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Biomedical subjects

H Gockel

Publications and source records attributed to H Gockel.

9 recordsLinked to original sources
PubMed2001

Influence of rate of change of frequency on the overall pitch of frequency-modulated tones.

The mechanism(s) determining pitch may assign less weight to portions of a sound where the frequency is changing rapidly. The present experiments explored the possible effect of this on the overall pitch of frequency-modulated sounds. Pitch matches were obtained between an adjustable unmodulated sinusoid and a sinusoidal carrier that was frequency modulated using a highly asymmetric function with the form of a repeating U or inverted U shaped function. The amplitude was constant during the 400-ms presentation time of each stimulus, except for 10-ms raised-cosine onset and offset ramps. In experiment 1, the carrier level was 50 dB SPL and the geometric mean of the instantaneous frequency of the modulated carrier, fc, was either 0.5, 1, 2, or 8 kHz. The modulation rate (fm) was 5, 10, or 20 Hz. The overall depth (maximum to minimum) of the FM was 8% of fc. For all carrier frequencies, the matched frequency was shifted away from the mean carrier frequency, downwards for the U shaped function stimuli and upwards for the repeated inverted U shaped function stimuli. The shift was typically slightly greater than 1% of fc, and did not vary markedly with fc. The effect of fm was small, but there was a trend for the shifts to decrease with increasing fm for fc = 0.5 kHz and to increase with increasing fm for fc = 2 kHz. In experiment 2, the carrier level was reduced to 20 dB SL and matches were obtained only for fc = 2 kHz. Shifts in matched frequency of about 1% were still observed, but the trend for the shifts to increase with increasing fm no longer occurred. In experiment 3, matches were obtained for a 4-kHz carrier at 50 dB SPL. Shifts of about 1% again occurred, which did not vary markedly with fm. The shifts in matched frequency observed in all three experiments are not predicted by models based on the amplitude- or intensity-weighted average of instantaneous frequency (EWAIF or IWAIF). The shifts (and the pitch shifts observed earlier for two-tone complexes and for stimuli with simultaneous AM and FM) are consistent with a model based on the assumption that the overall pitch of a frequency-modulated sound is determined from a weighted average of period estimates, with the weight attached to a given estimate being inversely related to the short-term rate of change of period and directly related to a compressive function of the amplitude.

Adolescent↗
PubMed2000

Frequency modulation detection interference produced by asynchronous and nonsimultaneous interferers.

The effect of asynchronous and nonsimultaneous interferers on detection of sinusoidal frequency modulation (FM) was compared with the effect of a synchronous interferer. In a two-interval, two-alternative forced-choice (2I-2AFC) adaptive procedure, listeners had to detect FM with a modulation frequency of 15 Hz, imposed on a 1-kHz sinusoidal carrier (the target). The 200-ms target was presented either alone (baseline condition), or with an interferer whose timing relative to the target was varied. The interferer was a 2.3-kHz sinusoidal carrier which was also frequency modulated at a rate of 15 Hz. Experiment one showed that thresholds for detection of FM increased significantly, both with a synchronous FM interferer, and also with asynchronous interferers (starting 200 ms before and stopping 200 ms after the target). Moreover, "gapped" interferers that were turned off during presentation of the target (presented for 200 ms before and for 200 ms after the target but not simultaneously) produced the same significant increase in thresholds as an asynchronous interferer that was not interrupted. In contrast, thresholds were not affected by the presence of a gapped unmodulated sinusoidal interferer. Experiment two showed that increasing the duration of the silent gap (centered on presentation of the target) between FM interferers from 200 to 600 ms did not abolish the interference. Thus nonsimultaneous FM interferers produced frequency modulation detection interference (FMDI) even when the silent gap between the interferers and target clearly led to the interferers and target being perceived as separate auditory objects. A possible explanation for the findings is the existence of an asymmetry in perception of steady and modulated sounds, as recently proposed by Cusack and Carlyon [Br. J. Audiol. 34.2, 112 (2000)]. Alternative explanations in terms of ringing in a hypothetical modulation filter bank and adaptation seem unlikely.

Adolescent↗
PubMed1999

Context dependence of fundamental-frequency discrimination: lateralized temporal fringes.

