Sparse Firing Research Articles

Realistic simulation of extracellular recordings

In this paper we present an efficient method to generate realistic simulations of extracellular recordings. The method uses a hybrid and computationally simple approach, where the features of the background noise arise naturally from its biophysical process of generation. The generated data resemble the characteristics of real recordings, as quantified by the amplitude and frequency distributions. Moreover, we reproduce real features that are specially challenging for the analysis of extracellular data, such as the presence of sparse firing neurons and multi-unit activity. We compare our simulations with real recordings from the human medial temporal lobe and exemplify their use for testing spike detection and sorting algorithms. These results show that this technique provides an optimal scenario for generating realistic simulations of extracellular recordings.

Finding your place when you are young: Recruitment of adult-generated neurons into song nucleus HVC

Event Abstract Back to Event Finding your place when you are young: Recruitment of adult-generated neurons into song nucleus HVC Sophie Scotto-Lomassese1, T. Roeske2, A. Garthe3 and Constance Scharff2* 1 Universite Pierre et Marie Curie, Laboratoire de Neurobiologie des Processus adaptatifs, France 2 Institute of Biology, Freie Universität Berlin, Department of Animal Behaviour, Germany 3 Center for Regenerative Therapies, Germany In adult songbirds, new neurons are born in the ventricular zone and after migration integrate into circuits throughout most of the telencephalon. New neurons also immigrate into HVC, a nucleus involved in song learning and production. HVC is composed of a heterogeneous population of inhibitory interneurons (HVCIN) and two populations of projection neurons that send axons towards the Robust nucleus of the Arcopallium (HVCRA) or the striatal nucleus Area X (HVCX). HVCRA neurons orchestrate the temporal sequence of the song via a sparse firing code. The renewal of this population raises the question whether old neurons perhaps instruct new ones. If cluster are connected via gap junctions, which are known to be expressed in HVC, they could potentially serve as functional units for new neurons to acquire their sparse song-related firing. We thus investigate the relative contribution of the different HVC cell types towards these clusters and whether new neurons integrate into particular cluster types using immunocytochemistry (cell birth and cell phenotype markers) in conjunction with stereotaxic injections of retrograde tracers into RA and Area X. Interestingly, we find that that 80% of the HVC neurons have one or more partners with direct soma contact. Clustering involved all neuron types, with two or three neurons per cluster the most common. HVCX neurons constitute 36% of HVC neurons and essentially all HVCX neurons were found in clusters. HVCRA neurons comprise 54% of HVC neurons and 80% occurred in clusters. Interneurons only contribute 10% of HVC neurons and 75% for HVCIN were found in clusters. 72% of new neurons were already incorporated into clusters one month after their birth. Moreover, these newly arriving cells did not associate with the most frequently encountered cluster type but preferentially joined the relatively rare single neurons or joined clusters of two cells. Thus, new neurons seem to participate in maintenance of the overall cluster distribution. We also analyzed the phenotype of the cell in direct contact with a new neuron and found that they are also not distributed according to frequency of occurrence of the different cell classes. Together, these results suggest that integration of new neurons into the HVC is not random and that clusters might participate in the regulation how new neurons incorporate into existing networks. Ultrastructural and intracellular dye injections are currently underway to clarify the presence of gap junctions between new and already existing neurons. Conference: 3rd Mediterranean Conference of Neuroscience , Alexandria, Egypt, 13 Dec - 16 Dec, 2009. Presentation Type: Oral Presentation Topic: Symposium 03 – Cellular regulation of adult-born neurons and their stem cells Citation: Scotto-Lomassese S, Roeske T, Garthe A and Scharff C (2009). Finding your place when you are young: Recruitment of adult-generated neurons into song nucleus HVC. Front. Neurosci. Conference Abstract: 3rd Mediterranean Conference of Neuroscience . doi: 10.3389/conf.neuro.01.2009.16.020 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Nov 2009; Published Online: 19 Nov 2009. * Correspondence: Constance Scharff, Institute of Biology, Freie Universität Berlin, Department of Animal Behaviour, Berlin, Germany, scharff@zedat.fu-berlin.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Sophie Scotto-Lomassese T. Roeske A. Garthe Constance Scharff Google Sophie Scotto-Lomassese T. Roeske A. Garthe Constance Scharff Google Scholar Sophie Scotto-Lomassese T. Roeske A. Garthe Constance Scharff PubMed Sophie Scotto-Lomassese T. Roeske A. Garthe Constance Scharff Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Increased bursting in layer 2/3 neurones of awake neocortex

