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PubMed1995

Evidence for frequency-dependent and frequency-independent components in increasing- and decreasing-loudness aftereffects.

Listening to a decreasingly intense tone leads to increasing loudness in a subsequent steady tone. Conversely, listening to an increasingly intense tone leads to decreasing loudness in a subsequent steady tone. Measurement entails a test stimulus changing in sound level to null any aftereffect, so that loudness is perceived as steady. Previous studies have shown that the aftereffects are frequency dependent: Carrier frequencies of adapting and test stimuli must be closely matched for the greatest aftereffects. In the present study, frequency-independent components were also indicated: Despite separation between adapting and test frequencies of up to two octaves, measurements always differed after decreasing and increasing sound-level adaptation, such that frequency functions for the two directions of adaptation never crossed. According to evidence from other negative adaptation effects in the auditory modality, explanation of the present aftereffects requires at least two mechanisms: Frequency-dependent components may reflect sensory processing, whereas frequency-independent components may be nonsensory in origin.

Attention↗

PubMedDate not supplied

Frequency selective effects of alcohol on auditory detection and frequency discrimination thresholds.

In the first of two experiments, the effects of ethyl alcohol on monaural and binaural thresholds for pure tones were measured for a range of frequencies. The results showed a frequency-specific effect in which low frequencies were more severely affected than higher ones. Also, monaural thresholds tended to be more affected by alcohol than binaural ones. The second experiment extended this exploration by measuring frequency discrimination at several different frequencies. In this case, we also obtained a frequency-dependent effect: the increase in discrimination thresholds above 1000 Hz was three times greater than that for lower frequencies. The data suggest that the choice of stimuli may influence the ability to detect changes in auditory performance after alcohol and may account in part for the differences among earlier studies. The results are consistent with the hypothesis that alcohol is acting centrally, at the level of mechanisms involved in the temporal and binaural summation of auditory signals, rather than influencing peripheral structures.

Adult↗

PubMed1993

Frequency-volume charts: comparison of frequency between elderly and adult patients.

Urinary frequency is a common complaint in the elderly and can be due to many different causes. To clarify the aetiology of frequency, patient-maintained frequency-volume charts were evaluated as a diagnostic tool. We studied 215 patients who complained of frequency. They were divided into 2 groups based on age: 85 were over 65 years of age (elderly group) and 130 were less than 64 years old (adult group). Compared with the adults, elderly patients had a smaller urinary volume during waking hours and a larger volume during sleeping hours, with more frequent episodes of voiding and a smaller volume voided during the latter period. Analysis of the cause of frequency led to the patients being subdivided into 6 diagnostic categories. Among elderly patients, nocturnal polyuria (37%) and an unstable bladder (34%) were frequent causes. In adult patients an unstable bladder (28%) and polyuria due to excessive fluid intake (23%) were most common. As a result of our findings, 108 patients were advised not to be concerned about their micturition and/or restriction of fluid intake. Seventy-six patients (35%) required anticholinergic medication. Frequency-volume charts, together with a detailed medical history, provide useful information on the diagnosis and treatment of frequency.

Adolescent↗

PubMed2005

High-frequency, but not low-frequency, transcutaneous electrical nerve stimulation reduces aspartate and glutamate release in the spinal cord dorsal horn.

Transcutaneous electrical nerve stimulation (TENS) is a commonly utilized non-pharmacological treatment for pain. Studies show that low- and high-frequency TENS utilize opioid, serotonin and/or muscarinic receptors in the spinal cord to reduce hyperalgesia induced by joint inflammation in rats. As there is an increase in glutamate and aspartate levels in the spinal cord after joint inflammation, and opioids reduce glutamate and aspartate release, we hypothesized that TENS reduces release of glutamate and aspartate in animals with joint inflammation by activation of opioid receptors. Using microdialysis and HPLC with fluorescence detection, we examined the release pattern of glutamate and aspartate in the dorsal horn in response to either low-frequency (4 Hz) or high-frequency (100 Hz) TENS. We examined the effects of TENS on glutamate and aspartate release in animals with and without joint inflammation. High-frequency, but not low-frequency, TENS significantly reduced spinal glutamate and aspartate in animals with joint inflammation compared with levels in those without joint inflammation. The reduced release of glutamate and aspartate by high-frequency TENS was prevented by spinal blockade of delta-opioid receptors with naltrindole. Thus, we conclude that high-frequency TENS activates delta-opioid receptors consequently reducing the increased release of glutamate and aspartate in the spinal cord.

