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PubMed1990

Inverse filter computation of the neural impulse giving rise to the auditory evoked potential.

An impulse response hypothesis for evoked potentials is tested. The auditory evoked potential (AEP) is shown to be the consequence of an impulse (the arrival of sensory signals in cortex) giving rise to an impulse response (the resonation of electrocortical activity in the form of group linear waves). To demonstrate this, pre- and post-stimulus EEG activity was recorded from subjects engaged in performance of an auditory odd-ball experiment. For each stimulus, the impulse required to account for the single auditory evoked potential (AEP) as a linear impulse response, was computed by use of the inverse of a filter obtained by autoregression analysis of the pre-stimulus EEG epoch. Single estimations of the impulse were then averaged. The average impulse exhibits a time course and topology consistent with the arrival of neural volleys in the cortex. The physical validity of the hypothesis is supported by a high lag correlation of the following values of the AEP to the average impulse. A further test calculation supports the linear additivity assumptions of the hypothesis.

Acoustic Stimulation↗

PubMed1983

Sensory afferent impulses originate from dorsal root ganglia as well as from the periphery in normal and nerve injured rats.

Single units were recorded in dorsal roots or in the sciatic nerve of anaesthetised rats. It was shown by making sections, by stimulation and by collision that some ongoing nerve impulses were originating from the dorsal root ganglia and not from the central or peripheral ends of the axons. In a sample of 2731 intact or acutely sectioned myelinated sensory fibres, 4.75% +/- 3.7% contained impulses generated within the dorsal root ganglia. In 2555 axons sectioned in the periphery 2-109 days before, this percentage rose to 8.6% +/- 4.8%. There was a considerable variation between animals; 0-14% in intact and acutely sectioned nerves and 1-21% in chronically sectioned nerves. The conduction velocity of the active fibres did not differ significantly from the conduction velocity of unselected fibres. The common pattern of ongoing activity from the ganglion was irregular and with a low frequency (about 4 Hz) in contrast to the pattern of impulses originating in a neuroma which usually have a higher frequency with regular intervals. Slight mechanical pressure on the dorsal root ganglion increased the frequency of impulses. Unmyelinated fibres were also found to contain impulses originating in the dorsal root ganglion. In intact or acutely sectioned unmyelinated axons, the percentage of active fibres 4.4% +/- 3.5% was approximately the same as in myelinated fibres but there were no signs of an increase following chronic section. Fine filament dissection of dorsal roots and of peripheral nerves and collision experiments showed that impulses originating in dorsal root ganglia were propagated both orthodromically into the root and antidromically into the peripheral nerve. It was also shown that the same axon could contain two different alternating sites of origin of nerve impulses: one in the neuroma or sensory ending and one in the ganglion. These observations suggest that the dorsal root ganglion with its ongoing activity and mechanical sensitivity could be a source of pain producing impulses and could particularly contribute to pain in those conditions of peripheral nerve damage where pain persists after peripheral anaesthesia or where vertebral manipulation is painful.

Afferent Pathways↗

PubMed1981

Effects of severe dopamine depletion on dopamine neuronal impulse flow and on tyrosine hydroxylase regulation.

Reserpine depletes dopamine (DA) levels and increases tyrosine hydroxylase (TH) activity in the rat corpus striatum. TH is activated not only by enhancement of DA neuronal impulse flow, but also by cessation of impulse flow. To assist in the understanding of the relative contribution of impulse flow to the regulation of TH activity in the DA depleted neuron, we examined the consequences of severe DA depletion on substantia nigra DA neuronal impulse flow and on in vivo TH activity in the rat corpus striatum. One day after reserpine or 30 min after the reversible reserpine-like compound, Ro4-1284, striatal DA levels were severely depleted and in vivo TH activity was enhanced about three-fold. DA depletion was found to significantly increase DA neuronal impulse flow. Although the DA neuron is firing faster than normal in the DA depleted rat, because there is no DA being released it is still not clear whether the elevation in TH activity is due to the enhancement of impulse flow or to the lack of DA at presynaptic receptor sites, or both. gamma-Butyrolactone (GBL), causes a cessation of DA neuronal impulse flow and activates TH by a presynaptic autoreceptor mechanism. GBL inhibited by over 50 percent the elevation in TH activity produced by severe DA depletion. This finding suggests that the enhanced TH activation after DA depletion in in large part due to increased DA impulse flow. Furthermore, the TH activity seen with GBL in DA depleted rats was significantly less than that seen after GBL administration in normal rats. This finding is consistent with the hypothesis that the DA storage granule also plays a role in TH regulation.

