The Claustrum Is Not Missing from All Monotreme Brains

Ashwell, Ken W.S.; Hardman, Craig D.; Paxinos, George

doi:10.1159/000080243

Cited by 46 publications

(51 citation statements)

References 58 publications

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“…Throughout the caudal 70 to 80% of the extent of the piriform lobe, the lateral surface was convex with minimal folding, whereas the ventral and medial surface was highly folded to an extent which varied markedly between individuals from the same geographic region (compare for example fi g. 1 c and 3 c). There was an extensive white matter core, which ran the entire dorsoventral extent of the piriform lobe and had a dense population of glial cells and some neurons in its dorsal segment [putative endopiriform nucleus - Ashwell et al, 2004]. Photomicrographs of the cytoarchitecture of the AO and Pir of the echidna are shown in fi gure 1 e to i.…”

Section: Resultsmentioning

confidence: 99%

“…Much of the material used for the present work has also been used for previous studies by our group of monotreme neuroanatomy [Hassiotis et al, 2004;Ashwell et al, 2004Ashwell et al, , 2005bAshwell, 2006a, b] and the reader is referred to those papers for details of specimen acquisition and tissue preparation. Only a brief account will be given here.…”

Section: Methodsmentioning

confidence: 99%

“…The procedures used for Nissl staining, enzyme-and immunohistochemistry of brain tissue have been described elsewhere [Hassiotis et al, 2004[Hassiotis et al, , 2005Ashwell et al, 2004]. Briefl y, the three live capture echidnas were overdosed by intramuscular injection of pentobarbitone sodium (60 mg/kg) and transcardially perfused with normal saline at 4 ° C for 10 min, 4% paraformaldehyde in 0.1 M phosphate buffer (4 ° C, pH 7.4) for 20 min, and cold (4 ° C) 0.1 M phosphate buffer for 10 min.…”

Section: Processing Of Tissuementioning

confidence: 99%

“…Details of immunohistochemistry have been described elsewhere [Hassiotis et al, 2004;Ashwell et al, 2004Ashwell et al, , 2005bAshwell, 2006a, b]. Negative controls for both enzyme and immunohistochemistry were performed by omitting the substrate in enzyme histochemical sections and omitting the primary antibody in immunohistochemical reactions.…”

Section: Processing Of Tissuementioning

confidence: 99%

“…The olfactory bulb of the echidna is large and folded [Ashwell, 2006a] and yet the olfactory tubercle of the echidna is poorly laminated and lacks some of the chemoarchitectural features of this region seen in therians [Ashwell, 2006b]. In previous studies on the cerebral cortex and claustrum of the echidna [Abbie, 1940;Hassiotis et al, 2004;Ashwell et al, 2004], the piriform cortex of the echidna has been noted in passing as extraordinarily extensive with potentially a large number of subregions, but those studies did not have suffi cient space to fully describe this region. The most recent study of the platypus olfactory system was undertaken by Hines [Hines, 1929] and was confi ned to analysis of Nissl-, myelin-and silver-stained material.…”

Section: Introductionmentioning

confidence: 99%

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The Anterior Olfactory Nucleus and Piriform Cortex of the Echidna and Platypus

