|
NEW YORK
TIMES (source) THE NEW YORKER (July/28/2003) The Mind’s Eye Do we control our brains or do our brains control
us? Oliver
Sacks, the author and
neurologist, describes how the experiences of blind people provide a
fascinating insight into the nature of consciousness. In the
last letter he wrote,Goethe observed: "The Ancients said that the
animals are taught through their organs; let me add to this, so are
men, but they have the advantage of teaching their organs in
return." He wrote this in 1832, a time when phrenology was at its
height, and the brain was seen as a mosaic of "little organs"
subserving everything from language to drawing ability to shyness.
Each individual, it was believed, was given a fixed measure of this
or that faculty, according to the luck of his birth. Although
we no longer pay attention, as the phrenologists did, to "bumps" on
the head (each of which, supposedly, indicated a brain-mind organ
beneath), neurology a and neuroscience have stayed close to the idea
of brain fixity and localisation - the notion, in particular, that
the highest part of the brain, the cerebral cortex, is effectively
programmed from birth: this part to vision and visual processing,
that part to hearing, that to touch, and so on. This would seem to
allow individuals little power of choice, of self-determination, let
alone of adaptation, in the event of a neurological or perceptual
mishap. But to
what extent are we - our experiences, our reactions - shaped,
predetermined, by our brains, and to what extent do we shape our own
brains? Does the mind run the brain or the brain run the mind - or,
rather, to what extent does one run the other? To what extent are we
the authors,the creators,of our own experiences? The effects of
effects of profound blindness can cast an unexpected light on this.
To become blind,especially in later life , presents one with a huge,
potentially overwhelming challenge:to find a new way of living, of
ordering one's world, when the old way has been
destroyed. A
DOZEN YEARS ago, I was sent an extraordinary book called Touching
the Rock: An Experience of Blindness. The author, John Hull, was
a professor of religious education who had grown up in Australia and
then moved to England. Hull had developed cataracts at the age of
13, and became blind in his left eye four years later. Vision in his
right eye remained reasonable until he was 35 or so, and then it
started to deteriorate. There followed a decade of steadily failing
vision, until, in 1983, at the age of 48, he became completely
blind. Touching
the Rock is
the journal he dictated in the three years that followed. It is full
of piercing insights relating to Hull's life as a blind person, but
most striking for me is Hull's description of how he experienced a
gradual attenuation of visual imagery and memory, and finally a
virtual extinction of them (except in dreams) - a state that he
called "deep blindness". By
this, Hull meant not only the loss of visual images and memories,
but a loss of the very idea of seeing, so that even the sense of
objects having "appearances", visible characteristics, vanished. He
could no longer, for example, imagine how the numeral 3 looked
unless he traced it in the air with his hand. He could construct
"motor " image of a 3, but not a visual one. Though at first
greatly distressed about the fading of visual memories and images,
Hull came to accept it with remarkable equanimity. He seemed to
regard this loss of visual imagery as a prerequisite for the full
development, the heightening, of his other senses. Two
years after becoming completely blind, Hull had apparently become so
non-visual as to resemble someone who had been blind from birth. In
a profoundly religious way, and in language sometimes reminiscent of
that of St John of the Cross, Hull has entered into this state,
surrendered himself with a sort of acquiescence and joy. And such
"deep" blindness he conceives as "an authentic and autonomous world,
a place of its own... Being a whole-body seer is to be in one of the
concentrated human conditions." Being
a "whole-body seer", for Hull, means shifting his attention, his
centre of gravity, to the other senses, and he writes again and
again of how these have assumed a new richness and power. Thus he
speaks of how the sound of rain can now delineate a whole landscape
for him, for its sound on the garden path is different from its
sound as it drums on the lawn, or on the bushes in his garden.
