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Biomedical subjects

F Delcomyn

Publications and source records attributed to F Delcomyn.

At least 19 recordsLinked to original sources
PubMed1995

An approach to validation of a leg simulation by the comparison of two dynamic models.

The dynamics of a jointed leg were simulated using two different models, one based on a recursive Newton-Euler method and one on a closed-form Lagrange method. To validate the models, the simulations were run in parallel and the intermediate steps and output of the two methods were compared to one another to reveal the presence and locations of errors. Sources of error and the use of this method for the detection of errors are discussed. Some errors could not have been detected using only a single simulation.

Acceleration↗
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

Empirical evaluation of two-sample statistical tests for differences of stepping phase during insect walking.

In order to determine which statistical tests can validly be applied to data that describe a temporal relationship between two or more repetitive movements by an animal, we evaluated empirically seven two-sample tests that seemed potentially useful: Student's t test, the Watson Williams test for means, the variance-ratio F test, the Watson Williams test for the concentration parameter k, the Wallraff test, the Mann Whitney test and the Watson U2 test. Evaluations were carried out on the timing (phases) of bursts of muscular activity in one leg relative to those in another during free walking in cockroaches. Each statistical test was evaluated by dividing randomly a single parent set of data into two subsets, each subset containing about half the original data set. This division was repeated 400 times, thus generating 400 different pairs of subsets. Each statistical test was used separately on the pairs of subsets to test the null hypothesis that the two samples of each pair came from the same population; this procedure generated 400 statistics for each test, one for each pair of subsets. An estimate of the reliability of each statistical test was obtained by comparing the number of times the test actually indicated a significant difference between subsets to the number of times it might be expected to do so out (20 out of 400 when tested at the 5% level of significance). This procedure was repeated on ten different sets of data. The outcome of the evaluation suggested that, from an empirical point of view, Student's t, the Mann Whitney, the Wallraff and the Watson U2 tests may be useful in assessing differences among the data we analyzed. The variance-ratio F test and the Watson Williams test for the concentration parameter k were clearly not usable. The Watson Williams test for means might be useful in some circumstances. Performing an arcsine transformation of the data did not significantly alter these results. Possible causes of the inapplicability of some of these tests to phase data are discussed.

Animals↗
PubMed1988

Individual differences and variability in the timing of motor activity during walking in insects.

The uniformity of the neural physiology of an animal population is a fundamental, rarely tested assumption in most neurophysiological work. In this study, the variability of the timing between the movements of pairs of legs during free walking in cockroaches was assessed. Phases (a measure of timing) of motor bursts in muscles of legs in the American cockroach, Periplaneta americana, were calculated for insects walking straight over a flat, level surface. Student's t, Wallraff, Mann Whitney and Watson U2 two-sample tests were used to compare the phases of motor bursts of the same pairs of legs in different insects. The comparisons showed that in spite of the homogeneity both of the animal population and of the conditions under which the insects walked, most of the inter-leg phases of the animals that were compared were significantly different statistically. Further testing of greater numbers of insects using analysis of variance to test for population uniformity confirmed that the insects we tested were not members of a single statistical population with respect to the timing of motor bursts of the legs during walking. We infer that this unexpectedly large variability in a population thought to be relatively homogeneous reflects subtle but biologically significant differences between animals. The possible sources of these differences and their consequences for the study of behavior and its physiological basis are discussed.

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↗
PubMed1988

Motor activity in the stump of an amputated leg during free walking in cockroaches.

1. A rhythmic pattern of motor activity was recorded in the stump of an amputated leg during free walking in cockroaches. 2. During relatively rapid walking, extensor (depressor) and flexor (elevator) muscles in the intact coxa of the amputated leg showed one burst of activity during each cycle of bursting in an adjacent, intact leg. However, during slower walking these muscles could show two or three bursts of activity during each cycle of bursting in an intact leg. 3. Motor bursts in the stump of an amputated leg showed features similar to those of bursts recorded from intact legs. Burst duration increased with an increase in period, and the bursts generally showed consistent timing (phase) relative to bursts in most of the intact legs. 4. The motor pattern recorded in a stump was very like that recorded in an intact leg during walking, and unlike that recorded during searching for a foothold (defined in the text). It is concluded that after the amputation of most of a leg, motor neurones innervating muscles in the stump of the amputated leg continue to be driven by the interneurones that normally drive the intact leg during walking. Analysis of the motor pattern in the stump may therefore reveal important features of the locomotor control system.

Amputation Stumps↗
PubMed1987

Motor activity during searching and walking movements of cockroach legs.

1. Rhythmic motor activity may be recorded in the legs of cockroaches during the execution of several different types of behaviour that involve leg movements. It was examined in detail during searching and walking. 2. During walking, motor activity always consisted of a series of bursts separated by silent periods. During searching, it was usually continual, but modulated in frequency. 3. Sometimes, the motor pattern recorded from a searching leg was burst-like rather than modulated. In these cases, it could nevertheless be reliably distinguished from the motor pattern recorded during walking by a simple analysis of the burst pattern. 4. An analysis of the motor pattern recorded during righting indicated that this pattern was more like that for walking than that for searching. Therefore, searching is not simply walking that lacks certain periodic sensory input due to leg contact with the ground. 5. It is concluded that walking and searching can be reliably distinguished from one another on the basis of an analysis of a record of motor activity in a single leg muscle only. An ability to distinguish between similar types of behaviour on the basis of the motor pattern may prove useful in a variety of experiments.

Animals↗
PubMed1981

Nickel chloride for intracellular staining of neurons in insects.

The advantages of nickel chloride (NiCl2) for intracellular staining of insect neurons are described. Nickel shares with cobalt the features of rapid migration, easy precipitation, and the capability of being silver-intensified. But, nickel-filled electrodes also have lower average resistances and pass current more readily than comparable electrodes filled with cobalt, making it the ion of choice for intracellular marking in many instances.

Animals↗
PubMed1980

Neural basis of rhythmic behavior in animals.

Timing of the repetitive movements that constitute any rhythmic behavior is regulated by intrinsic properties of the central nervous system rather than by sensory feedback from moving parts of the body. Evidence of this permits resolution of the long-standing controversy over the neural basis of rhythmic behavior and aids in the identification of this mechanism as a general principle of neural organization applicable to all animals with central nervous systems.

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↗