Animals↗

PubMed2004

Time-frequency analysis of auditory-nerve-fiber and basilar-membrane click responses reveal glide irregularities and non-characteristic-frequency skirts.

Although many properties of click responses can be accounted for by a single, frequency-dispersive traveling wave exciting a single, characteristic-frequency (CF) resonance, some properties, such as waxing and waning cannot. Joint time-frequency distributions (TFDs) were used to help understand click responses of cat single auditory-nerve (AN) fibers (CFs<4 kHz) and published measurements of chinchilla basilar-membrane (BM) motion. For CFs> 800 Hz, the peak energy of the response decreased in latency and frequency as the level increased, as expected. However, at high levels the trend reversed for AN, but not BM, responses. Normalized TFDs, which show the frequency with the peak energy at each response time, revealed glides, as previously reported. Classical theory predicts smooth, upward glides. Instead, at low CFs there were downward glides, and at other CFs glides had substantial irregularities. Finally, click skirts, defined as the longest-latency part of click responses, sometimes showed deviations from CF for above-threshold sound levels. Most of these phenomena are not explained by a single, frequency-dispersive traveling wave exciting a single CF resonance, but they can be accounted for by the interaction of two (or more) excitation drives with different latencies and frequency contents.

Acoustics↗

PubMed1983

Intensity discrimination as a function of level and frequency and its relation to high-frequency hearing.

This paper examines how intensity discrimination depends on the test frequency, the level, and the subjects's high-frequency hearing. Three experiments were performed. In the first experiment, intensity discrimination of pulsed tones was measured as a function of level at 1 and 14 kHz in five listeners. Results show less deviation from Weber's law at 14 kHz than at 1 kHz. In the second experiment, intensity discrimination was measured for a 1-kHz tone at 90-dB SPL as a function of the cutoff frequency of a high-pass masking noise in two listeners. Results show that the audibility of very high frequencies is important for frequency discrimination at 1 kHz. The DL increased by a factor between 1.5 and 2.0 as the cutoff frequency of the noise was lowered from 19 to 6 kHz. In the third experiment, thresholds from 6 to 20 kHz and intensity discrimination for a 1-kHz tone was measured in 12 listeners. Results show that the DLs at 80-dB SPL are correlated with the ability to hear very high frequencies. Results of all three experiments are consistent with the multiband version of the excitation-pattern model for intensity discrimination [Florentine and Buus, J. Acoust. Soc. Am. 70, 1646-1654 (1981)].

Adult↗

PubMed1989

Frequency discrimination in the goldfish (Carassius auratus): effects of roving intensity, sensation level, and the direction of frequency change.

The ability of goldfish to detect a change in the frequency of 400-Hz pure-tone bursts was studied using classical respiratory conditioning. The frequency discrimination threshold was measured at 15-, 35-, and 55-dB sensation level (SL), under conditions of (1) constant intensity, (2) roving intensity (plus and minus 6-dB burst-to-burst variation in intensity), (3) upward frequency change, and (4) downward frequency change. There was no overall effect of SL on frequency discrimination, but roving the intensity elevated thresholds by about 6 Hz (33%) and increased variability. Upward shifts in frequency elevated thresholds slightly (by 2 Hz or 10%) relative to downward shifts. These relatively small and statistically insignificant effects suggest that earlier measures of frequency discrimination in the goldfish are not due to the detection of simple changes in spike rate within individual peripheral channels.

Acoustic Stimulation↗

PubMed1994

The role of frequency resolution and temporal resolution in the detection of frequency modulation.

The experiment investigated subjects' ability to detect short-duration changes in frequency. In an adaptive, 2AFC task, three normal-hearing subjects were asked to distinguish a sinusoidal signal that increased in frequency in a series of discrete steps from a standard that was identical except that its frequency increased essentially continuously. The signals were 60 ms in duration with center frequencies of 0.25, 0.5, 1, 2, 3, 4, and 6 kHz. The smallest frequency increase between steps (FI) at which the stepped signal could be distinguished from the standard was determined as a function of the number of steps in the signal. As the number of steps increased and the step duration decreased, the FI at first decreased and then reached a roughly asymptotic level. Eventually, however, at a certain number of steps, the FI increased rapidly. The data were analyzed using a model of auditory temporal resolution that included a bank of bandpass filters, a nonlinearity, a temporal integrator, and a decision device. The analysis yielded ERDs that ranged from 3.8 to 5.0 ms and did not change systematically with frequency. Detector efficiency varied considerably, being greatest at 0.5 and 1 kHz, and declining at higher and lower center frequencies.

