Qualia realism and neural activation patterns

A thought experiment focuses attention on the kinds of commonalities and differences to be found in two small parts of visual cortical areas during responses to stimuli that are either identical in quality, but different in (retinal) location, or identical in location and different only in the one visible property of colour. Reflection on this thought experiment leads to the view that patterns of neural activation are the best candidates for causes of qualitatively conscious events (qualia). This view faces a strong objection, namely, that patterns can be realized in many media, and thus candidates for patterns that cause qualia might be realized in ways that would not plausibly result in consciousness. It is argued that this objection can be overcome if qualia-causing patterns of events must be realized within small spatial and temporal regions. Much more importantly, it is argued that this restriction on region size need not be ad hoc. The key concept needed to establish this important point is ‘natural salience’, i.e., distinction from background noise that does not depend on application of a criterion of selection. It is explained how natural salience could figure in an empirically-based theory that would entail size restrictions for qualia-causing neural activation patterns.

The question is then raised as to how the resulting view diverges from Chalmers’ (1996) account, which relies on the Principle of Organizational Invariance. A second thought experiment envisages replacement of neurons by computer chips with synaptic interfaces. Reflection on this thought experiment enables us to conceptually, and possibly empirically, separate the two views. An argument for preferring the patterns- as-causes (of qualia), or PACQ, view is given. Because natural salience does not plausibly produce strictly discontinuous boundaries between pattern and noise, questions naturally arise as to the relation of the PACQ view (as developed here) to panpsychism and to ‘emergence’. The PACQ view is distinguished from panpsychism, and it is explained how the former avoids what Seager (1995) calls ‘the combination problem', and is thus preferable to panpsychism. The relation of the PACQ view to ‘emergence’ is explained. The conclusion of the paper is that the PACQ view is a philosophically defensible and potentially scientifically fruitful view that offers qualia realists the best hypothesis concerning the neural causes of qualia.