• whereas bilateral damage of the inferior temporal lobe (the "what-system") causes impairment of
perceiving object identity from appearance and describing object appearance from memory.
• Furthermore, some patients with lesions in V1 but spared subcortical pathways (lateral geniculate
nucleus and pulvinar nucleus; the latter gets inputs from the retina via the superior colliculus in the
midbrain), are able to perceive motion in their otherwise blind fields (but they do not see stationary
objects). In contrast to "blindsight", where subjects are able to discriminate visual stimuli which they
are not consciously aware of having seen, patients are conscious of residual motion vision without
being forced to guess whether there is motion or not. They describe this experience, e.g., as "vague
and shadowy", similar to the experience of a normal subject who shuts his eyes, looks out of the
window, moves his hand in front of him and sees the shadows. Some patients can only detect fast-
moving stimuli, whereas others can only detect very slowly moving ones.
These examples suggest, as Semir Zeki (1997, p. 143) has pointed out, that "there may be many
more or less separate consciousnesses for different attributes at least of the visual world, based on
activities in separate visual areas." Thus, at least visual consciousness is in some sense modular
and not exclusively dependent either upon a single cortical area (or multiple, but intimately
connected areas) or upon the healthy functioning of the entire system. Despite our phenomenal
impression that our consciousness is indivisible and maybe even not spatial, lesions show that it is
possible to lose consciousness not only completely, but also in bits and pieces. Thus,
consciousness has aspects of divisibility and spatiality even if we cannot recognize them by
introspection.
II. Problems And Shortcomings
There are some crucial problems and limitations for NCC research, partially related with
philosophical issues. This is one reason why metatheoretical reflections are required, which are
part of what could be called neurophilosophy (Churchland, 1986).
II.1. "Smoke On The Water" Or "Riders On The Storm" - Limitations Of Correlations
Correlation implies neither causation nor identity (although it might be interpreted as an indication
for one of them). For example, a strict correlation of birth rates and the size of stork populations
does not mean that babies are made or brought by storks; and a strict correlation between the
movements of soccer-players on a TV screen and in the stadium from which there is a live
broadcast does not mean that the pictures on TV are identical with the soccer players (Zoglauer
1998, p. 106). Thus, NCC alone are not sufficient to prove that our conscious experience is caused
by or identical with neural events. There is even a tension between the ways of talking about
causation and identity here. But of course this depends strongly on our notions of causality and
identity, which I cannot discuss in this context. In any case, neural events need not necessarily be
identified with mental events or cause them. The correlations are compatible with very different
other dependencies and ontologies (see III.5.), e.g., there could be a common cause in the past for
both neural and mental states which are otherwise independent from each other (e.g., Gottfried
Wilhelm Leibniz' preestablished harmony), or a continued intervention of a causal agent, e.g. God,
synchronizing neural and mental states (e.g., occasionalism, as it was proposed by Arnold
Geulincx and Nicolas Malebranche), or both states are two aspects of one and the same underlying
microprocess, or the neural states are caused by the mental states and not vice versa, or the
correlations are just an improbable or unexplainable coincidence. Furthermore, correlation does not
imply identity because the simultaneous occurrence of a mental and a neural state is also
consistent with parallelism and epiphenomenalism. It is not possible to refute a sufficiently
sophisticated version of parallelism empirically, for instance by reference to NCC, because there is
no way to distinguish between identity and parallelism empirically, as it was already admitted by
Herbert Feigl (1958, p. 437 and 463).
II.2. "Private Investigations" Or "Empty Rooms"- Restricted Access For NCC
There are limitations of empirical access due to the well-known problem of subjectivity, the
problem of other minds, and the problem of self-deception.