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PubMed1984

NoSo and NoS pi thresholds as a function of masker level for narrow-band and wideband masking noise.

NoSo and NoS pi thresholds for a 500-Hz signal were determined as a function of masker level for masking noises having 600- and 50-Hz bandwidths centered on 500 Hz. Noise levels of 0, 10, 20, 30, 40, 50, and 60 dB/Hz were used for the 600-Hz bandwidth, and noise levels of 0, 10, 20, 30, 40, 50, 60, and 70 dB/Hz were used for the 50-Hz bandwidth. The So thresholds increased as a function of increasing noise level with a slope close to 1.0, for both the 50- and 600-Hz masker bandwidths. For the 600-Hz-wide masker, the S pi thresholds increased with a slope less than 1.0 for masker levels from 0 dB/Hz to approximately 20 dB/Hz, but increased with a slope close to 1.0 for masker levels above approximately 20 dB/Hz. For the 50-Hz-wide masker, the S pi thresholds increased with a slope less than 1.0 for masker levels from 0 dB/Hz to approximately 40 dB/Hz, but increased with a slope close to 1.0 for masker levels above approximately 40 dB/Hz. The results are discussed in terms of different binaural processes involving interaction between monaural critical bands centered on the signal frequency, and interaction involving monaural critical bands outside the monaural critical band centered on the signal. It was suggested that the narrow-band noise results are probably more appropriate than the wideband noise results when considering binaural interaction involving monaural critical bands centered on the signal frequency.

Auditory Threshold↗
PubMed2000

Spectral integration in the inferior colliculus of the mustached bat.

Acoustic behaviors including orientation and social communication depend on neural integration of information across the sound spectrum. In many species, spectral integration is performed by combination-sensitive neurons, responding best when distinct spectral elements in sounds are combined. These are generally considered a feature of information processing in the auditory forebrain. In the mustached bat's inferior colliculus (IC), they are common in frequency representations associated with sonar signals but have not been reported elsewhere in this bat's IC or the IC of other species. We examined the presence of combination-sensitive neurons in frequency representations of the mustached bat's IC not associated with biosonar. Seventy-five single-unit responses were recorded with the best frequencies in 10-23 or 32-47 kHz bands. Twenty-six displayed single excitatory tuning curves in one band with no additional responsiveness to a second signal in another band. The remaining 49 responded to sounds in both 10-23 and 32-47 kHz bands, but response types varied. Sounds in the higher band were usually excitatory, whereas sounds in the lower band either facilitated or inhibited responses to the higher frequency signal. Interactions were usually strongest when the higher and lower frequency stimuli were presented simultaneously, but the strength of interactions varied. Over one-third of the neurons formed a distinct subset; they responded most sensitively to bandpass noise, and all were combination sensitive. We suggest that these combination-sensitive interactions are activated by elements of mustached bat social vocalizations. If so, neuronal integration characterizing analysis of social vocalizations in many species occurs in the IC.

Acoustic Stimulation↗
PubMed2006

Interaction between location- and frequency-based inhibition of return in human auditory system.

Using a cue-target paradigm, this study investigated the interaction between location and frequency information processing in human auditory inhibition of return (IOR). The cue and the target varied in terms of location and frequency and participants were asked to perform a target detection, localization or frequency discrimination task. Results showed that, when neither location nor frequency of auditory stimuli was particularly relevant to the target detection task, there was a location-based IOR only if the cue and the target were identical in frequency and there was a frequency-based IOR only if the cue and the target were presented at the same location. When a particular feature of auditory stimuli, whether location or frequency, was directly relevant to the current task, the IOR effect was evident for this feature only if the cue and the target differed on the task-irrelevant feature, while the IOR effect was eliminated for the task-relevant feature when the cue and the target had the same task-irrelevant feature. Similarly, the IOR effect based on the task-irrelevant feature was evident when the cue and the target differed on the task-relevant feature, and was eliminated or reversed when the cue and the target shared the task-relevant feature. Theoretical implications of these findings for auditory IOR are discussed.

Acoustic Stimulation↗
PubMed1972

B cell activation in vivo by nonantigen-specific interaction with T cells. Frequency of immune responses increased by immunization with two antigens.

The number of direct (gammaM) hemolytic plaque responses of irradiated mice, repopulated with relatively small and limiting numbers of bone marrow and thymus cells, was increased by the simultaneous immunization with two antigen complexes instead of one. Anti-sheep responses were augmented by the following antigen combinations: SRBC + HRBC, SRBC + BRBC, and SRBC + CRBC. Limiting either thymocytes or bone marrow cells indicated that the antigen mixtures acted at the level of T cells increasing severalfold the number of triggered antigen-reactive cells. It was concluded that one of the antigens could have influenced the triggering of antigen-reactive cells specific for the other by promoting synergistic or derepressive T-T cell interactions. Moreover, bone marrow precursor cells could have been activated by the thymic inducers specific for the test antigens as well as by those specific for the second of the priming antigens.

