What we experience is never limited to our actual sensations. Impressions are always incomplete and require
a dash of subjectivity to render them whole.
Although genes are responsible for the gross anatomy
of the brain, our plastic neurons are designed to adapt to our
experiences. Like the immune system,
which alters itself in response to the pathogens it actually encounters, the
brain is constantly adapting to the particular conditions of life.
As long as we are alive, important parts of the brain are
dividing. The brain is not marble, it is
clay, and our clay never hardens.
The mind stalks the flesh; from our muscles we steal our moods.
Your head contains a hundred billion electrical cells, but not one
of them is you or knows you or cares about you.
If neuroscience knows anything, it is that there is no ghost in the
machine: there is only the vibration of the machinery.
While the corpus callosum lets each of us believe in his or her
singularity, every I is really plural.… When the corpus callosum is cut, the
multiple selves are suddenly free to be themselves.
Though the brain is enclosed by a single skull, it is actually made
of two separate lumps, which are designed to disagree with each other.
We give the world clarity by giving it names.
Music only excites us when it makes the auditory cortex struggle to
uncover its order.
Whenever a noise exceeds our processing abilities --- we can’t
decipher all the different sound waves hitting our hair cells --- the mind
surrenders. It stops trying to
understand the individual notes and seeks instead to understand the
relationships between the notes.
A work of music is not simply a set of individual notes arranged in
time. Music really begins when the
separate pitches are melted into a pattern.
Our sense of sound begins when a sound wave, hurtling through space
at 1,100 feet per second, collides with the eardrum. This shudder moves the
tiniest of three bones in the body, a skeleton locked inside the ear, pressing
them against the fluid-filled membranes of the cochlea. That fluid transforms the waves of compressed
air into waves of salty liquid, which in turn move hair cells. This minute movement opens ion channels, causing
the cells to swell with electricity. If
the cells are bent at a sharp enough angle for long enough, they fire an
electrical message onward to the brain.
Silence is broken. Sound has
begun.
Once the prefrontal cortex thinks it has seen a mountain, it starts
adjusting its own inputs, imagining a form in the blank canvas. In fact, in the lateral geniculate nucleus,
the thick nerve that connects the eyeball to the brain, ten times more fibers
project from the cortex to the eye than from the eye to the cortex. We make our eyes lie.
We can’t separate our own mental inventions from what really
exists. The exact same neurons respond
when we actually see a mountain and when we just imagine a mountain. There is no such thing as immaculate
perception.
Vision begins with an atomic disturbance. Particles of light alter the delicate
molecular structure of the receptors in the retina. This cellular shudder triggers a chain reaction
that ends with a flash of voltage. The
photon’s energy has become information.
Reality is not out there waiting to be witnessed; reality is made by
the mind.
