Go study this and master the vocabulary. Everyone is so familiar with our brains with their parietal lobes and sulci and ganglia, but do people ever stop to contemplate the cephalopod brain? Nooooo. And it’s pretty cool.
Possibly the most obvious difference is that the nervous system of most invertebrates develops ventrally, rather than dorsally, like ours. Imagine that your nervous system formed on the other side of your throat, so that as the brain expanded, it had to wrap itself around your esophagus.