Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “dynamic range”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources
PubMed2004

Activation of cannabinoid CB2 receptors suppresses C-fiber responses and windup in spinal wide dynamic range neurons in the absence and presence of inflammation.

Effects of the CB2-selective cannabinoid agonist AM1241 on activity evoked in spinal wide dynamic range (WDR) neurons by transcutaneous electrical stimulation were evaluated in urethane-anesthetized rats. Recordings were obtained in both the absence and the presence of carrageenan inflammation. AM1241, administered intravenously or locally in the paw, suppressed activity evoked by transcutaneous electrical stimulation during the development of inflammation. Decreases in WDR responses resulted from a suppression of C-fiber-mediated activity and windup. Abeta- and Adelta-fiber-mediated responses were not reliably altered. The AM1241-induced suppression of electrically evoked responses was blocked by the CB2 antagonist SR144528 but not by the CB1 antagonist SR141716A. AM1241 (33 microg/kg intraplantar [i.p.l.]), administered to the carrageenan-injected paw, suppressed activity evoked in WDR neurons relative to groups receiving vehicle in the same paw or AM1241 in the opposite (noninflamed) paw. The electrophysiological effects of AM1241 (330 microg/kg intravenous [i.v.]) were greater in rats receiving i.p.l. carrageenan compared with noninflamed rats receiving an i.p.l. injection of vehicle. AM1241 failed to alter the activity of purely nonnociceptive neurons recorded in the lumbar dorsal horn. Additionally, AM1241 (330 microg/kg i.v. and i.p.l.; 33 microg/kg i.p.l.) reduced the diameter of the carrageenan-injected paw. The AM1241-induced decrease in peripheral edema was blocked by the CB2 but not by the CB1 antagonist. These data demonstrate that activation of cannabinoid CB2 receptors is sufficient to suppress neuronal activity at central levels of processing in the spinal dorsal horn. Our findings are consistent with the ability of AM1241 to normalize nociceptive thresholds and produce antinociception in inflammatory pain states.

Analgesics↗
PubMed1998

Quinine reduces the dynamic range of the human auditory system.

The aim of the study was to evaluate and quantify quinine-induced changes in the human auditory dynamic range, as a model for cochlear hearing loss. Six otologically normal volunteers (21-40 years old) received quinine hydrochloride (15 mg/kg body weight) in two identical oral doses and one intravenous infusion. Refined hearing tests were performed monaurally at threshold, at moderate hearing levels and at high hearing levels. Quinine induced a maximal pure-tone threshold shift of 23 dB (1000-2000 Hz). The increase in the psychoacoustical click threshold agreed with an increase in the detection threshold of click-evoked otoacoustic emissions. The change in the stimulus-response relationship of the emissions reflected recruitment. The self-attained most comfortable speech level and the acoustic stapedius reflex thresholds were not affected by quinine administration. Quinine is a useful model substance for reversibly inducing complete loudness recruitment in humans as it acts specifically on some parts of the hearing function. Its mechanism of action on the molecular level is likely to reveal further information on the physiology of hearing.

Administration, Oral↗
PubMed1982

Effects of picrotoxin upon response characteristics of wide dynamic range neurons in the spinal cord of cat and monkey.

The effects of a subconvulsive dose of picrotoxin (0.5 mg/kg) upon response characteristics of wide dynamic range (WDR) neurons in the spinal dorsal horn were investigated in cats and Japanese macaques. After intravenous administration of picrotoxin, the low threshold mechanoreceptive field of WDR neurons were expanded, and the high threshold surround of the receptive field disappeared. Concomitantly, responses of WDR neurons to noxious heat stimulation were abolished. It was suggested that picrotoxin may close the presynaptic gate for nociceptive input to WDR neurons, enhancing excitatory action of tactile input on the same neurons.

Analgesics↗
PubMed1999

Cannabinoid suppression of noxious heat-evoked activity in wide dynamic range neurons in the lumbar dorsal horn of the rat.

