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At least 37 records · Page 2Linked to original sources
PubMed1998

Phasic firing time locked to cocaine self-infusion and locomotion: dissociable firing patterns of single nucleus accumbens neurons in the rat.

The activity of single nucleus accumbens (NAcc) neurons of rats was extracellularly recorded during intravenous cocaine self-administration sessions (0.7 mg/kg per infusion, fixed ratio 1). We reported previously that NAcc neurons showed a change, usually a decrease, in firing rate during the first 1 min after the cocaine-reinforced lever press. This postpress change was followed by a progressive reversal of that change, which began within the first 2 min after the press and was not complete until the last 1 min before the next lever press (termed the change + progressive reversal firing pattern). In the present study we documented a regular pattern of locomotion that occurred in parallel with the change + progressive reversal firing pattern. This observation suggested that discharges time locked to locomotion may determine the change + progressive reversal firing pattern. However, 55% of the neurons failed to show firing time locked to locomotion that could have contributed to the change + progressive reversal firing pattern. Moreover, for all neurons, the change + progressive reversal firing pattern was apparent even if the calculation of firing rate excluded all periods of locomotion. The present data showed that the change + progressive reversal firing pattern is not solely attributable to phasic changes in firing time locked to the execution of locomotion. The change + progressive reversal firing pattern closely mirrors changes in drug level and dopamine overflow observed by previous researchers and may thus be a component of the neurophysiological mechanism by which drug level regulates drug-taking behavior during an ongoing self-administration session.

Action Potentials↗
PubMed1996

Fire fatality study: demographics of fire victims.

Injury or death caused by fire is frequent and largely preventable. This study was undertaken to define the populations, locations, times and behaviours associated with fatal fires. Seven hundred and twenty-seven fatalities occurring within the State of New Jersey, between the years 1985 and 1991, were examined retrospectively. Most deaths were attributed to a combination of smoke inhalation and burn injury. Five hundred and seventy-four fatalities occurred in residential fires. Smoking materials were the most common source of ignition for residential fires. More than half of the fatal residential fires started between the hours of 11 p.m. and 7 a.m. Children and the elderly represented a disproportionate percentage of fire victims. Victims under the age of 11 years or over the age of 70 years constituted 22.1 per cent of the state population but 39.5 per cent of all fire fatalities. Fire-prevention efforts should target home fire safety, and should concentrate on children and the elderly. The development of fire-safe smoking materials should be encouraged.

Adolescent↗
PubMedDate not supplied

Demographic characteristics, fire experiences, and distress of residential fire survivors.

The United States has one of the highest per capita fire death rates in the world. Death rates alone, however, fail to reflect the breadth of loss experienced by residential fire survivors. Despite the frequency of home fires and the potential for loss, little is known about this vulnerable population. Interviews were conducted with 440 fire survivors 14 weeks after fires. Demographic characteristics of residential fire survivors, survivors' fire experiences, psychological distress after fires and the interrelationships among these variables were examined. This sample of urban fire survivors largely comprised poor, middle-aged African American women. Psychological distress was measured by the General Severity Index of the Brief Symptom Inventory, and the results showed that survivors were highly distressed, even in the absence of fire-related death or physical injury.

Adolescent↗
PubMed1988

Unilateral lesion of the nigrostriatal pathway decreases the firing rate and alters the firing pattern of globus pallidus neurons in the rat.

Activities of spontaneously firing neurons in the globus pallidus of intact rats and rats that survived unilateral lesions of the nigrostriatal pathway for 3 days, 1 week, or 6-11 weeks were compared. No significant differences in neuronal firing rate, firing pattern, and number of cells per pass were observed between chloral hydrate-anesthetized control and lesioned animals. However, in locally anesthetized animals, pallidal cells fired significantly faster than in chloral hydrate-anesthetized animals, and the lesion caused a decrease in the firing rates of pallidal cells 1 week and 6-9 weeks postlesion. In addition, significant differences in the firing pattern of pallidal cells, as determined by the ratio of the mean to median interspike intervals, were seen between locally anesthetized controls and animals surviving 3 days, 1 week, and 6-9 weeks postlesion. This altered firing pattern tended to return to normal with time. The number of cells per pass was not significantly altered by the lesion. Data from this study suggest that, in locally anesthetized animals, the removal of the tonic dopaminergic input to the basal ganglia causes pallidal cells to decrease their firing rates in a time-dependent fashion and causes reversable firing pattern changes. This suggests that tonically active dopamine neurons, probably acting through the striatopallidal pathway, regulate the firing rate and mechanisms controlling the temporal ordering of spontaneous discharges of globus pallidus neurons.

Action Potentials↗
PubMed2006

Dopamine D1/5 receptor modulation of firing rate and bidirectional theta burst firing in medial septal/vertical limb of diagonal band neurons in vivo.