4-Butyrolactone↗

PubMedDate not supplied

The relationship between temperament and impulsive behaviors in eating disordered subjects.

To date, few studies have examined the personality characteristics and clinical predictors of impulsive behaviors in eating disorders (ED). The aim of this work was to study the prevalence of a wide range of impulsive behaviors in a sample of 554 ED subjects and to examine the predictors of these behaviors. Subjects were diagnosed according to DSM-IV criteria as having anorexia nervosa restricting type (ANR; n = 183), anorexia nervosa binge eating/purging type (ANBP; n = 65), bulimia nervosa purging type (BNP; n = 244), and bulimia nervosa nonpurging type (BNNP; n = 62). Nine different types of impulsive behaviors were assessed in these groups. About 55% of the whole sample reported at least one type of impulsive behavior, 35% more than one, and about 13% more than three. According to findings, impulsive and multi-impulsive subjects are characterized by the presence of purging behavior and by specific temperamental features such as high levels of novelty seeking and low persistence. The prediction of impulsive behavior is further improved by considering the presence of a history of childhood abuse, maternal psychiatric morbidity, and some specific psychological symptoms such as maturity fears, perfectionism, depression, and obsessive-compulsive symptoms. The presence of impulsive behavior appears to be associated with overall higher levels of psychiatric symptomatology and eating psychopathology, thus indicating that they are an important feature to be considered in the assessment and treatment of ED.

Journal Article↗

PubMed1971

Inhibition of impulse activity in a sensory neuron by an electrogenic pump.

THE CRAYFISH TONIC STRETCH RECEPTOR NEURON MANIFESTS THREE PHENOMENA: (a) Impulse frequency in response to a depolarizing current decays exponentially to half the initial rate with a time constant of about 4 sec. (b) One or more extra impulses superimposed on steady activity result in a lengthening of the interspike interval immediately following the last extra impulse which is proportional to the number of extra impulses. However, above a "threshold' number of impulses the proportionality constant becomes abruptly larger. (c) Following trains of impulses, the resting potential of the cell is hyperpolarized by an amount proportional to impulse number. Such posttetanic hyperpolarization (PTH) decays approximately exponentially with a time constant of 11 sec, but this varies with membrane potential. These effects are attributed to the incremental increase of an inhibitory (hyperpolarizing) current with a long (relative to interspike interval) decay constant. We suggest that this inhibitory current is the result of increased electrogenic Na pumping stimulated by Na entering with each impulse. Evidence is presented that the three effects are reversibly inhibited by conditions which depress active Na transport: (a) Li substituted for Na in the bath; (b) application of strophanthidin; (c) K removal; (d) treatment with cyanide; (e) cooling. We conclude that a single process is responsible for the three responses described above and identify that process as electrogenic Na pumping. Our observations also indicate that electrogenic pumping contributes to this neuron's resting potential.

Action Potentials↗

PubMed2005

Weakly nonlinear analysis of impulsively-forced Faraday waves.

