Can you please illuminate further. Yes, they are both parts of reverse engineering, but they represent different theoretical approaches, and, as when people bore a tunnel under a mountain, it's not always sure they'll meet in between.
Neural nets seem more conducive to a bottom-up approach, because they can start with sensory input.
So is sensorimotor robotics, which models input and output systems. Brain science itself is a bottom-up approach. Learning systems tend to be bottom-up. Symbol systems and computation in general are top-down approaches. Artificial Intelligence is a top-down approach.