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G L Gerstein

Publications and source records attributed to G L Gerstein.

At least 55 records · Page 3Linked to original sources
PubMed1989

A low-cost single-board solution for real-time, unsupervised waveform classification of multineuron recordings.

We describe a low-cost single-board system for unsupervised, real-time spike sorting of recordings from a number of neurons on a single microelectrode. The maximum number of spike classes depends on the quality of the recording; it will typically be between 2 and 5. The spike sorter communicates with a conventional microcomputer through a standard serial port (RS232). For typical firing rates as measured in the mammalian central nervous system, this set-up will accommodate up to some 10 parallel spike sorters for as many separate microelectrodes.

Algorithms↗
PubMed1989

Spectral time-course analysis of firing patterns in the dorsal cochlear nucleus.

Many previous studies of central auditory neurons have involved independent analyses of spectral and temporal response properties. The spectral response analysis is useful for defining the frequency and intensity regions over which a neuron is excited or inhibited. However, the conventional spectral response analysis only defines this distribution for the synaptic polarity (excitation or inhibition) which dominates the duration of the response. PST histograms of dorsal cochlear nucleus neurons however, often exhibit both excitatory and inhibitory (i.e. pause) components. The distribution of these transient pause intervals may in turn be highly dependent on stimulus parameters suggesting that the spectral area of excitation and inhibition, when considered in terms of short time frames, may be time-dependent. We performed a temporal analysis of the spectral response areas of neurons in the rat dorsal cochlear nucleus and present here an example based on a neuron showing distinct pauser and buildup responses in its PST histograms. The resulting analysis yielded a time course of the spectral response area which indicates that the transient periods of inhibition may have the effect of narrowing the bandwidth of excitation during the early portion of stimulation. Possible implications of this time course are discussed in relation to the narrower tuning that cochlear nucleus neurons often display in response to frequency sweeps than to pure tones.

Acoustic Stimulation↗
PubMed1989

Neuronal assemblies.

This paper examines the concept of neuronal assembly as it has appeared in selected portions of the literature. The context is experimental access to real neuronal assemblies in working brains, as made possible by recent technological progress. One current measure of assembly organization is based on correlation of firing among neurons; recent observations show that such correlations can vary rapidly. In this paper, we demonstrate that dynamic firing correlation can be caused either by dynamic changes in neuronal connection strengths or, alternatively, by the effects of an unobserved (large) pool of other neurons. The static connectivity within the pool appears to be important in determining these effects.

Animals↗
PubMed1989

Dynamics of neuronal firing correlation: modulation of "effective connectivity".

1. We reexamine the possibilities for analyzing and interpreting the time course of correlation in spike trains simultaneously and separably recorded from two neurons. 2. We develop procedures to quantify and properly normalize the classical joint peristimulus time scatter diagram. These allow separation of the "raw" correlation into components caused by direct stimulus modulations of the single-neuron firing rates and those caused by various types of interaction between the two neurons. 3. A newly developed significance test ("surprise") is applied to evaluate such inferences. 4. Application of the new procedures to simulated spike trains allowed the recovery of the known circuitry. In particular, it proved possible to recover fast stimulus-locked modulations of "effective connectivity," even if they were masked by strong direct stimulus modulations of individual firing rates. These procedures thus present a clearly superior alternative to the commonly used "shift predictor." 5. Adopting a model-based approach, we generalize the classical measures for quantifying a direct interneuronal connection ("efficacy" and "contribution") to include possible stimulus-locked time variations. 6. Application of the new procedures to real spike trains from several different preparations showed that fast stimulus-locked modulations of "effective connectivity" also occur for real neurons.

Animals↗
PubMed1988

Cortical auditory neuron interactions during presentation of 3-tone sequences: effective connectivity.

