Dopamine and Reward Prediction: What your brain looks like on Rickroll

Posted on 06/14/2010 by scicurious

Today Sci is going to blog a paper that she has been meaning to blog for a long time. It’s one of those papers that people who do certain kinds of science snuggle with when they go to sleep at night.
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(Sci and this paper)
But the real reason that Sci loves this paper is that it’s the neurobiological equivilant of a RickRoll.
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And the question behind this paper is: what is the mechanism behind reward prediction?
ResearchBlogging.org Schultz, Dayan, and Montague. “A neural substrate of prediction and reward” Science, 1997.

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Filed under: Behavioral Neuro, Neuroscience | Tagged: , , , | 12 Comments »

Cheesecake-eating rats and food addiction, a commentary

Posted on 05/05/2010 by scicurious

As you might have noticed, Sci is really interested lately in the concept of food reward systems, in particular the issues associated with the effects of binge eating on reward systems in the brain, and the issue of “food addiction”.
And Sci is not the only one who is interested. Lots of other people in the scientific world (not to mention people outside the scientific world) are interested as well. And in the same issue of Nature Neuroscience that published the paper that Sci covered on dopamine and obesity in rats, David Epstein and Yavin Shaham wrote a commentary on the very same article. Yavin Shaham (the last author and thus the big kahuna) is a big guy in the dopamine and addiction world, and is an important researcher at the National Institute on Drug Abuse.
And these guys have some good points.
Points that Sci (figuring others probably don’t have easy access to Nature Neuroscience) wants to share with you.
Here we go.
ResearchBlogging.org Epstein and Shaham. “Cheesecake-eating rats and the question of food addiction” Nature Neuroscience, 2010

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Filed under: Addiction, Behavioral Neuro | Tagged: , , , , , | 2 Comments »

Dopamine and Obesity: The D2 Receptor

Posted on 04/01/2010 by scicurious

Sci would like to note that today’s entry is being written on the adorably tiny screen of her netbook, which is named Ruby. Everyone say hi to Ruby!
Unfortunately, this is because her wireless on her normal computer suddenly decided that it was too good for her modem. Perhaps it’s an April Fool’s Day joke. This is not a good time for this to happen, but of course the not good times ARE the times when this happens, as we all know. And so, until that gets fixed, we are stuck on the netbook, which may mean increased typos and various other things that happen when Sci’s hands are confined to a 10″ space.
Anyway.
A few days ago Sci looked at a recent study which has come out on dopamine and obesity, which showed changes in reward-related behaviors and changes in the dopamine D2 receptor after rats got really fat. This paper (which apparently some people decided to interpret as “food is just like heroin”, which is just silly) was based on the hypothesis that severe chronic overeating results in some changes in the brain which are similar to those seen in drug addiction.
Sci hasn’t really looked into this before, but this really began to interest her. She decided to dig in a little, and take a look at some of the clinical literature, in particular some of the human stuff.
And so here we go.
ResearchBlogging.org Wang et al. “Brain dopamine and obesity” The Lancet, 2001.

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Filed under: Addiction, Behavioral Neuro | Tagged: , , , | 7 Comments »

SFN Neuroblogging: Performance-enhancing Ritalin

Posted on 10/28/2009 by scicurious

Sci will admit that blogging SFN has been harder than she thought it would be. This is partially due to the lack of wireless on the poster floor (which would be REALLY hard to remedy), and partially due to…exhaustion. By the end of the second or third day, the posters all begin to blur before your eyes, and you bless anyone who is willing to send you a copy of their poster. This is because your notes, however extensive, become steadily less and less legible (Sci’s netbook is not optimal for this kind of note-taking). So as Sci tries to write about all the cool stuff she’s seen, she ends up squinting curiously at her notes and saying things like “task indecent via 02??? That doesn’t make any sense!!!”
If they keep up this neuroblogging for next year (please do!!!) and if Sci is picked again (Same Sci-time…midnightish…and same Sci url!), Sci wants to start setting up interviews with people who have awesome abstracts, so I can take better notes. Or possibly I could start begging poster copies ahead of time. Many presenters aren’t so good about sending them, and who can blame them? Sci has forgotten many a time. (As to why all poster-presenters don’t hand out copies of their posters, or allow pictures of posters to be taken, well, Sci will save that for another post).
Anyway, I shall forge on, and attempt to decipher my own handwriting! Especially because I recall being very excited about this particular poster and the implications.
K. M. TYE, L. D. TYE, J. J. CONE, E. F. HEKKELMAN, P. H. JANAK, A. BONCI; “Methylphenidate (Ritalin) enhances task performance and learning-induced amygdala plasticity via distinct D1 and D2 receptor mechanisms ”

