Shaping of discrete auditory inputs to extramodular zones of the lateral cortex of the inferior colliculus
Modularity; Mapping; Compartments; Immunocytochemistry; Multimodal; Patch-matrix; Topography
The multimodal lateral cortex of the inferior colliculus (LCIC) exhibits a modular-extramodular micro-organization that is evident early in development. In addition to a set of neurochemical markers that reliably highlight its modular-extramodular organization (e.g. modules: GAD67-positive, extramodular zones: calretinin-positive, CR), mature projection patterns suggest that major LCIC afferents recognize and adhere to such a framework. In adult mice, distinct afferent projections appear segregated, with somatosensory inputs targeting LCIC modules and auditory inputs surrounding extramodular fields. Currently lacking is an understanding regarding the development and shaping of multimodal LCIC afferents with respect to its emerging modular-extramodular microarchitecture. Combining living slice tract-tracing and immunocytochemical approaches in GAD67-GFP knock-in mice, the present study characterizes the critical period of projection shaping for LCIC auditory afferents arising from its neighboring central nucleus (CNIC). Both crossed and uncrossed projection patterns exhibit LCIC extramodular mapping characteristics that emerge from initially diffuse distributions. Projection mismatch with GAD-defined modules and alignment with encompassing extramodular zones becomes increasingly clear over the early postnatal period (birth to postnatal day 12). CNIC inputs terminate almost exclusively in extramodular zones that express CR. These findings suggest multimodal LCIC inputs may initially be sparse and intermingle, prior to segregation into distinct processing streams. Future experiments are needed to determine the likely complex interactions and mechanisms (e.g. activity-dependent and independent) responsible for shaping early modality-specific LCIC circuits.
Lamb-Echegaray Isabel D; Noftz William A; Stinson Jeremiah P C; Gabriele Mark L
Brain Structure & Function
2019
2019-11-15
Journal Article
<a href="http://doi.org/10.1007/s00429-019-01979-6" target="_blank" rel="noreferrer noopener">10.1007/s00429-019-01979-6</a>
PMID: 31729553
Palate Variation and Evolution in New World Leaf-Nosed and Old World Fruit Bats (Order Chiroptera)
cranial shape; Craniofacial; evolution; Evolutionary Biology; feeding-behavior; fluctuating asymmetry; food hardness; fossil; geometric; Integration; Modularity; Modularity; morphological integration; Morphometrics; Morphometrics; patterns; Phyllostomid; Pteropodid; record; skull morphology
Two bat families, the leaf-nosed (Phyllostomidae) and fruit bats (Pteropodidae), have independently evolved the ability to consume plant resources. However, despite their similar ages, species richness and the strong selective pressures placed on the evolution of skull shape by plant-based foods, phyllostomids display more craniofacial diversity than pteropodids. In this study, we used morphometrics to investigate the distribution of palate variation and the evolution of palate diversity in these groups. We focused on the palate because evolutionary alterations in palate morphology are thought to underlie much feeding specialization in bats. We hypothesize that the distribution of palate variation differs in phyllostomids and pteropodids, and that the rate of palate evolution is higher in phyllostomids than pteropodids. The results suggest that the overall level of palate integration is higher in adult populations of pteropodids than phyllostomids but that the distribution of palate variation is otherwise generally conserved among phyllostomids and pteropodids. Furthermore, the results are consistent with these differences in palate integration likely having a developmental basis. The results also suggest that palate evolution has occurred significantly more rapidly in phyllostomids than pteropodids. These findings are consistent with a scenario in which the greater integration of the pteropodid palate has limited its evolvability.
Sorensen D W; Butkus C; Cooper L N; Cretekos C J; Rasweiler J J; Sears K E
Evolutionary Biology
2014
2014-12
Journal Article
<a href="http://doi.org/10.1007/s11692-014-9291-6" target="_blank" rel="noreferrer noopener">10.1007/s11692-014-9291-6</a>