Acoustic Stimulation↗

PubMed1994

Psychoacoustic equivalence of frequency modulation and quasi-frequency modulation.

Frequency modulation (FM) is known to be reasonably approximated by quasi-frequency modulation (QFM) for small modulation indices, beta, but the range of beta for which this approximation is appropriate is unclear. Thresholds for discrimination between FM and QFM with equal beta's are obtained in order to estimate an upper bound on beta for determining when this approximation is valid psychoacoustically, i.e., when FM and QFM are indiscriminable. At low modulation frequencies (fm < or = 4 Hz), QFM is never a valid approximation to FM at any detectable modulation level since discrimination thresholds are below FM detection thresholds. For modulation frequencies between 8 and 32 Hz, discrimination thresholds are approximately -2.5 dB (20 log beta) and can be accounted for by detection of envelope fluctuations in the QFM signal. For modulation frequencies at 64 Hz and above, discrimination thresholds improve with increasing modulation frequency in the same manner as FM and QFM detection thresholds. Discrimination in this frequency region seems to be mediated by detection of the component 2fm Hz below the carrier, i.e., by the most detectable component in the FM signal which does not occur in the QFM signal.

Adult↗

PubMed1994

Descending frequency swept tones have lower thresholds than ascending frequency swept tones for a harbor seal (Phoca vitulina) and human listeners.

Many seal vocalizations consist of frequency swept tones. The signal detection thresholds of a harbor seal (Phoca vitulina) and of human listeners were measured using ascending and descending frequency swept tones at 1/3- and 1-oct bandwidths. The swept tones increased or decreased exponentially and traversed the same frequency range. The sweeps were centered on 2, 4, and 8 kHz for the seal study and 0.5, 1, and 2 kHz for the human listeners. The bandwidth of the sweep did not affect signal detection abilities of either the seal or human listeners. The seal had lower signal detection thresholds (1-5 dB) when presented with the descending frequency swept tones (F = 32.04, df = (1,31), p < 0.000001). Human listeners also had lower detection thresholds for descending frequency swept tones (t = -4.78, df = 52, p < 0.0001). Pinniped ascending frequency swept calls may not function as well as descending frequency sweeps for long-distance communicative signals.

Adult↗

PubMed1991

Effects of low-frequency stimulation on the tension-frequency relations of fast-twitch motor units in the cat.

1. Tension-frequency relations were measured in single fast-twitch motor units of the cat flexor digitorum longus (FDL) muscle before and after stimulating each unit with a series of 10-s trains at 20 Hz. The 20-Hz conditioning stimulation produced a combination of potentiating and fatiguing effects, similar to those previously reported to follow higher frequency stimulation of single motor units of the cat and maximal voluntary contractions in man. 2. The conditioning stimulation left three types of after effects: 1) short-term potentiation, 2) a somewhat longer lasting depression of maximal tension, and 3) a delayed depression of low-frequency responses (low-frequency fatigue). 3. The immediate potentiating effect of the conditioning stimulation was most prominent in fatigue-resistant (FR) motor units, whereas depression of maximal tension and low-frequency fatigue were most prominent in fatigue-intermediate (FI) and highly fatigable (FF) motor units. 4. On the basis of our results and those of other investigators, we propose that potentiation, depression of maximal tension, and low-frequency fatigue are independent phenomena, acting at distinct points in the excitation-contraction coupling process. 5. Our results suggest that both potentiation and low-frequency fatigue can result from rather modest amounts of preceding activity. Thus large changes in muscle force production are not unique to maximal contractions but are likely to follow sustained, submaximal contractions as well.

Animals↗

PubMed1990

Top-resolution frequency analysis of electrocardiogram with adaptive frequency determination. Identification of late potentials in patients with coronary artery disease.

