Search PubMed⌕ Search

Biomedical subjects

M I Cohen

Publications and source records attributed to M I Cohen.

At least 37 records · Page 2Linked to original sources
PubMed1996

High-frequency oscillations in membrane potentials of medullary inspiratory and expiratory neurons (including laryngeal motoneurons).

1. In midcollicular decerebrate, unanesthetized, paralyzed cats ventilated with a cycle-triggered pump system, the properties of high-frequency oscillations (HFOs, 50-100 Hz) in membrane potentials (MPs) of medullary inspiratory (I) and expiratory (E) cells were studied. Simultaneous recordings were taken from bilateral phrenic and recurrent laryngeal (RL) nerves and from cells in the intermediate ventral respiratory group (intVRG, 0-1 mm rostral to the obex) or the caudal ventral respiratory group (cVRG, 2-4 mm caudal to the obex). 2. Spectral coherence analyses were used to detect the presence of HFOs during I in I and E cell MPs. Cross-correlation histograms (CCHs) between the cell and phrenic signals were used to ascertain cell-nerve HFO phase relations and to identify cells as RL motoneurons. Of the 103 cells that had significant HFOs (cell-phrenic coherences > or = 0.1), measurable HFO peak lags in the CCH were seen in 53 cells: 1) RL cells (9 I cells and 7 E cells); and 2) other types of cell (8 intVRG I cells, 18 intVRG E cells, and 11 cVRG E cells). These cells had high HFO correlations; the cell-phrenic coherence range was 0.35-0.94, with a mean HFO frequency of 58 Hz. 3. The cell-phrenic HFO lag (in ms) was measured in the CCH as the lag of the primary peak (peak located nearest to 0 lag). The phase lag was defined as (lag of primary peak in ms)/(HFO period in ms). The phase lags differed markedly between two subsets of cells: 1) RL I cells had HFO depolarization peaks that lagged the phrenic HFO peaks (average cell-phrenic phase lag = -0.18); and 2) the non-RL cells, regardless of location (intVRG or cVRG) and type (I or E), had HFO depolarization peaks leading (preceding) the phrenic HFO peaks (average cell-phrenic phase lag = 0.28). In addition, the cVRG E cells had significantly shorter cell-phrenic phase lags than the intVRG E cells (0.23 vs. 0.31, respectively). 4. These lags can be compared with the (I unit)-phrenic phase lags (average approximately 0.3) found in earlier extracellular studies. 1) There is a transmission delay of about one half HFO cycle from excitatory I cells to RL I cells. 2) Because a depolarization peak in the MP of an E cell corresponds to the start of a hyperpolarizing wave, the excitatory bulbospinal pathways from I cells have transmission times comparable with those of the inhibitory intramedullary pathways from I cells to E cells. 5. These results indicate that study of HFO phase relations can furnish useful information on functional connectivity of medullary respiratory neurons during the I phase.

Animals↗
PubMed1995

Preferential correlations of a medullary neuron's activity to different sympathetic outflows as revealed by partial coherence analysis.

1. In vagotomized, paralyzed, decerebrate cats, simultaneous recordings were taken from one or more sympathetic nerves [cervical sympathetic (CS), inferior cardiac (IC), splanchnic (SP)] and from medullary neurons in vasomotor-related regions. Coherence analyses were used to ascertain the presence of sympathetic rhythms (2-6 Hz or "3-Hz rhythm," 7-13 Hz or "10-Hz rhythm") that were correlated between different signals. The occurrence of a significant peak at such a frequency in a unit-nerve coherence spectrum allowed the identification of a medullary neuron as sympathetic related. 2. A serendipitous example is given of a rostral ventrolateral medullary neuron that had significant unit-nerve 10-Hz coherence peaks for three sympathetic nerves (CS, IC, SP); but, as revealed by partial coherence analysis, the unit activity's correlation with one nerve's activity could be partially or completely dependent on its correlation with other nerve activities. Thus in this case the unit-CS and unit-IC coherences at 10 Hz were completely dependent on the SP rhythm, whereas the unit-SP coherence was not significantly affected by the CS and IC rhythms. This asymmetry suggests that the neuron was preferentially connected to SP-generating medullary circuits. 3. This example indicates the strength of partial coherence analysis as a means of studying differential connectivity between medullary sympathetic-related neurons and sympathetic output neuron populations.

