Auditory Cortex of the Long-Eared Hedgehog &lt;i&gt;(Hemiechinus auritus)&lt;/i&gt;

Batzri-Izraeli, R.; Kelly, Jack B.; Glendenning, K. K.; Masterton, R.B.; Wollberg, Z.

doi:10.1159/000115310

Cited by 23 publications

(18 citation statements)

References 23 publications

(46 reference statements)

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“…Perhaps the type 1 pattern is older in phylogeny, and the primary sensory areas represent the essential ancestral condition from which the (presumably more variable and complex) type 2 and type 3 patterns later emerged (platypus and echidna: Krubitzer et al, 1995). In mammals with a less differentiated cortical organization-such as marsupials (Lende, 1963) and insectivores (Lende and Sadler, 1967;Batzri-Izraeli et al, 1990)-thalamic input may have a more specific laminar distribution than it does in the cat (present results) and monkey (Hashikawa et al, 1995).…”

Section: Developmental Perspectivementioning

confidence: 60%

Auditory thalamocortical projections in the cat: Laminar and areal patterns of input

2000

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Thalamocortical projections were studied in adult cats using biotinylated dextran amines, wheat germ agglutinin conjugated to horseradish peroxidase, and autoradiography with tritiated leucine and/or proline. The input from 7 architectonically defined nuclei to 14 auditory cortical fields was characterized qualitatively and quantitatively. The principal results were that 1) every thalamic nucleus projected to more than 1 field (range, 4-14 fields; mean, 7 fields); 2) only the projection from the ventral division to some primary fields (primary auditory cortex and posterior auditory cortex) had a periodic, clustered distribution, whereas the input from other divisions to nonprimary areas was continuous; 3) layers III-V received >85% of the total axonal profiles; 4) in most experiments, five or more layers were labeled; 5) the projections to nonprimary auditory areas had many laterally oriented axons; 6) the heaviest input to layer I in all experiments was usually in its upper half, suggesting a sublaminar arrangement; 7) the largest axonal trunks (up to 6 microm in diameter) arose from the medial division and ended in layer Ia, where they ran laterally for long distances; 8) there were three projection patterns: type 1 had its peak in layers III-IV with little input to layer I, and it arose from the ventral division and the dorsal superficial, dorsal, and suprageniculate nuclei of the dorsal division; type 2 had heavy labeling in layer I and less in layers III-IV, arising from the dorsal division nuclei primarily, especially the caudal dorsal and deep dorsal nuclei; and type 3 was a trimodal concentration in layers I, III-IV, and VI that originated chiefly in the medial division and had the lowest density of labeling; and 9) the quantitative profiles with the three methods were very similar. The results suggest that the subdivisions of the auditory thalamus have consistent patterns of laminar distribution to different cortical areas, that an average of five or more layers receive significant input in a specific area, that a given thalamic nucleus can influence areas as far as 20 mm apart, that the first information to arrive at the cortex may reach layer I by virtue of the giant axons, and that several laminar patterns of auditory thalamocortical projection exist. The view that the auditory thalamus (and perhaps other thalamic nuclei) serves mainly a relay function underestimates its many modes for influencing the cortex on a laminar basis.

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Section: Developmental Perspectivementioning

confidence: 60%

Auditory thalamocortical projections in the cat: Laminar and areal patterns of input

2000

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“…The inputs from the LVN would therefore consist of a compensatory mechanism originating from the vestibular system. Cross modal compensation has previously been demonstrated after deafferentation or sensory deprivation in other modalities [72], [73] although the majority of compensation has been observed in cortical structures [74]–[76]. Whilst acting as a possible compensatory mechanism, the increase in VGLUT-2 expression could also lead to an increased release in glutamate due to larger vesicles [77] or to axonal sprouting [78].…”

Section: Discussionmentioning

confidence: 99%

Acoustic Overexposure Increases the Expression of VGLUT-2 Mediated Projections from the Lateral Vestibular Nucleus to the Dorsal Cochlear Nucleus

et al. 2012

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The dorsal cochlear nucleus (DCN) is a first relay of the central auditory system as well as a site for integration of multimodal information. Vesicular glutamate transporters VGLUT-1 and VGLUT-2 selectively package glutamate into synaptic vesicles and are found to have different patterns of organization in the DCN. Whereas auditory nerve fibers predominantly co-label with VGLUT-1, somatosensory inputs predominantly co-label with VGLUT-2. Here, we used retrograde and anterograde transport of fluorescent conjugated dextran amine (DA) to demonstrate that the lateral vestibular nucleus (LVN) exhibits ipsilateral projections to both fusiform and deep layers of the rat DCN. Stimulating the LVN induced glutamatergic synaptic currents in fusiform cells and granule cell interneurones. We combined the dextran amine neuronal tracing method with immunohistochemistry and showed that labeled projections from the LVN are co-labeled with VGLUT-2 by contrast to VGLUT-1. Wistar rats were exposed to a loud single tone (15 kHz, 110 dB SPL) for 6 hours. Five days after acoustic overexposure, the level of expression of VGLUT-1 in the DCN was decreased whereas the level of expression of VGLUT-2 in the DCN was increased including terminals originating from the LVN. VGLUT-2 mediated projections from the LVN to the DCN are likely to play a role in the head position in response to sound. Amplification of VGLUT-2 expression after acoustic overexposure could be a compensatory mechanism from vestibular inputs in response to hearing loss and to a decrease of VGLUT-1 expression from auditory nerve fibers.

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“…However, a number of recent studies of shrews [Catania et al, 1999a] moles Kaas, 1995, 1997a, b;Catania, 2000a] and hedgehogs [Batzri-Izraeli et al, 1990;Pobirsky et al, 1998;Catania et al, 2000] provide new information from ten species in three families. The fourth remaining family, solenodons, consists of two rare and endangered species that cannot be practically investigated beyond museum collections.…”

Section: Insectivore Phylogenymentioning

confidence: 99%

Cortical Organization in Insectivora: The Parallel Evolution of the Sensory Periphery and the Brain

Catania¹

2000

Brain Behav Evol

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Insectivores are traditionally described as a primitive group that has not changed much in the course of mammalian evolution. In contrast, recent studies reveal a great diversity of sensorimotor specializations among insectivores adapted to a number of different ecological niches, indicating that there has been significant diversification and change in the course of their evolution. Here the organization of sensory cortex is compared in the African hedgehog (Atelerix albiventris), the masked shrew (Sorex cinereus), the eastern mole (Scalopus aquaticus), and the star-nosed mole (Condylura cristata). Each of these four closely related species lives in a unique ecological niche, exhibits a different repertoire of behaviors, and has a different configuration of peripheral sensory receptors. Corresponding specializations of cortical sensory areas reveal a number of ways in which the cortex has evolved in parallel with changes to the sensory periphery. These specializations include expansion of cortical representations (cortical magnification), the addition or loss of cortical areas in the processing network, and the subdivision of areas into modules (barrels and stripes).

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Auditory Cortex of the Long-Eared Hedgehog <i>(Hemiechinus auritus)</i>

Cited by 23 publications

References 23 publications

Auditory thalamocortical projections in the cat: Laminar and areal patterns of input

Auditory thalamocortical projections in the cat: Laminar and areal patterns of input

Acoustic Overexposure Increases the Expression of VGLUT-2 Mediated Projections from the Lateral Vestibular Nucleus to the Dorsal Cochlear Nucleus

Cortical Organization in Insectivora: The Parallel Evolution of the Sensory Periphery and the Brain

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