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A Star in the Brainstem Reveals the First Step of Cortical Magnification

By Kenneth C. Catania, Duncan B. Leitch and Danielle Gauthier


A fundamental question in the neurosciences is how central nervous system (CNS) space is allocated to different sensory inputs. Yet it is difficult to measure innervation density and corresponding representational areas in the CNS of most species. These measurements can be made in star-nosed moles (Condylura cristata) because the cortical representation of nasal rays is visible in flattened sections and afferents from each ray can be counted. Here we used electrophysiological recordings combined with sections of the brainstem to identify a large, visible star representation in the principal sensory nucleus (PrV). PrV was greatly expanded and bulged out of the brainstem rostrally to partially invade the trigeminal nerve. The star representation was a distinct PrV subnucleus containing 11 modules, each representing one of the nasal rays. The 11 PrV ray representations were reconstructed to obtain volumes and the largest module corresponded to ray 11, the mole's tactile fovea. These measures were compared to fiber counts and primary cortical areas from a previous investigation. PrV ray volumes were closely correlated with the number of afferents from each ray, but afferents from the behaviorally most important, 11th ray were preferentially over-represented. This over-representation at the brainstem level was much less than at the cortical level. Our results indicate that PrV provides the first step in magnifying CNS representations of important afferents, but additional magnification occurs at higher levels. The early development of the 11th, foveal appendage could provide a mechanism for the most important afferents to capture the most CNS space

Topics: Research Article
Publisher: Public Library of Science
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Provided by: PubMed Central

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  1. (1989). A quantitative study of the projections of the gracile, cuneate and trigeminal nuclei and of the medullary reticular formation to the thalamus in the rat.
  2. (1943). Afferent areas in the brain of ungulates.
  3. (1993). Barrelettes – architectonic vibrissal representations in the brainstem trigeminal complex of the mouse. II. Normal post-natal development.
  4. (1995). Barreloids in adult rat thalamus: three-dimensional architecture and relationship to somatosensory cortical barrels.
  5. (1976). Barreloids in mouse somatosensory thalamus.
  6. (1975). Comparative anatomical studies of the SmI face cortex with special reference to the occurrence of "barrels" in layer IV.
  7. (1989). Cortical magnification factor and the ganglion cell density of the primate retina.
  8. (1999). Cortical organization in shrews: evidence from five species.
  9. (1993). Cowey A
  10. (2006). Cyto- and chemoarchitecture of the sensory trigeminal nuclei of the echidna, platypus and rat.
  11. (1983). Development of order in the rat trigeminal system.
  12. (1996). Development of trigeminal nucleus principalis in the rat: effects of target removal at birth.
  13. (1976). Disproportionate tonotopic representation for processing CF-FM sonar signals in the mustache bat auditory cortex.
  14. (2001). Early development of a somatosensory fovea: a head start in the cortical space race?
  15. Gutie ´rrez-Iba ´n ˜ez C, Iwaniuk AN, Wylie DR (2009) The independent evolution of the enlargement of the principal sensory nucleus of the trigeminal nerve in three different groups of birds.
  16. (1977). Magnification in striate cortex and retinal ganglion cell layer of owl monkey: a quantitative comparison.
  17. (1980). Magnification, receptive field area, and "hypercolumn" size in areas 3b and 1 of somatosensory cortex in owl monkeys.
  18. (2010). Mapping the face in the somatosensory brainstem.
  19. (1993). Morphology and topography of identified primary afferents in trigeminal subnuclei principalis and oralis.
  20. (1995). Organization of the somatosensory cortex of the star-nosed mole.
  21. (1986). Quantitative correlation between barrel-field size and the sensory innervation of the whiskerpad: a comparative study in six strains of mice bred for different patterns of mystacial vibrissae.
  22. (1984). Quantitative light and electron microscopic analysis of cytochrome oxidase-rich zones in the striate cortex of the squirrel monkey.
  23. (2005). Reconstruct: a free editor for serial section microscopy.
  24. Remple FE (2004) Tactile foveation in the star-nosed mole.
  25. (1942). Representation of cutaneous tactile sensibility in the cerebral cortex of the monkey as indicated by evoked potentials.
  26. (1990). Retinal ganglion cell density and cortical magnification factor in the primate. Vision Res 30: 1897–1911. A Star
  27. (1989). Retinal ganglion cell distribution in the cebus monkey: a comparison with the cortical magnification factors.
  28. (2001). Size gradients of barreloids in the rat thalamus.
  29. (1997). Somatosensory fovea in the star-nosed mole: behavioral use of the star in relation to innervation patterns and cortical representation.
  30. (1991). The Barrelettes – architectonic vibrissal representations in the brainstem trigeminal complex of the mouse. I. Normal structural organization.
  31. (1950). The cerebral cortex of man.
  32. (1995). The formation of a cortical somatotopic map.
  33. (1977). The neural representation of visual space.
  34. (1985). The organization of the neonatal rat’s brainstem trigeminal complex and its role in the formation of central trigeminal patterns.
  35. (1986). The rat brain in stereotaxic coordinates. Second edition.
  36. (1961). The representation of the visual field on the cerebral cortex in monkeys.
  37. (1985). The role of the principal sensory nucleus in central trigeminal pattern formation.
  38. (1970). The structural organization of layer IV in the somatosensory region (SI) of mouse cerebral cortex. The description of a cortical field composed of discrete cytoarchitectonic units.
  39. (2003). Trigeminal sensory system.
  40. (1979). Vibrissae representation in subcortical trigeminal centers in the neonatal rat.