Animals↗
PubMed1994

Analysis of recurrent laryngeal inspiratory discharges in relation to fast rhythms.

1. Inspiratory (I) activities of recurrent laryngeal (RL) motoneurons and efferent nerves were studied by autospectral, interval, and coherence analyses, with emphasis on fast rhythms of two types: medium-frequency oscillations (MFO, usual range 20-50 Hz for nerve autospectral peaks) and high-frequency oscillations (HFO, usual range 50-100 Hz). 2. In decerebrate, paralyzed, and artificially ventilated cats, recordings were taken from 27 isolated single RL fibers (14 cats) and 8 identified RL motoneurons in the medulla (6 cats), together with recordings of phrenic (PHR) and RL whole-nerve activities. In another 50 cats, RL and PHR nerve discharges were recorded simultaneously. 3. The autospectra of RL units showed prominent MFO peaks with frequencies close to that of the RL nerve MFO spectral peak, indicating presence of this type of fast rhythm in the units' discharges. Spectral analysis of RL unit activity in different segments of the I phase showed that the frequency of a unit's MFO was very close to the peak (maintained) firing rate of the unit during the portion of I analyzed. Thus a motoneuron's MFO spectral peak reflected its rhythmic discharge arising from the cell's refractoriness (and possibly with the rate changing in the course of I). 4. The coherences of motoneurons' MFOs to nerve MFOs were very low or 0, indicating that correlations between unitary MFOs of the RL population were rare and/or weak. 5. In those cats (19/20) that had discernible PHR nerve HFO autospectral peaks, about half of the recorded RL motoneurons (16/34) had HFO. For these motoneurons, the unit-nerve HFO coherences were substantial, indicating widespread correlations between unitary HFOs. 6. In a fraction of cats, coherence peaks in the MFO frequency range were observed between bilateral RL nerves, and between RL and PHR nerves, at frequencies that were subharmonics of the HFO frequency. 7. In light of theoretical considerations on the generation of aggregate rhythms from superposition of unitary rhythms, these observations indicate that, similarly, to the case of PHR motoneurons and nerves. 1) RL nerve MFO arises from superposition of uncorrelated, or at most partially correlated, MFOs of RL units, representing the rhythmic discharges of the cells. It is manifested therefore as a spectral deflection with a maximum in the band of peak firing rates of the units. 2) RL nerve HFO arises from correlated, common-frequency HFOs in a subpopulation of RL units, caused by HFO inputs from antecedent medullary I neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

A fast graphics printing program for neurophysiological data.

A program was written in assembly language for fast graphics screen dump of neurophysiological data during and after experiments. This program takes approximately 3 s to plot a 1024 x 768 graphics image. A resident program has also been produced, which allows a screen graphics image to be printed by using a keyboard command. A Pascal-compatible object file is available to interface the program with Turbo-Pascal programs.

Computer Graphics↗
PubMed1993

Timing of medullary late-inspiratory neuron discharges: vagal afferent effects indicate possible off-switch function.

1. In decerebrate paralyzed cats, we observed the responses of ventral and dorsal medullary inspiratory (I) neurons to two types of vagal afferent input that shorten neural I: lung inflation and vagal electrical stimulation. 2. A study population of 15 I neurons whose firing patterns suggested involvement in the inspiratory OFF-switch (IOS) was selected on the basis of two criteria: late onset of firing and excitation by vagal inputs. 3. Firing in relation to the end of I showed two types of response to vagal inputs. The pre-expiratory onset time (time from initial spike to end of I) was either unchanged (type 1 response in 5/15 neurons) or significantly changed (type 2 response in 10/15 neurons). 4. It is suggested that type 1 neurons, whose firing patterns remain closely locked to the end of I despite considerable changes of I duration, are involved in promoting the IOS, whereas type 2 neurons are either not involved (e.g., late-onset premotor neurons) or are involved at an earlier temporal processing stage.

Afferent Pathways↗
PubMed1993

Possible network interactions indicated by bilaterally coherent fast rhythms in expiratory recurrent laryngeal nerve discharges.

