Nearly every aspect of our everyday life perception involves integrating information from different sensory modalities, such as when localizing the origin of events from sight, ear and touch, maintaining a coherent image of our own body through visuo-motor integration, or communicating with others by speech and gestures. Building up and constantly updating these multisensory representations is crucial for organisms in order to react adequately to the ever-changing environment. Yet, despite the remarkable importance of attention state for understanding how individual sensory systems work (i.e., vision), there is still little understanding on how attention determines binding across sensory modalities. Contrary to what is often assumed in the literature, we argue that attention is a determinant factor in multisensory integration. This project adapts known paradigms for the study of attention to examine four several representative domains of perception for which multisensory integration plays a critical role; spatial localization, temporal estimation, body-schema and speech. The stress of this research project is therefore placed on brain functions and their associated neural processes regarded as a whole. The methodological approach to be followed will be based on psychophysical paradigms, electrophysiological correlates (ERPs) and functional magnetic resonance imaging (fMRI) and brain stimulation such as Transcranial Magnetic Stimulation (TMS). This combination of techniques will allow us to explore the interplay between multisensory integration and attention, studying how the activity in brain areas involved in multisensory integration may react to the manipulation of attention across space, time or modality. We are not only interested in discovering behavioural correlates or mapping the brain areas involved in this interplay but we want to unravel the neural mechanisms that underlies these behavioural responses, studying which areas interact with each other in a causal way. Our final objective is to make a significant contribution to the understanding of how the perceptual system works in multisensory environments.