Animals↗
PubMed1985

Binocular interaction in the VEP to grating stimulation. II. Spatial frequency effects.

The size specificity of the binocular interaction in the VEP was investigated. VEPs elicited by sine wave gratings were recorded on 3 subjects, with the exception of one experiment where 6 subjects were tested. The recording technique made it possible to obtain responses from each eye, even during binocular stimulation. The VEP amplitude for each eye during monocular stimulation was compared with the response of the same eye during binocular stimulation. A low binocular/monocular ratio indicated a high binocular interaction. When each eye was stimulated by the same spatial frequency, the binocular interaction was highest in the spatial frequency band of 2-4 c/d. When each eye was stimulated by a different spatial frequency, the binocular interaction decreased as the frequencies were made progressively more unequal. The bandwidth at half amplitude was about 1 octave around the center frequency.

Evoked Potentials, Visual↗
PubMed2006

Finite frequency quantum noise in an interacting mesoscopic conductor.

We present a quantum calculation based on scattering theory of the frequency-dependent noise of current in an interacting chaotic cavity. We include interactions of the electron system via long range Coulomb forces between the conductor and a gate with capacitance C. We obtain explicit results exhibiting the two time scales of the problem, the cavity's dwell time tau(D) and the RC time tau(C) of the cavity in relation to the gate. The noise shows peculiarities at frequencies of the order and exceeding the inverse charge relaxation time tau(-1) = tau(D)(-1) + tau(C)(-1).

Journal Article↗
PubMed1986

Interactions between speech and finger movements: an exploration on the dynamic pattern perspective.

Under the dynamic perspective for motor control, movement is viewed as an "emergent" property, arising from cooperative relationships among limit-cycle oscillators. This is in contrast to more traditional approaches to motor control in which a central representation of movement is usually assumed to exist. The assertion that coordination of movement arises from interactions between oscillatory processes leads to some unexpected predictions. In particular, interactions between frequency and amplitude of simultaneously performed speech and manual tasks are predicted, because the organism "parameterizes" all ongoing oscillatory processes as a "total unit." Using quantitative analyses, we have demonstrated that interactions between speaking and finger tapping do occur in both the amplitude and frequency domains. Such interactions, however, do not appear to be as simple as those predicted by proponents of the dynamic pattern perspective.

Female↗
PubMed1990

Staff interaction with vocally disruptive demented patients compared with demented controls.

This study addressed the effect of social isolation on vocally disruptive demented patients (V); the results center on the amount of time patients spent in interactions, and the differences in type and time of staff-patient interaction (IA), compared to controls (C). Semi-structured observations were collected (1100 hours) for 37 vocally disruptive patients and 37 controls, all residents of psychogeriatric wards. Quantitative analysis revealed a low frequency of interactions, elicited mainly for procedural matters and short duration of most interaction episodes. Multiple regression analysis showed a significant difference in the type of interaction: there was more correction of undesired behaviour for vocally disruptive patients than for controls. The results show that social isolation is part of the institutionalized demented patients' life. The dominance of short interaction episodes could contribute to overstimulation. The only significant difference found was the frequency of corrective interactions in the group of vocally disruptive patients. We conclude that this is not the cause of their behaviour, but it may reinforce it. Other factors that might cause and maintain this behaviour require investigation.

Aged↗
PubMed2000

Low-frequency otolith and semicircular canal interactions after canal inactivation.

During sustained constant velocity and low-frequency off-vertical axis rotations (OVAR), otolith signals contribute significantly to slow-phase eye velocity. The adaptive plasticity of these responses was investigated here after semicircular canal plugging. Inactivation of semicircular canals results in a highly compromised and deficient vestibulo-ocular reflex (VOR). Based on the VOR enhancement hypothesis, one could expect an adaptive increase of otolith-borne angular velocity signals due to combined otolith/canal inputs after inactivation of the semicircular canals. Contrary to expectations, however, the steady-state slow-phase velocity during constant velocity OVAR decreased in amplitude over time. A similar progressive decrease in VOR gain was also observed during low-frequency off-vertical axis oscillations. This response deterioration was present in animals with either lateral or vertical semicircular canals inactivated and was limited to the plane(s) of the plugged canals. The results are consistent with the idea that the low-frequency otolith signals do not simply enhance VOR responses. Rather, the nervous system appears to correlate vestibular sensory information from the otoliths and the semicircular canals to generate an integral response to head motion.