Ashwell¹,

Phillips²

2006

Brain Behav Evol

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The cyto- and chemoarchitecture of the anterior olfactory nucleus and piriform cortex of the short-beaked echidna and platypus were studied to determine: (1) if these areas contain chemically distinct subdivisions, and (2) if the chemoarchitecture of those cortical olfactory regions differs from therians. Nissl and myelin staining were applied in conjunction with enzyme reactivity for NADPH diaphorase and acetylcholinesterase, and immunoreactivity for calcium-binding proteins (parvalbumin, calbindin and calretinin) and tyrosine hydroxylase. Golgi impregnations were also available for the echidna. In the echidna, the anterior olfactory nucleus is negligible in extent and merges at very rostral levels with a four-layered piriform cortex. Several rostrocaudally running subregions of the echidna piriform lobe could be identified on the basis of Nissl staining and calcium-binding protein immunoreactivity. Laminar-specific differences in calcium-binding protein immunoreactivity and NADPH-d-reactive neuron distribution were also noted. Neuron types identified in echidna piriform cortex included pyramidal neurons predominating in layers II and III and non-pyramidal neurons (e.g., multipolar profusely spiny and neurogliaform cells) in deeper layers. Horizontal cells were identified in both superficial and deep layers. By contrast, the platypus had a distinct anterior olfactory nucleus and a three-layered piriform cortex with no evidence of chemically distinct subregions within the piriform cortex. Volume of the paleocortex of the echidna was comparable to prosimians of similar body weight and, in absolute volume, exceeded that for eutherian insectivores such as T. ecaudatus and E. europaeus. The piriform cortex of the echidna shows evidence of regional differentiation, which in turn suggests highly specialized olfactory function.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Processing Of Tissuementioning

confidence: 99%

Section: Processing Of Tissuementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Anterior Olfactory Nucleus and Piriform Cortex of the Echidna and Platypus

Ashwell¹,

Phillips²

2006

Brain Behav Evol

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Organization and evolution of the avian forebrain

2005

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Early 20th-century comparative anatomists regarded the avian telencephalon as largely consisting of a hypertrophied basal ganglia, with thalamotelencephalic circuitry thus being taken to be akin to thalamostriatal circuitry in mammals. Although this view has been disproved for more than 40 years, only with the recent replacement of the old telencephalic terminology that perpetuated this view by a new terminology reflecting more accurate understanding of avian brain organization has the modern view of avian forebrain organization begun to become more widely appreciated. The modern view, reviewed in the present article, recognizes that the avian basal ganglia occupies no more of the telencephalon than is typically the case in mammals, and that it plays a role in motor control and motor learning as in mammals. Moreover, the vast majority of the telencephalon in birds is pallial in nature and, as true of cerebral cortex in mammals, provides the substrate for the substantial perceptual and cognitive abilities evident among birds. While the evolutionary relationship of the pallium of the avian telencephalon and its thalamic input to mammalian cerebral cortex and its thalamic input remains a topic of intense interest, the evidence currently favors the view that they had a common origin from forerunners in the stem amniotes ancestral to birds and mammals.

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In search of common developmental and evolutionary origin of the claustrum and subplate

Bruguier

Suárez

Manger

et al. 2020

J of Comparative Neurology

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The human claustrum, a major hub of widespread neocortical connections, is a thin, bilateral sheet of gray matter located between the insular cortex and the striatum. The subplate is a largely transient cortical structure that contains some of the earliest generated neurons of the cerebral cortex and has important developmental functions to establish intra-and extracortical connections. In human and macaque some subplate cells undergo regulated cell death, but some remain as interstitial white matter cells. In mouse and rat brains a compact layer is formed, Layer 6b, and it remains underneath the cortex, adjacent to the white matter. Whether Layer 6b in rodents is homologous to primate subplate or interstitial white matter cells is still debated. Gene expression patterns, such as those of Nurr1/Nr4a2, have suggested that the rodent subplate and the persistent subplate cells in Layer 6b and the claustrum might have similar origins. Moreover, the birthdates of the claustrum and Layer 6b are similarly precocious in mice. These observations prompted our speculations on the common developmental and evolutionary origin of the claustrum and the subplate. Here we systematically compare the currently available data on cytoarchitecture, evolutionary origin, gene expression, cell types, birthdates, neurogenesis, lineage and migration, circuit connectivity, and cell death of the neurons that contribute to the claustrum and subplate. Based on their similarities and differences we propose a partially common early evolutionary origin of the cells that become claustrum and subplate, a likely scenario that is shared in these cell populations across all amniotes.

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The Claustrum Is Not Missing from All Monotreme Brains

Cited by 46 publications

References 58 publications

The Anterior Olfactory Nucleus and Piriform Cortex of the Echidna and Platypus

The Anterior Olfactory Nucleus and Piriform Cortex of the Echidna and Platypus

Organization and evolution of the avian forebrain

In search of common developmental and evolutionary origin of the claustrum and subplate

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