The effects of cannabinoid agonists on noxious heat-evoked firing of 62 spinal wide dynamic range (WDR) neurons were examined in urethan-anesthetized rats (1 cell/animal). Noxious thermal stimulation was applied with a Peltier device to the receptive fields in the ipsilateral hindpaw of isolated WDR neurons. To assess the site of action, cannabinoids were administered systemically in intact and spinally transected rats and intraventricularly. Both the aminoalkylindole cannabinoid WIN55,212-2 (125 microg/kg iv) and the bicyclic cannabinoid CP55,940 (125 microg/kg iv) suppressed noxious heat-evoked activity. Responses evoked by mild pressure in nonnociceptive neurons were not altered by CP55,940 (125 microg/kg iv), consistent with previous observations with another cannabinoid agonist, WIN55,212-2. The cannabinoid induced-suppression of noxious heat-evoked activity was blocked by pretreatment with SR141716A (1 mg/kg iv), a competitive antagonist for central cannabinoid CB1 receptors. By contrast, intravenous administration of either vehicle or the receptor-inactive enantiomer WIN55,212-3 (125 microg/kg) failed to alter noxious heat-evoked activity. The suppression of noxious heat-evoked activity induced by WIN55,212-2 in the lumbar dorsal horn of intact animals was markedly attenuated in spinal rats. Moreover, intraventricular administration of WIN55,212-2 suppressed noxious heat-evoked activity in spinal WDR neurons. By contrast, both vehicle and enantiomer were inactive. These findings suggest that cannabinoids selectively modulate the activity of nociceptive neurons in the spinal dorsal horn by actions at CB1 receptors. This modulation represents a suppression of pain neurotransmission because the inhibitory effects are selective for pain-sensitive neurons and are observed with different modalities of noxious stimulation. The data also provide converging lines of evidence for a role for descending antinociceptive mechanisms in cannabinoid modulation of spinal nociceptive processing.

Analgesics↗
PubMed1986

Wide-dynamic-range dorsal horn neurons participate in the encoding process by which monkeys perceive the intensity of noxious heat stimuli.

The role of dorsal horn wide-dynamic-range (WDR) and nociceptive-specific (NS) neurons in the encoding of the perceived intensity of noxious stimuli was determined while monkeys detected near-threshold changes in the intensity of noxious heat stimuli. Behavioral detection latencies were a reliable measure of the perceived intensity of these stimuli. There was a significant correlation between behavioral detection latency and neuronal discharge of WDR, but not NS neurons. In addition, WDR neurons exhibited greater activity on correctly detected vs non-detected trials, whereas NS neurons did not. We conclude that WDR neurons are involved in the encoding process by which monkeys perceive the intensity of noxious heat stimuli near detection threshold.

Animals↗
PubMed1990

Inhibition of nociceptive responses of wide-dynamic-range neurons by peripheral nerve stimulation.

Of 107 neurons from the sacral and coccygeal levels of the spinal cord in anesthetized intact rats examined, 62 wide-dynamic-range (WDR) neurons that responded to noxious heating of the tail were recorded. On the basis of their inhibitory responses through A-beta or A-delta afferent fibers to noxious stimulation, these neurons were classified into one of the following three types: Type I--neurons inhibited only by A-beta afferent nerve impulses; Type II--neurons inhibited only by A-delta afferent nerve impulses; Type III--neurons inhibited by both. The present results are compared with previously reported behavioral results.

Animals↗
PubMed1998

Cannabinoid modulation of wide dynamic range neurons in the lumbar dorsal horn of the rat by spinally administered WIN55,212-2.

