Cortico-cortical connectivity within ferret auditory cortex

• Published in: Journal of comparative neurology (1911) 2015-10, Vol.523 (15), p.2187-2210
• Main Authors: Bizley, Jennifer K., Bajo, Victoria M., Nodal, Fernando R., King, Andrew J.
• Format: Article
• Language: English
• Subjects: Animals; Auditory Cortex - anatomy & histology; auditory system; carnivore; Female; Ferrets - anatomy & histology; Male; multisensory; Mustela putorius; Mustela putorius furo; Neural Pathways - anatomy & histology; Neuroanatomical Tract-Tracing Techniques; topography; tract tracing
• ISSN: 0021-9967; 1096-9861
• DOI: 10.1002/cne.23784

ABSTRACT Despite numerous studies of auditory cortical processing in the ferret (Mustela putorius), very little is known about the connections between the different regions of the auditory cortex that have been characterized cytoarchitectonically and physiologically. We examined the distribution of retrograde and anterograde labeling after injecting tracers into one or more regions of ferret auditory cortex. Injections of different tracers at frequency‐matched locations in the core areas, the primary auditory cortex (A1) and anterior auditory field (AAF), of the same animal revealed the presence of reciprocal connections with overlapping projections to and from discrete regions within the posterior pseudosylvian and suprasylvian fields (PPF and PSF), suggesting that these connections are frequency specific. In contrast, projections from the primary areas to the anterior dorsal field (ADF) on the anterior ectosylvian gyrus were scattered and non‐overlapping, consistent with the non‐tonotopic organization of this field. The relative strength of the projections originating in each of the primary fields differed, with A1 predominantly targeting the posterior bank fields PPF and PSF, which in turn project to the ventral posterior field, whereas AAF projects more heavily to the ADF, which then projects to the anteroventral field and the pseudosylvian sulcal cortex. These findings suggest that parallel anterior and posterior processing networks may exist, although the connections between different areas often overlap and interactions were present at all levels. J. Comp. Neurol. 523:2187–2210, 2015. © 2015 Wiley Periodicals, Inc. A series of tracer injections was made into physiologically identified subfields of ferret auditory cortex. The authors describe the patterns of anterograde and retrograde projections between primary and secondary areas in this species and demonstrate that although there is considerable overlap, parallel anterior and posterior processing networks may exist.