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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.


Basic circuit of the mammalian neocortex. Abbreviations: SA, specific sensory afferents; NSA, non-specific sensory afferents; DP, deep pyramidal cell; SP, superficial pyramidal cell; I, intrinsic neurons (excitatory stellate cells and inhibitory interneurons are lumped together); rc, recurrent collateral. 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 3: Basic circuit of the mammalian neocortex. Abbreviations: SA, specific sensory afferents; NSA, non-specific sensory afferents; DP, deep pyramidal cell; SP, superficial pyramidal cell; I, intrinsic neurons (excitatory stellate cells and inhibitory interneurons are lumped together); rc, recurrent collateral. Arrows indicate direction of flow of activity. Open profiles: excitatory synaptic action; filled profiles: inhibitory synaptic action. From Shepherd (1974).

Mentions: Compared with these early successes, studies of the basic connectivity within the mammalian neocortex had barely begun. Nonetheless, evidence was obtained for thalamocortical activation of pyramidal cells, and the two types of actions through their axon collaterals: direct RE, and recurrent inhibition through inhibitory interneurons (see Phillips, 1959). There was an additional circuit element, thalamocortical activation through stellate cells onto the pyramidal cells, which could be viewed as analogous to the situation in the dentate and hippocampus, as an additional internal relay in the input pathway. An early version of the basic circuit for neocortex is shown in Figure 3.


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

Shepherd GM - Front Neuroanat (2011)

Basic circuit of the mammalian neocortex. Abbreviations: SA, specific sensory afferents; NSA, non-specific sensory afferents; DP, deep pyramidal cell; SP, superficial pyramidal cell; I, intrinsic neurons (excitatory stellate cells and inhibitory interneurons are lumped together); rc, recurrent collateral. 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 3: Basic circuit of the mammalian neocortex. Abbreviations: SA, specific sensory afferents; NSA, non-specific sensory afferents; DP, deep pyramidal cell; SP, superficial pyramidal cell; I, intrinsic neurons (excitatory stellate cells and inhibitory interneurons are lumped together); rc, recurrent collateral. Arrows indicate direction of flow of activity. Open profiles: excitatory synaptic action; filled profiles: inhibitory synaptic action. From Shepherd (1974).
Mentions: Compared with these early successes, studies of the basic connectivity within the mammalian neocortex had barely begun. Nonetheless, evidence was obtained for thalamocortical activation of pyramidal cells, and the two types of actions through their axon collaterals: direct RE, and recurrent inhibition through inhibitory interneurons (see Phillips, 1959). There was an additional circuit element, thalamocortical activation through stellate cells onto the pyramidal cells, which could be viewed as analogous to the situation in the dentate and hippocampus, as an additional internal relay in the input pathway. An early version of the basic circuit for neocortex is shown in Figure 3.

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.