Frequency analysis of the electrocardiogram with Fourier transform is a sensitive method of detecting late potentials. However, information about localization of late potentials is lost, frequency resolution is poor, and window functions have to be applied. We therefore analyzed multiple segments (25 msec long) of the surface electrocardiogram ("spectrotemporal mapping") with adaptive frequency determination (AFD), an autoregressive algorithm that is characterized by high-frequency resolution in very short segments without the use of window functions. Results were compared with those from Fourier transform and the Simson method. We studied 38 patients after myocardial infarction (MI) with sustained ventricular tachycardia (VT), 21 patients after MI without VT, and 18 healthy subjects. Frequency peaks could be clearly differentiated until a minimal interval of 6 Hz; with fast Fourier transform (Blackman Harris window) in a much longer segment (80 msec), the spectral peaks merged into one another at an interval of about 30 Hz. AFD revealed high-frequency components as narrow peaks in the range of 40-160 Hz in 28 of 38 patients (74%) after MI with VT. Because of the short segment size, exact localization of late potentials was possible; in most of the patients, the peaks occurred in segments inside the QRS complex and ended 20 +/- 10 msec after termination of the QRS complex. In patients after MI without VT, only four of 21 patients (19%) had spectral peaks in segments after the end of the QRS complex; however, 13 of 21 patients demonstrated microvolt potentials in segments within the QRS complex. These potentials did not extend beyond the end of normal ventricular activation. Only two of 18 healthy subjects showed abnormal AFD results. Patients with bundle branch block did not need to be excluded. AFD allowed good differentiation between late potentials and noise by a characteristic pattern of the spectral peaks. For the Simson method, patients with bundle branch block had to be excluded, and overall sensitivity was 42%. In five cases, the cause of failure of the Simson method could be identified as incorrect determination of the QRS limits due to noise. Thus, AFD is a promising method for detailed analysis of late potentials; it combines the advantages of frequency analysis (good differentiation between signal and noise and high-pass filters not necessary) and time domain analysis (localization of late potentials).

Coronary Disease↗

PubMed1997

Adrenergic control of the force-frequency and relaxation-frequency relations in patients with hypertrophic cardiomyopathy.

BACKGROUND: Exercise-induced enhancement of the force-frequency and relaxation-frequency relations has been studied in conscious animals but not in intact diseased human hearts. METHODS AND RESULTS: We evaluated left ventricular (LV) isovolumic contraction (dP/dt(max)) and relaxation (tau) during atrial pacing and dynamic exercise in 13 patients with nonobstructive hypertrophic cardiomyopathy (HCM) and 7 control subjects to investigate the influence of exercise on the force-frequency and relaxation-frequency relations. Group A consisted of 6 patients in whom the heart rate (HR)-dP/dt(max) relation was markedly enhanced during exercise (88+/-30%) compared with during pacing (34+/-15%). Group B consisted of 7 patients in whom the HR-dP/dt(max) relation showed similar enhancement during exercise (28+/-7%) and atrial pacing (28+/-11%). There was no difference in the HR-tau (derivative method [TD] and pressure half-time method [T(1/2)]) relation between pacing and exercise in groups A and B. Both the mean maximal wall thickness and the hypertrophy score in group B were greater than in group A (27+/-5 versus 19+/-2 mm and 7+/-1 versus 5+/-1 points, respectively; both P<.01). There was no difference in the LV peak systolic pressure, end-diastolic pressure, or the plasma level of catecholamines at baseline, at 50 W of exercise, and at peak pacing between groups A and B. The HR-dP/dt(max) relation in the control group was markedly enhanced during exercise (80+/-27%) compared with during pacing (32+/-14%). The HR-tau relation in the control group was enhanced during exercise (TD, 35+/-9%; T(1/2), 34+/-8%) compared with during pacing (TD, 12+/-7%; T(1/2), 14+/-7%). CONCLUSIONS: Exercise-induced enhancement of the relaxation-frequency relation was inhibited in all HCM patients, regardless of the degree of LV hypertrophy. The patients without exercise-induced enhancement of the force-frequency relation had more severe LV hypertrophy than the patients with the enhancement, indicating that the adrenergic control of the force-frequency relation may, at least in part, depend on the severity of LV hypertrophy or the stage of HCM.

Adult↗

PubMedDate not supplied

Use of frequency modulation combined with amplitude change to elicit frequency-specific whole-nerve response.

The averaged whole-nerve response to frequency modulation combined with amplitude change was recorded from the round window of the guinea pig. A downward shift of 20% in the frequency of a 500-Hz, 1-kHz or 2-kHz pure tone with an amplitude increase elicited the responses. The latency for each frequency was investigated at different intensities. The latency is greater for lower-frequency tones and this latency increase agrees well with the traveling wave delay for the intensity range used in this study. A downward shift with an amplitude decrease failed to yield the response. These findings suggest that the response to a downward shift of frequency with an amplitude increase results from new activation due to an apical extension of the envelope of the traveling wave and thus represents the activity in a restricted area of the basilar membrane. Thus, the frequency-modulated tone in downward direction with increased amplitude can be a frequency-specific stimulus.

Acoustic Stimulation↗

PubMed1983

Human frequency-specific whole-nerve response by use of frequency-modulated tone.

