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The microcircuit concept applied to cortical evolution: from three-layer to six-layer cortex.

Shepherd GM - Front Neuroanat (2011)

Bottom Line: Here we use the microcircuit concept to focus first on the principles of microcircuit organization of three-layer cortex in the olfactory cortex, hippocampus, and turtle general cortex, and compare it with six-layer neocortex.From this perspective it is possible to identify basic circuit elements for recurrent excitation and lateral inhibition that are common across all the cortical regions.These principles of microcircuit function provide a new approach to understanding the expanded functional capabilities elaborated by the evolution of the neocortex.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology, Yale University School of Medicine New Haven, CT, USA.

ABSTRACT
Understanding the principles of organization of the cerebral cortex requires insight into its evolutionary history. This has traditionally been the province of anatomists, but evidence regarding the microcircuit organization of different cortical areas is providing new approaches to this problem. Here we use the microcircuit concept to focus first on the principles of microcircuit organization of three-layer cortex in the olfactory cortex, hippocampus, and turtle general cortex, and compare it with six-layer neocortex. From this perspective it is possible to identify basic circuit elements for recurrent excitation and lateral inhibition that are common across all the cortical regions. Special properties of the apical dendrites of pyramidal cells are reviewed that reflect the specific adaptations that characterize the functional operations in the different regions. These principles of microcircuit function provide a new approach to understanding the expanded functional capabilities elaborated by the evolution of the neocortex.

No MeSH data available.


Comparison between the microcircuit organization of olfactory cortex and hippocampus. “Note the parallels in both the horizontal dimension (connections between subdivisions) and the vertical dimension (laminar organization of fiber systems according to their areas of origin.” Abbreviations: (1) OB, olfactory bulb; AOC, anterior olfactory cortex; APCV, ventral anterior piriform cortex; APCD, dorsal anterior piriform cortex; PPC, posterior piriform cortex; sup, superficial. (2) EC, entorhinal cortex; DG, dentate gyrus; prox, proximal; dist, distal; SL-M, stratum lacunosum-moleculare; SR, stratum radiatum; sup, superior; SP, stratum pyramidale; SO, stratum oriens. From Neville and Haberly (2004).
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Figure 9: Comparison between the microcircuit organization of olfactory cortex and hippocampus. “Note the parallels in both the horizontal dimension (connections between subdivisions) and the vertical dimension (laminar organization of fiber systems according to their areas of origin.” Abbreviations: (1) OB, olfactory bulb; AOC, anterior olfactory cortex; APCV, ventral anterior piriform cortex; APCD, dorsal anterior piriform cortex; PPC, posterior piriform cortex; sup, superficial. (2) EC, entorhinal cortex; DG, dentate gyrus; prox, proximal; dist, distal; SL-M, stratum lacunosum-moleculare; SR, stratum radiatum; sup, superior; SP, stratum pyramidale; SO, stratum oriens. From Neville and Haberly (2004).

Mentions: We have seen that a general similarity was early recognized between the microcircuit organization of olfactory cortex and hippocampus (Figures 1 and 2). This idea has been supported by subsequent work. Figure 9 illustrates a close comparison by Neville and Haberly (2004) between the main excitatory circuits in the two systems. In the olfactory cortex, there is a sequence of input from the OB to the distal apical dendrites, an intrinsic long association feedforward recombining pathway from the anterior olfactory cortex, and the long recurrent association fibers directed mainly from the anterior cortex to the more posterior cortices. In the hippocampus, there is similarly a main afferent input to the distal apical dendrites, an intrinsic feedforward pathway through the dentate gyrus, and the recurrent association fibers directed from CA3 to CA1.


The microcircuit concept applied to cortical evolution: from three-layer to six-layer cortex.

Shepherd GM - Front Neuroanat (2011)

Comparison between the microcircuit organization of olfactory cortex and hippocampus. “Note the parallels in both the horizontal dimension (connections between subdivisions) and the vertical dimension (laminar organization of fiber systems according to their areas of origin.” Abbreviations: (1) OB, olfactory bulb; AOC, anterior olfactory cortex; APCV, ventral anterior piriform cortex; APCD, dorsal anterior piriform cortex; PPC, posterior piriform cortex; sup, superficial. (2) EC, entorhinal cortex; DG, dentate gyrus; prox, proximal; dist, distal; SL-M, stratum lacunosum-moleculare; SR, stratum radiatum; sup, superior; SP, stratum pyramidale; SO, stratum oriens. From Neville and Haberly (2004).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3102215&req=5

Figure 9: Comparison between the microcircuit organization of olfactory cortex and hippocampus. “Note the parallels in both the horizontal dimension (connections between subdivisions) and the vertical dimension (laminar organization of fiber systems according to their areas of origin.” Abbreviations: (1) OB, olfactory bulb; AOC, anterior olfactory cortex; APCV, ventral anterior piriform cortex; APCD, dorsal anterior piriform cortex; PPC, posterior piriform cortex; sup, superficial. (2) EC, entorhinal cortex; DG, dentate gyrus; prox, proximal; dist, distal; SL-M, stratum lacunosum-moleculare; SR, stratum radiatum; sup, superior; SP, stratum pyramidale; SO, stratum oriens. From Neville and Haberly (2004).
Mentions: We have seen that a general similarity was early recognized between the microcircuit organization of olfactory cortex and hippocampus (Figures 1 and 2). This idea has been supported by subsequent work. Figure 9 illustrates a close comparison by Neville and Haberly (2004) between the main excitatory circuits in the two systems. In the olfactory cortex, there is a sequence of input from the OB to the distal apical dendrites, an intrinsic long association feedforward recombining pathway from the anterior olfactory cortex, and the long recurrent association fibers directed mainly from the anterior cortex to the more posterior cortices. In the hippocampus, there is similarly a main afferent input to the distal apical dendrites, an intrinsic feedforward pathway through the dentate gyrus, and the recurrent association fibers directed from CA3 to CA1.

Bottom Line: Here we use the microcircuit concept to focus first on the principles of microcircuit organization of three-layer cortex in the olfactory cortex, hippocampus, and turtle general cortex, and compare it with six-layer neocortex.From this perspective it is possible to identify basic circuit elements for recurrent excitation and lateral inhibition that are common across all the cortical regions.These principles of microcircuit function provide a new approach to understanding the expanded functional capabilities elaborated by the evolution of the neocortex.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology, Yale University School of Medicine New Haven, CT, USA.

ABSTRACT
Understanding the principles of organization of the cerebral cortex requires insight into its evolutionary history. This has traditionally been the province of anatomists, but evidence regarding the microcircuit organization of different cortical areas is providing new approaches to this problem. Here we use the microcircuit concept to focus first on the principles of microcircuit organization of three-layer cortex in the olfactory cortex, hippocampus, and turtle general cortex, and compare it with six-layer neocortex. From this perspective it is possible to identify basic circuit elements for recurrent excitation and lateral inhibition that are common across all the cortical regions. Special properties of the apical dendrites of pyramidal cells are reviewed that reflect the specific adaptations that characterize the functional operations in the different regions. These principles of microcircuit function provide a new approach to understanding the expanded functional capabilities elaborated by the evolution of the neocortex.

No MeSH data available.