Change detection in complex acoustic scenes

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The ability to detect changes around us, such as the appearance or disappearance of an object, has far-reaching implications for survival. These processes have received considerable attention in Vision research. In contrast, the processes by which listeners detect the appearance or disappearance of objects in busy acoustic scenes, comprised of many concurrent sources, remain poorly understood. This is surprising because often it is sound that alerts us to important changes in the scene: Hearing is sensitive to a much larger space than the other senses and in many cases we hear change before we see it (for example, somebody entering the room while your back is to the door; Sudden quiet from the kids' playroom indicating they are up to mischief..). Indeed, the auditory system is commonly assumed to play a key role in the brain's change-detection network by serving as an 'early warning device', rapidly directing attention to new events in the scene. The present project is classified as 'basic' research with the goal of understanding how listeners with normal hearing detect and process change-events (appearance or disappearance of sources) in auditory scenes. The behavioural and functional brain imaging experiments detailed here are designed to systematically explore listeners' change detection behavior, understand the relevant processes and identify their neural underpinnings: How are object appearance and disappearance events detected? What brain mechanisms are involved? Are change events detected automatically by the brain, even when listeners' attentional focus is elsewhere? What makes certain change events fundamentally more salient than others? Under what conditions do listeners perform well, and which situations result in reduced performance? In busy scenes, such as those we often face in the environment, behaviourally relevant scene changes often coincide in time with other events. How resilient are the auditory change detection mechanisms to irrelevant events occurring at the same time as the auditory change? Do auditory and visual perturbing events have the same detrimental effect on performance? These issues are important from the point of view of understanding perception and how the brain analyses and represents the dynamics of our surrounding environment. Furthermore, understanding what makes certain events pop out and grab attention, while other events go unnoticed is important for designing human-computer interfaces, and other devices intended to help professionals (operating room personnel, air traffic controllers, pilots, etc.) operate effectively in environments where the detection of change is critical. Additionally, since change detection is a major contributor to efficient interaction with the environment, understanding the profile of change detection in normal listeners can provide a measure against which to evaluate hearing impairment as well as the benefit obtained from hearing aids.