Presentation
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Bat Brains as a Window into the Neurobiology of Spoken Language
Poster D82 in Poster Session D, Wednesday, October 25, 4:45 - 6:30 pm CEST, Espace Vieux-Port
Nienke Hoeksema1, Peter Hagoort1,2, Sonja Vernes1,3; 1Max Planck Institute for Psycholinguistics, 2Donders Institute for Brain, Cognition and Behaviour, 3The University of St. Andrews
In order to learn and produce spoken language, we must be able to accurately perceive strings of sounds, store and retrieve them from memory, and reproduce them while monitoring our output at the same time. Whilst spoken language is uniquely human, a small group of animals, called vocal learners, does possess the skillset outlined above; they are able to learn to produce novel vocalizations. Interestingly, whilst some evolutionarily distant animals, such as bats, are vocal learners, strong evidence for this capability has not been found in most other mammals including our most closely-related relatives, non-human primates. A powerful way to understand how learning to produce new sounds is encoded in our brains and our DNA is to compare the brains of different vocal learners and vocal non-learners to see if certain similarities and differences can be found. Of particular interest is the bat Phyllostomus discolor, as it is a vocal learning mammal in which the neurogenetic, molecular, and neurobiological intricacies of vocal learning can be investigated to an extent that is not possible in humans. These investigations could lead us to a better understanding of how mammalian brains can facilitate vocal learning and give us insight into the biology and evolution of spoken language. In the current study, as one of the initial steps in this line of inquiry in P. discolor, we aimed to get a basic understanding of the structure and connectivity of the P. discolor brain to facilitate future comparative investigations into vocal learning. We used two complementary approaches: neuroimaging, to map the macroscale connectivity of the P. discolor brain, and neurogenetic mapping, to identify vocal learning-related regions in the P. discolor brain. To map the macroscale connectivity, we performed diffusion tensor imaging (DTI) and polarized light imaging (PLI). We are reconstructing the major white matter pathways of the P. discolor brain to create a white matter atlas. We are also mapping the connectivity of two cortical regions involved in social communication in P. discolor, the auditory and frontal cortex, via probabilistic tractography as previous research suggests increased and altered connectivity of such areas in vocal learners. To identify novel vocal-learning related regions in the P. discolor brain, we looked at the expression of a set of genes that show a unique pattern of expression in vocal motor brain regions in humans and songbirds. We hypothesize that these genes could guide us to vocal learning areas of interest in the P. discolor brain. Using immunohistochemistry, immunofluorescence, and in situ hybridization, we mapped the expression of 7 potential marker genes. This neurogenetic mapping revealed that these vocal-motor area marker genes are not dispersed uniformly across the P. discolor cortex, but are enriched and reduced in specific layers and cortical areas, highlighting candidate regions of homology that can be investigated further. Finally, we discuss how this study increased our knowledge of the structure of the P. discolor brain and how this can eventually help us better understand the neurobiology of vocal learning in all mammals, including humans.
Topic Areas: Animal Communication and Comparative/Evolutionary Studies, Speech Motor Control