Dendritic spines and linear networks

Yuste, Rafael; Urban, Rochelle

doi:10.1016/j.jphysparis.2005.09.014

Cited by 24 publications

(24 citation statements)

References 39 publications

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“…This difference is significant, robust, and maintained across a large range of experimental variables. We interpret these results as consistent with the hypothesis that dendritic spines serve as electrical isolators that promote linear integration (11,12,18,21). Our interpretation of these results depends on several assumptions.…”

Section: Discussionsupporting

confidence: 89%

“…This could explain why excitatory axons do not terminate on dendritic shafts. Finally, given how prevalent spines are in cortical circuits, the uncovering of their role in linearizing summation suggests that linear integration could be of the essence for cortical processing (21). A linear integration agrees with the excitatory connectivity in neocortex that is composed of a very distributed matrix with relatively few synaptic contacts between excitatory neurons (45).…”

Section: Discussionmentioning

confidence: 91%

“…A linear integration agrees with the excitatory connectivity in neocortex that is composed of a very distributed matrix with relatively few synaptic contacts between excitatory neurons (45). If the logic of the cortex is to distribute the information to a large number of postsynaptic cells as in a ''neuronal democracy,'' it is only fitting that those neurons integrate inputs linearly (21). Thus, the pyramidal neuron might be computationally simple, and its apparently complex dendritic morphology could paradoxically serve to linearize its input integration.…”

Section: Discussionmentioning

confidence: 99%

“…More generally, passive cable models predict that inputs onto dendrites will shunt each other if they are close (19,20). Therefore, dendritic spines could provide an electrically isolated postsynaptic region to prevent interaction between different excitatory inputs, resulting in a linear integration (21).…”

mentioning

confidence: 99%

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Dendritic spines linearize the summation of excitatory potentials

Araya

Eisenthal

Yuste

2006

Proc. Natl. Acad. Sci. U.S.A.

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135

113

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In mammalian cortex, most excitatory inputs occur on dendritic spines, avoiding dendritic shafts. Although spines biochemically isolate inputs, nonspiny neurons can also implement biochemical compartmentalization; so, it is possible that spines have an additional function. We have recently shown that the spine neck can filter membrane potentials going into and out of the spine. To investigate the potential function of this electrical filtering, we used two-photon uncaging of glutamate and compared the integration of electrical signals in spines vs. dendritic shafts from basal dendrites of mouse layer 5 pyramidal neurons. Uncaging potentials onto spines summed linearly, whereas potentials on dendritic shafts reduced each other's effect. Linear integration of spines was maintained regardless of the amplitude of the response, distance between spines (as close as <2 m), distance of the spines to the soma, dendritic diameter, or spine neck length. Our findings indicate that spines serve as electrical isolators to prevent input interaction, and thus generate a linear arithmetic of excitatory inputs. Linear integration could be an essential feature of cortical and other spine-laden circuits.second harmonic ͉ pyramidal cell ͉ glutamate uncaging ͉ two-photon I n neocortex and many other brain areas, most excitatory inputs terminate on dendritic spines (1); so, spines must therefore likely be of major importance for the functioning of neural circuits (2). Spines can compartmentalize calcium (3), partly because their peculiar morphologies, with a small head separated from the dendrite by a slender neck, enable the biochemical isolation between inputs (4-6). This compartmentalization is thought to underlie input-specific forms of synaptic plasticity, such as long-term potentiation (7-9).Theoretical work spanning several decades has suggested that spines are ideally poised to play a major role in altering the electrical properties of synaptic inputs (2, 10 -14). Indeed, recent work has called into question the view that the sole function of spines is one of biochemical compartmentalization. First, nonspiny neurons can compartmentalize calcium with as good a degree of biochemical isolation between inputs as spiny cells (15,16). Also, by using glutamate uncaging and second harmonic measurements of membrane potential on spines of layer 5 pyramidal neurons, we have demonstrated that the spine neck filters membrane potentials (17). The filtering was bidirectional, i.e., both spine potentials transmitted to the dendrite and dendritic potentials transmitted to the spine were strongly attenuated. This implies that spines could isolate inputs electrically, an idea previously suggested based on theoretical calculations (11,12,18). More generally, passive cable models predict that inputs onto dendrites will shunt each other if they are close (19,20). Therefore, dendritic spines could provide an electrically isolated postsynaptic region to prevent interaction between different excitatory inputs, resulting in a linear integration (21).Co...

