By admin 
“If the doors of perception were cleansed,” William Blake wrote, “everything would appear to man as it is, infinite.” But we are finite creatures, in time and in space, and there is a limit to how much reality we can bear — evolution gave us consciousness so that we may sieve the salient from the infinite, equipped it with attention so that we may narrow the aperture of perception to take in only what is relevant to us from the immense vista of now. The astonishing thing is that even though we all have more or less the same perceptual apparatus, you and I can walk the same city block together and perceive entirely different pictures of reality, because what is salient to each of us is singular to each particular consciousness — a function of who we are and what we want, of the sum total of reference points that is our lived experience, beyond the locus of which we cannot reach. (This is what makes the Mary’s Room thought experiment so compelling and unnerving, and why the best we can do to understand each other is not explanation but translation.)
Perception, then, is not a door but a mirror, not an automated computation of raw input data but a creative act that marshals all that we are and reflects us back to ourselves. Perhaps the most disorienting aspect of being alive together is that none of us will ever know what another perceives.
That is what Oliver Sacks (July 9, 1933–August 30, 2015) explores with his signature gift for bridging matter and meaning in the title essay of his altogether revelatory posthumous collection The River of Consciousness (public library), fusing his decades of medical practice as a neurologist studying how the brain works with a philosopher’s inquiry into what a mind is and a poet’s gift for rendering what it means to be alive.
Drawing on case studies of patients with peculiar neurological disorders and brain lesions that hurl them into “standstills” of consciousness — states in which time seems to freeze for them even though events and processes continue to unfold within and around them — he considers the temporal dimension of consciousness, most evident in our perception of motion — the change in spatial position over time.
Drawing on Francis Crick and Christof Koch’s landmark work on qualia — those wholly subjective and deeply interior experiences of what it is like to be oneself — he writes:
We do not merely calculate movement as a robot might; we perceive it. We perceive motion, just as we perceive color or depth, as a unique qualitative experience that is vital to our visual awareness and consciousness. Something beyond our understanding occurs in the genesis of qualia, the transformation of an objective cerebral computation to a subjective experience. Philosophers argue endlessly over how these transformations occur and whether we will ever be capable of understanding them.
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While the perception of a particular motion (for example) may be represented by neurons firing at a particular rate in the motion centers of the visual cortex, this is only the beginning of an elaborate process. To reach consciousness, this neuronal firing, or some higher representation of it, must cross a certain threshold of intensity and be maintained above it… To do that, this group of neurons must engage other parts of the brain (usually in the frontal lobes) and ally itself with millions of other neurons to form a “coalition.”
Such coalitions… can form and dissolve in a fraction of a second and involve reciprocal connections between the visual cortex and many other areas of the brain. These neural coalitions in different parts of the brain talk to one another in a continuous back-and-forth interaction. A single conscious visual percept may thus entail the parallel and mutually influencing activities of billions of nerve cells.
Finally, the activity of a coalition, or coalition of coalitions, if it is to reach consciousness, must not only cross a threshold of intensity but also be held there for a certain time — roughly a hundred milliseconds. This is the duration of a “perceptual moment.”
And yet it is because something immeasurable happens in those hundred milliseconds that we perceive the world not as it is but as we are.
Into the fourth wall he breaks a door to his qualia:
As I write, I am sitting at a café on Seventh Avenue, watching the world go by. My attention and focus dart to and fro: a girl in a red dress goes by, a man walking a funny dog, the sun (at last!) emerging from the clouds. But there are also other sensations that seem to come by themselves: the noise of a car backfiring, the smell of cigarette smoke as an upwind neighbor lights up. These are all events which catch my attention for a moment as they happen. Why, out of a thousand possible perceptions, are these the ones I seize upon? Reflections, memories, associations, lie behind them. For consciousness is always active and selective — charged with feelings and meanings uniquely our own, informing our choices and interfusing our perceptions. So it is not just Seventh Avenue that I see but my Seventh Avenue, marked by my own selfhood and identity.
To know this is to relinquish our habitual delusion of objective perception:
We deceive ourselves if we imagine that we can ever be passive, impartial observers. Every perception, every scene, is shaped by us, whether we intend it or know it, or not. We are the directors of the film we are making — but we are its subjects too: every frame, every moment, is us, is ours.
But how then do our frames, our momentary moments, hold together? How, if there is only transience, do we achieve continuity?
A century after Virginia Woolf contemplated the “moments of being” that make us who we are, he deepens the question and ventures an answer:
Our passing thoughts, as William James says (in an image that smacks of cowboy life in the 1880s), do not wander round like wild cattle. Each one is owned and bears the brand of this ownership, and each thought, in James’s words, is born an owner of the thoughts that went before, and “dies owned, transmitting whatever it realized as its Self to its own later proprietor.” So it is not just perceptual moments, simple physiological moments — though these underlie everything else — but moments of an essentially personal kind that seem to constitute our very being… We consist entirely of “a collection of moments,” even though these flow into one another like Borges’s river.
Complement with psychiatrist Iain McGilchrist on attention as an instrument of love and cognitive philosopher Andy Clarke on the power of expectation in how the mind renders reality, then revisit Oliver Sacks on despair and the meaning of life, the healing power of gardens, and the three essential elements of creativity.