In a two-interval, two-alternative, forced-choice (2I-2AFC) adaptive procedure, listeners discriminated between the fundamental frequencies (F0s) of two 100-ms harmonic target complexes. This ability can be impaired substantially by the presence of another complex (the "fringe") immediately before and after each target complex. It has been shown that for the impairment to occur (i) target and fringes have to be in the same frequency region; (ii) if all harmonics of target and fringes are unresolved then they may differ in F0; otherwise, they have to be similar [C. Micheyl and R. P. Carlyon, J. Acoust. Soc. Am. 104, 3006-3018 (1998)]. These findings have been discussed in terms of information about the fringe's F0 being included in the estimate of the F0 of the target, and in terms of auditory streaming. The present study investigated the role of perceived location and ipsilateral versus contralateral presentation of the fringes on F0 discrimination of the target. Experiment 1 used interaural level differences (ILDs), and experiment 2 used interaural time differences (ITDs) to create a range of lateralized perceptions of the 200-ms harmonic fringes. Difference limens for the F0 of the monaural target complex were measured in the presence and absence of the fringes. The nominal F0 was 88 or 250 Hz and could be the same or different for target and fringes. Stimuli were bandpass filtered between 125-625, 1375-1875, or 3900-5400 Hz. In both experiments, the effect of the fringes was reduced when their subjective location differed from that of the target. This reduction depended on the resolvability of both the fringes and the target. The effect of the fringes was reduced most (but still present), when fringes were presented purely contralaterally to the target. The results are consistent with the idea that the fringes produce interference when the listeners have difficulty segregating the target from the fringes, and that a difference in perceived location enhances segregation of the sequentially presented stimuli.

Humans↗
PubMed1998

Human intestinal epithelial cells down-regulate IL-8 expression in human intestinal microvascular endothelial cells; role of transforming growth factor-beta 1 (TGF-beta1).

Cytokines produced from intestinal epithelial cells may function as signals to neighbouring immune cells. In the present study we analysed the effects of colonic epithelial cell lines (HT-29, Caco-2, HCT-116, Colo-320) and freshly isolated intestinal epithelial cells on IL-8 expression in the SV-40T transfected human microvascular endothelial cell line (HMEC-1). Epithelial cell-conditioned media and transwells preventing physical contact between epithelial and endothelial cells were used. TGF-beta1 and IL-8 levels were determined by ELISA and Northern blot analysis. Increasing concentrations of IL-1beta led to increasing production of IL-8. The addition of epithelial cell-conditioned medium or epithelial cells to HMEC-1 cells in a two-compartment co-culture system resulted in a strong decrease in IL-8 at the protein and mRNA level. Decrease of IL-8 was markedly stronger when epithelial cells were co-cultured in contact with HMEC-1 cells, indicating that not only soluble factor(s) play a role in the induction of IL-8 suppression in HMEC-1 cells. MoAbs against TGF-beta1 partially inhibited down-regulation of endothelial IL-8 expression. In further studies, IL-8 expression in freshly isolated human intestinal microvascular endothelial cells (HIMEC) was also down-regulated by intestinal epithelial cells. Our results demonstrate that intestinal epithelial cells down-regulate IL-8 expression in HMEC-1 cells. TGF-beta1 is a candidate factor of epithelial-endothelial communication in the colonic mucosa.

Caco-2 Cells↗
PubMed1998

On possible cues in profile analysis: identification of the incremented component.

The ability to identify the frequency of the incremented component in a multitone complex was assessed in two conditions, both using the same 11-tone complexes (fixed frequency, equilog spaced, random phases). In the standard-plus-signal complex all components had equal level, except one of the inner nine, which was incremented in level by an in-phase addition of a sinusoid of the same frequency (the signal). The overall level and signal position were randomly varied on each presentation. In the "Standard-absent" condition the standard-plus-signal complex was presented first, and it was followed by a single sinusoid either at the signal frequency or at that of an adjacent component (below or above). In the "Standard-present" condition, a complex with equal-level components (the standard complex) was also presented on each trial, either before or after the standard-plus-signal complex (in random order). These two complexes were followed by the single sinusoid. In both conditions, the subjects had to indicate whether the signal frequency was the same as or different from the frequency of the single sinusoid. In a third condition, the ability to discriminate between the standard complex and the standard-plus-signal complex (with signal frequency uncertainty) was investigated. In all three conditions, thresholds for the increment in level for each signal frequency were estimated by the use of nine independent interleaved adaptive procedures. Results showed that the ability to identify the signal frequency was at least as good as the ability to discriminate between the two complexes. The results suggest that an increase in pitch strength of the incremented component is a possible cue in profile analysis tasks.

Auditory Perception↗
PubMed1998

Effects of ear of entry and perceived location of synchronous and asynchronous components on mistuning detection.

Listeners were required to detect mistuning imposed on the center ("target") component of a 200-ms complex consisting of the first seven harmonics of a 500-Hz fundamental. In the standard interval of each 2IFC trial, all components were frequency modulated in-phase by a 5-Hz sinusoid. In the signal interval the frequency modulation of the target component was inverted in-phase, thereby introducing a mistuning proportional to the depth of FM. In a similar experiment, using monaural presentation, Carlyon [J. Acoust. Soc. Am. 95, 2622-2630 (1994)] reported a substantial elevation of thresholds in the presence of an unmodulated asynchronous interferer with frequency identical to the mean frequency of the target. This was attributed to the interferer, causing the target component to be perceptually segregated from the remainder of the complex, thereby impairing across-frequency comparisons. Experiment 1 of the present study showed that an interferer presented contralaterally for 200 ms before and 100 ms after the signal complex (no simultaneous presentation) also impaired performance, but to a lesser extent than an ipsilaterally presented one. Experiment 2 showed that an interferer which was presented dichotically with an interaural level difference (ILD) of 10 dB, so that it was perceived contralaterally, had the same (large) effect as if it were presented ipsilaterally. Experiment 3 showed that, in the absence of any interferer, performance was impaired when the nontarget components were presented contralaterally to the target component. However, performance was not impaired when the nontarget components were presented dichotically with an ILD of 20 dB, so that they were perceived contralaterally to the target component. It is concluded that the level of performance in the mistuning task is determined by whether the target is presented to the same ear as the rest of the complex, rather than by its perceived location.

