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Journal Article 11.1: Lee, Y.-S., Hanke, M., Kraemer, D., Lloyd, S., & Granger, R. (2011). Neural architecture of auditory object categorization. i-Perception, 2(8), 756-756. doi:10.1068/ic756

Abstract: We can identify objects by sight or by sound, yet far less is known about auditory object recognition than about visual recognition. Any exemplar of a dog (e.g., a picture) can be recognized on multiple categorical levels (e.g., animal, dog, poodle). Using fMRI combined with machine-learning techniques, we studied these levels of categorization with sounds rather than images. Subjects heard sounds of various animate and inanimate objects, and unrecognizable control sounds. We report four primary findings: (1) some distinct brain regions selectively coded for basic (“dog”) versus superordinate (“animal”) categorization; (2) classification at the basic level entailed more extended cortical networks than those for superordinate categorization; (3) human voices were recognized far better by multiple brain regions than were any other sound categories; (4) regions beyond temporal lobe auditory areas were able to distinguish and categorize auditory objects. We conclude that multiple representations of an object exist at different categorical levels. This neural instantiation of object categories is distributed across multiple brain regions, including so-called “visual association areas,” indicating that these regions support object knowledge even when the input is auditory. Moreover, our findings appear to conflict with prior well-established theories of category-specific modules in the brain.

Journal Article 11.2: Salminen, N. H., Tiitinen, H., & May, P. J. C. (2012). Auditory spatial processing in the human cortex. The Neuroscientist, 18(6), 602-612. doi:10.1177/1073858411434209

Abstract: The auditory system codes spatial locations in a way that deviates from the spatial representations found in other modalities. This difference is especially striking in the cortex, where neurons form topographical maps of visual and tactile space but where auditory space is represented through a population rate code. In this hemifield code, sound source location is represented in the activity of two widely tuned opponent populations, one tuned to the right and the other to the left side of auditory space. Scientists are only beginning to uncover how this coding strategy adapts to various spatial processing demands. This review presents the current understanding of auditory spatial processing in the cortex. To this end, the authors consider how various implementations of the hemifield code may exist within the auditory cortex and how these may be modulated by the stimulation and task context. As a result, a coherent set of neural strategies for auditory spatial processing emerges.

Journal Article 11.3: Savel, S., & Drake, C. (2014). Auditory azimuthal localization performance in water as a function of prior exposure. Human Factors, 56(4), 772-783. doi:10.1177/0018720813503366

Abstract: We report two psychoacoustical experiments that assessed the relationship between auditory azimuthal localization performance in water and duration of prior exposure to the milieu.