• A New State of Mind

  "New research is linking dopamine to complex social phenomena and changing neuroscience in the process." (Seed)

  tags: dopamine, neuroscience, grue

  • The importance of dopamine was discovered by accident. In 1954 James Olds and Peter Milner
  • At first the dopamine neurons didn?t fire until the juice was delivered; they were responding to the actual reward. However, once the animal learned that the tone preceded the arrival of juice ? this requires only a few trials ? the same neurons began firing at the sound of the tone instead of the sweet reward. And then eventually, if the tone kept on predicting the juice, the cells went silent. They stopped firing altogether.
  • The software makes predictions about what will happen ? about how a checkers game will unfold for example ? and then compares these predictions with what actually happens. If the prediction is right, that series of predictions gets reinforced. However, if the prediction is wrong, the software reevaluates its representation of the game.
  • The crucial feature of these dopamine neurons, say Montague and Dayan, is that they are more concerned with predicting rewards than with the rewards themselves. Once the cells memorize the simple pattern ? a loud tone predicts the arrival of juice ? they become exquisitely sensitive to variations on the pattern. If the cellular predictions proved correct and the primates experienced a surge of dopamine, the prediction was reinforced. However, if the pattern was violated ? if the tone sounded but the juice never arrived ? then the monkey?s dopamine neurons abruptly decreased their firing rate. This is known as the ?prediction error signal.? The monkey got upset because its predictions of juice were wrong.
  • According to Montague, the reason abstract thoughts can be so rewarding, is that the brain relies on a common neural currency for evaluating alternatives. ?It?s clear that you need some way to compare your options, even if your options come from very different categories,? he says. By representing everything in terms of neuron firing rates, the human brain is able to choose the abstract thought over the visceral reward, as long as the abstraction excites our cells more than apple juice. That?s what makes ideas so powerful: No matter how esoteric or ethereal they get, they are ultimately fed back into the same system that makes us want sex and sugar

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