1. In a search for correlated fast rhythms in recurrent laryngeal (RL) expiratory (E) activities, we performed spectral and coherence analysis on bilateral RL nerve discharges in 54 midcollicular decerebrate, paralyzed cats. 2. Inspiratory (I) RL activities showed in almost all cases high-frequency oscillations (HFO, range 50-100 Hz) that were bilaterally coherent and also coherent to HFOs in phrenic (PHR) activities. In contrast, bilaterally coherent rhythms (range 24-54 Hz) in RLE discharges were found in only a fraction of the cats (6/54); in the other cats (48/54) such coherences were absent even though the auto-spectra showed the presence of similar fast rhythms on the two sides. The bilateral RLE coherences were associated with increased amplitude and prolonged duration of RLE activity, such as occurred following removal of phasic pulmonary stretch receptor inputs by vagotomy or by no-inflation. 3. Thus, although coherent fast rhythms are uncommon in RLE discharges, their occurrence under some conditions indicates the presence of short-time-scale interactions between neurons involved in this activity. This suggests that such rhythms are a general feature of neural networks.

Afferent Pathways↗
PubMed1992

Weakness of short-term synchronization among respiratory nerve activities during fictive vomiting.

In decerebrate, paralyzed cats, phrenic (PHR) and lumbar abdominal (ABD) nerve discharges during both neural respiration and fictive vomiting (FV) were subjected to spectral and coherence analyses. During respiration, PHR discharge exhibited high-frequency oscillation (HFO), manifested as a narrow spectral peak (range 57-90 Hz) in autospectra and left-right coherence spectra. During FV, the following occurred: 1) the HFO peak disappeared and was replaced by a broad peak with higher modal frequency (range 84-120 Hz), indicating elimination of inputs from the medullary inspiratory pattern generator. 2) Left-right PHR coherence spectra had no distinct peaks, indicating that correlations between opposite PHR discharges were now not frequency specific. 3) Although ABD and PHR autospectra were similar, PHR-ABD coherences were near zero, indicating lack of common inputs on a short time scale. 4) Nonzero coherences between ABD nerves were confined to ipsilateral pairs. Thus coherence analysis indicates that the outputs of the vomiting pattern generator are temporally dispersed on a short time scale and are not necessarily common to different motoneuron populations.

Abdomen↗
PubMed1992

The pediatrician's role in the diagnosis and treatment of substance abuse.

Abuse of drugs and alcohol is pervasive in our society. The role of the pediatrician as a health-care provider from birth through young adulthood includes recognizing the stigmata in newborns of prenatally ingested drugs as well as being able to treat neonatal drug withdrawal syndromes. Questioning about drug use and other closely related topics should be incorporated into all health-care maintenance visits, starting at the age of 10 y, with parental participation and anticipatory guidance being offered. Physical examination and laboratory testing are not as helpful in confirming an impression of substance abuse as a comprehensive interview and a full appreciation of the warning signs of substance abuse. Treatment of the problematic user with a multidisciplinary team that understands adolescent development and behavior as well as the problem of substance abuse is crucial. The decision to treat the teen in an ambulatory or inpatient setting is determined by the extent of abuse, underlying medical problems and psychopathology, and the degree of family dysfunction. The pediatrician must not avoid addressing these issues with patients. If, however, upon identifying an adolescent or a newborn with a drug problem, the pediatrician feels uncomfortable or ill-prepared to manage the patient, appropriate professional referrals are warranted. Despite exercising the referral option for treatment, as advocate for child and family, the pediatrician remains professionally bound to track all drug abuse-related referrals while continuing to participate in the general ongoing care of the patient and family. Finally, the pediatrician should retain a public advocacy role in the community by offering educational, preventive, and supportive efforts in the continuing struggle against drug abuse.

Adolescent↗
PubMed1992

Predicting success on conditional release for insanity acquittees: regionalized versus nonregionalized hospital patients.

This research compared the outcomes of two cohorts of insanity acquittees: one group was treated solely in the maximum security state forensic hospital before their release to the community (nonregionalized) and the other group was treated at the state forensic hospital and transferred for further treatment at less secure state regional hospitals (regionalized). This research describes the outcome of a group of insanity acquittees (regionalized patients) never previously studied. The applicability of a prediction model based on earlier research of insanity acquittees was tested on the patients. Findings on four outcome indicators are reported: rearrests within five years after release, overall functioning in the community five years after release, rehospitalizations for mental illness, and successful completion of the terms of the five-year conditional release (nonrevocation). Discriminant analysis was performed on the four outcome variables. The model was found to accurately predict the four types of outcome from 69 percent to 94 percent accurately for the nonregionalized insanity acquittees and from 87.5 percent to 95.8 percent for the regionalized patients. This model is currently being adapted to classify patients into potential high- and low-risk groups at the time of conditional release for the purpose of determining the intensity of outpatient supervision.