Parametrically-excited surface waves, forced by a repeating sequence of delta-function impulses, are considered within the framework of the Zhang-Viñals model [W. Zhang and J. Viñals, J. Fluid Mech. 336, 301 (1997)]. With impulsive forcing, the linear stability analysis can be carried out exactly and leads to an implicit equation for the neutral stability curves. As noted previously [J. Bechhoefer and B. Johnson, Am. J. Phys. 64, 1482 (1996)], in the simplest case of N=2 equally-spaced impulses per period (which alternate up and down) there are only subharmonic modes of instability. The familiar situation of alternating subharmonic and harmonic resonance tongues emerges only if an asymmetry in the spacing between the impulses is introduced. We extend the linear analysis for N=2 impulses per period to the weakly nonlinear regime, where we determine the leading order nonlinear saturation of one-dimensional standing waves as a function of forcing strength. Specifically, an analytic expression for the cubic Landau coefficient in the bifurcation equation is derived as a function of the dimensionless spacing between the two impulses and the fluid parameters that appear in the Zhang-Viñals model. As the capillary parameter is varied, one finds a parameter regime of wave amplitude suppression, which is due to a familiar 1:2 spatiotemporal resonance between the subharmonic mode of instability and a damped harmonic mode. This resonance occurs for impulsive forcing even when harmonic resonance tongues are absent from the neutral stability curves. The strength of this resonance feature can be tuned by varying the spacing between the impulses. This finding is interpreted in terms of a recent symmetry-based analysis of multifrequency forced Faraday waves [J. Porter, C. M. Topaz, and M. Silber, Phys. Lett. 93, 034502 (2004); C. M. Topaz, J. Porter, and M. Silber, Phys. Rev. E 70, 066206 (2004)].

Journal Article↗

PubMed2006

A fuzzy impulse noise detection and reduction method.

Removing or reducing impulse noise is a very active research area in image processing. In this paper we describe a new algorithm that is especially developed for reducing all kinds of impulse noise: fuzzy impulse noise detection and reduction method (FIDRM). It can also be applied to images having a mixture of impulse noise and other types of noise. The result is an image quasi without (or with very little) impulse noise so that other filters can be used afterwards. This nonlinear filtering technique contains two separated steps: an impulse noise detection step and a reduction step that preserves edge sharpness. Based on the concept of fuzzy gradient values, our detection method constructs a fuzzy set impulse noise. This fuzzy set is represented by a membership function that will be used by the filtering method, which is a fuzzy averaging of neighboring pixels. Experimental results show that FIDRM provides a significant improvement on other existing filters. FIDRM is not only very fast, but also very effective for reducing little as well as very high impulse noise.

Algorithms↗

PubMed2006

Clomipramine and selegiline: do they influence impulse control?

Anxiety disorders in dogs are often accompanied by loss of impulse control and can result in inappropriate behaviour such as destructiveness, excessive barking and aggression. The reduction of these undesirable actions is the focus of behaviour therapy. Clomipramine and selegiline have been approved for the treatment of separation anxiety in dogs, but there are anecdotal reports that they produce inconsistent therapeutic effect. Hence, the aim of this study was to verify the efficacy of clomipramine and selegiline for regulating impulse control by using a rat model based on the delay of reward procedure. The principle is that the animal has to decide between an immediate small food reward, normally preferred by impulsive animals, and a delayed large food reward. In this study, acute effects of clomipramine (0.3-10.0 mg/kg), selegiline (0.3-3.0 mg/kg), and diazepam (1.0-3.0 mg/kg) on the impulsive behaviour of two breeding lines of rats with different anxiety-related behaviour were investigated. Neither clomipramine nor selegiline had an effect on impulse control in either breeding line. However, motor activity was decreased by clomipramine and increased by selegiline. Diazepam led to an increase in impulsive behaviour of one rat line concomitant with an increase in motor activity. The results of this rat model for studying impulsive behaviour suggest that a single administration of selegiline and clomipramine has no influence on impulsive behaviour.

Animals↗

PubMed1977

The effects of calcium ions on the binomial parameters that control acetylcholine release during trains of nerve impulses at amphibian neuromuscular synapses.

