Limits...
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: Circuits for excitatory input and different types of inhibition of pyramidal cells in the olfactory cortex. (A) Feedforward (FF) inhibitory (I) circuit from LOT afferents (aff) and feedback (FB) inhibitory circuit onto pyramidal cells (P). (B) Feedback and feedforward circuits from pyramidal cell axons, including inhibitory control of the initial segment (IS); assn, association fibers. (C) Pathways for lateral inhibition, through long axons of basket cell onto distant pyramidal cell, or long axon collateral of pyramidal cell onto distant basket cell. Open profiles: excitatory synaptic action; filled profiles: inhibitory synaptic action. From Neville and Haberly (2004).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3102215&req=5

Figure 8: Top: Circuits for excitatory input and different types of inhibition of pyramidal cells in the olfactory cortex. (A) Feedforward (FF) inhibitory (I) circuit from LOT afferents (aff) and feedback (FB) inhibitory circuit onto pyramidal cells (P). (B) Feedback and feedforward circuits from pyramidal cell axons, including inhibitory control of the initial segment (IS); assn, association fibers. (C) Pathways for lateral inhibition, through long axons of basket cell onto distant pyramidal cell, or long axon collateral of pyramidal cell onto distant basket cell. Open profiles: excitatory synaptic action; filled profiles: inhibitory synaptic action. From Neville and Haberly (2004).

Mentions: Thanks to the pioneering studies of Lewis Haberly and more recently many others, much basic information is available on the mammalian olfactory pyramidal neurons and the olfactory cortical microcircuit. The afferent fibers in the LOT make excitatory glutamatergic synapses on the spines of distal apical dendrites of the pyramidal cells, acting on both AMPA and NMDA receptors. Synapses with similar properties are made by the axon collaterals that activate GABAergic inhibitory interneurons and also form the long re-excitatory association fibers. An addition to the classical microcircuit of Figure 1 is the feedforward inhibitory interneuron in the superficial layer of the cortex. This work has been summarized in Neville and Haberly (2004) and Wilson and Stevenson (2006). It has enabled detailed dissection of the excitatory and inhibitory circuits within the olfactory cortex, as indicated in Figure 8.


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

Shepherd GM - Front Neuroanat (2011)

Top: Circuits for excitatory input and different types of inhibition of pyramidal cells in the olfactory cortex. (A) Feedforward (FF) inhibitory (I) circuit from LOT afferents (aff) and feedback (FB) inhibitory circuit onto pyramidal cells (P). (B) Feedback and feedforward circuits from pyramidal cell axons, including inhibitory control of the initial segment (IS); assn, association fibers. (C) Pathways for lateral inhibition, through long axons of basket cell onto distant pyramidal cell, or long axon collateral of pyramidal cell onto distant basket cell. Open profiles: excitatory synaptic action; filled profiles: inhibitory synaptic action. From Neville and Haberly (2004).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 8: Top: Circuits for excitatory input and different types of inhibition of pyramidal cells in the olfactory cortex. (A) Feedforward (FF) inhibitory (I) circuit from LOT afferents (aff) and feedback (FB) inhibitory circuit onto pyramidal cells (P). (B) Feedback and feedforward circuits from pyramidal cell axons, including inhibitory control of the initial segment (IS); assn, association fibers. (C) Pathways for lateral inhibition, through long axons of basket cell onto distant pyramidal cell, or long axon collateral of pyramidal cell onto distant basket cell. Open profiles: excitatory synaptic action; filled profiles: inhibitory synaptic action. From Neville and Haberly (2004).
Mentions: Thanks to the pioneering studies of Lewis Haberly and more recently many others, much basic information is available on the mammalian olfactory pyramidal neurons and the olfactory cortical microcircuit. The afferent fibers in the LOT make excitatory glutamatergic synapses on the spines of distal apical dendrites of the pyramidal cells, acting on both AMPA and NMDA receptors. Synapses with similar properties are made by the axon collaterals that activate GABAergic inhibitory interneurons and also form the long re-excitatory association fibers. An addition to the classical microcircuit of Figure 1 is the feedforward inhibitory interneuron in the superficial layer of the cortex. This work has been summarized in Neville and Haberly (2004) and Wilson and Stevenson (2006). It has enabled detailed dissection of the excitatory and inhibitory circuits within the olfactory cortex, as indicated in Figure 8.

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.