> Eleven of those genes, they discovered, were still active on one side of the animals’ brains but not on the other, even after the animals had apparently forgotten about the shock.

What exactly does active genes mean here and how can they do that in a living slug and be different on both sides? Afaik, genes are mostly constant throughout one individuals' lifetime, and usually the same in all cells

With almost a GB of data in the DNA of a single cell and 100 billion human brain cells, the DNA sounds like a great storage medium for memories (725 exabytes)! But that's not how it works, right?