The medial septum/vertical limb of diagonal band complex (MS/vDB) consists of cholinergic, GABAergic, and glutamatergic neurons that project to the hippocampus and functionally regulate attention, memory, and cognitive processes. Using tyrosine hydroxlase (TH) immunocytochemistry and dark-field light microscopy, we found that the MS/vDB is innervated by a sparse network of TH-immunoreactive (putative catecholaminergic) terminals. MS/vDB neurons are known to fire in rhythmic theta burst frequency of 3-7 Hz to pace hippocampal theta rhythm. Extracellular single-unit recording in theta and non-theta firing MS/vDB neurons and antidromically identified MS/vDB-hippocampal neurons were made in urethan-anesthetized rats. Tail-pinch noxious stimuli and ventral tegmental area (VTA) stimulation (20 Hz) evoked spontaneous theta burst firing in MS/vDB neurons. Systemic D1/5 antagonists SCH23390 or SCH39166 (0.1 mg/kg iv) alone suppressed the spontaneous theta bursts, suggesting a tonic facilitatory endogenous dopamine D1 "tone" that modulates theta bursts in vivo. Activation of D1/5 receptor by dihydrexidine (10 mg/kg iv) led to an increase in mean firing rate in 60% of all theta and non-theta MS/vDB neurons with an increase in the number of theta bursts and spikes/burst in theta cells. In strong theta firing MS/vDB neurons, D1/5 receptor stimulation suppressed the occurrence of theta burst firing, whereas the overall increase in spontaneous mean firing rate remained. In low baseline theta MS/vDB neurons D1/5 receptor stimulation increases the occurrence of theta bursts along with a net increase in mean firing rate. Atropine injection consistently disrupts theta burst pattern and reduced the time spent in theta firing. Collectively, these data suggest that dopamine D1/5 stimulation enhances the mean firing rate of most MS/vDB neurons and also provides a state-dependent bidirectional modulation of theta burst occurrence. Some of these MS/vDB neurons may be cholinergic or GABAergic that may indirectly regulate theta rhythm in the hippocampus.

Acetylcholine↗
PubMed1996

Application of full-scale fire tests to characterize and improve the aircraft postcrash fire environment.

The Federal Aviation Administration (FAA) has conducted numerous full-scale fire tests for the purpose of characterizing the postcrash cabin fire environment and developing improved fire test criteria for cabin materials. The tests consistently demonstrated the importance of cabin flashover on occupant survivability. Flashover is basically a sudden, very rapid spread of fire, generating large quantities of heat, smoke, and toxic gases that quickly fill the cabin. Before flashover, the cabin environment is largely survivable; after flashover, occupant survival becomes highly unlikely. Thermal incapacitation is more important near the fire origin and at higher elevations, whereas toxic gas incapacitation is predominant away from the fire origin and at lower elevations. The FAA has developed and adopted improved fire test methods for seat cushions (fire blocking layers) and interior panels (low heat release). In both cases, the fire test methods are consistent with full-scale test results and serve to improve occupant survivability by delaying the onset of flashover, thereby providing substantially greater available time for occupant evacuation.

Accidents, Aviation↗
PubMed2006

Parents of preschool fire setters: perceptions of the child-play fire hazard.

The present study sought to learn about risk perceptions held by parents of preschool fire-setters. A 41-item survey was distributed to 60 parents whose children, aged 6 years and younger, had previously set fires and who were involved in intervention programmes throughout the US. Most parents did not think their children would play with matches/lighters, or knew how to use these items, although some had witnessed their children playing with matches/lighters previously. Most parents reported having taken precautions to keep matches/lighters out of reach and also educating their children about fire. Regardless, children not only set fires, but in 40% of cases climbed to access the match/lighter. Parents' perceptions of their children's proclivity for fire play were not consistent with their actual fire-play behaviour. Parents underestimated the likelihood that their children would play with matches/lighters. Although most reportedly undertook preventative measures aimed at thwarting fire play, these strategies were ineffective. Traditionally relied upon precautionary techniques, such as storing lighters out of reach and discussing the dangers of fire, were not sufficient to stem interest and resultant fire play.

Adolescent↗
PubMed2003

The three Rs of fire safety, emergency action, and fire prevention planning: promoting safety at the worksite.

Fire safety is of paramount importance for everyone. In many workplaces, the occupational health nurse's scope of practice encompasses safety related activities. Included within this role is the responsibility for fire safety, emergency action, and fire prevention planning. The Three Rs of fire safety, emergency action, and fire prevention plans are rules, responsibilities, and resources. Myriad building and fire safety codes, regulations, and standards exist with which an employer must comply. An employer's responsibility for installing, testing, inspecting, and maintaining fire safety related equipment is extensive. Emergency action and fire prevention planning begins with conducting a detailed physical survey and preparing site maps. It includes making key policy decisions, writing procedures, and training employees in those procedures by practicing and executing site drills. The best resources available for emergency planning are the local fire department and the property insurer. Planning ahead means an efficient emergency response if disaster strikes. It saves lives, limits property damage, and preserves the environment.

