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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.


“Schematic diagram of the principal intracortical connections of the turtle visual cortex based on neuroanatomical data (Smith et al., 1980) and the physiological observations reported here. Thalamocortical afferent volleys (1) provide direct excitation of pyramidal cell dendrites (a) and also powerfully excite inhibitory stellate cells (b). Feedforward inhibition is mediated by stellate cell-pyramidal cell contact (2). Local pathways also mediate reciprocal excitation between pyramidal cells (3) as well as feedback inhibition through pyramidal cell-stellate cell conact (4). There is also physiological support for inhibition of stellate interneurons (5), presumably arising from stellate cell-stellate cell contact. The pyramidal cells provide output from the cortex (6) by way of axons coursing primarily in the subcellular zone.” Kriegstein and Connors (1986). Open profiles: excitatory synaptic action; filled profiles: inhibitory synaptic action.
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Figure 5: “Schematic diagram of the principal intracortical connections of the turtle visual cortex based on neuroanatomical data (Smith et al., 1980) and the physiological observations reported here. Thalamocortical afferent volleys (1) provide direct excitation of pyramidal cell dendrites (a) and also powerfully excite inhibitory stellate cells (b). Feedforward inhibition is mediated by stellate cell-pyramidal cell contact (2). Local pathways also mediate reciprocal excitation between pyramidal cells (3) as well as feedback inhibition through pyramidal cell-stellate cell conact (4). There is also physiological support for inhibition of stellate interneurons (5), presumably arising from stellate cell-stellate cell contact. The pyramidal cells provide output from the cortex (6) by way of axons coursing primarily in the subcellular zone.” Kriegstein and Connors (1986). Open profiles: excitatory synaptic action; filled profiles: inhibitory synaptic action.

Mentions: They integrated their results by building on the circuit diagram of Smith et al. (1980). As shown in Figure 5, they also took into account the previous basic circuit diagrams for the other types of cortices in order to make comparisons with them. They summarized their conclusions as follows (Kriegstein and Connors, 1986):


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

Shepherd GM - Front Neuroanat (2011)

“Schematic diagram of the principal intracortical connections of the turtle visual cortex based on neuroanatomical data (Smith et al., 1980) and the physiological observations reported here. Thalamocortical afferent volleys (1) provide direct excitation of pyramidal cell dendrites (a) and also powerfully excite inhibitory stellate cells (b). Feedforward inhibition is mediated by stellate cell-pyramidal cell contact (2). Local pathways also mediate reciprocal excitation between pyramidal cells (3) as well as feedback inhibition through pyramidal cell-stellate cell conact (4). There is also physiological support for inhibition of stellate interneurons (5), presumably arising from stellate cell-stellate cell contact. The pyramidal cells provide output from the cortex (6) by way of axons coursing primarily in the subcellular zone.” Kriegstein and Connors (1986). Open profiles: excitatory synaptic action; filled profiles: inhibitory synaptic action.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: “Schematic diagram of the principal intracortical connections of the turtle visual cortex based on neuroanatomical data (Smith et al., 1980) and the physiological observations reported here. Thalamocortical afferent volleys (1) provide direct excitation of pyramidal cell dendrites (a) and also powerfully excite inhibitory stellate cells (b). Feedforward inhibition is mediated by stellate cell-pyramidal cell contact (2). Local pathways also mediate reciprocal excitation between pyramidal cells (3) as well as feedback inhibition through pyramidal cell-stellate cell conact (4). There is also physiological support for inhibition of stellate interneurons (5), presumably arising from stellate cell-stellate cell contact. The pyramidal cells provide output from the cortex (6) by way of axons coursing primarily in the subcellular zone.” Kriegstein and Connors (1986). Open profiles: excitatory synaptic action; filled profiles: inhibitory synaptic action.
Mentions: They integrated their results by building on the circuit diagram of Smith et al. (1980). As shown in Figure 5, they also took into account the previous basic circuit diagrams for the other types of cortices in order to make comparisons with them. They summarized their conclusions as follows (Kriegstein and Connors, 1986):

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.