Consider an illusion that has the benefit of being unbelievable each time you see it, no matter how many times that is. In the Checkerboard Illusion, the squares labeled A and B are the same color, same shade, same hue, same everything. Square A is actually lighter than it appears, square B darker. A photometer could tell you this. And so could your brain, but it doesn't. It knows they're the same because your eyes tell it so, but delivering unaltered information to your consciousness isn't its job. Rather, in regard to square B for instance, it takes what it expects (square B should be lighter because that's how a checkerboard is designed) and what it reasons (square B is darker than it should be but that's because it's in shadow), and lightens up square B in your reality to the way it should look. It alters your square B. It constructs it.
And consider the Dragon Illusion below (the voiceover says it all):
Perhaps more surprising than adjusting the hue of checkerboard squares or perceiving movement where there is none, our brain's ability to construct can also perform a disappearing act. In the Motion Induced Blindness illusion (below), focus your gaze on the blinking green dot and the yellow dots will disappear.
Here's how it works: In our peripheral vision, it's of survival advantage to notice what's moving - is that my prey?...a predator?...a mate? - and ignore what's still. So the brain continues to process the moving blue field and ceases to process the yellow dots. Once that pattern of processing is assembled, and as long as it lasts, the dots are no longer a part of your reality. Your brain can deconstruct as well as construct.
Construction is inescapable. But it isn't invariable. A phenomenal assortment of realities take shape from modifications to neural processes. Cross-wire number- with color-recognition areas of your brain and each number will be cast in a different color; cross-wire taste- with color-recognition and each flavor will be accompanied by a different hue. Such is the reality for someone possessing synesthesia. Disrupt the neurological connection between face-recognition and emotion-regulation areas and you will not recognize your mother ‘as' your mother. You'll admit this woman looks like her but be completely convinced that it is not her; it doesn't ‘feel' like her so your brain rejects her true identity. Such is the reality for someone suffering Capgras Syndrome.
Closer to home, your reality of your body is a neural construction. For instance, if you stimulate your index fingertip with vibration, a particular area of your somatosensory cortex will fire (let's call it area A) and you'll feel it in the tip of your finger as expected. Stimulate your middle finger and a different area of your somatosensory cortex will fire (area B) and you'll feel it in your middle finger, also as expected. But simultaneously stimulate your index and middle fingers with synchronized vibration and a third area of the somatosensory cortex will fire - an area between areas A and B - and you'll feel the sensation as coming from the space between those fingers. This constructed reality will feel just as real, even in the absence of an actual finger. So your brain uses the input from your senses (plus some genetic programming) to construct a map of your body, but it isn't limited by this input. Once constructed, this neural map becomes the territory of sensory reality.
Still closer to home, your most essential experience of reality, consciousness itself, is a construction. Though the brain executes numerous parallel processes, it presents consciousness to you as a unified experience. Your brain processes the sound of your friend's voice more quickly than the movement of her mouth, but you experience her voice and mouth in sync. Your brain processes color more quickly than form, but you enjoy a unified red 1967 Chevy Camaro SS as it speeds by. Turning asynchronous neural processes into the experience of synchrony is an on-the-fly construction. And we don't yet know how that's done; it's still a binding problem.
Like King Midas, the reality we experience takes its form by our touch. And just as his potential for experience goes way beyond gold, the experience we treasure is but a subset of what's possible. This blog will generally focus on the breadth of realities that humans construct, some toward health and happiness, some toward pain and suffering. The neurological mechanisms of these experiences will often be covered alongside emerging technologies that can help us move toward some constructions and away from others. The idea has been well summarized by the Master (William James):
"Our waking consciousness, rational consciousness as we call it, is but one special type of consciousness, whilst all about it, parted from it by the filmiest of screens there lie potential forms of consciousness entirely different. We may go through life without suspecting their existence; but apply the requisite stimulus, and at a touch they are there in all their completeness..."