Emergencies↗
PubMed1989

Motor unit firing rates and firing rate variability in the detection of neuromuscular disorders.

We have used automatic decomposition electromyography (ADEMG) to study 41 muscles in 29 patients with well-defined peripheral and central motor disorders. In motor neuron diseases motor unit action potentials (MUAPs) showed increased amplitudes, firing rates and firing variability. Relatively large MUAPs sometimes were not identified by the computer program if they lacked sufficient high-frequency signal content, or were too variable in shape. In myopathies the MUAPs showed reduced amplitudes, durations and turns, and sometimes dramatic increases in firing rates. Also, the mean number of MUAPs per recording site was often increased, indicating excessive recruitment. In polymyositis (the best studied myopathy) the nature and magnitude of the MUAP shape and firing abnormalities were usually similar at different levels of contractile force, suggesting that motor units are affected without regard to recruitment order. In upper motor neuron paresis (multiple sclerosis), the shape properties of the MUAPs were normal, but mean firing rates were reduced, and firing variability increased. These findings confirm many of the traditional criteria for distinguishing neurogenic from myopathic disease electrophysiologically at the level of the individual MUAP. In addition, they demonstrate the potential diagnostic sensitivity of MUAP firing rate measurements for detecting neuromuscular dysfunction, and for differentiating between some cases of central and peripheral paresis, but not for distinguishing peripheral neurogenic from myopathic weakness, since firing rates tend to increase in both. Increased firing rate variability may be a marker of central or peripheral neurogenic weakness.

Action Potentials↗
PubMed2001

On the firing maps of a general class of forced integrate and fire neurons.

Integrate and fire processes are fundamental mechanisms causing excitable and oscillatory behavior. Van der Pol [Philos. Mag. (7) 2 (11) (1926) 978] studied oscillations caused by these processes, which he called 'relaxation oscillations' and pointed out their relevance, not only to engineering, but also to the understanding of biological phenomena [Acta Med. Scand. Suppl. CVIII (108) (1940) 76], like cardiac rhythms and arrhythmias. The complex behavior of externally stimulated integrate and fire oscillators has motivated the study of simplified models whose dynamics are determined by iterations of 'firing circle maps' that can be studied in terms of Poincaré's rotation theory [Chaos 1 (1991) 20; Chaos 1 (1991) 13; SIAM J. Appl. Math. 41 (3) (1981) 503]. In order to apply this theory to understand the responses and bifurcation patterns of forced systems, it is fundamental to determine the regions in parameter space where the different regularity properties (e.g., continuity and injectivity) of the firing maps are satisfied. Methods for carrying out this regularity analysis for linear systems, have been devised and the response of integrate and fire neurons (with linear accumulation) to a cyclic input has been analyzed [SIAM J. Appl. Math. 41 (3) (1981) 503]. In this paper we are concerned with the most general class of forced integrate and fire systems, modelled by one first-order differential equation. Using qualitative analysis we prove theorems on which we base a new method of regularity analysis of the firing map, that, contrasting with methods previously reported in the literature, does not requires analytic knowledge of the solutions of the differential equation and therefore it is also applicable to non-linear integrate and fire systems. To illustrate this new methodology, we apply it to determine the regularity regions of a non-linear example whose firing maps undergo bifurcations that were unknown for the previously studied linear systems.

Action Potentials↗
PubMedDate not supplied

Fire interest, fire setting and psychopathology in Australian children: a normative study.

OBJECTIVE: Child and adolescent fire setting is associated with a broad pattern of antisocial behaviour and is associated with huge costs to the Australian community. Assessment and treatment options have principally been tested in clinically referred or incarcerated children and adolescents. Little information is available about fire setting in normal populations and thus opportunities for screening and early intervention are not well developed. METHOD: In this study, a large sample of 4- to 9-year-old children were assessed using a seven-item fire interest history screen with other measures of antisocial behaviour, children's mental health, parenting style and quality and parenting stress. These were followed-up with parent and teacher report measures and a diagnostic interview at 12 months. RESULTS: The fire history screening tool demonstrated utility in screening for early signs of fire setting. Prevalences of fire interest, and match- and fire-play were low overall but consistently higher for boys than for girls across ages. As expected, fire setting was associated with parental stress and a range of antisocial behaviours including conduct problems, hyperactivity, cruelty to animals and thrill-seeking temperament. In girls, it was also associated with anxiety/depression problems. CONCLUSIONS: Fire behaviours in children are related to broader psychopathology and family stress, and can be effectively identified in young children using a brief screening measure.