The role of cat's primary auditory cortex (AI) in both pattern discrimination and sound localization has been demonstrated by observing that ablations of it disrupt these functions. This research studied effective connectivity variations as a function of modifications in the temporal pattern of acoustic stimulation. Recordings of 10-15 neurons (simultaneously and separably) were made in AI of sedated cats. A bundle of 7 microelectrodes was stereotaxically placed along a tangential path. Stimuli were permutations of 3-tone bursts sequences. Each recorded neuron pair was analyzed off-line by cross-correlation. Cross-correlation of spike trains from neuron pairs showed signatures of direct and/or shared input. These appeared individually or in combination and for most pairs were present in spontaneous conditions. However, in stimulated conditions these spontaneous interactions were strongly modulated. The analysis detected differences in neuronal interaction during presentation of different tones. Similar differences occurred during presentation of any single particular stimulus if there was a history of different immediately previous tones. When individual neuron pair cross-correlations were put together to form an effective connectivity diagram among all recorded neurons, they turned out as different diagrams for different stimulus conditions.

Acoustic Stimulation↗
PubMed1988

On the significance of correlations among neuronal spike trains.

We consider several measures for the correlation of firing activity among different neurons, based on coincidence counts obtained from simultaneously recorded spike trains. We obtain explicit formulae for the probability distributions of these measures. This allows an exact, quantitative assessment of significance levels, and thus a comparison of data obtained in different experimental paradigms. In particular it is possible to compare stimulus-locked, and therefore time dependent correlations for different stimuli and also for different times relative to stimulus onset. This allows to separate purely stimulus-induced correlation from intrinsic interneuronal correlation. It further allows investigation of the dynamic characteristics of the interneuronal correlation. For the display of significance levels or the corresponding probabilities we propose a logarithmic measure, called "surprise".

Animals↗
PubMed1988

Unsupervised waveform classification for multi-neuron recordings: a real-time, software-based system. I. Algorithms and implementation.

We describe a new, mostly software-based device for the sorting of waveforms in an extracellular multi-neuron recording situation. The sorting algorithm is largely unattended, and, after an initial 'learning' process, works in real time. Shape comparisons are based on up to 8 time points in the waveform; these points (the reduced feature set) are chosen automatically by analyzing the current incoming data stream. A feasibility version has been implemented on a LSI-11/2 system, using FORTRAN for set-up calculations and assembler for the real-time operations. Detailed comparisons with performance of other sorting devices are presented in the companion paper.

Algorithms↗
PubMed1988

Unsupervised waveform classification for multi-neuron recordings: a real-time, software-based system. II. Performance comparison to other sorters.

The companion paper has described a new, fully automatic device for the sorting of action potential waveforms in real time. We present here a brief comparison of performance between this new device and several of the older, more traditional devices used for this purpose. We include in the comparison the performance of 3 human observers.

Algorithms↗
PubMed1988

Detecting spatiotemporal firing patterns among simultaneously recorded single neurons.

1. A particular firing pattern among simultaneously observed neurons represents a particular sequence of activity. If any multineuron pattern repeats significantly more than expected by chance, we may be observing a repeated state of a neural assembly as it processes similar units of information. 2. We present here an algorithm that rapidly finds all single or multineuron patterns that repeat two or more times within a block of data, as well as equations for calculating the number of patterns of given length and repetition that would be expected. The complexity of patterns for which it is practical to compute expected numbers is three to six spikes (inclusive). 3. Confidence limits are based on these expected numbers of patterns, so that is possible to identify groups of patterns that are worthy of further analysis. 4. These methods are tested against simulated multineuron data that has various types of known nonstationarities, with good agreement between observed and expected values. 5. Application to real spike trains shows a large excess of observed repeating patterns, of which some, but not all, are shown to be due to bursts of high frequency firing. 6. It should be possible to apply the new method as a filter in real time in order to search for an association between repeated pattern events and externally observable events (stimulus, behavior, etc.). Any repeated pattern events which cannot be so associated may represent a new indicator of internal events in the nervous system.

Algorithms↗
PubMed1986

A rapid method for production of sharp tips on preinsulated microwires.