Adult↗
PubMed1997

Auditory profile analysis: is there perceptual constancy for spectral shape for stimuli roved in frequency?

The ability to discriminate between two spectral shapes was investigated using a one-interval, two-alternative forced choice procedure. Each stimulus consisted of seven components equally spaced on a logarithmic frequency scale (frequency ratio of 1.2 between adjacent components). The two spectral shapes were produced by first generating a complex each of whose components was equally loud (when heard in isolation) and then increasing the level of either the third or the fifth component by a certain amount. To render pitch an unusable cue, the center frequencies of the stimuli were randomly varied between presentations (maintaining the ratio between adjacent components) over a range of about three octaves (279-2074 Hz). The data indicate that listeners were not able to distinguish between the two types of profiles even for very large increments in level of the third and the fifth components. The results suggest that there is no perceptual constancy for this type of spectral shape for stimuli roved over a sufficiently large frequency range. The spectral shape cannot be perceived independently of stimulus frequency. The results are related to the multi-channel model applied in profile analysis tasks.

Adult↗
PubMed1993

[Computer-aided anesthesia monitoring. Experiences with the use of three systems in heart surgery].

Basic monitoring in cardiac anaesthesia embraces at least 19 different parameters of haemodynamics and blood gas analysis. In special cases additional measurements may be desirable, providing a total of up to 44 variables displayed on various monitors, as depicted in Fig. 2. The recording of such an amount of data is only feasible with automated recording systems. Therefore, in the past 6 years we have introduced three different computer systems to our cardiac anaesthesia workplaces. The experiences in their handling are reported. MATERIAL AND METHOD. Three systems were investigated: (1) System S 4000 (Siemens, Germany), based on a central processor unit (PDP 11, DEC, Japan) connected with 20 bedside input/output terminals and Sirecust 404a monitors (Siemens). The system collected the data in a ring buffer with a capacity for about 24-48 h. (2) Patient Care Manager (PCM; Siemens, Germany), a single workplace system based on an IBM-compatible personal computer (PC) with the operating system environment DOS 5.0/Windows 3.0. In our test configuration it was connected with a Sirecust 1281 monitor (Siemens). (3) Monitor-Data-Manager (MDM) (our own development). This single workplace system is also based on an IBM-compatible PC running under DOS and was connected to four different monitors used in our cardiac surgery operating theatre (Fig. 2). A second computer (Sirecust S 425, Siemens) served as an interface between the two 404 monitors (not featuring a serial output like RS 232) and the PC. The self-developed program for that interface was memory resistant and executable with three key presses when the anaesthetic record was started. The three systems were compared with regard to their ease of use, function and practicability. RESULTS. System S 4000: Because of the older system architecture, the response time to key inputs was fairly long and the menu structure somewhat uncomfortable. A major drawback was the limited data buffer capacity and the lack of a long-term storage medium as well as the lack of compatibility with the industry standard for PCs. Software interfaces to other companies' monitors were not implemented, limiting the system to the Sirecust 404 devices. Patient-Care-Manager: The user interface is a Windows 3.0 application representing an up-to-date graphical environment. Unfortunately some Windows features were not fully used, e.g. the free positioning and sizing of graphic windows and the color options. Drug inputs were somewhat long-winded, limiting the system's suitability for the operating theatre. The main disadvantage, however, was the lack of interfaces to monitors other than those from Siemens. Monitor Data Manager: The system was designed to sample data from all monitors operating in our hospital's heart surgery department. Each parameter was displayed in a digital form to get close control over the recorded data (Fig. 1b); additionally calculated values like total peripheral resistance or oxygen demand could be drawn from a separate window. Furthermore, key inputs were reduced to minimum, making drug inputs faster than the hand-written protocol. The ease of performing calculations of continuous drug infusions (from microgram/kg/min to ml/h pump speed) was particularly appreciated by the users. Since the data were saved as an ASCII file, they could easily be imported by any spreadsheet like Lotus 1-2-3 or Excel, providing the whole variety of their graphical presentation or calculation features. Because of the high sampling rate (3 min), even short-lasting drug effects could be registered, making the system favourable for scientific studies. CONCLUSION. Automated monitor data record systems are considered to be a prerequisite not only for research in anaesthesia but also for quality assurance. A basic requirement for wide acceptance in clinical practice is a user interface that provides fast and convenient key inputs as well as further information about parameters not displayed on other monitors. In our h

Anesthesia↗