title: Large-scale reorganization of the tonotopic map in mouse auditory midbrain revealed by MRI.
abstract: The cortex is thought to be the primary site of sensory plasticity, particularly during development. Here, we report that large-scale reorganization of the mouse auditory midbrain tonotopic map is induced by a specific sound-rearing environment consisting of paired low- (16 kHz) and high-frequency (40 kHz) tones. To determine the potential for plasticity in the mouse auditory midbrain, we used manganese-enhanced MRI to analyze the midbrain tonotopic maps of control mice during normal development and mice reared in the two-tone (16 + 40 kHz) environment. We found that the tonotopic map emerged during the third postnatal week in normal mice. Before 3 weeks, a larger percentage of auditory midbrain responded to each of the suprathreshold test frequencies, despite the fact that the primary afferent projections are in place even before hearing onset. By 3 weeks, the midbrain tonotopic map of control mice was established, and manganese-enhanced MRI showed a clear separation between the 16- and 40-kHz responses. Two-tone rearing dramatically altered the appearance of these discrete frequency-specific responses. A significant volume of the auditory midbrain became responsive to both rearing frequencies, resulting in a large-scale reorganization of the tonotopic map. These results indicate that developmental plasticity occurs on a much greater scale than previously appreciated in the mammalian auditory midbrain.
authors.affiliation: Skirball Institute of Biomolecular Medicine, Department of Radiology, New York University School of Medicine, New York, NY 10016, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Yu
authors.forename: Dan H
authors.initials: DH
authors.lastname: Sanes
authors.forename: Orlando
authors.initials: O
authors.lastname: Aristizabal
authors.forename: Youssef Zaim
authors.initials: YZ
authors.lastname: Wadghiri
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Turnbull
mesh_terms: D000162:Acoustics; D000818:Animals; D001301:Audiometry, Pure-Tone; D001303:Auditory Cortex / Q000196:embryology / Q000502:physiology*; D001931:Brain Mapping; D007245:Inferior Colliculi / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008636:Mesencephalon / Q000502:physiology*; D051379:Mice