The effects of spinally administered cannabinoids on nociceptive responses of wide dynamic range (WDR) neurons in the lumbar spinal cord were investigated in urethane-anesthetized rats. Noxious thermal stimulation was applied with a Peltier device to regions of the ipsilateral hindpaw corresponding to the receptive fields of isolated neurons. WIN55,212-2 (100 microg, i.t.), applied topically on the dorsal spinal surface, suppressed noxious heat-evoked activity in spinal WDR neurons. By contrast, responsiveness was unchanged following administration of either vehicle or WIN55,212-3, the receptor-inactive enantiomer. WIN55,212-2, administered intrathecally to separate rats, produced antinociceptive effects in the tail-flick test with a time course and efficacy that paralleled the suppression of noxious heat-evoked activity. These results suggest that cannabinoid modulation of spinal nociceptive processing involves direct actions in the spinal dorsal horn and is related to the antinociceptive effects of intrathecally administered cannabinoids.

Animals↗
PubMed1999

Comparison of linear gain and wide dynamic range compression hearing aid circuits: aided speech perception measures.

OBJECTIVES: The goal of this study was to test the theoretical advantages of a single-channel wide dynamic range compression (WDRC) circuit for speech intelligibility and loudness comfort for five speech spectra. DESIGN: Twelve adolescents and young adults with moderate to severe hearing loss were fitted with the Siemens Viva 2 Pro behind-the-ear instrument set to DSL 4.0 targets for both linear gain and WDRC processing. Speech intelligibility was measured in the unaided, linear gain and WDRC conditions using two tasks in quiet: nonsense words and sentences. The items were digitally filtered to represent five speech spectra: average speech at 4 m, average speech at 1 m, own voice at ear level, classroom at 1 m, and shouted speech at 1 m. The subjects also rated the loudness of each hearing aid/speech spectrum combination using a categorical rating scale. RESULTS: Both the linear gain and WDRC settings provided improved speech recognition relative to the unaided condition, and the two circuits resulted in equivalent performance for average speech input levels. On average, the WDRC aid resulted in high and uniform speech recognition scores across the five spectra. In contrast, the linear gain aid resulted in a lower recognition score for soft speech and shouted speech relative to that obtained with an average speech level. Analysis of individual speech recognition benefit scores revealed that 11 out of 12 subjects had equal or greater performance with the WDRC processing than the linear processing. Subjective loudness ratings in the linear gain condition were compatible with decreased sensation level for soft speech and loudness discomfort for shouted speech. CONCLUSIONS: WDRC processing has potential applications in hearing aid fittings for listeners with moderate to severe hearing loss because it provides a consistently audible and comfortable signal across a wide range of listening conditions in quiet without the need for volume control adjustments.

Adolescent↗
PubMed1999

Comparison of performance with wide dynamic range compression and linear amplification.

This study compared subject performance and preference using a compression-limiting hearing aid set to linear amplification (program 1) and wide dynamic range compression (WDRC, program 2). The frequency responses of the hearing aid were matched to a 65 dB SPL signal and maximum output to a 90 dB SPL signal. Twenty subjects with moderate to moderately severe sensorineural hearing loss were tested. Speech recognition scores and speech reception thresholds were obtained both in quiet and in noise. Subjective preference for WDRC or linear amplification was measured via a paired-comparison procedure on "loudness appropriateness," "clarity," and "pleasantness" to continuous discourse presented in quiet and in noise. Results suggested that WDRC yielded better speech intelligibility in quiet for low-level signals and no difference in speech intelligibility in noise compared to linear amplification. Subjects preferred WDRC for loudness to both high- and low-level signals and for pleasantness to high-level signals.

Adolescent↗
PubMed2006

Multislice, dual-imaging sequence for increasing the dynamic range of the contrast-enhanced blood signal and CNR of myocardial enhancement at 3T.

