In the Journal of Neuroscience, this article outlines how activity of neurons can be decoded into a reconstructed image.

"Stanley claims the decoding algorithm is simple since each point in space can be reconstructed at high resolutions from 6 to 8 pairs of cells. The more neurons are tracked, the higher the quality of the reconstruction. The following still frames from a video (top) are actual reconstructions (bottom) from the activity of 177 cells in a cat’s brain."

via Futurefeeder