Monday question: Do neuromodulators have a unifying role?

We would never say that glutamate or GABA, the “basic” neurotransmitters, have a particular function. So why do attempt to give modulators like dopamine or oxytocin a defined role? Dopamine, for instance, is not only spread across the brain, but is also in the retina!

Or take oxytocin, “the love molecule”. It is not only involved in social behaviors but also cross-modal plasticity and modulating hippocampal fast spiking interneurons.

Do either dopamine or oxytocin – or any other neuromodulator for that matter – have a unifying function? Or did the brain evolve multiple independent uses for the modulators?

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3 thoughts on “Monday question: Do neuromodulators have a unifying role?

  1. Interesting question. One thought from the free energy minimization literature seems to be that each neuromodulator functions generally as a control on the precision of prediction errors, via synaptic gain control. So in top-down attention, acetlycholine controls precision, in reward it’s dopamine, in homeostatic vasodilation it’s perhaps oxtocin? The general scheme being the precision-weighting or salience of prediction errors within that ‘channel’.

    • Great comment –

      I was fairly unconvinced by dopamine having a unified role for a long time but I’m coming to believe in it more and more as time goes on. Surprisingly, my work on C. elegans has even reinforced that (having a small, tractable, discrete network does wonders for clarity of thought).

      I don’t know much about acetylcholine, but does that fit with its role in motor neurons or would that be a separate case?

      But oxytocin? Vasodilation doesn’t quite seem right. I think the only way to get a role out of it is to ignore the social side of things and think in terms of information processing; but I have no idea what the proper ‘channel’ would be for that.

      (Sorry if my post/comment has grammar errors, I have a massive head-cold right now and can’t think 100% =/ )

  2. I’ve seen Posner assign specific roles to neurotransmitters within attention systems: “…each of the networks has a dominant neuromodulator arising from subcortical brain areas. The alerting network is modulated by norepinepherine arising in the locus coeruleus, the orienting network by acetylcholine from the basal forebrain and the executive network by dopamine from the ventral tegmental area” (Posnter & Rothbart, 2009). Not that I buy this…

    See also Table 15.1 on p. 287 here, which includes lateralized norepinephrine:
    http://bit.ly/1brqtKr

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