A rapid method is described which makes it possible to obtain sharp, pencil-like tips on factory-insulated tungsten wires. These features cannot be achieved on preinsulated wire using electrolytic etching techniques. In essence, the cut end of an insulated 25 micron wire is ground on a flat metal surface containing a thin layer of powdered diamond. When both the wire and the diamond-covered disc are rotated simultaneously, a sharp pointed tip is produced within 2-5 min with a smoothly tapering sleeve of insulation. The resulting tips yielded high-quality single-unit spike trains when tested in rat cochlear nucleus. This method lends itself well to those single unit or multineuronal studies requiring rapid, low-cost electrode production, and minimum tissue damage.

Animals↗
PubMed1985

Evaluation of neuronal connectivity: sensitivity of cross-correlation.

Cross-correlation analysis of separable multi-unit activity is one of the most commonly used methods to investigate connectivity in neural networks. In the course of development of new analysis techniques which go beyond the study of pairs or triplets of neurons, the need arose for a simple yet versatile simulator to generate spike trains from networks of specified structure. The present paper describes such a simulator and presents some examples of its performance as analyzed by cross-correlation. We noted a distinct asymmetry in the sensitivity of cross-correlation for the presence of excitatory vs inhibitory connections. A theoretical analysis is given from which quantitative criteria for detectability were derived. It appears that indeed the sensitivity of cross-correlation for excitation is larger to an order of magnitude than it is for inhibition. Possible consequences of this finding are indicated, and the relation to commonly used methods to measure strength of interaction are discussed.

Action Potentials↗
PubMed1985

Representation of cooperative firing activity among simultaneously recorded neurons.

Simultaneous and separable extracellular recording of substantial populations of neurons under chronic and behavioral conditions is becoming experimentally feasible. We have recently described a conceptual transformation of such multiple spike train data that allows the experimenter to analyze the entire network of observed neurons as an entity rather than as a summation of neuron pairs. The basic transformation represents each of N neurons as a particle in an N-space. Each particle is given a "charge" that is related to the spike train of the corresponding neuron. The resulting forces on the N particles cause aggregation of those particles that represent neurons with time-related firing. The present paper extends the visualization and possibilities of this way of analyzing properties of neuronal assemblies. Data are taken from computer-simulated neuronal networks in order to provide known properties. We demonstrate projection of particle positions from the N space to a plane. Under the right conditions the spatial arrangement of the particles forms a Venn diagram of functional relationships in the entire neural network. We introduce revised force rules in the transformation that allow detection and study of inhibitory connections among the observed neurons. Sensitivity is lower than for excitatory connections. We introduce revised "charge" rules that improve "signal-to-noise" properties and in addition allow inference of directed connectivity. The original transformation only allows identification of neurons with time-related firing. The two-charge transformation allows explicit identification of presynaptic and postsynaptic neurons. Finally we examine sensitivity of the transformation to individual and near-coincident firing rates. Some criteria are presented for choice of charge normalization rules in the transformation.

Action Potentials↗
PubMed1985

Cooperative firing activity in simultaneously recorded populations of neurons: detection and measurement.

Recent advances in techniques for chronic recording from multiple extracellular microelectrodes allow simultaneous observation of firings of substantial populations of neurons. We describe a new conceptual representation of cooperative behavior within the observed neuronal population. This representation leads to a new technique for detecting and studying functional neuronal assemblies that are characterized by temporally related firing patterns. The representation may be applied to both dynamic and long-term aspects of cooperativity. The basic idea is to map activity of neurons into motions of particles in a multidimensional Euclidean space. Each neuron is represented by a point particle located in this space. In the simplest version of the mapping, each nerve impulse results in an increment in a "charge" associated with that particle; between firings the charges decay. The force exerted by any such particle on any other is, by analogy with some physical forces, proportional to the product of their charges and may depend on the Euclidean distance separating them. The force on a particle directly affects its velocity rather than its acceleration, as with actual particles in a viscous medium. These forces result in aggregation of those particles that correspond to neurons tending to fire together; separate clusters represent independent cooperative groups. Modification of the charges and forces permits inclusion of inhibitory interactions. Identification, measurement, and display of the resulting clusters can be performed with any of a number of algorithms. We illustrate the application of this approach to populations of computer-simulated neurons having both direct and indirect excitatory coupling.

