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Neural progenitors, patterning and ecology in neocortical origins.

Aboitiz F, Zamorano F - Front Neuroanat (2013)

Bottom Line: Specifically, we address the developmental modifications that had to take place to generate the neocortex, and to what extent these modifications were shared by other amniote lineages or can be considered unique to mammals.Thus, there is a highly conserved genetic and developmental battery that becomes modulated in different directions according to specific selective pressures.In the case of early mammals, ecological conditions like nocturnal habits and reproductive strategies are considered to have played a key role in the selection of the particular brain patterning mechanisms that led to the origin of the neocortex.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Psiquiatría, Facultad de Medicina y Centro Interdisciplinario de Neurociencia, Pontificia Universidad Católica de Chile Santiago, Chile.

ABSTRACT
The anatomical organization of the mammalian neocortex stands out among vertebrates for its laminar and columnar arrangement, featuring vertically oriented, excitatory pyramidal neurons. The evolutionary origin of this structure is discussed here in relation to the brain organization of other amniotes, i.e., the sauropsids (reptiles and birds). Specifically, we address the developmental modifications that had to take place to generate the neocortex, and to what extent these modifications were shared by other amniote lineages or can be considered unique to mammals. In this article, we propose a hypothesis that combines the control of proliferation in neural progenitor pools with the specification of regional morphogenetic gradients, yielding different anatomical results by virtue of the differential modulation of these processes in each lineage. Thus, there is a highly conserved genetic and developmental battery that becomes modulated in different directions according to specific selective pressures. In the case of early mammals, ecological conditions like nocturnal habits and reproductive strategies are considered to have played a key role in the selection of the particular brain patterning mechanisms that led to the origin of the neocortex.

No MeSH data available.


Related in: MedlinePlus

The cerebral hemispheres of reptiles and mammals. The pallium of reptiles has medial/dorsomedial (MC), dorsal (DC, corresponding to the avian hyperpallium) and lateral (LC) cortices; and a dorsal ventricular ridge, whose anterior part (ADVR) corresponds to the avian nido and mesopallium. The MC of reptiles corresponds to the hippocampus (HIP) of mammals, and the LC is homologous to the mammalian olfactory cortex (OC). The mammalian neocortex (NC) comprises two moieties, one dorsal (NCd, receiving lemnothalamic somatosensory and visual inputs), and one lateral (NCl, receiving auditory and visual collothalamic inputs). AM, pallial amygdalar formation, CL, claustrum, CS, corpus striatum, PSP, pallial-subpallial boundary.
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Figure 2: The cerebral hemispheres of reptiles and mammals. The pallium of reptiles has medial/dorsomedial (MC), dorsal (DC, corresponding to the avian hyperpallium) and lateral (LC) cortices; and a dorsal ventricular ridge, whose anterior part (ADVR) corresponds to the avian nido and mesopallium. The MC of reptiles corresponds to the hippocampus (HIP) of mammals, and the LC is homologous to the mammalian olfactory cortex (OC). The mammalian neocortex (NC) comprises two moieties, one dorsal (NCd, receiving lemnothalamic somatosensory and visual inputs), and one lateral (NCl, receiving auditory and visual collothalamic inputs). AM, pallial amygdalar formation, CL, claustrum, CS, corpus striatum, PSP, pallial-subpallial boundary.

Mentions: The architecture of the mammalian neocortex differs significantly from brain structures that are observed in other amniotes. We will first make a brief account of the organization of the reptilian and avian brains in order to provide sufficient background for the discussion. The neocortex and other structures to be commented here belong to the pallium, i.e., the “roof” of the cerebral hemisphere or telencephalon, which is separated from the more ventral subpallium by the pallio-subpallial boundary in the lateral telencephalon (see Figure 2). In mammals, the pallium is further subdivided into the medial pallium (hippocampus), dorsal pallium (neocortex), lateral pallium (dorsal olfactory cortex and other structures like the dorsolateral claustrum and parts of the insular region), and a newly described subdivision between the lateral pallium and the subpallium, termed the ventral pallium (in mammals, this gives rise to the pallial claustroamygdaloid complex, olfactory bulbs and ventral olfactory cortex). In all species, the ventral pallium is characterized by lack of expression of Emx1 (a marker of all other pallial subdivisions), and the strong expression of Lhx9 in the ventricular surface. The gene Pax6 is expressed in the VZ of all pallial regions and a small region of the subpallium (for further details, see Fernández et al., 1998; Puelles et al., 1999, 2000; Medina and Abellán, 2009; Medina et al., 2011). While the correspondences of the medial pallium with the hippocampus, and of the lateral pallium with the olfactory cortex are conserved in all amniotes, there has been controversy about the homologies of the dorsal and ventral pallial regions across species (Northcutt, 1969; Northcutt and Kaas, 1995).