Cohort Studies↗
PubMed1991

Fast rhythms in phrenic motoneuron and nerve discharges.

1. Fast rhythms in discharges of individual phrenic (PHR) motoneurons were studied by spectral and interval analyses; and they were compared, using coherence analysis, with similar rhythms in whole-PHR nerve discharge. The purpose of this study was to ascertain the origin of the two rhythms, manifested as distinct spectral peaks, in PHR motoneuron and nerve discharge: medium-frequency oscillations (MFO, usual range 20-50 Hz); and high-frequency oscillations (HFO, usual range 50-100 Hz). 2. In paralyzed artificially ventilated cats, unit recordings were taken from 1) 26 isolated single PHR fibers (in 8 sodium pentobarbital-anesthetized cats) and 2) 27 identified PHR motoneuron somata in the spinal cord (in 5 decerebrate cats). Simultaneous whole-PHR activity was monophasically recorded from the contralateral PHR nerve for 1 and from both PHR nerves for 2. 3. The signals were subjected to time- and frequency-domain analyses. The latter included a novel application of coherence analysis to the study of population synchrony. 4. The autospectra of all PHR units showed prominent MFO peaks in the frequency range of the nerve MFO spectral peaks, as well as harmonic peaks, indicating the presence of this type of fast rhythm in the units' discharges. Spectral analysis of the augmenting PHR activities in different segments of the inspiratory (I) phase showed that the frequency of unit MFO and of nerve MFO rose during the course of I. Further, cycle-triggered histogram and interval analysis indicated that the frequencies of unit MFO autospectral peaks were very close to the peak firing rates of the units during the portion of I analyzed. Thus unit MFO spectral peaks reflected the rhythmic and augmenting discharges of the motoneurons, and similar nerve MFO peaks reflected the superposition of individual motoneuron discharges. 5. The coherences of motoneurons' MFOs to nerve MFOs were low or zero, indicating that only partial and weak MFO correlations occurred within the PHR motoneuron population. 6. In those cats (n = 11) that had clear PHR nerve HFO spectral peaks, about one-half of the recorded PHR motoneurons had HFO, as indicated by HFO peaks in the unit autospectra and/or the unit-nerve coherences. 7. For motoneurons having HFO, the coherence between unit and nerve HFOs was substantial, particularly when the latter were strong, indicating HFO correlations among a number of PHR motoneurons. 8. In the light of theoretical considerations on the generation of aggregate rhythms from superposition of unitary rhythms, these observations indicate the following.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Progression of experimental infantile hydrocephalus and effects of ventriculoperitoneal shunts: an analysis correlating magnetic resonance imaging with gross morphology.

Although previous ultrasonographic studies did monitor ventricular enlargement successfully in experimentally-induced models of feline hydrocephalus, the resolution of neuroanatomic detail was relatively poor after placement of a ventriculoperitoneal (VP) shunt because the skull had ossified over the coronal sutures. Therefore, the present study employed magnetic resonance imaging to follow the progression of ventriculomegaly more accurately, as well as to evaluate the compensatory effects of VP shunting. Hydrocephalus was induced in kittens between 7 and 10 days old by injection of kaolin into the cisterna magna. Age-matched controls received similar injections of saline. At 9 to 14 days after the kaolin injection, the hydrocephalic animals received VP shunts. Anesthetized kittens were scanned at various intervals before and after shunt placement and were killed for morphological correlation. The features observed on the magnetic resonance imaging scans were consistent with the gross morphological changes that accompanied ventricular enlargement. The lateral ventricle began to enlarge as early as 1 day after the kaolin injection, and within 3 days, both the occipital and temporal horns, along with the 4th ventricle, showed signs of moderate dilatation. By 5 days, a bilateral communication had been established through the septum pellucidum. Continued expansion of the ventricular system occurred from 6 to 20 days after injection, to the point where the cerebral cortex was reduced to less than 25% of its original thickness. The internal capsule was stretched and edematous, the caudate nucleus was compressed ventrolaterally, and the cerebellar hemispheres were eroded and/or compressed. Animals in which shunts were successfully placed demonstrated a dramatic improvement in behavior, and a reduction of about 50% in the size of the lateral ventricles within 2 days. In some cases, the lateral ventricles became slit-like within 1 week. When they were killed, about half of the animals that received shunts exhibited mild to moderate ventriculomegaly. These results indicate that magnetic resonance imaging is an excellent method for visualizing the morphological changes associated with this animal model, that these alterations occur soon after the onset of hydrocephalus, and that VP shunting can successfully reduce ventriculomegaly.