1. A study has been made of the effects of changing the external calcium concentration [Ca](o) on the binomial parameters p and n that control the average quantal content (m) of the end-plate potential (e.p.p.) during trains of nerve impulses at synapses in amphibian striated muscle.2. In high external calcium concentrations (0.4 mM </= [Ca](o) < 1.0 mM) the increase in m of a test impulse following a conditioning impulse at different intervals (< 100 msec) was due to an increase in the number of quanta available for release, n; the increase in m of successive e.p.p.s in a short high frequency train was primarily due to an increase in n.3. In high external calcium concentrations (1.0 mM </= [Ca](o) < 10 mM) there was a decrease in m of a test impulse following a short high frequency conditioning train (4-5 impulses, 20-100 Hz) at different intervals (200 msec < 5 sec) and this was due to a decrease in the number of quanta available for release, n; in a long high frequency train (20 impulses, 20-100 Hz) there was an increase in m for the first few successive e.p.p.s followed by a depression of m which eventually reached a steady state and these changes in m were due to changes in n; the higher the frequency the greater was the depression in n during the steady-state period.4. In high calcium concentrations, the steady-state m reached in the first 20 impulses during continual stimulation at high frequency gave way to a decline in m over several minutes until a new depressed steady-state value of m was reached and this was maintained during the longest periods of stimulation (30 min); this decline in m was primarily due to a decline in the number of quanta available for release.5. These changes in the number of quanta available for release during trains of impulses are predicted in terms of a hypothesis in which facilitation is due to the accumulation of a residual calcium-receptor complex in the nerve terminal that determines the fraction of a pool of quanta which contributes to n, and depression is due to a decrease in the number of quanta in this pool.

Acetylcholine↗

PubMed1987

Actions of trains and pairs of impulses from single primary afferent fibres on single spinocervical tract cells in cat.

1. In cats under chloralose anaesthesia single lumbosacral dorsal root ganglion cells of hair follicle afferent fibres were stimulated intracellularly to produce trains or pairs of impulses. At the same time, single spinocervical tract (s.c.t.) neurones were recorded extracellularly, from their axons in the upper lumbar spinal cord. Afferent fibre-neurone pairs were chosen in which the receptive field of the fibre was contained within the excitatory receptive field (firing zone) of the neurone. 2. Trains of impulses of 2.0 Hz were less effective in increasing the probability of s.c.t. cell firing than trains at 0.67 Hz, and this latter rate was usually less effective than trains at 0.33 Hz. 3. Successive responses to individual members of a train of hair follicle afferent impulses were variable. In some pairs of units succeeding responses declined until a fairly consistent plateau was reached. In others there was no decline and the responses remained irregular. 4. Pairs or short trains of impulses revealed two phenomena: over the first 5 ms or so following an impulse in a group II hair follicle afferent fibre, a second or small group of impulses produced a greater response from the s.c.t. neurone but at intervals of 25-200 ms there was a profound depression of the responses evoked by the second member of a pair of impulses. For A delta afferent fibres the early facilitation lasted for at least 25 ms. 5. It is concluded that a single impulse in a single hair follicle afferent fibre from within the excitatory receptive field of a s.c.t. neurone has complex actions on transmission through that neurone. An initial excitatory influence is followed by a long-lasting depression that influences transmission through the system for at least 1500 ms. Possible mechanisms underlying this depression are discussed.

Action Potentials↗

PubMed1982

Spectral analysis of impulse noise for hearing conservation purposes.

Damage-risk criteria for impulse noise does not presently take the spectrum of the impulse into account; however, it is known that the human auditory system is spectrally tuned. The present paper advocates the extension to impulse noise of the noise dose concept which is widely used for continuous noise. This approach is based upon sound exposure instead of sound pressure. An A-weighting filter or an octave band analysis can then be used to take the spectral content of the impulses into account. The equipment needed for applying these procedures for impulse noise is an integrating sound level meter or a digital Fourier processor. Generalized spectral methods have been evaluated by means of an impulse simulation applied to a mathematical model of the human hearing mechanism. The results of this simulation agree with the most recent experiments on impulse noise and fully support the proposed rating methods. This conclusion must be emphasized as it leads the derivation of a uniform procedure for predicting loudness and damage risk for hearing which is applicable for continuous noise as well as for impulse noise.

Environmental Exposure↗

PubMed1997

The mechanical waveform of the basilar membrane. I. Frequency modulations ("glides") in impulse responses and cross-correlation functions.

