Our understanding of how perception operates in real-world environments has been substantially advanced by studying both multisensoryprocesses and "top-down" control processes influencing sensory processing via activity from higher-order brain areas, such as attention, memory, and expectations. As the two topicshave been traditionally studied separately, the mechanisms orchestrating real-world multisensory processingremain unclear.Past work has revealed that the observer's goals gate the influence of many multisensory processes on brain and behavioural responses, whereas some other multisensory processes mightoccur independently of these goals. Consequently, other forms of top-down control beyond goaldependence are necessaryto explain the full range of multisensory effects currently reported at the brain and the cognitive level. These forms of control includesensitivity to stimulus context as well as the detection of matches(or lack thereof) between a multisensory stimulus and categorical attributes of naturalistic objects (e.g. tools, animals). In this review we discuss and integrate the existing findings that demonstrate the importance of such goal-, object-and context-based top-down control over multisensory processing. We then put forward a few principles emerging from this literature review with respect to the mechanisms underlying multisensory processing, and discuss their possible broader implications. Attention, multisensory, control, object, audiovisual, brain mapping 3 Research from the past 30 years has demonstrated a whole range of behavioural benefits engendered by integrating information across the senses (multisensory integration, MSI), including faster motor responses and facilitated object recognition in noisy environments (e.g. Stein 2012). In a separate and independent manner, studies employing unisensory stimuli have been critically advancing our understanding of the nature and the importance of top-down mechanisms that control information processing. Thetopdown nature of these mechanisms lies in that they shape perceptual processing of new inputs by activating information stored in higher-order brain areas (e.g. Summerfield and Egner 2009).
Key words:Studies of top-down control have traditionally focused on attentional (i.e. goaldependent)mechanisms, which promote the processing of stimulior objects in the environment that areimportant tothe current behavioural goals of the observer (e.g.Desimone and Duncan 1995). These mechanisms enhance the processing of stimuli appearing in task-relevant spatial locations and/or moments in time. These mechanisms likewise facilitate the processingof those stimuli whose attributes (e.g. colour red), feature dimensions (e.g. shape) or identity (e.g. a particular face) match the observer's goals.Simultaneously, it has been increasingly recognised in the literature that information processing issensitive to other types oftop-down processes, principally those gauged by thememory of past stimulation and one's expectations (see Figure 1A for a summar...