Afferent connections to the diencephalon in the marsupial phalanger and the question of sensory convergence in the “Posterior Group” of the thalamus

Röckel, A; Heath, Christopher; Jones, E.G.

doi:10.1002/cne.901450107

Cited by 75 publications

(19 citation statements)

References 45 publications

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“…In con trast, in all Australian metatherian mammals thus far studied -possums [Rockel et al, 1972;Haight and Neylon, 1978a], native cats [Haight and Neylon, 1981] and tammar wallabies -the medial and lateral regions of the ventrobasal complex are cyto-architectonically distinct. In the tammar, the ventral posteromedial nucleus is very similar in appearance to that in cats, whereas the ventral posterolateral nucleus is very small compared to that in cats [Berman and Jones, 1982], Most of the ventrobasal thalamic region in the tammar is occupied by the ventral posteromedial nu cleus, a situation also reported in the opossums [Pubols and Pubols, 1966;Sousa et al, 1971], Ventral Postero-inferior and Ventral Posteromedial Nuclei A ventral postero-inferior nucleus was identified in the dorsal thalamus of the tammar wallaby.…”

Section: Midline Nucleimentioning

confidence: 99%

“…Thalamic studies of opossums and possums show that the medial geniculate nucleus cannot be easily differentiated into subregions [see Johnson, 1977;Rockel et al, 1972;Haight and Neylon, 1978a;Aitkin and Gates, 1983]. In the tammar wallaby, the medial geniculate nuclei were found to be highly differen tiated and three nuclei were distinguished on the basis of their cyto-architectonic properties.…”

Section: Medial Geniculate Nucleimentioning

confidence: 99%

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A Cyto-Architectonic Description of the Thalamus of the Tammar Wallaby, Macropus eugenii

Mayner

1989

Brain Behav Evol

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Very few studies are available on the cyto-architectural features of the thalamus of metatherian mammals. Most of these studies describe the thalamus of a polyprotodont metatherian, the North American opossum, Didelphis virginiana. Studies on diprotodont metatherians are fewer still. There are two descriptions of the thalamus of the Australian possum Trichosurus vulpecula. The only part of the thalamus that has been described in the wallabies is the lateral geniculate nucleus. Hence, there was a need for a description of the thalamus in a wallaby. This study describes the organisation and the cyto-architectonics of the thalamus of the tammar, Macropus eugenii. Except for the midline nuclei, the boundaries of all other nuclei are well demarcated due to their well-differentiated nuclear components. Within the lateral posterior complex, a pulvinar nucleus was identified, and the pre-tectal nuclei show extensive differentiation, as do the medial geniculate nuclei. Also, a small centre-median nucleus was identified. The anteroventral nucleus retains its dorsal position for its entire rostrocaudal extent. The nucleus of the optic tract is located in a dorsal position in the tammar, as it is in cats. The general conclusion from this study is that the nuclear organisation of the thalamus in the tammar, a metatherian mammal, is complex and comparable in most respects to that in cats, eutherian mammals.

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Section: Midline Nucleimentioning

confidence: 99%

Section: Medial Geniculate Nucleimentioning

confidence: 99%

A Cyto-Architectonic Description of the Thalamus of the Tammar Wallaby, Macropus eugenii

Mayner

1989

Brain Behav Evol

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“…It would appear that uncrossed inputs to LP are either absent [Pearson et al, 1976;Royce et al, 1976;Sanderson and Pearson, 1977;Sanderson et al, 1978;Wye-Dvorak, 1984] or minuscule [Sanderson et al, 1979;Sanderson and Pearson, 1981]. In the mar supial brush-tailed possum, Trichosurus vulpécula, the LP receives strong projections from the superior colli culus [Rockel et al, 1976] and projects to primary and secondary visual areas of cortex [Haight et al, 1980], substantially overlapping the LGd cortical projec tion. Though the placental LP-pulvinar was believed for many years to lack direct retinal inputs in placen tal mammals, extensive bilateral retinal inputs have now been demonstrated in cats [Berman and Jones, 1977].…”

Section: Retinal Projections To Non-lgd Centresmentioning

confidence: 99%

Retinal Projections in Two Australian Polyprotodont Marsupials: Kowari, Dasyuroides byrnei, and Fat-Tailed Dunnart, Sminthopsis crassicaudata (Dasyuridae)

