Talk:Pleasure center

Alternative Interpretations of Brain Self-Stimulation Work

This Wikipedia entry basically is nothing but a kind of popular neo-phrenology. It takes what are complex neuroscience findings and turns them into appealingly simplistic but ultimately misleading soundbites. It is in all honesty troubling to have the mesolimbic mesocortical dopamine system and its associated structures in the hypothalamus and basal forebrain presented as "THE pleasure center" in the brain. There are several major problems with this. First of all, the evidence is overwhelming that there is no center for anything in the brain, only distributed networks that support a particular function. Indeed, even control over micturition is organized in a distributed network (there is no 'micturition center' in the brain!), so how could something at once both elemental and also complex as pleasure be anything but highly distributed? Indeed the evidence is that brain opioid systems are closer to a 'pleasure system' in the brain than brain dopamine systems, particularly if one were to focus on the pleasure of consummation as opposed to the anticipatory pleasure of the chase after a reward.

Additionally, what Olds co-discovered (with Milner and Elliott Valenstein) was that animals would self-stimulate an entire trajectory of systems, starting with the VTA and running up through the lateral hypothalamus and into the ventral basal ganglia and nucleus accumbens (and even into some basal forebrain regions). The $64,000 question is what does it mean that animals experience such stimulation as positive and select it? Does that mean that the trajectory of these systems demarcates the substrate for all pleasure in the brain? I do not believe so, but this continues to be an appealingly simplistic conclusion. Instead, an alternative interpretation is that this trajectory of neural systems is the distributed network of systems required for basic motivational arousal, and that the stimulation of this generates a positive affective state, perhaps best described with terms like 'positive expectancy', 'enthusiastic exploration' or even simply 'hopefulness'. Unfortunately, these concepts do not sell as well as "pleasure center" concepts. However, this difference may be critical.

Recent work argues convincingly that this system is not "the pleasure center" but rather a system for generalized motivational arousal and for reward prediction/sensitization, what Jaak Panksepp has called a generalized expectancy or SEEKING system. There is a ton of other work underlining that this mesolimbic dopamine system is not particularly involved in the pleasure of consummation of rewards (that requires more opioid systems in the brain - see excellent work by Kent Berridge), but it is absolutely required for the SEEKING of rewards, and probably also for the avoidance of punishments (what one might conceptualize as 'the seeking of safety'). Further underlining the silliness of calling the nucleus accumbens "the pleasure center" is evidence that in some areas of the accumbens, electrical stimulation can produce aversive (unpleasurable) responding. Unfortunately, beginning psychology and neuroscience students are likely to come to this page and regard this page as gospel, when it badly needs to be rewritten by a real expert (in that sense, it's in about the same shape as the general Emotion entry in Wikipedia, which frankly is a mess).

James Olds made a huge contribution, no question about that, but I do not believe that the current presentation of his findings (that this electrical brain stimulation work found "the pleasure center" for the brain is accurate. This equation of the mesolimbic dopamine system with the sum total of pleasures in the brain is recurrent in the popular media, and is, at least at this point, frankly unsupported.

For the most thorough, detailed and erudite review of this subject as of this date, I would consult the following reference: Alcaro, A., Huber, R. & Panksepp, J. (2007). Behavioral functions of the mesolimbic dopaminergic system: An affective neuroethological perspective. Brain Research Reviews, 56, 283-321. this review offers a unifying hypothesis linking together addiction, brain self stimulation work, and tons of research on motivation, into a unifying hypothesis. Unfortunately this simplistic equation of the mesolimbic dopamine system with pleasure in the brain continues to be one of the most widely quoted misrepresentations of basic neuroscience available anywhere. One would only hope that the Wikipedia entry on this does better justice to the neuroscience. Olds clearly deserves considerable credit, but he should get credit for the interpretation of his work that makes the most scientific sense.

