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F Delcomyn

Publications and source records attributed to F Delcomyn.

13 recordsLinked to original sources
PubMed1992

Identification of bursts in spike trains.

A computer algorithm to identify 'bursts' in trains of spikes is described. The algorithm works by constructing a histogram of interspike intervals, then analyzing the histogram to detect the critical interval value in the distribution that represents the break between short intervals within a burst and the longer intervals between bursts. When such a value is found, it is used as the 'threshold' to determine those intervals in the spike train that lie within a burst and those that lie between bursts and, thereby, to identify the beginning and end of each burst in the train. The validity of the bursts is evaluated with a chi-square test. The performance of the algorithm and how it can be assessed is discussed.

Algorithms↗
PubMed1991

Activity and directional sensitivity of leg campaniform sensilla in a stick insect.

1. The mechanoreceptive campaniform sensilla, which are arranged in groups on insect legs, were studied in the stick insect Cuniculina impigra. In middle and rear legs, the most posterior trochanteral campaniform group (group 1) is oriented so as to be stimulated by compressional cuticular forces acting on the posterior articulation of the trochanter with the coxa. 2. Recordings from nerve Tr2, which innervates this campaniform group, confirmed that the sensilla were directionally sensitive to cuticular stress generated by imposed or active movements of the femur. Different individual sensilla had different thresholds of response, but all responded qualitatively in the same way to a given stimulus. 3. Posteriorward horizontal deflection of the femur-trochanter relative to the coxa (at right angles to the normal plane of movement) produced a strong excitation of the group 1 sensilla. Anteriorward horizontal deflection caused a sharp reduction of on-going background activity in the group. Imposed vertical movements of the femur usually had little effect on the activity of the campaniform sensilla. 4. Active depression of the femur-trochanter by the animal reduced on-going background activity in proportion to the strength of the depression movement. Elevation that simulated muscle-generated lifting of the leg strongly increased activity. 5. It is concluded that campaniform group 1 functions to signal passive horizontal and active vertical movements around the trochantero-coxal joint of the leg. This dual pattern of response means that the animal cannot interpret signals from this campaniform group without also having information about muscle activity.

Animals↗
PubMed1991

Perturbation of the motor system in freely walking cockroaches. I. Rear leg amputation and the timing of motor activity in leg muscles.

1. The effects of amputation of a rear leg on the pattern of motor activity in the legs of freely walking cockroaches (Periplaneta americana L.) were studied. 2. Amputation affected both the frequency and the timing (phase) of motor bursts during a stepping cycle. Bursts in the stump of an amputated rear leg and in the contralateral (intact) rear leg often occurred at two or three times the frequency of bursts in the other legs. The remaining legs also showed multiple bursting during some steps. 3. Amputation affected the phase of motor bursts in two different ways. First, for every leg pair, phase was more variable after amputation, whether or not the mean phase was affected. Second, for some leg pairs, the mean phase itself was altered. During most steps, the timing of motor bursts in the stump of the amputated leg was walking-speed-dependent relative to bursts in the anterior legs. In contrast, the timing of bursts in the stump relative to bursts in the legs across the body from it showed no such speed-dependent timing. Timing between bursts in pairs of intact legs also showed either speed-dependent or speed-independent effects, depending on the pair under consideration. 4. The effects of amputation were not consistent. After loss of a leg, bursts in some leg pairs occurred synchronously in some insects and alternately in others. Even in single insects there were cases in which the timing between bursts in two legs switched from one value to another during walking. 5. These effects of amputation were manifest during slow walking only. At higher speeds, the timing of motor bursts in different pairs of legs was consistently closer to that seen during walking in intact insects. 6. Three conclusions are drawn from these results. (i) During slow walking, sensory feedback from the legs helps maintain the timing of adjacent ipsilateral leg pairs, but has little influence on contralateral pairs. (ii) During slow walking, either sensory input is quite variable, or it has variable effects on the motor pattern. (iii) During fast walking, sensory input from the legs seems to play a minimal role, if any, in the timing of the motor pattern of walking.

Amputation, Surgical↗
PubMed1991

Perturbation of the motor system in freely walking cockroaches. II. The timing of motor activity in leg muscles after amputation of a middle leg.