Based on the results of animal experiments performed previously, a human study of the compound action potential (AP) to frequency-modulated (FM) tone was achieved, using the transtympanic electrode, in order to obtain frequency-specific APs. Clearly recognizable responses were elicited by a downward shift of 20% in the frequency of a 515-, 1 150- or 2 230-Hz pure tone (with a slight amplitude increase). The latency for each frequency was investigated at different intensities. The latency is greater for lower-frequency tones and, as in the animal experiments, this latency increase agrees with the traveling delay for the intensity range used in this study. The latency-intensity curves of the three frequencies do not tend to converge with increase in the intensity of the tone. The latency at moderate intensity is similar to that for the short tone burst at threshold intensity. These findings suggest that the FM tone in downward direction can be a frequency-specific stimulus even at relatively high intensities. Combined use of the tone burst (low intensity) and this FM tone (high intensity) may be useful in clinical tests.

Action Potentials↗

PubMed1985

Low-frequency sensorineural hearing loss. Brainstem response, speech and high-frequency audiometry.

Four cases of acquired, unilateral sensorineural hearing loss are presented. The low-frequency octave threshold changes are considered compatible with the low-frequency tails of neurons with characteristic frequencies of 2, 4 and 9 kHz. Zero speech discrimination was found in two patients with high-frequency threshold preservation at and above 4 kHz. Normal auditory brainstem responses were obtained in the two patients with low-frequency hearing loss confined to the frequency bands below 2 and 4 kHz respectively. Only wave I could be reliably identified in the two patients with single frequency threshold preservation at 2 and 9 kHz, while both presented a second, low amplitude wave with latency corresponding to our normative values for wave V. The latter may represent a delayed and pathological wave III.

Adolescent↗

PubMed2004

Age-of-acquisition effects in reading aloud: tests of cumulative frequency and frequency trajectory.

Several studies have reported that the age at which a word is learned affects skilled reading. This age-of-acquisition effect is potentially important for theories of reading and learning. The effect has been difficult to pin down, however, because the age at which a word is learned is correlated with many other lexical properties. Zevin and Seidenberg (2002) analyzed these phenomena, using connectionist models that distinguished between cumulative frequency (the total number of times a word is experienced) and frequency trajectory (the distribution of these experiences over time). The models prompted a reevaluation of the empirical literature on this topic. The present research tested and confirmed three behavioral predictions derived from these models. First, cumulative frequency has an impact on skilled word naming, more so than standard measures of frequency derived from such norms as those of Kucera and Francis (1967). Second, frequency trajectory affects age of acquisition: The timing of exposure to words affects how rapidly they are learned. However, frequency trajectory does not affect skilled reading aloud, because the consistencies in mapping between spelling and sound eventually wash out the effects of early differences in frequency of exposure. Thus, in skilled performance, the timing of exposure to words is less important than the amount of exposure. The results clarify the conditions under which age-dependent learning effects occur in reading aloud.

Adolescent↗

PubMed2006

HIV-specific cytotoxic cell frequencies measured directly ex vivo by the Lysispot assay can be higher or lower than the frequencies of IFN-gamma-secreting cells: anti-HIV cytotoxicity is not generally impaired relative to other chronic virus responses.

CD8(+) T cells in HIV-infected patients are believed to contribute to the containment of the virus and the delay of disease progression. However, the frequencies of HIV-specific CD8(+) T cells, as measured by IFN-gamma secretion and tetramer binding, often do not correlate with a delay in disease progression during chronic infection. Using the Lysispot and ELISPOT assays, we measured the frequencies of cytotoxic and IFN-gamma-secreting T cells responding to overlapping peptides from Gag, Nef, Env, and Pol consensus HIV-1 clade B sequences. PBMC from the majority of HIV-infected subjects have significant frequencies of HIV-specific cells that killed targets within 5 h directly ex vivo. The relative frequencies of IFN-gamma-secreting and cytotoxic cells varied markedly between different HIV peptide pools within the same patient, and some T cells lysed targets without secreting IFN-gamma. These results indicate that measurement of IFN-gamma production alone may be insufficient to evaluate the breadth of the HIV-specific T cell response. Also, neither the CTL to IFN-gamma ratios nor the ex vivo CTL frequencies specific for different HIV proteins were consistently lower than responses specific for two other chronic viral infections, human CMV and EBV, within the same subjects. Thus ex vivo cytotoxic T cell frequencies do not provide evidence for a model of "preterminal differentiation" of HIV-specific CD8(+) T cells during chronic HIV infection. Analysis of the frequency of directly cytotoxic HIV-specific T cells may be of considerable value in the assessment of disease progression and the potential efficacy of HIV vaccines.

Adult↗