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Filed under: Academia, Physiology/Pharmacology | Tagged: , , , , , , , | 9 Comments »

A Balloon in your Stomach and your Brain

Posted on 09/23/2009 by scicurious

Sci is still tracking her caloric intake every day for the goddess (well, mostly for herself, but also for the goddess). It’s very long, slow haul. Sci still considers days when she eats no more than 2000 calories (preferably a little less) as good days. That may not seem like much of a diet, but compared to my previous intake, it’s quite a big cut. And many days I just don’t make it.
But obviously, this has stayed on my mind. I can’t help thinking about how we register food in the brain, how we tell when we are full, and if there’s a difference between when we know we are full vs when we KNOW we are full. Sci will admit there’s often a big difference between when I feel myself getting full and when I stop eating.
But then I found something that made the issue even more near and dear to my heart. It could have something to do with dopamine!
ResearchBlogging.org Tomasi et al. “Association of body mass and brain activation during gastric distention: implications for obesity” PLoS ONE, 2009

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Filed under: Physiology/Pharmacology | Tagged: , , , , | 5 Comments »

Some more questions on Ritalin

Posted on 09/16/2009 by scicurious

Sci got this comment to her Ritalin post the other day:

It sounds like you are suggesting that cocaine taken in the same form as Ritalin — as low-dose, slow release pills — would produce the same effects as the ADHD medication does. But, clearly, the FDA has seen fit to outlaw cocaine and place its seal of approval on doctor-prescribed Ritalin. Not that I think the FDA is infallible or anything, but did they really make the mistake of controlling one substance and permitting another that are essentially equivalents? Benzoylmethylecgonine and methylphenidate are clearly not the same chemical compounds, but if they act in synonymous ways on the brain, shouldn’t they be treated equally under the law?
And what about the all-touted maxim that patients who have not been prescribed Ritalin should not take it but those who have been shouldn’t miss a dose? Is there really such a neurological difference between those with ADHD and those who haven’t been diagnosed with it, or is it just a matter of how much rapport you establish with your psychiatrist? (I am not trying to patronize; I legitimately want to know!)
Similarly, are their patients for whom controlled doses of cocaine would yield medical benefits equal to or exceeding those of Ritalin? Or are there manifold side effects that discourage the use of cocaine as an ADHD/ concentration medication in spite of its similarities to Ritalin?
Personally, I’m skeptical of many of the diagnoses of ADHD that I see and of the politician-worthy campaigns that I hear that deny the efficacy of Ritalin for patients who have not been diagnosed with ADHD. It seems to me that for a disorder whose diagnosis is so imprecise and objective, it’s a convenient coincidence that most takers of Ritalin who have been diagnosed with ADHD (regardless of whether or not the diagnosis is accurate) show marked improvement in concentration…

As you can see, it’s long and has a lot of questions. And some of them are very good ones. But I knew that answering it within the comment thread was going to be long, and also I needed to use lots of links. So congrats, cerebration! You’re getting your very own post!!!
Here we go.

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Filed under: Neuroscience | Tagged: , , , , , | 9 Comments »

Things I like to Blog About: Ritalin

Posted on 09/14/2009 by scicurious

It seems, from the time I first heard about it, there’s been an eternal flare-up about Ritalin, and its similar counterparts, including things like Concerta and Tranquillyn. Issues with who should get it, who HAS attention-deficit/hyperactivity disorder (ADHD), whether or not ADHD is is even a real diagnosis. Issues about whether people who DON’T have ADHD should get Ritalin, and whether it’s ethical to use Ritalin (or other stimulant medications used for ADHD) for things like “cognitive enhancement”, whether it amounts to use of something that is no more harmful than using caffeine, or whether it’s something more sinister.
But that’s not what Sci is going to blog about today. Because I get a lot of people asking me whether Ritalin is bad, mentioning they’ve snorted it once or twice or took it once or twice and it did/didn’t work for them, etc, etc. But Sci’s a scientist. She hopes that people might be able to determine for themselves whether Ritalin is good or bad, once they know how it works.
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This is Ritalin, aka Methylphenidate.