Increased bursting in layer 2/3 neurones of awake neocortex

Sparse firing frequency-based neuron spike train classification

Peri-stimulus time histograms (PSTHs) reveal the temporal distribution of action potentials, averaged over many stimulus presentations. PSTHs have been used as model responses to solve the classification problem, in which a single response (i.e., spike train) is assigned to one of a set of response models evoked by a set of stimuli. In this study, we developed and applied a sparse firing frequency-based method to classify individual spike trains of slowly adapting pulmonary stretch receptors (SARs). Extracellularly recorded individual SAR spike trains were evoked by one of three different lung inflation volumes in anesthetized, paralyzed adult male New Zealand White rabbits. Three different PSTH-based firing frequency response models (i.e., one for each stimulus) were constructed from two-thirds of the responses to the 600 inflations presented at each volume, while the remaining one-third were used as responses to be classified. An instantaneous firing frequency representation of each remaining "test response" was computed from their individual spike trains, using one of two forms: sparse and filled. The sparse format assigned instantaneous firing rate values only in bins that contained spikes, while the filled format assigned values to intervening bins too. Classification was performed by computing the Euclidean distance between the response spike trains and the three PSTH-based models using both sparse and filled representations. When comparing the two representations with regard to classification accuracy, we found that the sparse representation does not diminish performance appreciably, while reducing computational burden significantly.

Enigmas of the Dentate Gyrus

We are rapidly approaching a better understanding of the mechanisms that allow our brains to form distinct representations for similar events or episodes. McHugh et al. have brought that goal one step closer by showing that NMDA receptor-dependent synaptic plasticity in the dentate gyrus is necessary for immediate differentiation between environments with similar features.

Action potential timing determines dendritic calcium during striatal up-states.

Up-states represent a key feature of synaptic integration in cortex and striatum that involves activation of many synaptic inputs. In the striatum, the sparse firing and tight control of action potential timing is in contrast to the large intracellular membrane potential depolarizations observed during the up-state. One hallmark of striatal spiny projection neurons is the delay to action potential generation in both up-states and suprathreshold depolarization by somatic current injection. By studying somatic and dendritic intracellular calcium ([Ca2+]i) transients during spontaneous up-states in cortex-striatum-substantia nigra organotypic cultures, we show that the delay between up-state onset and action potential generation determines dendritic peak [Ca2+]i. Peak [Ca2+]i from single action potentials reached maximum values when action potentials were close to up-state onset and sharply decayed to near subthreshold up-state [Ca2+] levels as a function of time (tau = 47 +/- 26 msec for tertiary dendrite). Similarly, a precisely timed action potential elicited during subthreshold up-states through somatic current injection established that the delay between up-state onset and action potential generation is the critical variable that controls peak [Ca2+]i. Blocking NMDA channels internally with high intracellular Mg2+ ([Mg2+]i) (10 mm) abolished the dependency of peak [Ca2+]i on action potential timing during spontaneous up-states. Finally, high [Mg2+]i specifically blocked [Ca2+]i transients that resulted from local NMDA application in conjunction with backpropagating action potentials. We conclude that precisely timed, single action potentials during striatal up-states control peak dendritic calcium levels. We suggest that this mechanism might play an important role in synaptic plasticity of the corticostriatal pathway.