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Proc Biol Sci. 2018 Apr 25;285(1877). pii: 20180178. doi: 10.1098/rspb.2018.0178.

Functional MRI in the Nile crocodile: a new avenue for evolutionary neurobiology.

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Faculty of Psychology, Institute of Cognitive Neuroscience, Biopsychology, Universitätsstraße 150, 44780, Bochum, Germany.
School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown, Johannesburg 2193, South Africa.
Department of Neurophysiology, Faculty of Medicine, Ruhr-University Bochum, Universitätsstraße 150, 44780, Bochum, Germany.
Stellenbosch Institute for Advanced Study (STIAS), Wallenberg Research Centre at Stellenbosch University, Stellenbosch 7600, South Africa.
Faculty of Psychology, Institute of Cognitive Neuroscience, Biopsychology, Universitätsstraße 150, 44780, Bochum, Germany


Crocodilians are important for understanding the evolutionary history of amniote neural systems as they are the nearest extant relatives of modern birds and share a stem amniote ancestor with mammals. Although the crocodilian brain has been investigated anatomically, functional studies are rare. Here, we employed functional magnetic resonance imaging (fMRI), never tested in poikilotherms, to investigate crocodilian telencephalic sensory processing. Juvenile Crocodylus niloticus were placed in a 7 T MRI scanner to record blood oxygenation level-dependent (BOLD) signal changes during the presentation of visual and auditory stimuli. Visual stimulation increased BOLD signals in rostral to mid-caudal portions of the dorso-lateral anterior dorsal ventricular ridge (ADVR). Simple auditory stimuli led to signal increase in the rostromedial and caudocentral ADVR. These activation patterns are in line with previously described projection fields of diencephalic sensory fibres. Furthermore, complex auditory stimuli activated additional regions of the caudomedial ADVR. The recruitment of these additional, presumably higher-order, sensory areas reflects observations made in birds and mammals. Our results indicate that structural and functional aspects of sensory processing have been likely conserved during the evolution of sauropsids. In addition, our study shows that fMRI can be used to investigate neural processing in poikilotherms, providing a new avenue for neurobiological research in these critical species.


audio-visual stimulation; dorsal ventricular ridge; hierarchical processing; poikilotherms; reptile

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