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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.


Top: Olfactory cortical areas on the ventrolateral surface of the cerebrum of the rat. Abbreviations: AOC, anterior olfactory cortex; ctx, cortex; olfac tub, olfactory tubercle. From Neville and Haberly (2004). Bottom: Basic circuit of the mammalian piriform (olfactory) cortex. Abbreviations: LOT, lateral olfactory tract; SP, superficial pyramidal cell; DP, deep pyramidal cell; S, stellate cell; C, centrifugal fiber. Arrows indicate direction of flow of activity. Open profiles: excitatory synaptic action; filled profiles: inhibitory synaptic action. From Shepherd (1974).
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Figure 1: Top: Olfactory cortical areas on the ventrolateral surface of the cerebrum of the rat. Abbreviations: AOC, anterior olfactory cortex; ctx, cortex; olfac tub, olfactory tubercle. From Neville and Haberly (2004). Bottom: Basic circuit of the mammalian piriform (olfactory) cortex. Abbreviations: LOT, lateral olfactory tract; SP, superficial pyramidal cell; DP, deep pyramidal cell; S, stellate cell; C, centrifugal fiber. Arrows indicate direction of flow of activity. Open profiles: excitatory synaptic action; filled profiles: inhibitory synaptic action. From Shepherd (1974).

Mentions: One of the first basic cortical circuits to be identified was of mammalian olfactory cortex. Figure 1 (top) provides a reminder that olfactory cortex is defined as the main region that receives direct input through the lateral olfactory tract (LOT) from the output cells (mitral and tufted) of the olfactory bulb. We focus here on the region occupying the piriform cortex beneath and adjacent to the LOT. The hippocampus is located in the medial temporal area, and neocortex in the dorsal part, as we discuss below.


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

Shepherd GM - Front Neuroanat (2011)

Top: Olfactory cortical areas on the ventrolateral surface of the cerebrum of the rat. Abbreviations: AOC, anterior olfactory cortex; ctx, cortex; olfac tub, olfactory tubercle. From Neville and Haberly (2004). Bottom: Basic circuit of the mammalian piriform (olfactory) cortex. Abbreviations: LOT, lateral olfactory tract; SP, superficial pyramidal cell; DP, deep pyramidal cell; S, stellate cell; C, centrifugal fiber. Arrows indicate direction of flow of activity. Open profiles: excitatory synaptic action; filled profiles: inhibitory synaptic action. From Shepherd (1974).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: Top: Olfactory cortical areas on the ventrolateral surface of the cerebrum of the rat. Abbreviations: AOC, anterior olfactory cortex; ctx, cortex; olfac tub, olfactory tubercle. From Neville and Haberly (2004). Bottom: Basic circuit of the mammalian piriform (olfactory) cortex. Abbreviations: LOT, lateral olfactory tract; SP, superficial pyramidal cell; DP, deep pyramidal cell; S, stellate cell; C, centrifugal fiber. Arrows indicate direction of flow of activity. Open profiles: excitatory synaptic action; filled profiles: inhibitory synaptic action. From Shepherd (1974).
Mentions: One of the first basic cortical circuits to be identified was of mammalian olfactory cortex. Figure 1 (top) provides a reminder that olfactory cortex is defined as the main region that receives direct input through the lateral olfactory tract (LOT) from the output cells (mitral and tufted) of the olfactory bulb. We focus here on the region occupying the piriform cortex beneath and adjacent to the LOT. The hippocampus is located in the medial temporal area, and neocortex in the dorsal part, as we discuss below.

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.