Animals↗
PubMed2003

Interactions of zero-frequency and oscillating magnetic fields with biostructures and biosystems.

This review points to the investigations concerning the effects of zero-frequency (DC) and oscillating (AC) magnetic fields (MFs) on living matter, and especially those exerted by weak DC and low-frequency/low-intensity AC MFs. Starting from the analysis of observations on the action of natural magnetic storms (MSs) or periodic geomagnetic field (GMF) variations on bacteria, plants and animals, which led to an increasing interest in MFs in general, this survey pays particular attention to the background knowledge regarding the action of artificial MFs not only at the ionic, molecular or macromolecular levels, but also at the levels of subcellular regions, in vitro cycling cells, in situ functioning tissues or organs and total bodies or entire populations. The significance of some crucial findings concerning, for instance, the MF-dependence of the nuclear or cellular volumes, rate of cell proliferation vs. that of cell death, extent of necrosis vs. that of apoptosis and cell membrane fluidity, is judged by comparing the results obtained in a solenoid (SLD), where an MF can be added to a GMF, with those obtained in a magnetically shielded room (MSR), where the MFs can be partially attenuated or null. This comparative criterion is required because the differences detected in the behaviour of the experimental samples against that of the controls are rather small per se and also because the evaluation of the data often depends upon the peculiarity of the methodologies used. Therefore, only very small differences are observed in estimating the MF-dependence of the expression of a single gene or of the rates of total DNA replication, RNA transcription and protein translation. The review considers the MF-dependence of the interactions between host eukaryotic cells and infecting bacteria, while documentation of the harmful effects of the MFs on specific life processes is reported; cases of favourable action of the MFs on a number of biological functions are also evidenced. In the framework of studies on the origin and adaptation of life on Earth or in the Universe, theoretical insights paving the way to elucidate the mechanisms of the MF interactions with biostructures and biosystems are considered.

Animals↗
PubMed2005

Space-frequency model of ultrawide-band interactions in free-electron lasers.

The principle of operation of intense radiation devices such as microwave tubes, free-electron lasers, and masers, is based on a distributed interaction between an electron beam and electromagnetic radiation. Some of the effects emerging during the interaction involve a continuum of frequencies in their broadband spectrum. We developed a three-dimensional, space-frequency theory for the analysis and simulation of radiation excitation and propagation in electron devices and free-electron lasers operating in an ultrawide range of frequencies. The total electromagnetic field (radiation and space-charge waves) is presented in the frequency domain as an expansion in terms of transverse eigenmodes of the (cold) cavity, in which the field is excited and propagates. The mutual interaction between the electron beam and the electromagnetic field is fully described by coupled equations, expressing the evolution of mode amplitudes and electron beam dynamics. The approach is applied in a numerical particle code WB3D, simulating wideband interactions in free-electron lasers operating in the linear and nonlinear regimes.

Journal Article↗
PubMed2001

Static magnetic field measurements in residences in relation to resonance hypotheses of interactions between power-frequency magnetic fields and humans.

Bowman et al. used epidemiologic data to test a model in which subjects were classified as being "in-resonance" or "not-in-resonance" for 60-Hz magnetic-field exposures depending on single static magnetic-field measurements at the centers of their bedrooms. A second paper by Swanson concluded that a single static magnetic-field measurement is insufficient to meaningfully characterize a residential environment. The main objective of this study was to investigate exposure-related questions raised by these two papers in two U.S. data sets, one containing single spot measurements of static magnetic fields at two locations in homes located in eight states, and the other repeated spot measurements (seven times during the course of one year) of the static magnetic fields at the centers of bedrooms and family rooms and on the surfaces of beds in 51 single-family homes in two metropolitan areas. Using Bowman's criterion, bedrooms were first classified as being in-resonance or not-in-resonance based on the average of repeated measurements of the static magnetic field measured on the bed where the presumed important exposure actually occurred. Bedrooms were then classified a second time using single spot measurements taken at the centers of bedrooms, centers of family rooms, or on the surfaces of beds, as would be done in the typical epidemiologic study. The kappa statistics characterizing the degree of concordance between the first (on-bed averages) and second (spot measurements) methods of assessing resonance status were 0.44, 0.33, and 0.67, respectively. This level of misclassification could significantly affect the results of studies involving the determination of resonance status.

Adolescent↗
PubMed1994

Population responses to multifrequency sounds in the cat auditory cortex: one- and two-parameter families of sounds.