Animals↗
PubMed1989

Effects of contralateral superior laryngeal nerve stimulation on dorsal medullary inspiratory neurons.

The effects of superior laryngeal nerve (SLN) stimulation on phrenic (PHR) nerve activity and on activity of dorsal respiratory group (DRG) inspiratory (I) neurons contralateral to the stimulus were examined in decerebrate, paralyzed cats. Stimulation caused bilateral PHR suppression followed by recovery at ca. 30 ms. Most DRG neurons (70%) contralateral to the stimulus were inhibited, but average onset of inhibition lagged that of PHR suppression. This contrasts sharply with the observation in an earlier study that inhibition of ipsilateral I neurons on the average preceded PHR suppression. The remaining neurons (30%) were not inhibited. Only 22% of contralateral neurons were excited by SLN stimulation, in contrast to 52% of ipsilateral neurons. Thus, contralateral DRG I neurons do not mediate the onset of bilateral PHR suppression by SLN stimulation and are probably inhibited through a longer pathway than that for the ipsilateral unit responses.

Action Potentials↗
PubMed1989

Dorsal medullary inspiratory neurons: effects of superior laryngeal afferent stimulation.

In decerebrate paralyzed cats ventilated with a cycle-triggered pump, we examined the responses of inspiratory (I) neurons in the region of the ventrolateral nucleus tractus solitarius (NTS) to single electrical stimuli delivered to the ipsilateral superior laryngeal nerve (SLN). Sixty-five I neurons were classified as: I(-), I(0), I(+, early), I(+, late) or I(other) on the basis of responses to lung inflation, and as I(bulbophrenic) or I(non-bulbophrenic) on the basis of evidence of an excitatory projection to the contralateral phrenic motoneuron pool. The peristimulus histograms of contralateral phrenic activity showed an early peak of excitation with average latency of 4.9 +/- 0.1 ms (mean +/- S.E.M.), followed by depression at 7.3 +/- 0.2 ms, start of recovery from depression at 22.7 +/- 1.0 ms, and recovery to control levels at 28.4 +/- 1.1 ms. The peristimulus histograms of ipsilateral I unit activity showed an initial excitation (latency 2.9 +/- 0.3 ms), followed by spiking silence (latency 6.0 +/- 0.6 ms) and recovery to control discharge frequency at 38.8 +/- 3.6 ms. This time of inhibition was significantly longer than the time of phrenic depression, suggesting that other bulbophrenic excitatory projections are able to rapidly compensate for decreased NTS output. Subgroups of I neurons, as classified by lung inflation tests, did not differ significantly with respect to these timing variables. In contrast, latencies of excitation for I(bulbophrenic) neurons were significantly less than for I(non-bulbophrenic) neurons.

Action Potentials↗
PubMed1989

Inspiratory-modulated neurons of the rostrolateral pons: effects of pulmonary afferent input.

In decerebrate, paralyzed cats ventilated with a cycle-triggered pump, firing of inspiratory (I) and I-modulated neurons in the pontine respiratory group was markedly increased by withholding lung inflation, indicating strong inhibition by lung afferents. Spectral analysis showed that only a small minority of I-modulated neurons had high-frequency oscillations (HFO), in contrast to medullary I neurons, indicating that the pontine neurons are not closely linked to medullary I networks.

Action Potentials↗
PubMed1989

Changes in frequency content of inspiratory neuron and nerve activities in the course of inspiration.

In decerebrate paralyzed cats, the spectra and coherences of inspiratory (I) nerve activities and of medullary I neuron discharges were compared between different stages of I. The correlated high-frequency oscillations (HFOs) in the activities had common time courses of frequency and strength, which were influenced by lung afferent input; whereas the time courses for the uncorrelated medium-frequency oscillations (MFOs) depended on individual activity patterns. These results indicate that HFOs are characteristic of the common I pattern generator, whereas MFOs are specific to individual activities.

Action Potentials↗