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.

He developed a new technique, called cellular profiling by image registration (PrImR), which is the first to enable scientists to investigate a large number of genes in a compact brain and determine which are turned on simultaneously. This technique enabled Tomer to determine each cell’s molecular fingerprint, defining cell types according to the genes they express, rather than just based on their shape and location as was done before.

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.

This ancestral structure was likely a group of densely packed cells, which received and processed information about smell and directly controlled locomotion. It may have enabled our ancestors crawling over the sea floor to identify food sources, move towards them, and integrate previous experiences into some sort of learning.

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.