PURPOSE: To develop a multislice, first-pass perfusion imaging sequence for increasing the effective dynamic range of the contrast-enhanced blood signal and the contrast-to-noise ratio (CNR) of myocardial wall enhancement. MATERIALS AND METHODS: A hybrid echo-planar imaging (EPI) pulse sequence was modified to acquire data for both the arterial input function (AIF) and the myocardium, using two different saturation-recovery time delays (TDs) and spatial resolutions, after a single saturation pulse. Five healthy subjects were scanned at 3T in three short-axis levels of the heart per heartbeat during passage of a high-dose bolus of contrast agent. The T(1)-weighted signal-time curve of the blood was converted to AIF using empirical conversion tables derived from phantom experiments. RESULTS: In all subjects the calculated AIF was consistently less distorted and higher for the short-TD protocol than for the long-TD protocol (peak concentration: 5.0 +/- 1.0 mM vs. 3.0 +/- 0.6 mM; P < 0.01). A combination of EPI, long TD, high-dose bolus of contrast agent, and 3T imaging yielded relatively strong peak enhancement in the myocardium (CNR = 11.9 +/- 3.3). CONCLUSION: Our dual-imaging approach at 3T seems promising for acquiring both a relatively accurate AIF and a high CNR of myocardial wall enhancement in multiple slices per heartbeat.

Adult↗
PubMedDate not supplied

Acclimatization in wide dynamic range multichannel compression and linear amplification hearing aids.

Acclimatization was studied in hearing-impaired patients with no previous hearing aid (HA) experience who were fit bilaterally with either wide dynamic range multichannel compression (WDRMCC) or linear amplification (LA) HAs. Throughout 40 weeks of normal HA use, we monitored changes in nonsense syllable perception in speech-spectrum noise. Syllable recognition for WDRMCC users improved by 4.6% over the first 8 weeks, but the 2.2% improvement for LA users was complete in 2 to 4 weeks. Consonant confusion analyses indicated that WDRMCC experience facilitated consonant identification, while LA users primarily changed their response biases. Furthermore, WDRMCC users showed greater improvement for aided than unaided stimuli, while LA users did not. These results demonstrate acclimatization in new users of WDRMCC HAs but not in new users of LA HAs. A switch in amplification type after 32 weeks produced minimal performance change. Thus, acclimatization depended on the type of amplification and the previous amplification experience.

Adaptation, Physiological↗
PubMed2003

Effect of the speed of a single-channel dynamic range compressor on intelligibility in a competing speech task.

Using a "noise-vocoder" cochlear implant simulator [Shannon et al., Science 270, 303-304 (1995)], the effect of the speed of dynamic range compression on speech intelligibility was assessed, using normal-hearing subjects. The target speech had a level 5 dB above that of the competing speech. Initially, baseline performance was measured with no compression active, using between 4 and 16 processing channels. Then, performance was measured using a fast-acting compressor and a slow-acting compressor, each operating prior to the vocoder simulation. The fast system produced significant gain variation over syllabic timescales. The slow system produced significant gain variation only over the timescale of sentences. With no compression active, about six channels were necessary to achieve 50% correct identification of words in sentences. Sixteen channels produced near-maximum performance. Slow-acting compression produced no significant degradation relative to the baseline. However, fast-acting compression consistently reduced performance relative to that for the baseline, over a wide range of performance levels. It is suggested that fast-acting compression degrades performance for two reasons: (1) because it introduces correlated fluctuations in amplitude in different frequency bands, which tends to produce perceptual fusion of the target and background sounds and (2) because it reduces amplitude modulation depth and intensity contrasts.

Adolescent↗
PubMed1999

ConFlo III - an interface for high precision delta(13)C and delta(15)N analysis with an extended dynamic range.

