Neuroimaging studies of auditory perception and attention

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Our auditory environment is often comprised of a myriad of sounds and yet there has been a paucity of work investigating how sound "objects" are represented in the brain and how attention is deployed to a particular sound object within a noisy environment. Determining how attention is allocated in complex auditory scenes is of interest for both practical and theoretical reasons. On the practical side, this information can guide the development of training regimens to help individuals with attention problems. On the theoretical side, it can provide insight into the neural mechanisms mediating auditory perception, attention, and cognition. The proposed research program combines behavioural techniques with scalp-recording of event-related brain potentials (ERPs) and is developed around two distinct but interleaved themes: (1) assessing the representation of concurrent sound objects in memory using a change detection paradigm, and (2) assessing the deployment of attention within a noisy environment. We will examine the surprising failure of listeners to detect salient changes in auditory scenes (i.e., change deafness). This change deafness may occur because of a failure to properly encode various sound objects in memory and/or a problem in comparing various scenes. We will examine these hypotheses by comparing the neural activity associated with the encoding and retention processes. In addition, we will examine the similarities and differences in neural activity for change blindness and change deafness. The deployment of attention during auditory scenes will be investigated by asking participants to indicate whether an auditory scene is comprised of a predefined target sound (among other sounds occurring simultaneously at various locations). We anticipate that the deployment of auditory attention will be characterized by enhanced neural activity contralateral to the target location and that this neural activity will differ when attention is directed to sound identity (e.g., talker's voice) compared to attention allocated to location (i.e., talker's location). We will use the knowledge gained from these studies to refine our current object-based account of auditory attention.