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Anatomy and physiology of the thick-tufted layer 5 pyramidal neuron.

Ramaswamy S, Markram H - Front Cell Neurosci (2015)

Bottom Line: By virtue of having the widest local axonal and dendritic arborization, the TTL5 neuron encompasses various local neocortical neurons and thereby defines the dimensions of neocortical microcircuitry.The TTL5 neuron integrates input across all neocortical layers and is the principal output pathway funneling information flow to subcortical structures.This review summarizes key discoveries and identifies potential avenues of research to facilitate an integrated and unifying understanding on the role of a central neuron in the neocortex.

View Article: PubMed Central - PubMed

Affiliation: Blue Brain Project, Ecole Polytechnique Fédérale de Lausanne, Campus Biotech Geneva, Switzerland.

ABSTRACT
The thick-tufted layer 5 (TTL5) pyramidal neuron is one of the most extensively studied neuron types in the mammalian neocortex and has become a benchmark for understanding information processing in excitatory neurons. By virtue of having the widest local axonal and dendritic arborization, the TTL5 neuron encompasses various local neocortical neurons and thereby defines the dimensions of neocortical microcircuitry. The TTL5 neuron integrates input across all neocortical layers and is the principal output pathway funneling information flow to subcortical structures. Several studies over the past decades have investigated the anatomy, physiology, synaptology, and pathophysiology of the TTL5 neuron. This review summarizes key discoveries and identifies potential avenues of research to facilitate an integrated and unifying understanding on the role of a central neuron in the neocortex.

No MeSH data available.


Related in: MedlinePlus

Diverse sources of afferent excitatory and inhibitory input to, and targets of efferent excitatory output from TTL5 neurons. An illustration of the TTL5 neuron in the local neocortical microcircuit showing diverse sources of excitatory and inhibitory inputs, and targets of excitatory output. Schematic representations of the various neuron types afferent to the TTL5 neuron are shown according to their known dendritic, peri-somatic or axonal innervation domains. Local electrogenic properties, and their likely layers of origin are shown to the left of the TTL5 schematic in the center. PoM—posterior medial nucleus; VPM—ventral posterior medial nucleus; L5STPC—layer 5 slender-tufted pyramidal cell; MC—Martinotti cell; NGC—neurogliaform cell; SBC—small basket cell; ChC—chandelier cell; LBC—large basket cell; NBC—nest basket cell; BP—bipolar cell; BTC—bitufted cell; DBC—double bouquet cell; TTL5—thick-tufted layer 5 pyramidal neuron.
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Figure 4: Diverse sources of afferent excitatory and inhibitory input to, and targets of efferent excitatory output from TTL5 neurons. An illustration of the TTL5 neuron in the local neocortical microcircuit showing diverse sources of excitatory and inhibitory inputs, and targets of excitatory output. Schematic representations of the various neuron types afferent to the TTL5 neuron are shown according to their known dendritic, peri-somatic or axonal innervation domains. Local electrogenic properties, and their likely layers of origin are shown to the left of the TTL5 schematic in the center. PoM—posterior medial nucleus; VPM—ventral posterior medial nucleus; L5STPC—layer 5 slender-tufted pyramidal cell; MC—Martinotti cell; NGC—neurogliaform cell; SBC—small basket cell; ChC—chandelier cell; LBC—large basket cell; NBC—nest basket cell; BP—bipolar cell; BTC—bitufted cell; DBC—double bouquet cell; TTL5—thick-tufted layer 5 pyramidal neuron.

Mentions: The expansive TTL5 dendritic arbor can be demarcated into distinct functional domains based on characteristic afferent inputs received from GABAergic local circuit interneurons (see Figure 4 for a schematic of the diverse sources of afferent excitatory and inhibitory input to, and targets of efferent excitatory output from TTL5 neurons). The division of the TTL5 dendritic arbor into these functional domains endows enhanced capabilities for the integration of varied streams of synaptic input. Martinotti cells preferentially target distal TTL5 dendrites and terminal tufts, while small basket cells predominantly target the proximal apical and basal dendrites and the soma (Thomson et al., 1996; Kawaguchi and Kubota, 1997; Somogyi et al., 1998; Wang et al., 2002; Silberberg and Markram, 2007; Ali and Thomson, 2008). TTL5 innervation by nest and large basket cells appears to be rather heterogeneous, covering the entire dendritic arbor (Wang et al., 2002). Synaptic contacts from bipolar, double bouquet and bitufted cells are made onto the proximal and distal dendrites for the most part (for reviews see Somogyi et al., 1998; Markram et al., 2004; Figure 4). Chandelier cells exclusively target the TTL5 AIS through axo-axonic synaptic contacts (Somogyi et al., 1982; Howard et al., 2005; Szabadics et al., 2006). Neurogliaform cells in the supragranular layers innervate distal TTL5 dendrites through metabotropic GABAB receptors mediating slow inhibition (Tamás et al., 2003; Oláh et al., 2007; Figure 4). Furthermore, terminal TTL5 dendritic tufts are innervated by a local plexus of axons from GABAergic intereneurons residing in layer 1, also giving rise to slow inhibition through GABAB receptors (Zhu, 2000; Zhu and Zhu, 2004; Figure 4).