The purpose of this investigation is to present evidence from experimental as well as model results on temporal variations of the frequency of oscillation in the basilar membrane's impulse response. Stimuli were either clicks leading to a direct estimate of the impulse response, or bands of pseudo-random noise (one or two octaves wide) which lead to an indirect estimate of the impulse response via a cross-correlation procedure. The noise bands were centered at the best frequency of the BM location under observation. Responses were obtained from the basal turn of the guinea-pig cochlea, from a location with a best frequency (for the weakest stimuli) between 17.0 and 18.5 kHz. Data acquisition was done with a sample frequency of 208 kHz. Input-output cross-correlation functions were found to share with impulse responses the property that the initial oscillations have a noticeably lower frequency than the later ones. During the impulse response the frequency of oscillation increases gradually. This increase occurs and continues to beyond the time that the oscillations reach the largest amplitude. This frequency variation is called a "glide." Using the "analytic signal" method the frequency of oscillation is found to increase continually throughout the duration of the main lobe of oscillation, even at the lowest tested stimulus intensities (about 20 dB SPL). At high stimulus intensity both the direct and indirect impulse response change their appearance drastically but the glide retains its basic form. In the case of the direct impulse response estimate the glide can be attributed to temporal variation of the degree of nonlinearity. For the indirect impulse response this is not true, because with a constant level noise stimulus there is no regular temporal variation of nonlinearity. In this case the glide should be interpreted as an intrinsic property of the cochlear system. From our and others' data the glide was found to exist over a topographic frequency range of best frequencies of at least from 1.76 to 18 kHz. Two examples of present-day models of the cochlea are discussed of which one is found to demonstrate the glide phenomenon in its response, and the other one does not.

Acoustic Stimulation↗

PubMed2005

Relationships between ground reaction force impulse and kinematics of sprint-running acceleration.

The literature contains some hypotheses regarding the most favorable ground reaction force (GRF) for sprint running and how it might be achieved. This study tested the relevance of these hypotheses to the acceleration phase of a sprint, using GRF impulse as the GRF variable of interest. Thirty-six athletes performed maximal-effort sprints from which video and GRF data were collected at the 16-m mark. Associations between GRF impulse (expressed relative to body mass) and various kinematic measures were explored with simple and multiple linear regressions and paired t-tests. The regression results showed that relative propulsive impulse accounted for 57% of variance in sprint velocity. Relative braking impulse accounted for only 7% of variance in sprint velocity. In addition, the faster athletes tended to produce only moderate magnitudes of relative vertical impulse. Paired t-tests revealed that lower magnitudes of relative braking impulse were associated with a smaller touchdown distance (p < 0.01) and a more active touchdown (p < 0.001). Also, greater magnitudes of relative propulsive impulse were associated with a high mean hip extension velocity of the stance limb (p < 0.05). In conclusion, it is likely that high magnitudes of propulsion are required to achieve high acceleration. Although there was a weak trend for faster athletes to produce lower magnitudes of braking, the possibility of braking having some advantages could not be ruled out. Further research is required to see if braking, propulsive, and vertical impulses can be modified with specific training. This will also provide insight into how a change in one GRF component might affect the others.

Acceleration↗

PubMed2003

Effects of varying impulse number on cotransmitter contributions to sympathetic vasoconstriction in rat tail artery.

We examined the contributions of the cotransmitters norepinephrine (NE), ATP, and neuropeptide Y (NPY) to sympathetically evoked vasoconstriction in the rat tail artery in isolated vascular rings by using 1-100 stimulation impulses at 20 Hz. Phentolamine (2 microM), the alpha-adrenoceptor antagonist, markedly reduced responses to all stimuli, although responses to lower impulse numbers were reduced less than responses to longer trains. The purinergic receptor antagonist suramin (100 microM) reduced all responses, but to a much greater extent with few impulse trains. Responses were further reduced or abolished by addition of the second antagonist. Any remaining responses were abolished by the NPY-Y(1) receptor antagonist BIBP-3226 (75 nM). NPY had a direct agonist action and potentiated sympathetically mediated responses. NPY (75 nM) potentiated responses and BIBP-3226 decreased responses to 2- and 20-impulse trains. Both affected responses from 2 impulses to >20 impulses, but there was no preferential effect on purinergic contributions to responses because neurally released NPY potentiated both "pure" NE and ATP responses equally. We conclude that all three cotransmitters contribute significantly to vascular responses and their contribution varies markedly with impulse numbers. There is considerable synergy between cotransmitters, especially with lower impulse numbers where NPY contributions are greater than expected.