208.105.164.62 (talk) 22:30, 25 June 2009 (UTC) DFWatt, Harvard Medical School

I encourage you to improve this article, since you clearly know quite a bit about the topic. Let me point out, though, that the literature contains substantial advocacy for the views that you are dismissing -- I might go so far as to say that they are the majority views. A Wikipedia article should try to integrate the views of the whole community rather than the personal views of the editors who work on it. This can be painful -- I know that it is for me when I write about the hippocampus, my own research topic -- but in a way it is also quite educational. Regards, Looie496 (talk) 15:37, 26 June 2009 (UTC)

Response to feedback and some additional thoughts about pleasure

Hi Looie496 - I appreciate your feedback and suggestion. I agree that writing a balanced review by definition means at least incorporating if not necessarily validating other points of view aside from the ones that you happen to believe are the best interpretation of the data. Unfortunately, I'm simply too swamped right now trying to finish a book chapter on motivation to invest the amount of time it would take to really adequately do justice to the subject and write a really good Wikipedia entry. We are probably talking about 5 hours of work at least if not longer to really explore the science. I agree that Kent Berridge's work is a fine example of work that separates SEEKING (more DA driven) from LIKING (more dependent on opioids).

Let me say this, that despite a long history of confusion about the functions of the mesolimbic dopamine projections and the associated ventral basal ganglia as "the reward system" in the brain, I do think that more authors and researchers are starting to realize that there are many systems in the brain broadly defined that support pleasure and positive affect, and increasingly, it looks as though opioids are really central to the experience of pleasure, while dopamine is more central to the pursuit of pleasure. Of course, the enthusiastic pursuit of any reward, whether it is the deep meaning of Einstein's relativity, or your favorite cup of coffee has a positive valence associated with it, in the sense that we are enthusiastic, hopeful, outgoing, and engaged in the active exploration and manipulation of the environment. This is clearly pleasurable, but it can't be seen as the sum total of pleasures underwritten by the brain's networks. Since this generalized motivational arousal system is extremely plastic, and can be linked to all kinds of things, getting animals to self-stimulate it is not really that different from getting someone to take amphetamine (a dopamine reuptake blocker). There is not much functional difference. In some sense what you are doing is getting the motivational system to chase its own tail, to pursue things that activate it directly (either via chemical or electrical means). Every creature with this system can be sensitized (including humans) to either drugs or electrical stimuli that will activate the system 'artificially' (instead of its normal activation by the availability of a real reward). This is the system that all addictions in some sense have to "latch onto" in order to take over the motivational spaces of someone and crowd out other things from those motivational spaces. As a clear indication that pleasure broadly defined is not the same as this generalized SEEKING/WANTING system, people with increasingly malignant addictions will tell you that they often times get minimal to no pleasure anymore from their addiction but they can't stop craving the source of the addiction. This suggests that there has to be some kind of separation between the pleasures of consumption as opposed to the more anticipatory pursuit after the reward. In severely dysfunctional addictions, what we see is really the separation between pleasure and motivation. As people's motivational spaces are captured by darker and darker activities that yield less in the way of joy and increasing amounts of suffering, why doesn't the brain "get it"? I believe it is simply because something has captured this system for general motivational arousal, and the best way to do so is to hinge the activation of this mesolimbic dopamine system to a single activity or drug. This allows one motivational 'attractor' to in a sense gravitationally swallow all the other motivational attractors, almost like a black hole. More precisely, those artificial activators eventually win all the competitions with all available natural activators, rendering them motivationally irrelevant. This creates a totally obsessed creature or human, such that nothing else can be appealing to it, obviously a very bad situation.

Dopamine is at the core of the brain's motivational system, and all of the systems involved in brain self stimulation work are immediate targets of the ventral tegmental dopamine system. There are many unanswered questions however about the neurodevelopmental course of this system and how it is bootstrapped early in development, along with its interdigitation with other reticular activating system structures, processes, and modulators. In this sense, the notion of a dopaminergic projection system with primary targets in the basal forebrain, basal ganglia, and hypothalamus as a motivational system is still just a correlate and not really an explanation. It still doesn't really explain how a conscious organism for example looks out and catches a glimpse of its favorite food, which activates some internal craving or desire which in turn engages motor machinery and attentional machinery to go after the reward despite a whole bunch of frustrating obstacles.

