Quality space computations for consciousness

The quality space hypothesis about conscious experience proposes that conscious
sensory states are experienced in relation to other possible sensory
states. For instance, the colour red is experienced as being more like orange,
and less like green or blue. Recent empirical findings suggest that subjective
similarity space can be explained in terms of similarities in neural activation patterns.
Here, we consider how localist, workspace, and higher-order theories of
consciousness can accommodate claims about the qualitative character of experience
and functionally support a quality space. We review existing empirical
evidence for each of these positions, and highlight novel experimental tools,
such as altering local activation spaces via brain stimulation or behavioural training,
that can distinguish these accounts.