Documentation of slice position

Has anybody an idea how to document the position of the brain slice at a MEA chamber, and how to integrate into MEA system? In the analysis, the exact position (= brain region) and each recorded signal should be correlated...thanks for any suggestion

Dear Kosmodrom,
usually the amplifier is placed on a microscope. Any cheap camera will do to document the position of the slice in relation to the electrodes.

Frank MCS