Population responses to multi-frequency sounds were recorded in primary auditory cortex of anesthetized cats. The sounds consisted of single-tone stimuli; two-tone stimuli; and nine-tone stimuli, with the tones evenly spaced on a linear frequency scale. The stimuli were presented through a sealed, calibrated sound delivery system. Single units, cluster activity (CA) and the short-time mean absolute value of the envelope of the neural signal (MABS) were recorded extracellularly from six microelectrodes simultaneously. The CA and MABS were interpreted as measures of the activity of large populations of neurons, in contrast with the single unit activity which is presumably recorded from single neurons. The responses of the MABS signal to simple stimuli were generally similar to those of the CA, but were more stable statistically. Thus, the MABS is better suited for studying the activity of populations of neurons. The responses to tones near the best frequency were strongly influenced by a second tone, even when the second tone was outside the single-tone response area. These influences could be both facilitatory and suppressory. They could not be predicted from the responses to single tones. The responses to the nine-tone stimuli could be explained qualitatively by the responses to the two-tone stimuli. It is concluded that the population responses in primary auditory cortex are shaped by the contributions of the individual frequencies appearing in the stimulus and by the interactions between pairs of frequencies. Interactions between stimulus components are therefore a necessary component of any attempt to explain the processing of complex sounds in the auditory cortex. They may play a role in a global representation of the stimulus spectrum in the primary auditory cortex. The presence of higher-order interactions cannot be excluded by the results presented here.

Acoustic Stimulation↗
PubMed2006

A third mode of DNA binding: Phosphate clamps by a polynuclear platinum complex.

We describe a 1.2 A X-ray structure of a double-stranded B-DNA dodecamer (the Dickerson Dodecamer, DDD, [d(CGCGAATTCGCG)]2) associated with a cytotoxic platinum(II) complex, [{trans-Pt(NH3)2(NH2(CH2)6(NH3+)}2-mu-{trans-Pt(NH3)2(NH2(CH2)6NH2)2}] (TriplatinNC). TriplatinNC is a multifunctional DNA ligand, with three cationic Pt(II) centers, and directional hydrogen bonding functionalities, linked by flexible hydrophobic segments, but without the potential for covalent interaction. TriplatinNC does not intercalate nor does it bind in either groove. Instead, it binds to phosphate oxygen atoms and thus associates with the backbone. The three square-planar tetra-am(m)ine Pt(II) coordination units form bidentate N...O...N complexes with OP atoms, in a motif we call the Phosphate Clamp. The geometry is conserved among the 8 observed phosphate clamps in this structure. The interaction appears to prefer O2P over O1P atoms (frequency of interaction is O2P > O1P, base and sugar oxygens > N). The high repetition and geometric regularity of the motif suggests that this type of Pt(II) center can be developed as a modular nucleic acid binding device with general utility. TriplatinNC extends along the phosphate backbone, in a mode of binding we call "Backbone Tracking" and spans the minor groove in a mode of binding we call "Groove Spanning". Electrostatic forces appear to induce modest DNA bending into the major groove. This bending may be related to the direct coordination of a sodium cation by a DNA base, with unprecedented inner-shell (direct) coordination of penta-hydrated sodium at the O6 atom of a guanine.

Amines↗
PubMed2003

Soup kitchen consumer perspectives on the quality and frequency of health service interactions.

OBJECTIVE: Whilst previous research has repeatedly documented premature mortality and high morbidity among seriously disadvantaged and homeless populations, far less is known of the extent and nature of their interactions with health services. DESIGN AND SETTING: This cross-sectional case study describes health service utilization patterns and explores participant-reported difficulties in accessing health care, adhering to prescribed treatment and maintaining continuity of care amongst 100 users of a charity-run soup kitchen in urban Sydney. Participants and results. The study describes a largely welfare-dependent population sample with poor health who are frequent users of the health system (85% had seen a general practitioner in the preceding 6 months). The homeless were more likely to report difficulties accessing health care when needed [odds-ratio 3.15; 95% confidence interval (CI) 1.04-9.62]. One in three respondents reported difficulty adhering to prescribed treatment following their last health care visit. Affordability (P < 0.0001), not understanding instructions (P = 0.007), and not agreeing with advice (P < 0.0001) were the main factors associated with adherence difficulties. One in four failed to return for follow-up visits as advised, largely associated with attitudinal barriers such as a history of not believing problems would be addressed (P = 0.05), not trusting health professionals (P = 0.04), and not knowing where to get help in the past (P = 0.05). CONCLUSION: These results reinforce the important role of free primary care in reducing access barriers for the disadvantaged, but also highlight possible reasons for service interactions being ineffective in a substantial proportion of cases.

Adolescent↗