ScienceDaily reports on a recent paper in Cell by R. Tomer and group (here) looks at the similarities between the vertebrate cortex and the mushroom bodies in insects and marine worms.
Using this new method, they found similarities that imply an evolutionary common ancestor (rather than independent evolution) of mushroom bodies and the pallium (cerebral cortex). The common ancestor would be living about 600 million years ago.
As well as having the similar cell types, developing in a similar way, it is interesting that mushroom bodies and palliums have similar functions.
It appears that the general pattern is: taking in sensory information and integrating it in sensory-associative areas, using this ‘perception’ to orientate movement, and learning/remembering its environment. This part of various brains is a good candidate to product whatever amount or degree of consciousness the animal possesses.