Antisocial Personality Disorder↗
PubMed1996

Simulating effects of fire on northern Rocky Mountain landscapes with the ecological process model FIRE-BGC.

A mechanistic, biogeochemical succession model, FIRE-BGC, was used to investigate the role of fire on long-term landscape dynamics in northern Rocky Mountain coniferous forests of Glacier National Park, Montana, USA. FIRE-BGC is an individual-tree model-created by merging the gap-phase process-based model FIRESUM with the mechanistic ecosystem biogeochemical model FOREST-BGC-that has mixed spatial and temporal resolution in its simulation architecture. Ecological processes that act at a landscape level, such as fire and seed dispersal, are simulated annually from stand and topographic information. Stand-level processes, such as tree establishment, growth and mortality, organic matter accumulation and decomposition, and undergrowth plant dynamics are simulated both daily and annually. Tree growth is mechanistically modeled based on the ecosystem process approach of FOREST-BGC where carbon is fixed daily by forest canopy photosynthesis at the stand level. Carbon allocated to the tree stem at the end of the year generates the corresponding diameter and height growth. The model also explicitly simulates fire behavior and effects on landscape characteristics. We simulated the effects of fire on ecosystem characteristics of net primary productivity, evapotranspiration, standing crop biomass, nitrogen cycling and leaf area index over 200 years for the 50,000-ha McDonald Drainage in Glacier National Park. Results show increases in net primary productivity and available nitrogen when fires are included in the simulation. Standing crop biomass and evapotranspiration decrease under a fire regime. Shade-intolerant species dominate the landscape when fires are excluded. Model tree increment predictions compared well with field data.

Journal Article↗
PubMed1997

Criminal recidivism and family histories of schizophrenic and nonschizophrenic fire setters: comorbid alcohol dependence in schizophrenic fire setters.

Life-time criminality, family history, and situational factors during a fire-setting offense were compared between 44 fire setters who had been diagnosed with schizophrenia or delusional psychosis and 260 nonpsychotic fire setters who had undergone a pretrial forensic psychiatric evaluation. The same comparisons were made between alcoholic (n = 25) and nonalcoholic (n = 19) schizophrenic fire setters. Medical and criminal records were studied. Life-time criminal histories of schizophrenic and nonschizophrenic fire setters were not significantly different with respect to multiple fire setting and violent offenses. Nonschizophrenic and alcoholic schizophrenic fire setters had, in general, a high rate of criminal offenses. The family history of schizophrenic fire setters was often characterized by the father's alcoholism and the mother's psychosis. Comorbid familial alcoholism increased life-time criminal recidivism among schizophrenic fire setters.

Adult↗
PubMed2005

Post-fire surface water quality: comparison of fire retardant versus wildfire-related effects.

An understanding of the environmental effects of the use of wildland fire retardant is needed to provide informed decision-making regarding forest management. We compiled data from all post-fire surface water monitoring programs where the fire retardant constituents ammonia, phosphorus, and cyanide were measured, and data were available in the public domain. For streams near four major wildfires, we evaluated whether these chemicals originated primarily from fire or from retardant use. We compared measured concentrations in streams where chemical wildland fire retardant was applied with concentrations in streams draining areas where retardant was not used. Correlations with calcium provided an additional line of evidence, because calcium concentrations in ash are much higher than in retardant. Ammonia, phosphorus, and total cyanide were found in streams in burned areas where retardant was not used, at concentrations similar to those found in areas where retardant was applied. Concentrations of weak acid dissociable cyanide were generally non-detected or very low, whether or not wildland fire retardant was used in the watershed. These results indicate that the application of wildland fire retardant had minimal effects on proximate surface water quality. Cyanide concentrations in post-fire stormwater runoff were not affected by the presence of ferrocyanide in the retardant formulas and were due to pyrogenic sources.

Ammonia↗
PubMed2006

Impact of a community based fire prevention intervention on fire safety knowledge and behavior in elementary school children.

The objective of this study was to determine the impact of a community based fire prevention intervention directed only to parents on the fire safety knowledge and behavior in elementary school children. This was a prospective, quasi-randomized controlled study in which third and fourth grade students from two elementary schools in an urban, poor, minority community completed knowledge/behavior surveys at baseline and following completion of the intervention. The intervention group received an in-home visit from fire department personnel who installed free lithium smoke detectors and provided a fire escape plan. After accounting for a small difference in baseline summary scores of knowledge and behavior between the control and intervention groups, this study found a modest improvement in fire safety behavior among children whose families received a fire prevention intervention reflecting a change in household fire safety practices. However, there was no significant change in fire safety knowledge.

Case-Control Studies↗