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<p>On Tue, 14 Jan, 2020 at 6:05 PM Ben Zaiboc wrote:</p>
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<div>Here is a hypothesis that is at least theoretically
testable: The experience of redness is accompanied by
the presence of certain neural circuits in parts of
the visual cortex. (in V8, in the occipital lobe), and
that temporarily knocking out these circuits (via
local electrodes, or a drug, or some other means)
would prevent the perception of redness (as well as
all other colours, quite possibly).</div>
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<div> If this was done precisely enough, it would at
least demonstrate that the perception of colour was
dependent on these circuits. If some kind of neural
interface was developed that could link to precise
sets of neurons, you could maybe even pinpoint
circuits that only affect the perception of a specific
hue and saturation of redness and not other colours.
With enough investigation of this kind, you could
probably even tease out the entire route of a large
neural circuit that travels round the visual areas,
the thalamus and other parts of the brain, and be able
to say "this circuit here, is redness (Hue 0, Sat 67%)
(Strawberry, as it happens). If interrupting or
disrupting that circuit removes that specific redness
quale (such that the subject would report that they
can't see it, and tests could verify that), then
you've pinned it down. You now know what that quale
actually is.</div>
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Rafal Smigrodzki <a class="moz-txt-link-rfc2396E" href="mailto:rafal.smigrodzki@gmail.com"><rafal.smigrodzki@gmail.com></a> replied:<br>
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<div>### I think you are on the right track in general but
going in the wrong direction: Qualia are best understood
as properties of conscious brains, rather than low- and
mid-level local circuits. Pinpointing which precise part
of a color rosetter in the visual cortex is necessary to
trigger conscious perception of a specific hue doesn't
tell you that much. Instead I think we will understand the
problem better once we move up in our level of analysis,
to the detailed workings of whole large-scale networks
within the brain.</div>
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<div>Most likely the answer will be a nothingburger, a huge
load of details and a dismissal of the question of "What
are qualia, for real?", rather than something
groundbreaking, mystery-busting and spiritually uplifting.
It would be like our modern answer to "What is life?" -
which is just a mass of details about genetics,
metabolism, control theory and the like, rather than the
discovery of the mystic "elan vital".</div>
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<div>But, who knows? Future neuroscience and AI research
will maybe tell.</div>
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<div>Rafal</div>
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<p>I expect you're right, and the whole brain, or at least large
parts of it, will be involved.</p>
<p>Even so, it's possible that we could identify a specific pattern
in the large-scale networks, and show that it's necessary and
sufficient to produce the sensation of the colour 'strawberry'. To
be sure, that would be a huge load of details, but it would also
answer the question "what is the strawberry-colour quale?", very
precisely. And I wouldn't be at all surprised if that answer was
only valid for one specific individual. In fact, I'd be very
surprised if it wasn't.</p>
<p>I suspect a clear and precise answer like this still wouldn't
satisfy some people, though!</p>
<p>Another potential problem is that it might not just be specific
to a single individual, but also to a specific point in time (i.e.
it changes over time, because of related changes in the
individuals brain due to experience, learning, etc.)</p>
<p>In fact, thinking about it, this seems inevitable.</p>
<p>I still think, though, that the hypothesis 'qualia are patterns
of neural activation' can be shown to be falsifiable, given the
appropriate technology.</p>
<p>Ben Zaiboc<br>
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