Haight

Sanderson

1988

Brain Behav Evol

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Retinal projections were examined in two small dasyurids, the kowari and the fat-tailed dunnart, following injections of ³H-proline into one eye. In both animals retinal fibres terminate in the dorsal and ventral lateral geniculate nuclei (LGd, LGv), the lateral posterior nuclear complex, the pretectum, the superior colliculus, the suprachiasmatic nucleus of the hypothalamus and the nuclei of the accessory optic system. The lateroposterior thalamic complex and the accessory optic nuclei receive projections from the contralateral eye only; the remaining centres receive bilateral inputs. Both LGd contain an undifferentiated Β or medial segment and an Α or lateral segment that comprises further cellular sublaminae, 4 in the kowari and 3 in the dunnart. There is substantial overlap of crossed and uncrossed terminals in both segments, though in each animal a narrow cell lamina next to the optic tract receives only crossed projections and the lateral part of the Β segment receives only uncrossed projections. There is a cell-sparse zone within the Α segment that receives a predominately uncrossed projection in the kowari and a crossed projection in the dunnart. In both marsupials the density of crossed and uncrossed terminals is equal, a feature of dasyurid quolls but not of another dasyurid, the Tasmanian devil. Additionally, retinal terminals do not form dense clusters within the LGd neuropil. This feature is characteristic of quolls, but not of other mammals, marsupial or placental, all of which display LGd terminal clusters. These findings suggest that the functional organisation of the LGd in these dasyurids may differ from that found in other marsupials.

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“…This is likely because of overlapping axon terminations in the posterior thalamus from cells in the spinal cord and the inferior colliculus (Jones and Burton 1974;LeDoux et al 1987;Rockel et al 1972). These data suggest that a role of the posterior thalamus might be to process convergent sensory information from multiple systems.…”

Section: Discussionmentioning

confidence: 92%

Termination Zones of Functionally Characterized Spinothalamic Tract Neurons Within the Primate Posterior Thalamus

Davidson

Zhang

Khasabov

et al. 2008

Journal of Neurophysiology

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. The primate posterior thalamus has been proposed to contribute to pain sensation, but its precise role is unclear. This is in part because spinothalamic tract (STT) neurons that project to the posterior thalamus have received little attention. In this study, antidromic mapping was used to identify individual STT neurons with axons that projected specifically to the posterior thalamus in Macaca fascicularis. Each axon was located by antidromic activation at low stimulus amplitudes (Ͻ30 A) and was then surrounded distally by a grid of stimulating points in which 500-A stimuli were unable to activate the axon antidromically, thereby indicating the termination zone. Several nuclei within the posterior thalamus were targets of STT neurons: the posterior nucleus, suprageniculate nucleus, magnocellular part of the medial geniculate nucleus, and limitans nucleus. STT neurons projecting to the ventral posterior inferior nucleus were also studied. Twenty-five posterior thalamus-projecting STT neurons recorded in lumbar spinal cord were characterized by their responses to mechanical, thermal, and chemical stimuli. Sixteen of 25 neurons were recorded in the marginal zone and the balance was located within the deep dorsal horn. Thirteen neurons were classified as wide dynamic range and 12 as high threshold. One-third of STT neurons projecting to posterior thalamus responded to noxious heat (50°C). Two-thirds of those tested responded to cooling. Seventy-one percent responded to an intradermal injection of capsaicin. These data indicate that the primate STT transmits noxious and innocuous mechanical, thermal, and chemical information to multiple posterior thalamic nuclei.

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Afferent connections to the diencephalon in the marsupial phalanger and the question of sensory convergence in the “Posterior Group” of the thalamus

Cited by 75 publications

References 45 publications

A Cyto-Architectonic Description of the Thalamus of the Tammar Wallaby, <i>Macropus eugenii</i>

A Cyto-Architectonic Description of the Thalamus of the Tammar Wallaby, <i>Macropus eugenii</i>

Retinal Projections in Two Australian Polyprotodont Marsupials: Kowari, <i>Dasyuroides byrnei, </i>and Fat-Tailed Dunnart, <i>Sminthopsis crassicaudata </i>(Dasyuridae)

Termination Zones of Functionally Characterized Spinothalamic Tract Neurons Within the Primate Posterior Thalamus

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