Cell Aggregation↗
PubMed1983

Interactions between cat striate cortex neurons.

A series of simultaneous recordings from several striate cortex neurons were made in paralyzed, anesthetized cats. Recordings were obtained with one or two bundles of extra fine wires and originated from one and two cortical orientation columns. Standard PST histograms and, in some cases, response planes were used to analyse the neuronal receptive fields. Functional connectivity between neurons was assessed by cross-correlation of their spike trains. It was found that 61% of neuronal pairs found within a column shared the same input, either excitatory or inhibitory, Even if neurons in a pair belonged to two different columns separated by 1mm lateral distance, 40% of pairs still exhibited shared input coordination. This type of coordination could also encompass all combinations of simple and complex fields in the pair. Direct connections between neurons were found almost exclusively within columns: excitatory connections were found in 20% of cases and inhibitory in 8%. Direct connections were often accompanied by the other types of interactions. Only one example of excitatory and one of inhibitory direct connections were found between columns. In both cases preferred orientations were almost identical.

Animals↗
PubMed1983

Favored patterns in spike trains. I. Detection.

Traditional spike-train analysis methods cannot identify patterns of firing that occur frequently but at arbitrary times. It is appropriate to search for recurring patterns because such patterns could be used for information transfer. In this paper, we present two methods for identifying "favored patterns" --patterns that occur more often than is reasonably expected at random. The quantized Monte Carlo method identifies and establishes significance for favored patterns whose detailed timing may vary but that do not have extra or missing spikes. The template method identifies favored patterns whose occurrences may have extra or missing spikes. This method is useful when employed after the results of the first method are known. Studies with simulated spike trains containing known interpolated patterns are used to establish the sensitivity and accuracy of the quantized Monte Carlo method. Certain trends with regard to parameters of the detected patterns and of the analysis methods are described. Application of these methods to neurophysiological data has shown that a large proportion of spike trains have favored patterns. These findings are described in the accompanying paper (3).

Action Potentials↗
PubMed1983

Favored patterns in spike trains. II. Application.

In this paper we apply the two methods described in the companion paper (4) to experimentally recorded spike trains from two preparations, the crayfish claw and the cat striate cortex. Neurons in the crayfish claw control system produced favored patterns in 23 of 30 spike trains under a variety of experimental conditions. Favored patterns generally consisted of 3-7 spikes and were found to be in excess by both quantized and template methods. Spike trains from area 17 of the lightly anesthetized cat showed favored patterns in 16 of 27 cases (in quantized form). Some patterns were also found to be favored in template form; these were not as abundant in the cat data as in the crayfish data. Most firing of the cat neurons occurred at times near stimulation, and the observed patterns may represent stimulus information. Favored patterns generally contained up to 7 spikes. No obvious correlations between identified neurons or experimental conditions and the generation of favored patterns were apparent from these data in either preparation. This work adds to the existing evidence that pattern codes are available for use by the nervous system. The potential biological significance of pattern codes is discussed.

Action Potentials↗
PubMed1980

Two behavioral paradigms for study of rapid changes in functional grouping of neurons.

Recent progress in extracellular recording technology and in analytic methodology for the resulting spike trains are making practical the simultaneous registration of twenty or more neurons. This begins to make possible the direct experimental observation of functional neuronal assemblies, particularly as they dynamically change in membership or properties during a behavioral task. Behavioral paradigms appropriate for such experiments have very stringent requirements in order, with high likelihood, to produce changes in neuronal assembly structure during the time that stable recording can be maintained. We describe two motor system paradigms that seem to be appropriate, the first with crayfish claw, the second with monkey paw. The crayfish task involves a rapid learning of claw position. The monkey task involves a preset state which determines the responses to a subsequent somatosensory discrimination.

Animals↗