Anatomy and physiology of the thick-tufted layer 5 pyramidal neuron.

Ramaswamy S, Markram H - Front Cell Neurosci (2015)

Diverse sources of afferent excitatory and inhibitory input to, and targets of efferent excitatory output from TTL5 neurons. An illustration of the TTL5 neuron in the local neocortical microcircuit showing diverse sources of excitatory and inhibitory inputs, and targets of excitatory output. Schematic representations of the various neuron types afferent to the TTL5 neuron are shown according to their known dendritic, peri-somatic or axonal innervation domains. Local electrogenic properties, and their likely layers of origin are shown to the left of the TTL5 schematic in the center. PoM—posterior medial nucleus; VPM—ventral posterior medial nucleus; L5STPC—layer 5 slender-tufted pyramidal cell; MC—Martinotti cell; NGC—neurogliaform cell; SBC—small basket cell; ChC—chandelier cell; LBC—large basket cell; NBC—nest basket cell; BP—bipolar cell; BTC—bitufted cell; DBC—double bouquet cell; TTL5—thick-tufted layer 5 pyramidal neuron.
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4481152&req=5

Figure 4: Diverse sources of afferent excitatory and inhibitory input to, and targets of efferent excitatory output from TTL5 neurons. An illustration of the TTL5 neuron in the local neocortical microcircuit showing diverse sources of excitatory and inhibitory inputs, and targets of excitatory output. Schematic representations of the various neuron types afferent to the TTL5 neuron are shown according to their known dendritic, peri-somatic or axonal innervation domains. Local electrogenic properties, and their likely layers of origin are shown to the left of the TTL5 schematic in the center. PoM—posterior medial nucleus; VPM—ventral posterior medial nucleus; L5STPC—layer 5 slender-tufted pyramidal cell; MC—Martinotti cell; NGC—neurogliaform cell; SBC—small basket cell; ChC—chandelier cell; LBC—large basket cell; NBC—nest basket cell; BP—bipolar cell; BTC—bitufted cell; DBC—double bouquet cell; TTL5—thick-tufted layer 5 pyramidal neuron.
Mentions: The expansive TTL5 dendritic arbor can be demarcated into distinct functional domains based on characteristic afferent inputs received from GABAergic local circuit interneurons (see Figure 4 for a schematic of the diverse sources of afferent excitatory and inhibitory input to, and targets of efferent excitatory output from TTL5 neurons). The division of the TTL5 dendritic arbor into these functional domains endows enhanced capabilities for the integration of varied streams of synaptic input. Martinotti cells preferentially target distal TTL5 dendrites and terminal tufts, while small basket cells predominantly target the proximal apical and basal dendrites and the soma (Thomson et al., 1996; Kawaguchi and Kubota, 1997; Somogyi et al., 1998; Wang et al., 2002; Silberberg and Markram, 2007; Ali and Thomson, 2008). TTL5 innervation by nest and large basket cells appears to be rather heterogeneous, covering the entire dendritic arbor (Wang et al., 2002). Synaptic contacts from bipolar, double bouquet and bitufted cells are made onto the proximal and distal dendrites for the most part (for reviews see Somogyi et al., 1998; Markram et al., 2004; Figure 4). Chandelier cells exclusively target the TTL5 AIS through axo-axonic synaptic contacts (Somogyi et al., 1982; Howard et al., 2005; Szabadics et al., 2006). Neurogliaform cells in the supragranular layers innervate distal TTL5 dendrites through metabotropic GABAB receptors mediating slow inhibition (Tamás et al., 2003; Oláh et al., 2007; Figure 4). Furthermore, terminal TTL5 dendritic tufts are innervated by a local plexus of axons from GABAergic intereneurons residing in layer 1, also giving rise to slow inhibition through GABAB receptors (Zhu, 2000; Zhu and Zhu, 2004; Figure 4).

Bottom Line: By virtue of having the widest local axonal and dendritic arborization, the TTL5 neuron encompasses various local neocortical neurons and thereby defines the dimensions of neocortical microcircuitry.The TTL5 neuron integrates input across all neocortical layers and is the principal output pathway funneling information flow to subcortical structures.This review summarizes key discoveries and identifies potential avenues of research to facilitate an integrated and unifying understanding on the role of a central neuron in the neocortex.

View Article: PubMed Central - PubMed

Affiliation: Blue Brain Project, Ecole Polytechnique Fédérale de Lausanne, Campus Biotech Geneva, Switzerland.

ABSTRACT
The thick-tufted layer 5 (TTL5) pyramidal neuron is one of the most extensively studied neuron types in the mammalian neocortex and has become a benchmark for understanding information processing in excitatory neurons. By virtue of having the widest local axonal and dendritic arborization, the TTL5 neuron encompasses various local neocortical neurons and thereby defines the dimensions of neocortical microcircuitry. The TTL5 neuron integrates input across all neocortical layers and is the principal output pathway funneling information flow to subcortical structures. Several studies over the past decades have investigated the anatomy, physiology, synaptology, and pathophysiology of the TTL5 neuron. This review summarizes key discoveries and identifies potential avenues of research to facilitate an integrated and unifying understanding on the role of a central neuron in the neocortex.

No MeSH data available.


Related in: MedlinePlus