perceptual-motor thresholds in the order of 30 to 40 milliseconds (Poppel, 1985). There is even a
sophisticated confusion of the objective temporal order.
Take the phenomenon of the "cutaneous rabbit", as Daniel Dennett (1991, p. 142 f.) called it: The
subjects's arm rests cushioned on a table, and mechanical tappers are placed at two or three
locations along the arm, up to a foot apart. A rhythmic series of taps is delivered by the tappers, e.g.
five at the wrist followed by two near the elbow and three more on the upper arm. The taps are
delievered in intervalls between 50 and 200 milliseconds. The astonishing effect is that the subject
feels the taps travelling in regular sequence over equidistant points up the arm - as if a little animal
were hopping along it. But the brain obviously cannot "know" about a tap at the elbow until after it
happens. So there is a change in the representation of the intervals, a mistaken interpretation after
the taps are registered.
Another example are two alternately flashing lights in a dark room, separated by a distance not too
large, which are perceived as one single, rapid moving dot. If the lights have different colors, it
seems to the subject that there is a change in color in the middle of the move (although the second
light is not yet shining at this very moment!). If one is not willing to believe in clairvoyance, we must
assume that our brain can predate this flashing somewhat into the past.
An even more surprising discovery were Benjamin Libet's (1993) experimental findings of neural
delays, retrograde stimulus masking and subjective referral backwards in time. The comparison
between an electrical stimulus applied to the hand and a stimulus applied directly to the
corresponding cortex area demonstrates that we perceive the hand but not the cortex stimulus 0,5
seconds later. But we do not realize this delay, because our brain shifts it back into the past. Thus,
there seems to be a double illusion: our experience of time is, contrary to common sense, pretty
much behind the events and we are not able to realize this because our temporal frame of
reference is also shifted. Furthermore, some informations could be masked by later informations. In
addition, Libet and others have also demonstrated that unconscious brain processes (marked by a
"readiness potential") occur at least 0,35 seconds before the conscious intention to act, although it
seems to us that our intention causes our action.
These results are subject to controversial interpretations, to be sure (e.g., Churchland, 1981, and
Gomes, 1998). But they suggest that what is objectively determinable as an unequivocal order of
before-and-after need not respond necessarily and unequivocally to our subjective experience. The
spatiotemporal representation of some stimuli seems to be a construct of our neural activities and
need not correspond to the real order (just as it is pretty well documented that we remove our hand
from the fire before we feel the pain, contrary to our subjective experience). There is no need for
more precision as long as these constructs are not biologically disadvantageous, sorted out by the
sieves of evolution. Furthermore, there is no neuroanatomical center where everything comes
together. There is no "Cartesian Theatre", as Dennett (1991) has called this view, which underlies
our somewhat misguided conception of temporal order and leads to an infinite regress (the well-
known homunculus problem). There is a symphony of distributed, parallel-processed
representations or "multiple drafts" instead, interacting with each other, organizing themselves in a
complex, nonlinear way and bound together by spatial and temporal patterns, guided perhaps by
far-reaching synchronized neural activities (Metzinger, 1995, and Singer, 1996).
I.3. "Paint It Black" Or "In The White Room" - NCC And A Vision Of The Brain
NCC reveal properties and functions of consciousness which cannot be elucidated either by
introspective phenomenology or by psychological experiments alone - vision, for instance (cf. Zeki,
1993, 1997). Here, the studies of lesions due to stroke, ischaemia, injury, tumor, carbon monoxide
poisoning and so on are very instructive. They give important insights in the neural organisation
underlying consciousness.
• For instance, for a person with cerebral achromatopsia due to a lesion of V4 in the fusiform gyrus
it is sometimes not only impossible to perceive colors anymore but also to imagine, remember and
dream them. (In some cases color imagery is preserved in achromatopsics probably due to an
afferent disconnection of visual input to stored color representations i.e. an impairment of bottom-up
but not top-down processing.)
• Bilateral damage of the parieto-occipital lobe (the "where-system") leads to an inability to localize
visual stimuli in space and to accurately describe the location of familiar objects or landmarks from
memory,