Tuesday, May 26, 2009

"Motivation": Cortex vs. Limbic System

I speculate that dopamine affects how easy or hard it is to initiate activities. This particularly seems to affect activities requiring significant energy, like exercise, and/or decision making, like planning a trip or moving. I introduced this idea a little bit in an earlier blog post.

I found that when I was dopamine deficient, I couldn't initiate exercise myself. I could tag along if someone else initiated it though, and feel better during and after. A woman from my church invited me to go walk with her on Tuesday mornings, and I could do that. My husband and I joined a twice weekly yoga class, and I could go to that.

It seemed silly to me that I couldn't initiate these sorts of things myself. In the past I treated this as a moral failing, and beat myself up about it. That made me feel awful, but I still mostly wouldn't be able to do it. This most recent time I was more accepting about it. I still tried to convince myself to go exercise, but was more gentle about it. Sometimes I would succeed in going and exercising by myself, but mostly I wouldn't. Instead of treating it as a moral failing, I treated it as a science experiment. What was different about the times when I was able to go and exercise?

Once I got the dopamine increased enough I could mostly initiate exercise by myself no problem. It wasn't that I was trying harder, or being more morally upright. It just felt like a road block that had been there was just gone.

When I studied more about dopamine, and what affects it, I realized that dopamine levels seemed to correspond to how easy or hard it was to initiate that sort of activity. When dopamine levels were mostly low, I would only be able to do it as a follower or after some sort of experience that sufficiently increased dopamine. Now that dopamine levels are mostly ok (got the bupropion working right), I can initiate exercise myself most of the time, except after experiences that sufficiently decrease dopamine.

All this made me realize that the concept we call "motivation" really has more facets than I'd realized before. What you think about how much you "should" do something, how much you want to do it, and what you think about where it ranks in your priority and value schemes are one set of factors. How you feel when your think about doing something -- how your biochemistry reacts to the idea -- is another. They're controlled by different parts of your brain (cortex vs. limbic system), and are not always in sync.

I suspect that the latter part is the one that's more tied into physiological state -- how much dopamine, energy, etc. you've got to start with and how those change in reaction to your proposed activity, like exercise. It can agree and reward you with an added burst of dopamine, which makes it real easy and appealing to go off and initiate the activity. It can also disagree and make you feel uneasy about it (not sure if this is it decreasing dopamine, increasing stress chemicals, or both), and make it real hard.

It seems to me that in some cases the meaning of "motivation" is pretty clear:
  • Motivated = cortex decides to do it, limbic system agrees, you do it
  • Unmotivated = cortex decides not to do it
However, what do we say about the case where the cortex decides to do it but the limbic system disagrees? Generally this is where things gets tough and we are prone to beat ourselves up. I bet we end up in this state more often when dopamine is low. I also bet that when dopamine is low and we end up in this state, we're much less likely to be able to force ourselves to initiate the activity anyway. Here's the trap: the way we think about failing to initiate activities like this can further decrease dopamine, making it even harder next time.

I certainly find myself in that state much less often now. For a few months, before using the bupropion to increase dopamine tone, I was in that state almost all the time. I exercise much more often now than I did then. I don't actually decide to exercise any more often -- likely I decide to do it less frequently. The difference is that now it's much easier to follow through on that decision. Does that reflect a difference in "motivation" or not?


  1. I have been treated with antidepressants for years. Recently, Abilify was added to the mix as a catalyst for the other drugs. I have been experiencing lack of focus and concentration, difficulty following through and making decisions and worst of all, a complete lack of enthusiasm for all the things which once gave me great pleasure, like painting and writing. I have ben told Abilify decreases the production of dopamine. Please, can anyone help me?

  2. Hi Moira. What you describe does sound like what I associate with dopamine being low. I'm not sure from your comment if you are describing what you experienced before changing the medication or after. Have those issues improved or worsened after adding the Abilify?

    I don't have any experience with Abilify. I did some searching and found an article here that looks relevant:

    Studies in animals suggest that aripiprazole’s partial agonism stabilizes dopamine D2 receptor-mediated neurotransmission; in hyperdopaminergic states, aripiprazole behaves more like an antagonist blocking the effects of increased dopamine levels, while in a hypodopaminergic state it produces agonist effects.

    So, according to this, it doesn't affect the production of dopamine. Instead it affects the dopamine receptors to make them less stimulated than they would normally be when dopamine release is high, and more stimulated than they would be when it is low.

    In theory this could help someone to feel as if they were in a higher dopamine state in the case where their real dopamine state is low enough that it would cause less receptor stimulation than the drug does. I expect it's a matter of trial and error whether or not that would result in a helpful effect for a given person. It's important to stay in communication with the prescribing doctor about how the things you mentioned (lack of focus, enthusiasm, etc.) change before and after modifying the medications.

    Another thing I noticed is that the wikipedia page says that it takes 14 days for the level of Abilify in a person's blood to reach its steady state value for a given dosage. Its effects may be different depending on whether it's gotten to that steady state level or not.

  3. Hey Anne,

    Maybe this is a bit out of date, but as a person struggling with the exact aforementioned motivational problems, I would love to find a solution to my sometimes paralyzing situation.
    Would be really happy to hear from you.
    Please send me an e-mail at: tom hashnl@gmail.com
    (remove the space).