Distribution-free graphical and statistical analysis of serial dependence in neuronal spike trains

Statistical long-term correlations in dissociated cortical neuron recordings

The study of nonlinear long-term correlations in neuronal signals is a central topic for advanced neural signal processing. In particular, the existence of long-term correlations in neural signals recorded via multielectrode array (MEA) could provide interesting information about changes in interneuron communications. In this study we propose a new method for long-term correlation analysis of neuronal burst activity based on the periodogram alpha slope estimation of the MEA signal. We applied our method to recordings taken from cultured networks of dissociated rat cortical neurons. We show the effectiveness of the method in analyzing the activity changes as well as the temporal dynamics that take place during the development of such cultures. Results demonstrate that the alpha parameter is able to divide the network development in three well-defined stages, showing pronounced variations in the long-term correlation among bursts.

The estimation of long-term memory characteristics in MEA neuronal culture recordings

The nonlinear analysis of multichannel MEA recordings from neuronal networks is becoming a central topic in Neuroengineering. Up-to-date these kind of analyses required complex ad hoc methods. In this paper we introduce a new approach that allows the analysis of the whole-neuronal-network-activity with well-established nonlinear signal processing methods. In particular, we show here the estimation of long-term-memory behaviors through the Periodogram method in the bursting activity of cortical neuron cultures during development. Moreover, we show how this method is able to highlight structural activity changes of the network.

How do TTX and AP5 affect the post-recovery neuronal network activity synchronization?

A lot of methods were created in last decade for the spatio-temporal analysis of multi-electrode array (MEA) neuronal data sets. The greater part of these methods does not consider the network as a whole but performs an analysis channel by channel. In this paper we illustrate how a very simple approach that considers the total network activity, is able to show interesting neuronal network features. In particular we perform two different analyses: a connectivity examination studying networks at different days in vitro and an analysis of the long period effects of the administration of two common neuro-active drugs, i.e. TTX and AP5. Our analysis is performed considering burst topology, i.e. cataloguing network bursts as Global (if they involve more than the 25% of the MEA channels) or Local (if less that 25%). This division allows, in the first analysis, to understand the network connectivity (increasing from div 1 to 6) and decreasing till reaching a plateau (from div 6 to 10). The second analysis highlights a substantial difference between the long period effects of TTX and AP5. While TTX induces a massive Global activity explosion, sign of a prolonged inhibitory synapse depression, AP5 shows only a modest Local activity increase, mark of the low effect of NMDA receptors on a mature neuronal network without inputs.

Controlling bursting in cortical cultures with closed-loop multi-electrode stimulation

One of the major modes of activity of high-density cultures of dissociated neurons is globally synchronized bursting. Unlike in vivo, neuronal ensembles in culture maintain activity patterns dominated by global bursts for the lifetime of the culture (up to 2 years). We hypothesize that persistence of bursting is caused by a lack of input from other brain areas. To study this hypothesis, we grew small but dense monolayer cultures of cortical neurons and glia from rat embryos on multi-electrode arrays and used electrical stimulation to substitute for afferents. We quantified the burstiness of the firing of the cultures in spontaneous activity and during several stimulation protocols. Although slow stimulation through individual electrodes increased burstiness as a result of burst entrainment, rapid stimulation reduced burstiness. Distributing stimuli across several electrodes, as well as continuously fine-tuning stimulus strength with closed-loop feedback, greatly enhanced burst control. We conclude that externally applied electrical stimulation can substitute for natural inputs to cortical neuronal ensembles in transforming burst-dominated activity to dispersed spiking, more reminiscent of the awake cortex in vivo. This nonpharmacological method of controlling bursts will be a critical tool for exploring the information processing capacities of neuronal ensembles in vitro and has potential applications for the treatment of epilepsy.

Topographical and physicochemical modification of material surface to enable patterning of living cells

Precise control of the architecture of multiple cells in culture and in vivo via precise engineering of the material surface properties is described as cell patterning. Substrate patterning by control of the surface physicochemical and topographic features enables selective localization and phenotypic and genotypic control of living cells. In culture, control over spatial and temporal dynamics of cells and heterotypic interactions draws inspiration from in vivo embryogenesis and haptotaxis. Patterned arrays of single or multiple cell types in culture serve as model systems for exploration of cell-cell and cell-matrix interactions. More recently, the patterned arrays and assemblies of tissues have found practical applications in the fields of Biosensors and cell-based assays for Drug Discovery. Although the field of cell patterning has its origins early in this century, an improved understanding of cell-substrate interactions and the use of microfabrication techniques borrowed from the microelectronics industry have enabled significant recent progress. This review presents the important early discoveries and emphasizes results of recent state-of-the-art cell patterning methods. The review concludes by illustrating the growing impact of cell patterning in the areas of bioelectronic devices and cell-based assays for drug discovery.

Odor, drug and toxin analysis with neuronal networks in vitro: extracellular array recording of network responses

Neurons, by virtue of intrinsic electrophysiological mechanisms, represent transducers that report the dynamics of cell death, receptor-ligand interactions, alterations in metabolism, and generic membrane perforation processes. In cell culture, mammalian neurons form fault-tolerant, spontaneously active systems with great sensitivity to their chemical environment and generate response profiles that are often concentration- and substance-specific. Changes in action potential patterns are usually detected before morphological changes and cell damage occur, which provides sensitivity and reversibility. Such biological systems can be used to screen rapidly for novel pharmacological substances, toxic agents, and for the detection of certain odorants. Existing simple culture preparations can already be employed effectively for the detection of chemical compounds. So far, three strategies have been investigated in pilot experiments: (1) Substance-dependent major changes in spontaneous native activity patterns. All synaptically active agents (e.g. glutamate, strychnine, N-methyl D-aspartic acid) as well as metabolic poisons generate such changes. (2) Substance-dependent changes in network oscillations via disinhibition. The regularized, oscillatory activity is altered by synaptically and metabolically active substances, ion channel blockers, and toxins. (3) Detection of paroxysmal responses indicating major, pathological membrane currents in large subpopulation of cells. We have explored these three strategies via 64 channel array recordings using spontaneously active murine spinal cord cultures. The glycine receptor blocker strychnine reliably generated increased multichannel bursting at 5-20 nM and regular, coordinated bursting above 5 microM. During biculline-induced network oscillations many compounds alter oscillation frequencies or terminate activity in a substance-specific manner. Finally, the gp120 protein of the AIDS virus (at 1 microgram/ml) produces massive, unique paroxysmal discharges that may last as long as 2 min. These results indicate that cultured neuronal networks are practical systems that can be used for the detection and identification of a great variety of chemical substances. The concept of dynamic fingerprinting to identify specific compounds is discussed.