Adenosine Triphosphate↗

PubMed1975

Vestibular nystagmus and teleost oculomotor neurons: functions of electrotonic coupling and dendritic impulse initiation.

1. Nystagmus in the horizontal plane is evoked in fish by mechanical stimulation of the ampulla of the horizontal semicircular canal or by electrical stimulation of the nerve from this canal. The movements are conjugate and the slow phase is away from the side of stimulation. 2. Medial rectus motoneurons were recorded from intracellularly, during nystagmus. During the slow phase (induced by ipsilateral stimulation), impulses arise abruptly from the base line and appear to arise at a distance from the cell body. During the fast phase (evoked by contralateral stimulation), impulses appear to arise from large PSPs that must be generated at or near the cell body. 3. In the curarized fish, stimulation of the nerve from the contralateral horizontal canal evokes spikes that arise from large EPSPs and that are blocked relatively easily by hyperpolarizing currents. Stimulation of the nerve from the ipsilateral horizontal canal evokes spikes that arise abruptly from the base line and that are much more difficult to block by hyperpolarizing currents. Little if any underlying PSP is observed when these impulses are delayed or blocked. Thus impulses evoked by stimulation of contralateral and ipsilateral side are initiated near to and far from the cell soma, respectively. 4. If impulses evoked by contralateral stimulation fail to excite the cell body due to injury, antidromic spikes are not occluded. Thus contralateral stimulation initiates impulses in the dendrites. 5. Cell bodies of neighboring motoneurons are coupled electrotonically, and graded antidromic stimulation evokes graded depolarizing potentials which result from electrotonic spread of spike activity from adjacent neurons. These depolarizing potentials are adequate to excite the cells in the presence of a background EPSP evoked by contralateral canal stimulation. In this manner coupling tends to synchronize cells during the fast phase of the nystagmus. 6. Antidromic responses of neighboring cells fail to interact with dendritic inputs to a particular cell, although indirect evidence indicates antidromic spikes invade the impulse-initiating regions in the dendrites. Thus coupling between dendrites is negligible and dendritic inputs can mediate the smoothly graded movements of the slow nystagmic phase. Coupling between somata is too weak to cause significant interaction between dendritically evoked impulses (unless the cell bodies are depolarized by EPSPs). 7. Rhythmic firing can be recorded in a single presynaptic fiber corresponding to either the slow or the fast phase of nystagmus, but not to both. Oculomotor neurons appear to be "relay cells" that, during the fast phase of the nystagmus receive a synchronized synaptic input which is initiated in a higher level command nucleus.

Animals↗

PubMed2006

Relationship between impulsivity, hyperactivity and working memory: a differential analysis in the rat.