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Dendritic spines linearize the summation of excitatory potentials

Araya

Eisenthal

Yuste

2006

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

135

113

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“…The location of spines on the dendrite relative to the cell body has functional implications for a neuron (Holthoff et al, 2002;Yuste and Urban, 2004). To determine whether SCI results in changes in spine distribution, we used a modified Sholl's analysis.…”

Section: Dendritic Spine Redistribution After Scimentioning

confidence: 99%

Neuropathic Pain Memory Is Maintained by Rac1-Regulated Dendritic Spine Remodeling after Spinal Cord Injury

Tan¹,

Stamboulian²,

Chang³

et al. 2008

J. Neurosci.

112

155

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Localized increases in synaptic strength constitute a synaptic basis for learning and memory in the CNS and may also contribute to the maintenance of neuropathic pain after spinal cord injury (SCI) through the de novo formation or elaboration of postsynaptic dendritic structures. To determine whether SCI-induced dendritic spine remodeling contributes to neuronal hyperexcitability and neuropathic pain, we analyzed spine morphometry, localization, and functional influence in dorsal horn (DH) neurons in adult rats 1 month after sham surgery, contusion SCI, and SCI treated with a selective inhibitor of Rac1 activation, NSC23766. After SCI, DH neurons located in lamina IV-V exhibited increased spine density, redistributed spines, and mature spines compared with control neurons, which was associated with enhancement of EPSCs in computer simulations and hyperexcitable responsiveness to innocuous and noxious peripheral stimuli in unit recordings in vivo. SCI animals also exhibited symptoms of tactile allodynia and thermal hyperalgesia. Inhibition of the small GTP-binding protein Rac1 ameliorated post-SCI changes in spine morphology, attenuated injury-induced hyperexcitability of wide-dynamic range neurons, and progressively increased pain thresholds over a 3 d period. This suggests that Rac1 is an important intracellular signaling molecule involved in a spinal dendritic spine pathology associated with chronic neuropathic pain after SCI. Our report provides robust evidence for a novel conceptual bridge between learning and memory on the one hand, and neuropathic pain on the other.

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Neurotypical subjective experience is caused by a hippocampal simulation

Faw¹,

Faw

2016

WIRES Cognitive Science

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We propose that the phenomenon known to neurologically intact people as 'Subjective Experience' is best understood as the activation of various sites in both extrinsic and intrinsic networks by a brand new episodic memory engram (i.e., a complex theta wave coding pattern originating from field CA1 of the hippocampus). Like a media news outlet, the hippocampal complex receives reportage from widely distributed structures around the brain and organizes and binds those reports together into a brand new episodic memory (i.e., a virtual-reality, movie-like, unified, contextualized, but vastly simplified summation of what just happened). This memory pattern is then 'broadcast' back to structures across the brain (via bidirectional pathways to and from the entorhinal cortex and perirhinal area) for error correction, to expedite predictive processing, and to inform sites in both extrinsic and intrinsic networks of one unified history. It is the cortical activation by the new episodic memory engram that gives rise to the event of experiencing. Because episodic memory is the only unified and contextualized representation of self-in-the-world in the brain, and because it informs most of the major cortices about 'what just happened,' it is subjectively misinterpreted as the actual interaction of the body/mind with its environment. This misinterpretation offers insight into many of the distinct and mysterious features of neurotypical subjective experience and the pathologies of consciousness. WIREs Cogn Sci 2017, 8:e1412. doi: 10.1002/wcs.1412 For further resources related to this article, please visit the WIREs website.

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Dendritic spines and linear networks

Cited by 24 publications

References 39 publications

Dendritic spines linearize the summation of excitatory potentials

Dendritic spines linearize the summation of excitatory potentials

Neuropathic Pain Memory Is Maintained by Rac1-Regulated Dendritic Spine Remodeling after Spinal Cord Injury

Neurotypical subjective experience is caused by a hippocampal simulation

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