Neural progenitors, patterning and ecology in neocortical origins.

Aboitiz F, Zamorano F - Front Neuroanat (2013)

The cerebral hemispheres of reptiles and mammals. The pallium of reptiles has medial/dorsomedial (MC), dorsal (DC, corresponding to the avian hyperpallium) and lateral (LC) cortices; and a dorsal ventricular ridge, whose anterior part (ADVR) corresponds to the avian nido and mesopallium. The MC of reptiles corresponds to the hippocampus (HIP) of mammals, and the LC is homologous to the mammalian olfactory cortex (OC). The mammalian neocortex (NC) comprises two moieties, one dorsal (NCd, receiving lemnothalamic somatosensory and visual inputs), and one lateral (NCl, receiving auditory and visual collothalamic inputs). AM, pallial amygdalar formation, CL, claustrum, CS, corpus striatum, PSP, pallial-subpallial boundary.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3824149&req=5

Figure 2: The cerebral hemispheres of reptiles and mammals. The pallium of reptiles has medial/dorsomedial (MC), dorsal (DC, corresponding to the avian hyperpallium) and lateral (LC) cortices; and a dorsal ventricular ridge, whose anterior part (ADVR) corresponds to the avian nido and mesopallium. The MC of reptiles corresponds to the hippocampus (HIP) of mammals, and the LC is homologous to the mammalian olfactory cortex (OC). The mammalian neocortex (NC) comprises two moieties, one dorsal (NCd, receiving lemnothalamic somatosensory and visual inputs), and one lateral (NCl, receiving auditory and visual collothalamic inputs). AM, pallial amygdalar formation, CL, claustrum, CS, corpus striatum, PSP, pallial-subpallial boundary.
Mentions: The architecture of the mammalian neocortex differs significantly from brain structures that are observed in other amniotes. We will first make a brief account of the organization of the reptilian and avian brains in order to provide sufficient background for the discussion. The neocortex and other structures to be commented here belong to the pallium, i.e., the “roof” of the cerebral hemisphere or telencephalon, which is separated from the more ventral subpallium by the pallio-subpallial boundary in the lateral telencephalon (see Figure 2). In mammals, the pallium is further subdivided into the medial pallium (hippocampus), dorsal pallium (neocortex), lateral pallium (dorsal olfactory cortex and other structures like the dorsolateral claustrum and parts of the insular region), and a newly described subdivision between the lateral pallium and the subpallium, termed the ventral pallium (in mammals, this gives rise to the pallial claustroamygdaloid complex, olfactory bulbs and ventral olfactory cortex). In all species, the ventral pallium is characterized by lack of expression of Emx1 (a marker of all other pallial subdivisions), and the strong expression of Lhx9 in the ventricular surface. The gene Pax6 is expressed in the VZ of all pallial regions and a small region of the subpallium (for further details, see Fernández et al., 1998; Puelles et al., 1999, 2000; Medina and Abellán, 2009; Medina et al., 2011). While the correspondences of the medial pallium with the hippocampus, and of the lateral pallium with the olfactory cortex are conserved in all amniotes, there has been controversy about the homologies of the dorsal and ventral pallial regions across species (Northcutt, 1969; Northcutt and Kaas, 1995).

Bottom Line: Specifically, we address the developmental modifications that had to take place to generate the neocortex, and to what extent these modifications were shared by other amniote lineages or can be considered unique to mammals.Thus, there is a highly conserved genetic and developmental battery that becomes modulated in different directions according to specific selective pressures.In the case of early mammals, ecological conditions like nocturnal habits and reproductive strategies are considered to have played a key role in the selection of the particular brain patterning mechanisms that led to the origin of the neocortex.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Psiquiatría, Facultad de Medicina y Centro Interdisciplinario de Neurociencia, Pontificia Universidad Católica de Chile Santiago, Chile.

ABSTRACT
The anatomical organization of the mammalian neocortex stands out among vertebrates for its laminar and columnar arrangement, featuring vertically oriented, excitatory pyramidal neurons. The evolutionary origin of this structure is discussed here in relation to the brain organization of other amniotes, i.e., the sauropsids (reptiles and birds). Specifically, we address the developmental modifications that had to take place to generate the neocortex, and to what extent these modifications were shared by other amniote lineages or can be considered unique to mammals. In this article, we propose a hypothesis that combines the control of proliferation in neural progenitor pools with the specification of regional morphogenetic gradients, yielding different anatomical results by virtue of the differential modulation of these processes in each lineage. Thus, there is a highly conserved genetic and developmental battery that becomes modulated in different directions according to specific selective pressures. In the case of early mammals, ecological conditions like nocturnal habits and reproductive strategies are considered to have played a key role in the selection of the particular brain patterning mechanisms that led to the origin of the neocortex.

No MeSH data available.


Related in: MedlinePlus