1. The effects of amputation of a middle leg on the motor pattern in the legs of freely walking cockroaches (Periplaneta americana L.) were studied. 2. The general effects of amputating a middle leg are similar to those arising from amputation of a rear leg. These effects are: multiple bursting, more variable and inconsistent timing (phase) between bursts and a tendency for timing effects to appear only during relatively slow walking. 3. The phase of bursts in the amputated stump relative to bursts in the leg in front of it was speed-dependent. However, the phase of stump bursts relative to bursts in the legs across from and behind the stump were not especially dependent on the speed of walking. In general, the phases of bursts in most leg pairs seemed relatively little affected by the amputation except for an increase in scatter. 4. It is concluded that loss of a middle leg disrupts the motor pattern less severely than does loss of a rear leg. The implications of this and other results for the understanding of motor control are discussed.

Amputation, Surgical↗
PubMed1990

A slope-based approach to spike discrimination in digitized data.

A spike discrimination algorithm based on the analysis of spike up- and down-slopes can advantageously replace those based only on amplitude with a minimal increase of programming complexity and processing time. Such an algorithm was developed to sort muscle depolarizations from nerve spikes in electromyograms in insects. It could also be used to sort spikes according to their direction of travel in bipolar recordings from mixed nerves.

Action Potentials↗
PubMed1989

Walking in the American cockroach: the timing of motor activity in the legs during straight walking.

The timing of bursts of motor activity in extensor muscles in the coxae of pairs of legs in intact freely walking American cockroaches was studied. The timing of bursts in adjacent and non-adjacent leg pairs generally reflected the common alternating tripod gait of these insects. Detailed study of the timing further revealed two previously unreported features. 1) The timing of extensor bursts in the middle legs relative to bursts in the rear legs was more variable than it was relative to those in the front legs. This difference in variability was statistically significant for the means of bursts when all insects were considered together as well as for bursts in individual insects. An apparent difference in variability of the timing of burst starts compared to burst ends for any one leg pair was not significant. 2) There was a shift in the timing of motor bursts relative to one another when an insect walked fast such that motor bursts in the middle legs tended to lag farther behind those in the front legs, and those in the rear legs tended to lag farther behind those in the middle legs compared to the timing during slow walking. This shift was apparent in both burst starts and burst ends, although more obvious in the former. It occurred in both ipsilateral and contralateral leg pairs, and in both the mean data and the data for individual insects. The implications of these characteristics of the timing data are discussed in terms of the neural organization of insect walking.

Animals↗
PubMed1988

An improved electrode design for en passant recording from small nerves.

1. A modification of the oil and hook electrode technique for recording extracellularly from fine nerves is described. 2. It uses a fine hook and a plastic tube that can be manipulated independently, and through which a high-viscosity oil or grease may be forced over the nerve. 3. The suitability of the electrode for high-quality and long-term recording is discussed.

Animals↗
PubMed1977

Semiautomatic processing of neurophysiological data: part II--a computer program for data reduction.

This paper describes a program for the processing of trains of nerve or muscle impulses (spikes). The program is designed to allow the efficient use of semiautomatic or manual measuring devices. It will handle up to six different sets of spikes and one cyclic,non-spike event (e.g., changing light intensity or limb position, etc.) Output may include computed interspike intervals and instantaneous frequencies, phase relationships between sets of spikes and between spikes and the non-spike event, and parameters of bursts found in the spike trains. Output is presented numerically and in the form of line-printer graphs,

Action Potentials↗
PubMed1976

Programming for the inexperienced users: machine independence and free-format input.

Two programming techniques which can make the use of computers less troublesome to inexperienced users are described. The first has the object of making programs readily transferable from one machine to another, thereby facilitating transfer of programs between individuals. The second consists of a FORTRAN subroutine, described in detail, which allows numbers to be read by a program without being confined to specific columns on a punched card, thereby greatly simplifying data preparation.

Computers↗
PubMed1976

Semiautomatic processing of neurophysiological data: part I--a device for measuring potential intervals from film.

This paper describes the operation and construction of an electromechanical device designed to make measurements on oscillograph recordings of nerve or muscle potentials for subsequent computer analysis. The device consists of a motor-driven shaft which moves the record past a fixed cursor, and an electronic counter which records the movements of the shaft, thereby providing a cumulative tally of the distance of the current position of the cursor from some arbitrary origin on the record. When the device is connected to a paper tape punch, the operator can punch the distance measurement associated with potential along the record onto the tape. The format of data on the tape readily allows further analysis by computer.

Action Potentials↗