Temporal Aspects of Subjective Visual Experience: Evidence from Stimulus-evoked Hallucination

AbstractOur understanding of human visual perception generally rests on the assumption that conscious visual states represent, in some qualitative fashion, the complex interaction between spatially structured variations in the ambient optic array and our visual nervous systems. The existence of visual hallucinations (or purely subjective visual experience) in a number of pathologies as well as in experimental contexts questions the assumption that what we see in the environment is necessarily determined by spatial structure in the distal stimulus. The experimental data go further by showing that conscious states of apparent vision (i.e., apperception) are triggered by temporal stimulation that does not ultimately relate to what the observer ‘sees’ in the apperceptive field. We have shown that the subjective experience of complex colour and forms is evoked by flickering light and, critically that the incidence and type of subjective experience varies with flicker frequency and phase (Becker & Elliott, 2006; Becker et al., 2008; Elliott et al., 2012). In this contribution, I shall outline evidence that subjective experiences, perhaps also hallucinations, arise from dynamic systems states with very well defined temporal structure. This structure is both measurable and refers to well- known perceptual timing quanta – leading in turn to novel and perhaps radical conclusions about the relationship between dynamic systems and perceptual (and perhaps more generally psychological) experience