Redefining the Avian Auditory Functional Hierarchy: Selectivity and Tolerance in the Auditory Cortex of European Starlings
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1
The University of Chicago, Organismal Biology and Anatomy, United States
The ability to recognize auditory objects is thought to depend on neural responses that are selective between categories of the objects and tolerant of variation within those categories. The songs of European starlings (Sturnus vulgaris) consist of series of motifs, temporally discrete vocal elements that are unique to specific individuals. Starlings can recognize motifs of other individuals despite variability in low-level acoustic features, making starlings good models for the study of how relevant and irrelevant variation in vocal communication signals are processed. We measured selectivity and tolerance in six areas of the starling auditory cortex to determine if there were differences among areas that would indicate hierarchical processing. Starlings were operantly trained to differentially recognize sets of conspecific songs, and then extracellular responses of single units were recorded under urethane anesthesia. Neurons were presented with song stimuli comprising one or more variants of several distinct motif types. Selectivity among types and among variants of the same type (tolerance) were estimated using a novel generalized linear mixed model that provides a statistically rigorous framework for characterizing neuronal response distributions. We found significant differences among areas in selectivity, tolerance, and the effects of training. The L2b and L1 subdivisions of field L had the least selectivity and tolerance. The caudal nidopallium (NCM) and subdivision L3 of field L were more selective than other areas, and L3 was the most selective of all. Tolerance was greater in the medial mesopallium (CMM) than in NCM and greater in the lateral mesopallium (CLM) than in all other structures except L3, which had a non-unimodal distribution of tolerance. Sensitivity to songs that were familiar and those that were not also distinguished the responses of CMM and NCM. The observed organization is inconsistent with the traditional view of field L at the bottom of the cortical hierarchy, but mirrors a recently discovered neocortex-like radial circuit in the avian auditory cortex. The results also suggest a divergence within the starling cortex into processing streams that respond to complementary aspects of the variability in communicative sounds.
Acknowledgements
This work was supported by National Institute of Deafness and Other Communication Disorders grants DC007206 and F32DC008752.
Keywords:
auditory,
Forebrain,
hierarchy,
object recognition,
Selectivity,
starling,
Sturnus vulgaris,
tolerance
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster (but consider for Participant Symposium)
Topic:
Sensory: Audition
Citation:
Meliza
C and
Margoliash
D
(2012). Redefining the Avian Auditory Functional Hierarchy: Selectivity and Tolerance in the Auditory Cortex of European Starlings.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00355
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Received:
30 Apr 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Dr. C Daniel Meliza, The University of Chicago, Organismal Biology and Anatomy, Chicago, United States, cdm8j@virginia.edu