"Rain," he writes, "has a way of bringing out the contours of
everything; it throws a coloured blanket over previously invisible
things; instead of a fragmented world, the steadily falling rain
creates continuity of acoustic experience...presents the fullness of
an entire situation all at once." Hull
comes to feel an intensity of being-in-the-world, beyond anything he
knew when he was sighted. Blindness now becomes for him "a dark,
paradoxical gift". This is not just "compensation" he emphasises,
but a whole new mode of human being. Important studies of adaptation in the brain were
begun in the 1970s by, among others, Helen Neville, a cognitive
neuroscientist now working in Oregon. She showed that in
prelingually deaf people (that is, those who had been born deaf or
become deaf before the age of two or so) the auditory parts of the
brain had not degenerated or atrophied. These had remained active
and functional, but with an activity and a function that were new:
they had been transformed, "reallocated" in
Neville's term, for processing visual language. Comparable studies
in those born blind, or early blinded, show that the visual areas of
the cortex, similarly, may be reallocated in function, and used to
process sound and touch. 'Even
though I am totally blind I consider myself a visual person.I "see"
objects. I can see my hands typing the keyboard now'
With
the reallocation of the visual cortex to touch and other senses,
these can take on a hyperacuity that perhaps no sighted person can
imagine. Geerat Vermeij, a blind biologist, has been able to
delineate many new species of mollusc based on tiny variations in
the shapes and contours of their shells. Faced
with such evidence, neurologists began to concede that there might
be a certain flexibility or plasticity in the brain, at least in the
early years of life. But when this critical period was over, it was
assumed, the brain became inflexible, and no further changes of a
radical type could occur. The experiences that Hull so carefully
recounts give the lie to this. It is clear that his perceptions, his
brain, did finally change, in a fundamental way. Indeed, Alvaro
Pascual-Leone and his colleagues in Boston have recently shown that,
even in adult sighted volunteers, as little as five days of being
blindfolded produces marked shifts to non-visual forms of behaviour
and cognition, and they have demonstrated the physiological changes
in the brain that go along with this. The
brain, clearly, is capable of changing even in adulthood, and I
assumed that Hull's experience was typical of acquired blindness -
the response, sooner or later, of everyone who becomes blind, even
in adult life. Had I
been wrong, or at least one-sided, in accepting Hull's experience as
a typical response to blindness? Had I been guilty of emphasising
the mode of response too strongly, oblivious to the possibilities of
radically different responses? In
this, it seemed, he had been extremely successful, developing a
remarkable power of generating, holding, and manipulating his mind,
so much so that he had been able to construct an imagined
visual world that seemed almost as real and intense to him as the
perceptual one he had lost - and, indeed, sometimes more real, more
intense, a sort of controlled dream or hallucination. This imagery,
moreover, enabled him to do things that might have seemed scarcely
possible for a blind man. "I
replaced the entire roof guttering of my multi-gabled home
single-handed," he wrote, "and solely on the strength of the
accurate and well-focused manipulation of my now totally pliable and
responsive mental space." (Torey later expanded on this episode,
mentioning the great alarm of his neighbours at seeing a blind man,
alone, on the roof of his house - and, even more terrifying to them,
at night, in pitch darkness). In his
new memoir, Out of Darkness, he explores how his life has
been affected by blindness. Torey's father was the head of a large
film studio in Hungary before the war and would often give his son
scripts to read. "This," Torey writes, "gave me the opportunity to
visualise stories, plots and characters, to work my imagination - a
skill that was to become a lifeline and source of strength in the
years ahead." He
emphasised to me the importance of a most critical choice at this
juncture: "I immediately resolved to find out how far a partially
sense-deprived brain could go to rebuild a life." Put this way, it
sounds abstract, like an experiment. But in his book one senses the
tremendous feelings underlying his resolution - the horror of "the
empty darkness", "the grey fog that was engulfing me -and the
passionate desire to hold on to light and sight, to maintain, if
only in memory and imagination, a living visual world. John
Hull, who did not use his potential for imagery in a deliberate way,
lost it in two or three years, and became unable to remember which
way round a 3 went; Torey, on the other hand, soon became able to
multiply four-figure numbers by each other, as on a blackboard,
visualising the whole operation in his mind. He
became able "to imagine,to visualise for example, the inside of a
differential gearbox in action - as if from inside it's casing. I
was able to watch the cogs bite, lock and revolve, distributing the
spin as required. I began to play around with this internal view in
connection with mechanical and technical problems visualising how
subcomponents relate in the atom, or the living cell." This powerful
imagery was crucial, Torey thought, in enabling him to arrive at a
solution of the brain-mind problem by visualising the brain "as a
perpetual juggling act of interacting routines." Living in the world of the blind
SOON
AFTER READING Torey's manuscript, I received proofs of yet another
memoir by a blind person: Sabriye Tenberken's My Path Leads to
Tibet. Tenberken has travelled, often alone, throughout Tibet,
where for centuries blind people have been treated as less than
human and denied education, work or any role in the community.
