Assessing audiotactile interactions: Spatiotemporal factors and role of visual experience

This thesis investigated the crossmodal interactions occurring between hearing and touch. Chapters 1 to 6 present the background to this topic and an introduction to the underlying mechanisms of crossmodal perception. Chapter 1 provides a historical overview on the pioneering studies in this issue, whereas in the successive ones the main behavioural evidence on is described. Specific aspects are presented across the chapters, with Chapter 2 presenting the studies using detection/discrimination tasks, intensity tasks, or investigating texture perception or crossmodal sensory illusions and pseudosynaesthetic correspondences. In the subsequent chapters, more specific aspects are taken into consideration, such as the temporal (Chapter 3) and the spatial (Chapter 4) constraints characterizing audiotactile interactions. In Chapter 5, special attention is given to the neural substrates of the audiotactile sensory interplay, in both humans and monkeys. Since there is considerable evidence showing that visual deprivation influences how touch and hearing interact, Chapter 6 will be devoted to explore this topic in more detail. The following chapters present the experimental studies designed to empirically investigate different aspects of audiotactile interactions. Chapter 7 contains experimental studies examining the potential existence of a sensory dominance between hearing and touch, by investigating different portions of the peripersonal space and/or spatial arrangement of the stimuli. Chapter 8 is focused on evaluate the capability of humans in matching the frequency pattern of auditory, tactile and crossmodal stimuli. The spatial factors affecting audiotactile interactions will be explored in Chapter 9, by evaluating how the perception of apparent motion in one modality is biased by the presentation of apparent moving stream in the other modality. The investigation of crossmodal compatibility effects is the topic of Chapter 10. Since visual deprivation has been proved to influence how touch and hearing interact, the last chapter (Chapter 11) will be devoted to compare either spatial or temporal perception, as well as the construction of frames of reference for tactile processing - in relation with auditory stimulation- in blind and sighted individuals.