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Filed under: Physiology/Pharmacology | Tagged: , , , | 31 Comments »

Dopamine: Reach out and Touch Someone

Posted on 07/28/2009 by scicurious

As some of you may know by now, Sci blogs a bit about dopamine. Dopamine seems pretty simple at first look (one chemical, one transporter, five receptors, how hard can it be?), but in fact, dopamine modulates a huge number of processes, particularly those related to learning and motivation. We talk a lot about dopamine being a “pleasure” molecule, and in a way it in, but it’s more complicated than that. It’s not just pleasure, it’s motivation and reward processes, which in a way are deeper than just the pleasure you might feel at having sex or eating a pizza. Obviously dopamine can have some pretty big effects on things like, for example, motivated movement (Parkinson’s), or disregulated motivational processes (drug addiction).
But what about touch? Can dopamine levels influence how you process touch, and how well you can do on a test for it?
Pleger, et al. “Influence of dopaminergically mediated reward on somatosenory decision-making” PLoS Biology, 2009.

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Filed under: Neuroscience | Tagged: , , , | 1 Comment »

Dopamine Neurons: Reward, Aversion, or Both?

Posted on 05/27/2009 by scicurious

If you can’t tell by now, Sci is something of a dopamine junkie.
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Ooooh yeah. See that? That’s great. You wanna hit?

Anyway, when one first learns about dopamine, you learn about a “reward” molecule, the one that makes you feel good. Sounds like dope for a reason. But over time, scientist have found that it’s not just about reward with dopamine. Dopamine has a lot more to do with things we like to call salience and value. The salience of a cue is in part related to its strength, and it part related to what its connected with. Basically, a cue is high salience if it gives you a good reason to pay attention. It isn’t attention itself, it’s being connected to something worth paying attention to. This is connected to the item’s value. After all, if it’s something I don’t value, the article isn’t going to be very salient to me, it won’t be worth paying attention to.
So as of recently, it’s been assumed that dopamine neurons fire in response to value-related signals. Sci’s dopamine neurons fire in response to pizza, and a crack addict’s neurons fire in response to cocaine. And of course, if they encode value-related stimuli, dopamine neurons should be inhibited by aversive stimuli, because those have negative value. So while my dopamine neurons fire in response to pizza, they should be really inhibited in response to brussels sprouts.

Right? Well…wrong. And this is something that has puzzled scientists for a while. Some studies show inhibition of dopamine neurons in response to negative stimuli, and some show both negative and POSITIVE dopamine response to negative stimuli. So what’s up with that? Are the neurons firing for negative stimuli just some random wackos that get off on brussels sprouts?
Well, it’s possible that they aren’t wackos. It’s possible that the dopamine neurons really do just encode value-relation. Not whether that value is positive or negative. Scientists recently have tried to test this, and what they found clarifies a lot of things we didn’t know about the firing of dopamine neurons.
So what do you need to make a groundbreaking paper (in this case a paper in Nature)? Some juice, some air, and a couple of monkeys.

ResearchBlogging.org Matsumoto and Hikosaka. “Two types of dopamine neuron distinctly convey positive and negative motivational signals” Nature, 2009.

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Filed under: Neuroscience | Tagged: , , , | 15 Comments »

Basking in the Dopamine Glow

Posted on 05/14/2009 by scicurious

Sometimes, the world gets Sci down a little. Perhaps it’s being a whole YEAR old. That’s very old indeed in bloggy years. Ok, it’s not as old as the ancients who started back in ’04. They’re REALLY old. So maybe Sci is just entering blog middle age.
Be that as it may, Sci need to raise her spirits. And she’s going to do it in the only way Sci CAN: with chocolate, and with one hell of an amazing paper.
First, here’s your chocolate:
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Chocolove’s Crystallized Ginger in Dark Chocolate Bar. This is Sci’s favorite chocolate. Easy to get, rich, dark, and makes you feel kind of healthy while you’re eating it. After all, both dark chocolate and ginger are supposed to be good for you! But really, the dark chocolate on this is lovely and rich, and the crystallized ginger adds both the sweetness and the spice. Lovely. Sci has also been known to enjoy the dark chocolate with raspberries in it.
And now, here’s your paper! I warn you, this one is technical. Explanations ahead. Possibly also drawings. Which may be very bad. We all know how much I suck at art…
ResearchBlogging.org Gubernator et al. “Flourescent flase neurotransmitters visualize dopamine release from individual presynaptic terminals” Science, 2009.
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(Your taste of things to come).

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Filed under: Neuroscience | Tagged: , , , | 16 Comments »

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