The Frontal Cortex

Primal Information

Over at Not Exactly Rocket Science, Ed Yong has a great summary of a new paper trying to figure out why information (at least in primates) can be just as rewarding as primal, biological rewards, such as calories and sex.

Ethan Bromberg-Martin and Okihide Hikosaka trained two thirsty rhesus monkeys to choose between two targets on a screen with a flick of their eyes; in return, they randomly received either a large drink or a small one after a few seconds. Their choice of target didn’t affect which drink they received, but it did affect whether they got prior information about the size of their reward. One target brought up another symbol that told them how much water they would get, while the other brought up a random symbol.

After a few days of training, the monkeys almost always looked at the target that would give them advance intel, even though it never actually affected how much water they were given. They wanted knowledge for its own sake. What’s more, even though the gap between picking a target and sipping some water was very small, the monkeys still wanted to know what was in store for them mere seconds later. To them, ignorance is far from bliss.

[SNIP]

This preference for knowledge about the future was intimately linked to the monkeys’ desire for water. The same neurons in the middle of their brains signalled their expectations of both rewards – the watery prizes and knowledge about them.

All the neurons in question release the signalling chemical dopamine. While the monkeys were making their choices, Bromberg-Martin and Hikosaka recorded the activity of 47 dopamine neurons in their midbrains. These neurons became very excited when the monkeys saw a symbol that predicted a large amount of water, while the symbol that cued a smaller drink inhibited the neurons. The same dopamine neurons were excited during trials where the monkey only saw the symbol that heralded forthcoming information, and they were inhibited if they monkey only saw the other non-informative symbol.

So the same population of midbrain neurons signal changes in both the thirst for water and for knowledge. The more active they are, the stronger that thirst is. One monkey had a stronger preference for early information than the other and indeed, its dopamine neurons were more active when it saw the informative symbol. Even for each individual monkey, the neurons were more active on specific trials where they showed a preference for advanced knowledge.

These experiments elegantly demonstrate an essential feature of the human mind, which is how evolution bootstrapped our penchant for ideas to the same reward circuits that govern our animal appetites. In other words, the political activist on hunger strike might still be relying on his reward circuity, even though he’s actually denying himself caloric treats: the cause is simply more important than food. That’s what makes ideas so powerful: No matter how esoteric or ethereal or abstract they get, they are ultimately plugged back into the same system that makes us want sex and sugar. The end result is that we can crave knowledge and facts just like a thirsty person craves water.

UPDATE: And doesn’t this also help explain the allure of suspenseful narratives? A good story, after all, is simply the artful denial of information – Will Elizabeth marry Darcy? Will Jason Bourne survive Moscow? – so that the audience craves resolution, which arrives in the form of information. The happy ending is a universal human reward.

Comments

  1. #1 Mozglubov
    July 17, 2009

    That is a pretty interesting study… some good Friday afternoon reading!

  2. #2 Joe Linker
    July 17, 2009

    At what level intelligence? “These neurons became very excited…” This is simply metaphor; still, the neurons became excited? And again? If a neruon has intellignece, does an amoeba? Well, maybe, but not until they come together in cooperation does anything at all happen. Emergence. The end result can’t be predicted by a study of the individual… A bit cryptic, but the neurons are still waking up, wanting a bit more coffee, and most of them are not all that excited about having to go downtown so early this morning, to earn a bit of bread – not by bread alone? :)

  3. #3 Julie Simon Lakehomer
    July 17, 2009

    At last an explanation of my intense science reading: books, articles, blogs-as long as they’re well written, I love ‘em. Also, I wonder if this explains why reading is a great way to end the day-pleasant, reassuring. Or is the end-of-day reading a puzzle for the same neurotransmitter reason? As for Comment #2, maybe Joe should read “Wetware,” by Dennis Bray: talk about sentient cells!

  4. #4 Joe Linker
    July 17, 2009

    # 3 above: Thanks for “Wetware” recommendation, Julie. I took a quick look in Open Library and I think I will check it out. Last chapter title noted: Amoeba redux. I can already feel a few neurons getting excited!

  5. #5 Krishna Bhaskar
    July 18, 2009

    The original “Bewitched” movie was out, I think in 1968 – and the Devil was male.
    Do you know what was one of his activities? He tore the last pages of mystery novels in Bookshops.
    I suppose he’d know a thing or two about temptation :.)

  6. #6 Karen McKenzie
    July 18, 2009

    Before I read the details of the experiment, my first reaction was “information that inspires Hope is just as impacting if not more than actually experienced, biological stimuli”. It gives us the perception (or should I say deception) of control and heightens anticipation. After all, how many of us have had sex just to find out that the teasing and anticipation beforehand was much more satisfying!? Incidentally, there are also potent torture tactics based on this premise of the power of perception over experience. Anyway it’s interesting that we feel better when we can “see” a demonstrative dopaminergic reaction that confirms what we already “knew”.

  7. #7 royniles
    July 18, 2009

    Everything we or other organisms do is based on expectations, and any hint that there is knowledge available that would affect those expectations, either for the better and especially if for the worse, would seem to be be synonymous with the offer of a reward.

  8. #8 Nancilee Wydra
    July 19, 2009

    You were the highlight of the Chautauqua Week on the Brain…..but didn’t answer my query

    Can our atoms inform us?
    They’ve been in so many marvels
    Never created: never destroyed
    Forever alone or in combination

    Combined in a threesome; a liquid
    With P79 and N118 at the center, a glitter
    One valued by necessity
    The others’ worth only by designation

    I stare at my hand and wonder where my atoms have been
    They are unique, these 7 followed by 27 zeros atoms of me
    While they don’t think, act or speak: they are in me and of me
    As I am of them, and cannot be helped but be informed by their past

    Obviously I am asking a question that implies memory but perhaps it is in the combination that nuances not memories exactly might exist. How else am I more than my parts?

  9. #9 David Kerlick
    July 20, 2009

    When one gets down to the level of individual atoms, there’s no such thing as memory. All protons (neutrons, electrons) are indistinguishable in the sense of quantum statistics, and there is no way of saying which one had which history. Once you specify the isotope and the energy levels if it is above its ground state, the description is essentially complete. The complexity comes about in very much larger ensembles!

  10. #10 royniles
    July 20, 2009

    Not to mention that the atoms that support our structures today will not be the same as those that replace them tomorrow.

  11. #11 Anna
    July 23, 2009

    Well, this certainly explains engineers and scientists.

  12. #12 racecar
    July 26, 2009

    I think it’s a little misleading or at least premature to draw the conclusion that the desire for abstract information uses the same reward circuitry as the desire for sustenance. Isn’t there the possibility that the monkeys were retaining their conditioned response even though half the time they failed to receive a reward? They could have simply been expecting water every time, even through the disappointments. A more convincing follow-up in my opinion would be to repeat the same experiment with an abstract informational reward. For example, instead of giving them water, give them a colored ball, with the symbols predicting what color the ball would be. I’m not sure if the rhesus monkeys would maintain interest in this kind of experiment, but the results of this study alone don’t strongly support the conclusion.

  13. #13 Raul
    August 17, 2009

    I don’t think that the “turn on” was knowing something but rather the elimination of “not knowing.” Royniles wrote that “Everything we or other organisms do is based on expectations.” I would agree because our non-meditative minds constantly think about the past and the future. One need not read books about this but just look at our own minds. Not knowing what will happen next causes anxiety in most people thus they try to speculate what will happen. I think the hypothesis “To them, ignorance is far from bliss” should have been the thesis for the experiment.