An Ongoing Subthreshold Neuronal State Established Through Dynamic Coassembling of Cortical Cells

Hoshino, Osamu

doi:10.1162/neco.2008.08-07-589

Cited by 20 publications

(13 citation statements)

References 30 publications

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“…A conductance-based, integrate-and-fire neuron model is employed (Hoshino 2006(Hoshino , 2008. GABA transporters, located on the axon terminals of F and L cells, regulate ambient GABA concentration.…”

Section: Methodsmentioning

confidence: 99%

Insufficient augmentation of ambient GABA responsible for age-related cognitive deficit

et al. 2010

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Age-related degeneration of intracortical inhibition could underlie declines in cognitive function during senescence. Based on a hypothesis that a decrease in basal concentration of ambient (extrasynaptic) GABA with aging leads to depressing intracortical inhibition, we investigated how the basal concentration affects stimulus-evoked activity (as signal), ongoing-spontaneous activity (as noise) of neurons and their (signal-to-noise) ratio S/N. We simulated a neural network model equipped with a GABA transport system that regulates ambient GABA concentration in a neuronal activity-dependent manner. An increase in basal concentration augmented ambient GABA, increased GABA-mediated inhibitory current, and depressed ongoing-spontaneous activity while still keeping stimulus-evoked activity. This led to S/N improvement, for which it was necessary for the reversal potential of GABA transporter to be close to the resting potential of neurons. Above the resting potential, ongoing-spontaneous activity was predominantly enhanced due to excessive GABA-uptake from the extracellular space by transporters. Below the resting potential, stimulus-evoked activity was predominantly depressed, caused by excessive GABA-release. We suggest that the insufficient augmentation of ambient GABA due to a decrease in its basal concentration may be one of the possible causes of cognitive deficit with aging, increasing ongoing-spontaneous neuronal activity as noise. GABA transporter may contribute to improving S/N, provided that its reversal potential is close to the resting potential.

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Section: Methodsmentioning

confidence: 99%

Insufficient augmentation of ambient GABA responsible for age-related cognitive deficit

et al. 2010

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“…A conductance-based, integrate-and-fire neuron model (Hoshino, 2006(Hoshino, , 2008 with an ambient (extrasynaptic) GABA regulatory system (Hoshino, 2009) is employed. GABA transporters are located on the axon terminals of L and F cells.…”

Section: Neural Network Modelmentioning

confidence: 99%

Neuronal Responses Below Firing Threshold for Subthreshold Cross-Modal Enhancement

Hoshino

2011

Neural Computation

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Multisensory integration (such as somatosensation-vision, gustation-olfaction) could occur even between subthreshold stimuli that in isolation do not reach perceptual awareness. For example, when a somatosensory (subthreshold) stimulus is delivered within a close spatiotemporal congruency, a visual (subthreshold) stimulus evokes a visual percept. Cross-modal enhancement of visual perception is maximal when the somatosensory stimulation precedes the visual one by tens of milliseconds. This rapid modulatory response would not be consistent with a top-down mechanism acting through higher-order multimodal cortical areas, but rather a direct interaction between lower-order unimodal areas. To elucidate the neuronal mechanisms of subthreshold cross-modal enhancement, we simulated a neural network model. In the model, lower unimodal (X, Y) and higher multimodal (M) networks are reciprocally connected by bottom-up and top-down axonal projections. The lower networks are laterally connected with each other. A pair of stimuli was presented to the lower networks, whose respective intensities were too weak to induce salient neuronal activity (population response) when presented alone. Neurons of the Y network were slightly depolarized below firing threshold when a cross-modal stimulus was presented alone to the X network. This allowed the Y network to make a rapid (within tens of milliseconds) population response when presented with a subsequent congruent stimulus. The reaction speed of the Y network was accelerated, provided that the top-down projections were strengthened. We suggest that a subthreshold (nonpopulation) response to a cross-modal stimulus, acting through interaction between lower (primary unisensory) areas, may be essential for a rapid suprathreshold (population) response to a congruent stimulus that follows. Top-down influences on cross-modal enhancement may be faster than expected, accelerating reaction speed to input, in which ongoing-spontaneous subthreshold excitation of lower-order unimodal cells by higher-order multimodal cells may play an active role.

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“…In that situation, ambient-GABA-mediated tonic inhibition of principal cells contributed to regulating the overall network activity. We also showed that the transient dynamic linkage of cell assemblies, referred to as ''dynamic coassembling'' (Hoshino 2008b), contributed to achieving ongoing subthreshold membrane oscillations.…”

Section: Discussionmentioning

confidence: 87%

Local intracortical circuitry not only for feature binding but also for rapid neuronal responses

et al. 2010

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Neurons of primary sensory cortices are known to have specific responsiveness to elemental features. To express more complex sensory attributes that are embedded in objects or events, the brain must integrate them. This is referred to as feature binding and is reflected in correlated neuronal activity. We investigated how local intracortical circuitry modulates ongoing-spontaneous neuronal activity, which would have a great impact on the processing of subsequent combinatorial input, namely, on the correlating (binding) of relevant features. We simulated a functional, minimal neural network model of primary visual cortex, in which lateral excitatory connections were made in a diffusive manner between cell assemblies that function as orientation columns. A pair of bars oriented at specific angles, expressing a visual corner, was applied to the network. The local intracortical circuitry contributed not only to inducing correlated neuronal activation and thus to binding the paired features but also to making membrane potentials oscillate at firing-subthreshold during an ongoing-spontaneous time period. This led to accelerating the reaction speed of principal cells to the input. If the lateral excitatory connections were selectively (instead of "diffusively") made, hyperpolarization in ongoing membrane potential occurred and thus the reaction speed was decelerated. We suggest that the local intracortical circuitry with diffusive connections between cell assemblies might endow the network with an ongoing subthreshold neuronal state, by which it can send the information about combinations of elemental features rapidly to higher cortical stages for their full and precise analyses.

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An Ongoing Subthreshold Neuronal State Established Through Dynamic Coassembling of Cortical Cells

Cited by 20 publications

References 30 publications

Insufficient augmentation of ambient GABA responsible for age-related cognitive deficit

Insufficient augmentation of ambient GABA responsible for age-related cognitive deficit

Neuronal Responses Below Firing Threshold for Subthreshold Cross-Modal Enhancement

Local intracortical circuitry not only for feature binding but also for rapid neuronal responses

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