Page 18 - The 'X' Chronicles Newspaper - September 2023
P. 18

18                            Brains May Predict The Future

             To Make Sense of the

              Present, Brains May

               Predict The Future

                 Continued from Page 17

        Enter predictive coding theory, which
        offers specific formulations of how
        brains can be Bayesian. Predictive coding
        gets its name from a technique for
        transmitting telecommunications signals
        more efficiently: Because video files
        contain a lot of redundancy from one
        frame to the next, it’s inefficient to

        encode every pixel in every image when           internal model that gets adjusted; with emotions and moods can be formulated in
        compressing the data. Instead, it makes          motor      control,     it’s    the    actual predictive coding terms: Emotions could
        more sense to encode the differences             environment. (For the latter, imagine that be states the brain represents to minimize
        between adjacent frames and then work            you want to raise your hand. If your hand prediction error about internal signals
        backward to interpret the entire video.          is not already raised, that discrepancy such as body temperature, heart rate or

                                                         generates a large prediction error — blood pressure. If the brain recognizes
        In 1982, scientists found that this idea has     which can be minimized if you simply that it’s agitated, for instance, then it
        a neat application in neuroscience —             move your hand.)                                 knows all those factors are going up.
        because it appears to explain how                                                                 Perhaps that’s also how the concept of

        neurons in the retina encode information         Experiments in perception and motor selfhood can emerge.
        about a visual stimulus and transmit it          control have so far provided the strongest
        along the optic nerve. It’s also been            evidence for predictive coding theory. In Most of the work being done in this vein
        cemented as a principle of how the               a 2018 paper published in the Journal of focuses on how predictive coding might
        brain’s reward system functions:                 Neuroscience,            for        example, explain            neuropsychiatric           and
        Dopamine neurons encode the magnitude            experimenters had subjects read the word developmental disorders. “The idea,”
        of the mismatch between an expected              “kick” on a screen, then had them listen Friston said, “is that if the brain is an
        reward and the actual reward that’s              to a distorted recording of the word inference machine, an organ of statistics,
        received.  These prediction errors,              “pick” that sounded like a loud whisper. then when it goes wrong, it’ll make the
        researchers say, help animals update their       Many heard “kick” instead, and fMRI same sorts of mistakes a statistician will
        future expectations and drive decision-          scans revealed that the brain represented make.”  That is, it will make the wrong

        making.                                          the initial “k” or “p” sound most strongly inferences by placing too much or too
                                                         — the sound that correlated to a little emphasis on either predictions or
        But despite these examples, scientists           prediction error. If the brain were simply prediction errors.
        mostly saw predictive coding as a process        representing its perceptual experience,
        specific to certain networks. Functional         the strongest signal should have Aspects of autism, for instance, might be
        magnetic resonance imaging tests and             corresponded to “ick” instead (because characterized by an inability to ignore
        other types of experiments have begun to         that was represented both on screen and prediction errors relating to sensory
        change that.                                     in the audio).                                   signals at the lowest levels of the brain’s

                                                                                                          processing hierarchy. That could lead to a
        A Universal Framework                            But efforts are also ongoing to widen preoccupation with sensations, a need for
                                                         predictive coding’s relevance beyond repetition and predictability, sensitivity to
        Part of what makes the predictive coding perception and motion — to establish it certain illusions, and other effects.  The
        hypothesis so compelling is its incredible as the common currency of everything reverse might be true in conditions that
        explanatory power. “What I find going on in the brain. “It’s like having are associated with hallucinations, like
        convincing is how so many things all get building blocks with which different schizophrenia:  The brain may pay too

        accounted for under this story,” said strategies can be built,” Clark said. much attention to its own predictions
        Andy Clark, a professor of logic and Different brain regions simply trade in about what is going on and not enough to
        metaphysics at the University of different kinds of prediction.                                   sensory information that contradicts
        Edinburgh and an expert on the theory.                                                            those predictions. (Experts are quick to
                                                         Friston, among others, claims this applies caution, however, that autism and
        First, it unifies perception and motor to higher cognitive processes including schizophrenia are much too complicated
        control under a single computational attention and decision-making. Recent to be reduced to a single explanation or
        process. The two are essentially opposite computational work on the prefrontal mechanism.)
        sides of the same coin: In each case, the cortex has implicated predictive coding

        brain minimizes prediction errors, but in in working memory and goal-directed                                        (Continued on Page 19)
        different ways. With perception, it’s the behaviors. Some researchers theorize that
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