title: The cat's meow: A high-field fMRI assessment of cortical activity in response to vocalizations and complex auditory stimuli.
abstract: Sensory systems are typically constructed in a hierarchical fashion such that lower level subcortical and cortical areas process basic stimulus features, while higher level areas reassemble these features into object-level representations. A number of anatomical pathway tracing studies have suggested that the auditory cortical hierarchy of the cat extends from a core region, consisting of the primary auditory cortex (A1) and the anterior auditory field (AAF), to higher level auditory fields that are located ventrally. Unfortunately, limitations on electrophysiological examination of these higher level fields have resulted in an incomplete understanding of the functional organization of the auditory cortex. Thus, the current study uses functional MRI in conjunction with a variety of simple and complex auditory stimuli to provide the first comprehensive examination of function across the entire cortical hierarchy. Auditory cortex function is shown to be largely lateralized to the left hemisphere, and is concentrated bilaterally in fields surrounding the posterior ectosylvian sulcus. The use of narrowband noise stimuli enables the visualization of tonotopic gradients in the posterior auditory field (PAF) and ventral posterior auditory field (VPAF) that have previously been unverifiable using fMRI and pure tones. Furthermore, auditory fields that are inaccessible to more invasive techniques, such as the insular (IN) and temporal (T) cortices, are shown to be selectively responsive to vocalizations. Collectively, these data provide a much needed functional correlate for anatomical examinations of the hierarchy of cortical structures within the cat auditory cortex.
authors.affiliation: Department of Anatomy and Cell Biology, University of Western Ontario, London, ON N6A 5C2, Canada; Cerebral Systems Laboratory, University of Western Ontario, London, ON N6A 5C2, Canada.
authors.forename: Amee J
authors.initials: AJ
authors.lastname: Hall
authors.affiliation: Department of Physiology and Pharmacology, University of Western Ontario, London, ON N6A 5C2, Canada; Cerebral Systems Laboratory, University of Western Ontario, London, ON N6A 5C2, Canada; National Centre for Audiology, University of Western Ontario, London, ON N6A 5C2, Canada.
authors.forename: Blake E
authors.initials: BE
authors.lastname: Butler
authors.affiliation: Department of Physiology and Pharmacology, University of Western Ontario, London, ON N6A 5C2, Canada; Department of Psychology, University of Western Ontario, London, ON N6A 5C2, Canada; Brain and Mind Institute, University of Western Ontario, London, ON N6A 5C2, Canada; Cerebral Systems Laboratory, University of Western Ontario, London, ON N6A 5C2, Canada; National Centre for Audiology, University of Western Ontario, London, ON N6A 5C2, Canada. Electronic address: steve.lomber@uwo.ca.
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Lomber
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001303:Auditory Cortex / Q000033:anatomy & histology* / Q000502:physiology*; D001306:Auditory Pathways / Q000033:anatomy & histology / Q000502:physiology; D001931:Brain Mapping; D002415:Cats / Q000033:anatomy & histology* / Q000502:physiology*; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging
keywords: Auditory cortex; Cat; Complex sounds; Functional hierarchy; fMRI