber. Often, the distance between the imaging chamber and the imaging lens setup is small (<0.5 cm), making placement of microelectrodes difficult. Furthermore, in awake animals or in repeat anesthetized imaging chambers, it is often convenient to be able to record optically without introduction of electrodes into the field of view.