BACKGROUND: Impulsivity is a behavioural trait that comprises several distinct processes. It is a key feature of many psychopathologies such as mania, addictive disorders or attention deficit-hyperactivity disorders. To date, the aspects of impulsiveness involved in these pathologies have not yet been explicitly defined. In these disorders, sensation or drug seeking and cognitive deficits are closely related, but the nature of these relationships remains largely unknown. A new animal model of impulsiveness based on spontaneous inter-individual differences is proposed here to help clarify the relationship between characteristic aspects of impulsive-related pathologies. METHODS: Rats were divided into sub-groups according to their scores in three operant tasks with varying degrees of behavioural inhibition, timing and motor vs. cognitive impulsivity demands. These tasks included a fixed consecutive number schedule (ability to complete an action to receive a reinforcer), a multiple fixed-interval/extinction schedule of reinforcement (high level of responding), and a delayed reward task (delay discounting). In addition, measurements of locomotor responses to novelty and to amphetamine in a circular corridor, and working memory in an 8-arm radial maze were obtained. RESULTS: Substantial behavioural inter-individual differences were observed in each task, whereas few inter-task relationships were found. Impulsive rats, as defined in a task requiring inhibition of premature responses, presented a higher increase in amphetamine-induced locomotion. Reduced working memory performance was only observed in hyperactive rats in an extinction schedule. CONCLUSION: This novel approach shows that distinct aspects of impulsiveness and hyperactivity can be expressed based on large inter-individual differences that vary from poorly to highly adapted behaviours ones in a normal population of rats. Inhibitory deficit was related to a higher response to psychostimulants a characteristic of rats predisposed to amphetamine self-administration and related to higher limbic dopaminergic activity, whereas working memory capacity was only related to hyperactivity. This approach allows for the identification of particular individuals presenting distinct behavioural characteristics of impulsive-related psychopathologies. These individuals may be of great interest in the modelling of these disorders and the exploration of their neurobiological bases.

Journal Article↗

PubMed2005

[Relationship between impulse noise and continuous noise inducing hearing loss by dosimeter measurement in working populations].

OBJECTIVE: To compare the dose-response relationship differences between impulse noise exposure workers and continuous noise exposure workers in prevalence of noise inducing hearing loss using dosimeter measurement. METHODS: Thirty-two mechanical workers in a workshop were selected as impulse noise group and 163 textile workers in a textile factory as continuous noise group. SH-126 dosimeter was used to measure A weighted equal sound level of eight hours (L(Aeq.8 h)) during full working duration with equal energy rule for the selected workers. The cumulative noise exposure (CNE) was calculated by L(Aeq.8 h) and noise working years with equal energy rule for each worker. Hearing thresholds were measured by audiometer by routine method and adjusted by age and gender with GBZ49 - 2002. Hearing loss was diagnosed by GBZ49 - 2002 for each worker. RESULTS: CNE of impulse noise group [(103.2 +/- 4.2) dB (A) .year] was found lower than the continuous noise group [(110.6 +/- 6.0) dB (A) .year] by significance, P < 0.05. The hearing loss prevalence of impulse noise group (68.8%) was similar as continuous noise group (65%) without significance, P > 0.05. Strata analysis showed the hearing loss prevalence in 100 - 104 dB (A) .year and 105 - 109 dB (A) .year of impulse noise group was double than that of continuous noise group (76.9%, 90.9% vs 30.4%, 50.0%), P < 0.05. The chi-square test showed a relationship between CNE and hearing loss prevalence that was in high significance (P < 0.01) in both impulse noise group and continuous noise group. Logistic regression model showed the dose-response relationship curve of impulse noise group was left shift and sharp slope. CONCLUSION: The damage of impulse noise on hearing loss was much more than that of continuous noise according to equal energy rule of dosimeter data.

Adult↗

PubMed1979

[Structure and correlation of "fast" and "slow" background impulse activity of visual cortex neurons].

Background and optically modified impulse activity of neurons in visual cortex of unanaesthetized rabbits was analyzed. By means of joint interval histograms it was shown that neurons can be distinguished by the ratio of burts (intervals to 15-40 ms) and extraburst activity and by the shape of transition from one from of activity to another. The extraburst activity comprises 63% of impulses and its ratio to bursts of 2 or 3 and more impulses was 27:3:1. Burts impulse distribution showed a relative stability of timing pattern within bursts and small number of burst impulses (2.4 on the average). Bursts of 3 and more impulses (3.6 on the average) are not rhythmical and 79% of them contained long intervals (18.6 +/- 2.4 ms) before the shortest one (7.9 +/- 0.9 ms). Optical stimulation resulted in bursts containing core impulses, shorter intervals and beginning with the shortest interval in most neurons. This may testify to the increase of the EPSP steepness and amplitude. 20% of cortical neurons showed background bursts containing more impulses and shorter intervals in comparison with evoked bursts.

Animals↗