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The most vivid part of the mind bubbles up through sensation and new experience when unencumbered by analytical thought
For some 2,500 years, humans have located the mind in the brain inside our heads. But we ought to consider the origin of mind with an open mind. Is the mind truly within the brain? Or is this an illusion?
I gained some insight back in the 1980s, as college drew to a close. I was in my 20s and working in Mexico for the World Health Organization on a project to study curanderos – folk healers – in a region where the press of modernisation of a local dam, La Presa Miguel Alemán, 250 miles south-east of Mexico City, was changing communities and local medical services. One morning, on a horseback journey to interview a local healer as part of my project, the saddle on my horse loosened and, with feet still strapped into the stirrups, I was dragged, they tell me, a hundred yards over gravel and rock, my head banging against the ground beneath the horse’s racing hooves. When the young and frightened horse finally came to a stop, my riding companions thought I must be dead, or at least that I’d broken my neck. I did break my teeth and nose, and damaged my arm. The head trauma induced a state of global amnesia that lasted about a day.
In the aftermath of the horse accident, I became attuned to a level of knowing beneath personal identity, personal belief and personal expectation. I had no idea what to call this change in ‘me’ so I never discussed it with anyone, putting it into a category of some existential wakeup call to lighten up, given life’s fragility following that near-death accident, to be grateful to be able to move my neck, be alive, be awake and aware. I didn’t think of it then as a gift, but I realise now it was one of those unplanned experiences that are turning points, even if we don’t realise their impact at the time.
How do all these layers of reality, these domains of life, find some common home, some common ground of understanding? Two terms that offer some insight and indicate how information is processed in our minds and brains are ‘top-down’ and ‘bottom-up’. These terms are sometimes used for the anatomical location of processing: the higher cortex (seat of executive function) at the top, the lower brainstem (heart rate, breathing) and limbic areas (emotion) at the bottom. But the same terms are also used for layers of processing not related to the anatomical distribution of up and down. Instead, they are used for the degree of processing of information.
In the view we will be using here, top-down refers to ways we have experienced things in the past and created generalised summaries or mental models, also known as schema, of those events. For example, if you’ve seen many dogs, you’ll have a general mental model or image of a generic dog. The next time you see a furry canine strolling by, your top-down processing might use that mental model to filter incoming visual input, and you won’t really see the uniqueness of this dog in front of you. You have overlaid your generalised image of ‘dog’ on top of the here-and-now perceptual stream of energy that creates the neural representation of ‘dog’. What you actually have in awareness is that amalgam of the top-down filtering of your experience.
So here, ‘top’ means that prior experience is activated, making it difficult to notice the unique and vibrant details of what is happening here and now. The top-down generalised notion of dog will shade and limit your perception of the actual animal in front of you. The benefit of top-down is that it makes your life more efficient. That’s a dog, I know what it is, I don’t need to expend any more energy than needed on insignificant, non-threatening things, so I’ll take my limited resources and apply them elsewhere. It saves time and energy, and therefore is cognitively efficient. That’s top-down processing.
On the other hand, if you’ve never seen a spiny anteater before, the first time you come across one on the trail, it will capture all of your attention, engaging your bottom-up processing so that you are seeing with beginner’s eyes. These are eyes leading to circuitry in the brain, not shaping and altering ongoing perception through the top-down filters of prior experience. You’ll be taking in as much pure sensation from eyesight as possible, without the top-down filter altering and limiting what you see now based on what you’ve seen before.
When we travel to a foreign country, bottom-up perceiving can fill our journey with a profound sense of being alive. Time seems extended, days full, and we’ve seen more details in a few hours than we might have seen in a week in our familiar life. What seen means for bottom-up perception is that we become more attentive to novelty, seeing the unique aspects of what is, literally, in front of our eyes. The social psychologist Ellen Langer at Harvard University calls this ‘mindfulness’, and has done numerous studies to reveal the health benefits of being open to the freshness of the present moment.
The novel experience of foreign travel, in contrast to the sense of dullness in our lives back home, also reminds us of what life is like in familiar terrain: top-down can dominate bottom-up and give us a familiar sense of the same-old, same-old. A street at home with just as much detail seems dull compared with the novelty of a street in a foreign town seen for the first time. This loss of attention to the familiar can be called top-down dominance. Prior learning creates top-down filters through which we screen incoming data and lose the detail of things seen for the first time…