Abstract

This talk focusses on simple skin sensations such as temperature and touch, but aims to address somewhat foundational questions about perception. Why are sensations so qualitatively different from each other, given their shared code of action potentials reaching the CNS ? ‘Labelled line’ theories explain sensory quality in terms of a ‘label’ carried by the originating receptor and nerve. In the first part of the talk, I will suggest that warmth and cold indeed function as labelled lines from the human skin, despite surprising levels of noise in sensory quality perception. The second part of the talk deals with spatial perception. Classical theories postulated a distinct sensory quality of ‘thereness’, or local sign, associated with a stimulus. This quality was explained in terms of motor signals required to orient towards the stimulus. These theories frequently cited self-touch, as when one hand strokes the other, as an example. The experience of spatial touch would derive from the moving hand, rather than the touched hand. I report a series of experiments testing this hypothesis, but failing to find strong evidence for motor-based theories of space. I explore an alternative hypothesis, that the skin supports a spatial ‘tactile field’, akin to the visual field.