Revealing the distribution of transmembrane currents along the dendritic tree of a neuron from extracellular recordings.

Revealing the current source distribution along the neuronal membrane is a key step on the way to understanding neural computations, however, the experimental and theoretical tools to achieve sufficient spatiotemporal resolution for the estimation remain to be established. Here we address this problem using extracellularly recorded potentials with arbitrarily distributed electrodes for a neuron of known morphology. We use simulations of models with varying complexity to validate the proposed method and to give recommendations for experimental applications. The method is applied to in vitro data from rat hippocampus

Szimmetria és optimumok elágazásai = Symmetry and bifurcations of optima

A projekt keretében a szimmetria és optimális viselkedés viszonyát vizsgáltuk mechanikai, adaptív dinamikai (evolúciós) és populáció-dinamikai feladatokban. Tartószerkezetek esetén megállapítottuk, hogy a szimmetrikus elrendezés gyakran javítható kis aszimmetria bevezetésével és pontos kritériumot határoztunk meg annak eldöntésére, hogy egy adott szerkezet adott szimmetria-sértő változók terében potenciálisan javítható-e. A kritérium nem igényel mechanikai számítást, pusztán az adott változók és a szerkezet szimmetria-csoportjának ismeretében elvégezhető. Egyszerű szerkezeti példákon illusztráltuk az eredményeinket és adtunk egy, a mérnöki gyakorlathoz közeli példát is. Kimutattuk, hogy az evolúció adaptív dinamikai modellje keretében a szimmetria-sértés létrejöhet és osztályoztuk ennek típusait, konkrét biológiai példákkal illusztrálva ezeket. Diszkrét populáció-dinamikai modelleket vizsgálva megmutattuk, hogy a modellben jelentkező diszkrét ciklusok zajjal szembeni stabilitása szorosan összefügg a vonatkozó sűrűségfüggvény aszimmetriájával. Rámutattunk, hogy diszkrét populációkban (és a valós esetek ilyenek) kaotikus dinamikára jellemző paraméterek csak megfelelő mértékű zaj jelenlétében mérhetőek. A projekt kiterjedt térbeli testek egyensúlyi helyzetei és geometriája közötti összefüggések vizsgálatára is. Ennek keretében sikerült igazolnunk V.I. Arnold egy sejtését, mely szerint létezik olyan homogén, konvex test melynek pontosan két egyensúlyi helyzete van. | In this project we investigated the relationship between symmetry and optima in the context of engineering structures, evolutionary processes and population dynamics. In case of engineering structures we found that symmetric structures can be often improved by introducing small asymmetres. We formulated a group-theoretic criterium to decide whether a given structure could be potentially improved in the space of given symmetry-breaking variables. We illustrated our results on simple examples, we also provided an example close to practical engineering. We studied evolution in the framework of adaptive dynamics and described the symmetry-breaking bifurcations in this process. We also provided biological examples for symmetry-breaking. We investigated discrete population models and showed that a discrete population can produce chaotic behaviour only in teh presence of environmental noise. We also studied the equilibria and geometry of three-dimensional solids and proved an earlier conjecture by V.I.Arnold about the existence of a convex, homogeneous object with just two equilibrium points

Method for spike detection from microelectrode array recordings contaminated by artifacts of simultaneous two-photon imaging

The simultaneous utilization of electrophysiological recordings and two-photon imaging allows the observation of neural activity in a high temporal and spatial resolution at the same time. The three dimensional monitoring of morphological features near the microelectrode array makes the observation more precise and complex. In vitro experiments were performed on mice neocortical slices expressing the GCaMP6 genetically encoded calcium indicator for monitoring the neural activity with two-photon microscopy around the implanted microelectrodes. A special filtering algorithm was used for data analysis to eliminate the artefacts caused by the imaging laser. Utilization of a special filtering algorithm allowed us to detect and sort single unit activities from simultaneous two-photon imaging and electrophysiological measurement

From End to End: Gaining, Sorting, and Employing High-Density Neural Single Unit Recordings

The meaning behind neural single unit activity has constantly been a challenge, so it will persist in the foreseeable future. As one of the most sourced strategies, detecting neural activity in high-resolution neural sensor recordings and then attributing them to their corresponding source neurons correctly, namely the process of spike sorting, has been prevailing so far. Support from ever-improving recording techniques and sophisticated algorithms for extracting worthwhile information and abundance in clustering procedures turned spike sorting into an indispensable tool in electrophysiological analysis. This review attempts to illustrate that in all stages of spike sorting algorithms, the past 5 years innovations' brought about concepts, results, and questions worth sharing with even the non-expert user community. By thoroughly inspecting latest innovations in the field of neural sensors, recording procedures, and various spike sorting strategies, a skeletonization of relevant knowledge lays here, with an initiative to get one step closer to the original objective: deciphering and building in the sense of neural transcript

Correction: Method for spike detection from microelectrode array recordings contaminated by artifacts of simultaneous two-photon imaging.

[This corrects the article DOI: 10.1371/journal.pone.0221510.]