One can put a diffractive optical element infront of the sensor and obtain 25 instantaneous images, each at a different depth.

http://waf.eps.hw.ac.uk/research/live_cell_imaging.html

Couple this with high resolution techniques and your at the current research front and could possibly solve the question:

What happens in a synapse?

It is theoretically possible to image at 40nm resolution with 100fps and therefore see the transport of vesicles.

One can expect important discoveries on how the brain works using these techniques.