A newly developed interface coupling a CHN combustion device (elemental analyser 'EA') to an isotope ratio mass spectrometer is described and evaluated. The purpose of the device is to extend the dynamic range of delta(13)C and delta(15)N analysis from less than 2 orders of magnitude to more than 3 orders of magnitude. Carbon isotope ratio measurements of atropine as a model compound have been performed analysing between 1 µg to 5 mg C with acceptable to excellent precision (0.6 to 0.06 per thousand, delta-notation). The correction due to the blank signal is critical for sample amounts smaller than 4 µg C. The maximum sample weight is determined by the combustion capacity of the EA. Larger sample amounts are measured using dilution of a small part of the EA effluent with helium. The dilution mechanism works virtually free of isotope fractionation. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗
PubMed1986

Prolonged discharge of wide-dynamic-range spinal neurons evoked by formaldehyde injected in their cutaneous receptive fields.

In decerebrate, unanesthetized cats, subcutaneous injection of formaldehyde solutions (0.05 ml, 2.5%) in the receptive fields of spinal wide-dynamic-range neurons elicited an immediate and continuous discharge or burst activity in the neurons that lasted 10 to 55 min. This discharge was reduced by conditioning stimulation of the medial raphe nucleus and was completely abolished by morphine (3 mg/kg, i.v.). Low-threshold cutaneous mechanoreceptive neurons in the dorsal horn and dorsal column nuclei did not show a sustained response.

Animals↗
PubMed1988

Intensity coding and the dynamic range problem.

The psychophysical data on intensity discrimination indicate that certain schemes are unlikely as general intensity codes at the level of the auditory nerve and indirectly suggest that the most likely code is one based upon the firing rates of frequency-localized groups of fibers. A detection-theory analysis of a rate-based intensity code indicates that information from very few fibers can, if the information is appropriately combined, account for psychophysical discrimination even at high intensities. This suggests that fibers with similar CFs can code intensity over a wide range and that complex spectra can be represented at the level of the auditory nerve by a rate-CF code over the dynamic range of hearing. The analysis also indicates, however, a substantial discrepancy between the psychophysical data on the dependence of discrimination thresholds on level and the predicted discrimination behavior of a representative population of auditory nerve fibers. Thus, if intensity coding is based on localized firing rate, this fundamental psychophysical behavior does not result solely from peripheral processes.

Differential Threshold↗
PubMed2003

Application of co-eluting structural analog internal standards for expanded linear dynamic range in liquid chromatography/electrospray mass spectrometry.

Non-linear standard calibration curves occur frequently in liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS), necessitating the use of non-linear regression curve fitting or a reduction in assay dynamic range. Non-linearity can be minimized by the use of stable isotope internal standards, if the cause of curve bending is ionization saturation. Unfortunately, stable isotope internal standards can be difficult or expensive to synthesize. Structural analog internal standards, if sufficiently close to analytes both in chemical structures and HPLC retention times, may mimic the effect of stable isotope internal standards. Tentative experimental evidence supporting this concept is presented in this paper.

Animals↗
PubMed2002

Changes of wide dynamic range neuronal responses to mechanical cutaneous stimuli following acute compression of the rat sciatic nerve.

To investigate the changes in central neuronal activity in response to cutaneous stimulation following acute nerve compression, the responses of wide dynamic range dorsal horn neurons (n = 13) to graded mechanical cutaneous stimuli (brush, press, pinch, and squeeze) were recorded in anesthetized male Sprague-Dawley rats before and during compression, and after the release of the compression. A small vascular clip (pinching force, 120 g) was applied to compress the sciatic nerve for 30 min. In 12 neurons, background activities increased transiently for 1.5 to 4 min after nerve compression. Similarly, after the release of the compression, 7 neurons showed a transient increase in background activities. The responses to brush, press, and pinch were inhibited significantly 10 min after the nerve compression. The responses to press and pinch recovered gradually after the release of the compression. Responses to squeeze were little affected throughout the experimental period. Acute compression of the rat sciatic nerve can cause short periods of continuous increased spontaneous firing and can attenuate the dorsal horn neuronal responses to cutaneous stimuli. In particular, the neuronal responses to innocuous stimuli were more susceptible to compression of the nerve than the responses to noxious stimuli.

Acute Disease↗