Journal of Computational Neuroscience

Erratum to: Odour supported place cell model and goal navigation in rodents.

Publication Date: 2010 Feb 27 PMID: 20195732
Authors: Kulvicius, T. - Tamosiunaite, M. - Ainge, J. - Dudchenko, P. - Worgotter, F.
Journal: J Comput Neurosci

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Erratum to: Path-finding in real and simulated rats: assessing the influence of path characteristics on navigation learning.

Publication Date: 2010 Feb 27 PMID: 20195731
Authors: Tamosiunaite, M. - Ainge, J. - Kulvicius, T. - Porr, B. - Dudchenko, P. - Worgotter, F.
Journal: J Comput Neurosci

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Erratum to: Self-influencing synaptic plasticity: recurrent changes of synaptic weights can lead to specific functional properties.

Publication Date: 2010 Feb 27 PMID: 20195730
Authors: Tamosiunaite, M. - Porr, B. - Worgotter, F.
Journal: J Comput Neurosci

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Mixed mode oscillations as a mechanism for pseudo-plateau bursting.

Publication Date: 2010 Feb 26 PMID: 20186476
Authors: Vo, T. - Bertram, R. - Tabak, J. - Wechselberger, M.
Journal: J Comput Neurosci

We combine bifurcation analysis with the theory of canard-induced mixed mode oscillations to investigate the dynamics of a novel form of bursting. This bursting oscillation, which arises from a model of the electrical activity of a pituitary cell, is characterized by small impulses or spikes riding on top of an elevated voltage plateau. Oscillations with these characteristics have been called "pseudo-plateau bursting". Unlike standard bursting, the subsystem of fast variables does not possess a stable branch of periodic spiking solutions, and in the case studied here the standard fast/slow analysis provides little information about the underlying dynamics. We demonstrate that the bursting is actually a canard-induced mixed mode oscillation, and use canard theory to characterize the dynamics of the oscillation. We also use bifurcation analysis of the full system of equations to extend the results of the singular analysis to the physiological regime. This demonstrates that the combination of these two analysis techniques can be a powerful tool for understanding the pseudo-plateau bursting oscillations that arise in electrically excitable pituitary cells and isolated pancreatic beta-cells.

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Reduced models for binocular rivalry.

Publication Date: 2010 Feb 25 PMID: 20182782
Authors: Laing, C. R. - Frewen, T. - Kevrekidis, I. G.
Journal: J Comput Neurosci

Binocular rivalry occurs when two very different images are presented to the two eyes, but a subject perceives only one image at a given time. A number of computational models for binocular rivalry have been proposed; most can be categorised as either "rate" models, containing a small number of variables, or as more biophysically-realistic "spiking neuron" models. However, a principled derivation of a reduced model from a spiking model is lacking. We present two such derivations, one heuristic and a second using recently-developed data-mining techniques to extract a small number of "macroscopic" variables from the results of a spiking neuron model simulation. We also consider bifurcations that can occur as parameters are varied, and the role of noise in such systems. Our methods are applicable to a number of other models of interest.

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The local and non-local components of the local field potential in awake primate visual cortex.

Publication Date: 2010 Feb 24 PMID: 20180148
Authors: Gawne, T. J.
Journal: J Comput Neurosci

The Local Field Potential (LFP) is the analog signal recorded from a microelectrode inserted into cortex, typically in the frequency band of approximately 1 to 200 Hz. Here visual stimuli were flashed on in the receptive fields of primary visual cortical neurons in awake behaving macaques, and both isolated single units (neurons) and the LFP signal were recorded from the same unipolar microelectrode. The fall-off of single unit activity as a visual stimulus was moved from near the center to near the edge of the receptive field paralleled the fall-off of the stimulus-locked (evoked) LFP response. This suggests that the evoked LFP strongly reflects local neuronal activity. However, the evoked LFP could be significant even when the visual stimulus was completely outside the receptive field and the single unit response had fallen to zero, although this phenomenon was variable. Some of the non-local components of the LFP may be related to the slow distributed, or non-retinotopic, LFP signal previously observed in anesthetized animals. The induced (not time-locked to stimulus onset) component of the LFP showed significant increases only for stimuli within the receptive field of the single units. While the LFP primarily reflects local neuronal activity, it can also reflect neuronal activity at more distant sites, although these non-local components are typically more variable, slower, and weaker than the local components.

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Computational modeling of GABA(A) receptor-mediated paired-pulse inhibition in the dentate gyrus.

