Modality general and modality specific coding of hedonic valence

The pleasant or unpleasant qualities that attach to our perceptions help to determine whether we approach or avoid environmental stimuli, shaping their affordances. How do brains create this affective perceptual dimension? The traditional answer is that sensory areas serve only as conduits for external impressions that are then modulated by heteromodal limbic structures in subsequent phases. Here we raise the possibility that, in addition to these well established gain control effects, sensory systems might also have a more direct role in representing the pleasantness component of perception, as supported by several strands of recent brain imaging evidence. In conjunction with a shared valence code that is independent of its sensory origins, valence representations interleaved within sensory brain areas may support finer grained experiential distinctions between how things look, sound, feel, taste and smell good or bad to us, offering a higher dimensional space of evaluative discriminations.