I think suggesting a single neurotransmitter system might underlie such a massive cognitive process is a little simplistic. I'm confident that 5-HT *mediates* error detection, probably via the 2Ar, 2Cr, and maybe a few others, but given how few neurons in the brain are actually serotonergic, I doubt they carry the whole load. I imagine that a lot of this is encoded structurally, rather than chemically.

I disagree with the association between attention and consciousness - I think the systems of attention may play a role in the particular quality of our consciousness, but I think, globally, the phenomena of consciousness is largely independent of attention (or any one particular cognitive process). I subscribe (broadly) to Tononi's theories so consciousness has a lot less to do with specific interacting cognitive tasks and more to do with how information is integrated on a cellular level.

Blessings

~ND