Publication Date: 2010 Feb 23 PMID: 20177763
Authors: Jedlicka, P. - Deller, T. - Schwarzacher, S. W.
Journal: J Comput Neurosci

Paired-pulse inhibition (PPI) of the population spike observed in extracellular field recordings is widely used as a read-out of hippocampal network inhibition. PPI reflects GABA(A) receptor-mediated inhibition of principal neurons through local interneurons. However, because of its polysynaptic nature, it is difficult to assign PPI changes to precise synaptic mechanisms. Here we used a detailed network model of the dentate gyrus to simulate PPI of granule cell action potentials and analyze its network properties. Our computational analysis indicates that PPI results mainly from a combination of perisomatic feed-forward and feedback inhibition of granule cells by basket cells. Feed-forward inhibition mediated by basket cells appeared to be the most significant source of PPI. Our simulations suggest that PPI depends more on somatic than on dendritic inhibition of granule cells. Furthermore, PPI was modulated by changes in GABA(A) reversal potential (E(GABA)) and by alterations in intrinsic excitability of granule cells. In summary, computer modeling provides a useful tool for determining the role of synaptic and intrinsic cellular mechanisms in paired-pulse field potential responses.

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Cross-trial correlation analysis of evoked potentials reveals arousal-related attenuation of thalamo-cortical coupling.

Publication Date: 2010 Feb 23 PMID: 20177762
Authors: Sobolewski, A. - Kublik, E. - Swiejkowski, D. A. - Leski, S. - Kaminski, J. K. - Wrobel, A.
Journal: J Comput Neurosci

We describe a computational method for assessing functional connectivity in sensory neuronal networks. The method, which we term cross-trial correlation, can be applied to signals representing local field potentials (LFPs) evoked by sensory stimulations and utilizes their trial-to-trial variability. A set of single trial samples of a given post-stimulus latency from consecutive evoked potentials (EPs) recorded at a given site is correlated with such sets for all other latencies and recording sites. The results of this computation reveal how neuronal activities at various sites and latencies correspond to activation of other sites at other latencies. The method was used to investigate the functional connectivity of thalamo-cortical network of somatosensory system in behaving rats at two levels of alertness: habituated and aroused. We analyzed potentials evoked by vibrissal deflections recorded simultaneously from the ventrobasal thalamus and barrel cortex. The cross-trial correlation analysis applied to the early post-stimulus period (<25 ms) showed that the magnitude of the population spike recorded in the thalamus at 5 ms post-stimulus correlated with the cortical activation at 6-13 ms post-stimulus. This correlation value was reduced at 6-9 ms, i.e. at early postsynaptic cortical response, with increased level of the animals' arousal. Similarly, the aroused state diminished positive thalamo-cortical correlation for subsequent early EP waves, whereas the efficacy of an indirect cortico-fugal inhibition (over 15 ms) did not change significantly. Thus we were able to characterize the state related changes of functional connections within the thalamo-cortical network of behaving animals.

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Encoding and decoding amplitude-modulated cochlear implant stimuli-a point process analysis.

Publication Date: 2010 Feb 23 PMID: 20177761
Authors: Goldwyn, J. H. - Shea-Brown, E. - Rubinstein, J. T.
Journal: J Comput Neurosci

Cochlear implant speech processors stimulate the auditory nerve by delivering amplitude-modulated electrical pulse trains to intracochlear electrodes. Studying how auditory nerve cells encode modulation information is of fundamental importance, therefore, to understanding cochlear implant function and improving speech perception in cochlear implant users. In this paper, we analyze simulated responses of the auditory nerve to amplitude-modulated cochlear implant stimuli using a point process model. First, we quantify the information encoded in the spike trains by testing an ideal observer's ability to detect amplitude modulation in a two-alternative forced-choice task. We vary the amount of information available to the observer to probe how spike timing and averaged firing rate encode modulation. Second, we construct a neural decoding method that predicts several qualitative trends observed in psychophysical tests of amplitude modulation detection in cochlear implant listeners. We find that modulation information is primarily available in the sequence of spike times. The performance of an ideal observer, however, is inconsistent with observed trends in psychophysical data. Using a neural decoding method that jitters spike times to degrade its temporal resolution and then computes a common measure of phase locking from spike trains of a heterogeneous population of model nerve cells, we predict the correct qualitative dependence of modulation detection thresholds on modulation frequency and stimulus level. The decoder does not predict the observed loss of modulation sensitivity at high carrier pulse rates, but this framework can be applied to future models that better represent auditory nerve responses to high carrier pulse rate stimuli. The supplemental material of this article contains the article's data in an active, re-usable format.

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