Additionally, an interesting question to ask is "how does a neural system create an internal sense of pleasure"? This is not at all obvious, and hardly self-evident. What does it mean that certain kinds of neural activities are pleasurable? When you start thinking about this, you have to concede that this exposes a core mystery in neuroscience, namely that within a conscious system, certain kinds of neural 'resonances' are somehow positive, while others are negative? These positive and negative neural activations have to be considered intrinsic properties of the system, and their qualities in some sense probably have to be somehow genetically coded. But how is this instantiated? Why are certain kinds of neural activations positive and other kinds are negative? Why is the experience of tissue damage (pain) intrinsically negative? These are really deep mysteries that go to the heart of the fundamental question of how the brain creates a conscious state. When you start a grapple with these mysteries, it becomes clear that the simple correlation between a ventral tegmental dopamine system and motivation does not really illuminate any of these fundamental mysteries. I believe that the only way we can begin to answer these questions is by assuming that at the core of a proto-conscious neural architecture is likely to be some kind of 'virtual body' in the brain in which stimuli that suggest preserved homeostasis are intrinsically positive, while stimuli that imply threatened homeostasis are intrinsically negative. There is so much we don't really understand about how the brain instantiates a conscious state, and this is really the central and still unanswered mystery of neuroscience. Whatever you think pleasure is, whatever correlations you can build to that notion, it still begs this fundamental question, because pleasure of course implies a conscious state of a positive kind. Perhaps pleasure is the elemental currency (along with unpleasure) for that conscious architecture. It would be a mistake to think that modern neuroscience for all its impressive achievements has more than just scratched the surface of these profound mysteries. A correlation is not an explanation.

best, Doug Watt Harvard Medical School —Preceding unsigned comment added by 207.180.129.233 (talk) 03:45, 3 July 2009 (UTC)

Are you familiar with Kent Berridge's ideas about the distinction between "seeking" ("reward"; affected by dopaminergic drugs) and "liking" ("pleasure", affected by opiates and cannabinoids)? He has been pushing this story for quite a number of years, and it generally seems to me to make sense. Looie496 (talk) 05:14, 3 July 2009 (UTC)

Nothing quite matching the rat pleasure center in humans

The way I read the popular literature, nothing has been shown to produce great pleasure on electrical stimulation in the way that the rat pleasure center seems to in rats. And there has been plenty of opportunity to find such a center since brain stimulation is done to conscious humans during neurosurgery. The way this article reads, certain locations are associated to certain kinds of pleasure, but that's not the same as being the equivalent of the pleasure center in rats. Can anyone justify this analysis with a citation? Can someone with real knowledge in the field comment? The source cited for the human pleasure center doesn't convince me that there's a scientific consensus that we even have a pleasure center the way rats seem to.

Mark Foskey (talk) 00:51, 30 April 2008 (UTC)

I would say there is a strong scientific consensus that the same circuitry exists in humans. The brain stimulation done in neurosurgery almost never impacts the medial forebrain bundle, which is the key pathway. However, fMRI studies and drug studies are quite consistent with the pathway from the VTA to nucleus accumbens being the key in humans just as it is in rats. Implanting electrodes in humans just to test this would not be ethical, but there were some publications from the 1960s and 1970s, by Robert G. Heath and others, in which electrodes were implanted in the human brain and reported to give pleasurable effects on stimulation. (Note, I haven't read this article very closely and don't guarantee that is is correct, but I'm confident that what I just wrote is correct.) Looie496 (talk) 00:54, 26 June 2009 (UTC)

Merge/redirect The pleasure center to here?

Back in 2009, someone created The pleasure center, a duplicate article to this one. In 2010, a merge tag was put on the duplicate article, but I can find no evidence that the proposed merge was ever discussed. Normally for a duplicate article, I'd boldly merge the articles, but for this one, I'm not sure if a redirect wouldn't be better. The duplicate article seems pop-sciencey and possibly gives undue weight to some sources. Maybe someone who has more subject knowledge on this area of neuroscience can make a judgement on whether the content is salvageable. Thanks, Quasihuman (talk • contribs) 23:41, 16 June 2012 (UTC)

I don't think I knew that the other page existed, but yes, I definitely think they should be merged. It makes no sense at all to keep them both, and this is the better title. On a quick read (and I fit your description of someone with subject knowledge), I'd say that most of the sub-sections of the other page can be reliably sourced with non-pop sources. So I'd suggest keeping the content here, leaving out the introductory material of the other page, merging the sub-sections of the other page into here, and then we can see about polishing it up. --Tryptofish (talk) 23:55, 16 June 2012 (UTC)

Thanks, I'll go ahead and do that tomorrow. Quasihuman (talk • contribs) 00:26, 17 June 2012 (UTC)

 Done. Quasihuman (talk • contribs) 10:20, 17 June 2012 (UTC)