​TEDTalk: Your brain hallucinates your conscious reality | Anil Seth 

  • Consciousness has less to do with intelligence and more to do with our nature 

  • Our conscious experience of the world around us and of ourselves within it are kinds of controlled hallucinations that happen with, through, and because of our living bodies

  • Think of consciousness in the same way we think of being alive: 

    • At one time people thought the property of being alive could not be explained by physics and chemistry, that life had to be more than just mechanism 

      • We no longer think that. 

      • As the properties of living systems can be explained in terms of physics and chemistry (i.e reproduction, metabolism, homeostasis,) the basic mystery of what life is started to fade away 

        • People no longer proposed magical solutions like a force of life or élan vital  

    • As with life, so with consciousness 

  • What are the properties of consciousness?

    • Experiences of the world around us: Multi-sensory, panoramic, 3D fully immersive inner movie 

    • Conscious sense of self: The specific experience of being me or of being you, the lead character in this inner movie 

  • Experience in the inner world: 

  • Your brain is locked inside a bony skull. There are no lights or sounds inside the skull, only streams of electrical impulses which are only indirectly related to things out in the world, (whatever they may be)

    • Perception (figuring out what's there) is a process of informed guesswork 

      • The brain combines these sensory signals with its prior expectations or beliefs about what the world is and the way the world is, to form its best guess of what caused those signals (neurons) to fire. 

    • The brain doesn’t hear sound or see light, what we perceive is its best guess of what’s out there in the world 

    • The brain uses its prior expectations built deeply into the circuits of the cortices

      •  (i.e. The expectation built into the visual cortex that a cast shadow dims the appears of a surface; this gives rise to optical illusions as in the case below: 

  • The sensory information that comes into the brain may not change, but the brain can be primed between separate experiences of it to perceive it differently in later iterations 

    • Priming changes perception 

  • Perception does not depend only on signals coming into the brain from the outside world, It depends as much if not more on perceptual predictions flowing int he opposite direction 

    • We don’t just perceive the world, we actively generate it. 

    • The world we experience comes as much, if not more, from the inside out, as from the outside in. 

  • THESIS: IF Hallucination is a kind of uncontrolled perception, THEN perception is a kind of controlled hallucination.

    • The brain’s predictions are being reigned in by sensory information from the world 

    • In fact, we’re all hallucinating all the time, including right now.

    • When we agree about our hallucinations, we call that reality. 

  • Your experience of being a self, the specific experience of being you, is also a controlled hallucination generated by the brain 

  • Experience of being a person seems so familiar, so unified and so continuous that it’s difficult 

    • Bodily self: Having a body vs. being a body 

    • Perspectival self: Perceiving the world from 1st person point of view 

    • Volitional self: Intending to do things and being the cause of things that happen int he world 

    • Narrative self and social self: Being a continuous and distinctive person over time built from a rich set of memories and social interactions 

  • Experiments show that the basic background experience of being a united self is a fragile construction of the brain 

  • Bodily self: How does the brain generate the experience of being a body and of having a body? 

    • The brain makes its best guess about what is and what is not part of its body 

      • i.e. Rubber hand illusion 

        • People can “assimilate” external objects and feel them as parts of themselves 

    • Sensory signals coming from within the body continually tell the brain info such as: 

      • state of internal organs, heart rate, blood pressure, digestion, etc.

        • called Interoception: Perception and regulation of the internal state of the body (is what keeps us alive)

          • Experience of being /having a body are deeply grounded in perceiving our bodies from within 

    • Experiences of the body from the inside are very different from experience of the world around us 

      • My experiences of the body from within are different in that I don’t really perceive them at all unless something goes wrong 

  • Perception of the internal state of the body is NOT about figuring out what’s there, it’s about control and regulation: keeping physiological variables within the tight bounds that are compatible with survival 

  • When the brain uses predictions to figure out what’s there, we perceive objects as the causes of sensations. But when the brain uses predictions to control and regulate things we experience how well or how badly that control is going 

    • Our most basic experiences of being a self, of being an embodied organism, are deeply grounded in the biological mechanisms that keep us alive 

  • All of our conscious experiences, since they all depend on the same mechanisms of predictive perceptions  all stem form the basic drive to stay alive 

    • We experience the world and ourselves with, through, and because of our living bodies 

  • Summary:

    • What we consciously see/hear/perceive depends on our brain’s best guess of what’s out there based on electrical impulses it reads from within a dark, sealed encasement of hard bone. 

    • The world we experience comes from the inside out, not just the outside in.

    • The rubber hand illusion shows that this even applies to what is and what is not our body.

    • These self-related predictions depend critically on sensory signals coming from deep inside the body.

    • Finally, experiences of being an embodied self are more about control and regulation than figuring out what’s there. 

  • So, our experiences of the world around us and ourselves within it are controlled hallucinations that have been shaped by millions of years of evolution to keep us alive in worlds full of danger and opportunity. We predict ourselves into existence. 

  • Three closing implications: 

    1. Just as we can misperceive the world, we can misperceive ourselves when the mechanisms of prediction go wrong 

      • We have to treat the mechanisms not just the symptoms ​

    2. "What it means to be me" cannot be reduced or or uploaded to a software program running on a robot. WE are biological flesh and blood animals whose conscious experiences are shaped at all lvels by the biological mechanims that keep us alive. Just making computers smarter is not going to make them sentient. 

    3. Our own individual universe, our way of being conscious, is just one possible way of being conscious, and even human consciousness generally is just a tiny region in a vast space of possible conscoiusnesses. Our individual self and worlds are unique to each of us but they're all grounded in biological mechanims shared with many other living creatures. 

  • We are part of, and not apart from, the rest of nature. 

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