Almost single handedly, Tenberken transformed the prospects of blind
people over the past half-dozen years, devising a form of Tibetan
Braille, establishing schools for the blind, and integrating the
graduates of these schools into their communities. Tenberken
herself impaired vision almost from birth, but was able to make out
faces and landscapes until she was 12.As a child in Germany, she had
a particular predilection for colours, and loved painting, and when
she was no longer able to decipher shapes and forms she could still
use colours to identify objects. Tenberken has, indeed an intense
synaesthesia. "As
far back as I can remember," she writes, "numbers and words have
instantly triggered colours in me ... number four, for example [is]
gold. Five is light green.Nine is vermillion... Days of week, as
well as months, have their colours, too." Her synaesthesia has
persisted and been intensified, it seems,by her blindness. These disparities do not faze her in the least -
she is happy to have so vivid a visual imagination. Hers is
essentially an artistic
imagination, which can be
impressionistic, romantic: whereas Torey's imagination is that of an
engineer, and has to be factual, accurate down to the last
detail. If we
are sighted, we build our own images, using our eyes, our visual
information, so instantly and seamlessly that it seems to us we are
experiencing "reality" itself. One may need to see people who are
colour-blind, or motion-blind, who have lost certain cerebral
visual capacities from cerebral injury,to realise the enormous
synthesis, the dozens of subsystems involved in the subjectively
simple act of seeing. But can a visual image be built using
nonvisual information - information conveyed by the other senses, by
memory, or by verbal description? There
has been much recent work on the neural bases of visual imagery, and
it is now generally accepted that visual imagery activates the
cortex in a similar way, and with almost the same intensity, as
visual perception itself. And yet studies on the effects of
blindness on the human cortex have shown that functional changes may
start to occur in a few days, and can become profound as the days
stretch into months or years. Torey,
who is well aware of all this research, attributes Hull's loss of
visual imagery and memory to the fact that he did not struggle to
maintain it, to heighten and systematise and use it, as Torey
himself did. Perhaps Torey was able to stave off an otherwise
inevitable loss of neuronal function in the visual cortex; but
perhaps, again, such neural degeneration is quite variable,
irrespective of whether or not there is conscious visualisation.
But what if their differences reflect an
underlying predisposition independent of blindness? What of visual
imagery in the sighted? I first became conscious that there could be
huge variations in visual imagery and visual memory when I was 14 or
so. My mother was a surgeon and comparative anatomist, and I had
brought her a lizard's skeleton from school. She gazed at this
intently for a minute, turning it round in her hands, then put it
down and without looking at it again did a number of drawings of it,
rotating it mentally by 30 degrees each time, so that she produced a
series, the last drawing exactly the same as the first.I could not
imagine how she had done this, and when she said that she could
"see" the skeleton in her mind just as clearly and
vividly as if she were looking at it, and that she simply rotated the image through a twelfth
of a circle each time, I felt bewildered, and very stupid. I could
hardly see anything with my mind's eye at most, faint,
evanescent images over
which I had no control. I was, however, to get a vivid idea of what mental
imagery could be like when, during the 1960s,I had a period of
experimenting with large doses of amphetamines.
These can produce striking perceptual changes, inducing dramatic
enhancements of visual imagery and memory. For a period of two weeks
or so, I found that I could do the most accurate anatomical
drawings. I could mentally project the image onto the paper before
me and trace its outlines with a pencil. But when the
amphetamine-induced state faded, after a couple of weeks, I could no
longer visualise, no longer project images, no longer draw nor have
I been able to do so in the decades since. A few
months ago, at a medical conference in Boston, I spoke of Torey's
and Hull's experiences of blindness. Alter my talk,a man came up to
me and asked how well, in my estimation, sighted people could
function if they had no visual imagery. He went on to say that he
had no visual imagery whatever, at least none that he could
deliberately evoke, and that no one else in his family had any
either. So is
Torey's greatly developed visual imagery not as indispensable as he
takes it to be? Might he have done everything he did, from
carpentry, to roof repair to making a model of the mind, without any
conscious imagery at all? Simple
visual imagery may suffice for the design of a screw, an engine or a
surgical operation, and it may be relatively easy to model these
essentially reproductive forms of imagery or to simulate them by
constructing video games or virtual realities of various sorts. Such
powers may be invaluable, but there is something passive and
mechanical and impersonal about them which makes them utterly
different from the higher and more intimate powers of the
imagination, where there is a continual struggle for concepts and
form and meaning, calling upon all the powers of the self.
Imagination dissolves and transforms, unifies and creates, while
drawing upon the "lower" powers of memory and association. It is by
such imagination, such "vision", that we create or construct our
individual worlds. At
this level, one can no longer say of one's mental landscapes what is
visual, what is auditory, what is image, what is language, what is
intellectual, what is emotional - they are all fused together and
imbued with our own individual perspectives and values. Such a
unified vision shines out from Hull's memoir no less than from
Torey's, despite the fact that one has become "nonvisual" and the
other "hypervisual". What seems at first to so decisive a difference
between the two men is finally, a radical one, so far as personal
development and sensibility go. Even though the paths they have
followed might seem irreconcilable both men have "used" blindness to
release their own creative capacities and emotional selves, and both
have achieves a rich and full realisation of their own individual
worlds. © Oliver Sacks. This is an extract from an article
first published in The New Yorker, For more details, visit www.oliversacks.com
|
||
