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Biomedical subjects

M Teghtsoonian

Publications and source records attributed to M Teghtsoonian.

At least 19 recordsLinked to original sources
PubMed2000

The perception of waning signals: decruitment in loudness and perceived size.

When a tone or broad-band noise sweeps smoothly from a moderate intensity to a low one, the loudness at the end of the sweep is far less than what would be predicted from its intensity. The accelerated reduction in loudness, which was first reported by Canévet (1986) and confirmed in several later reports, has been called loudness decruitment, and has been tentatively interpreted as the result of some form of adaptation. Since both simple and induced adaptation have distinctive temporal profiles, we undertook a series of studies in which we varied the duration of a tone whose intensity was continuously changing, to see whether the effect of duration on decruitment resembled the effects of duration on adaptation. We discovered that the magnitude of decruitment remained unaffected when the duration of the sweep was reduced far below the durations of 90 to 180 sec that have been used in previous studies. The same effect was observed for durations of around 20 sec, but it declined rapidly to a low level at the lowest duration of 1.0 sec. This temporal pattern is strikingly different from what has been reported for either simple or ipsilaterally induced adaptation, which suggests that neither form of adaptation can account for the entire effect. We also wanted to know whether an analogous phenomenon could exist for a sensory modality other than hearing. In the present study, observers were asked to judge the apparent size of a solid disk on a computer monitor, the disk increased or decreased continuously in area, or appeared as a series of separate areas, either in random order or in ordered progressions. We found that, as in the case of loudness, apparent size decreased more rapidly when the areas decreased continuously than would have been predicted from the actual areas themselves. We also found that some part of the accelerated shrinkage was due to a response bias in the observers' judgments that stemmed from knowledge that every value in a continuously changing series is predictably smaller (or larger, for a growing series). Whether the remaining part of the effect is a sensory phenomenon is an important issue for future research.

Adolescent↗
PubMed1997

Range of acceptable stimulus intensities: an estimator of dynamic range for intensive perceptual continua.

The dynamic range (DR) of a sensory system is the span (usually given in log units) from the lowest to highest intensities over which a continuously graded response is evoked, and may be a distinctive feature of each such system. Teghtsoonian (1971) proposed that, although DR varies widely over sensory systems, its subjective size (SDR) is invariant. Assuming the psychophysical power law, the exponent for any continuum is given by the ratio of subjective span to DR, both quantities expressed logarithmically. Thus, exponents are inversely related to the DR and many be interpreted as indexes of it. Because DR can be difficult or even dangerous to measure directly, we sought to define a smaller range representing some fixed proportion of DR that could be used in its place to test the hypothesis of an invariant subjective range. Observations manipulated the intensities of five target continua to produce the broadest range they found acceptable and reasonably comfortable, a range of acceptable stimulus intensities (RASIN). Combined with an assumed constant SDR (derived from previous research), RASINs accurately predicted exponents obtained by magnitude production from the same observers on the five continua, as well as exponents reported in the literature.

Hand Strength↗
PubMed1995

On the nature and meaning of sinuosity in magnitude-estimation functions.

Magnitude-estimation functions for single observers, derived from multiple judgments of closely spaced stimuli, exhibit a sinuous form in logarithmic coordinates, an observation frequently confirmed since first reported by Luce and Mo (1965). We propose that this can result from reliance on a restricted pool of responses, called "preferred numbers" by Baird and Noma (1975). We describe a model featuring a response band centered on an assumed power function, from which the observer selects from among preferred numbers with equal probability. In simulations, the expected values of these selections oscillate around the underlying power function with an appearance similar to that of Luce-Mo functions. The appearance of these functions depends on values assumed for the scale factor of the power function, the range of intensities considered, and the width of the band from which responses are drawn. We conclude that sinuosity in magnitude-estimation functions does not disconfirm the psychophysical power law.

Arousal↗
PubMed1990

Distinguishable types of dyspnea in patients with shortness of breath.

Dyspnea frequently accompanies a variety of cardiopulmonary abnormalities. Although dyspnea is often considered a single sensation, alternatively it may encompass multiple sensations that are not well explained by a single physiologic mechanism. To investigate whether breathlessness experienced by patients represents more than one sensation, we studied 53 patients with one of the following seven conditions: pulmonary vascular disease, neuromuscular and chest wall disease, congestive heart failure, pregnancy, interstitial lung disease, asthma, and chronic obstructive pulmonary disease. Patients were asked to choose descriptions of their sensation(s) of breathlessness from a dyspnea questionnaire listing 19 descriptors. Cluster analysis was used to identify natural groupings among the chosen descriptors. We found that patients could distinguish different sensations of breathlessness. In addition, we found an association between certain groups of descriptors and specific conditions producing dyspnea. These findings concur with those in an earlier study in normal volunteers in whom dyspnea was induced by various stimuli. We conclude that different types of dyspnea exist in patients with a variety of cardiopulmonary abnormalities. Furthermore, different mechanisms may mediate these various sensations.

Adult↗
PubMed1989

Distinguishable sensations of breathlessness induced in normal volunteers.

Various theories about the genesis of dyspnea have often assumed that the sensation is similar from patient to patient and is generated by a single underlying mechanism. To investigate whether breathlessness induced in normal volunteers by different stimuli represents one or more than one sensation, we studied 30 subjects in whom breathlessness was induced by each of 8 different stimuli: breath-holding, CO2 inhalation, inhalation of CO2, with ventilation voluntarily targeted below the level dictated by chemical drive, breathing with a resistive load, breathing with an elastic load, voluntary elevation of functional residual capacity, voluntary limitation of tidal volume, and exercise. For each stimulus, subjects were asked to choose description of their sensation(s) of breathlessness from a questionnaire listing 19 descriptors. The responses from this questionnaire were evaluated using cluster analysis to search for relationships among descriptors and to identify natural groupings. We found that distinct groups of descriptors emerged, i.e., subjects could distinguish different sensations of breathlessness. In addition, we found an association between certain descriptor groups and stimuli. We conclude that the term breathlessness may encompass multiple sensations, and, therefore, may not be explainable by a single physiologic mechanism.

Adult↗
PubMed1987

On the relation between the growth of loudness and the discrimination of intensity for pure tones.

The intensity jnd is often assumed to depend on the slope of the loudness function. One way to test this assumption is to measure the jnd for a sound that falls on distinctly different loudness functions. Two such functions were generated by presenting a 1000-Hz tone in narrow-band noise (925-1080 Hz) set at 70 dB SPL and in wideband noise (75-9600 Hz) set at 80 dB SPL. Over a range from near threshold to about 75 dB SPL, the loudness function for the tone is much steeper in the narrow-band noise than in the wideband noise. At 72 dB SPL, where the two loudness curves cross, the tone's jnd was measured in each noise by a block up-down two-interval forced-choice procedure. Despite the differences in slope (and in sensation level), the jnd (delta I/I) is nearly the same in the two noises, 0.22 in narrow-band noise and 0.20 in wideband noise. The mean value of 0.21 is close to the value of 0.25 interpolated from Jesteadt et al. [J. Acoust. Soc. Am. 61, 169-176 (1977)] for a 1000-Hz tone that had the same loudness in quiet as did our 72-dB tone in noise, but lay on a loudness function with a much lower slope. These and other data demonstrate that intensity discrimination for pure tones is unrelated to the slope of the loudness function.

Acoustic Stimulation↗
PubMed1984

Testing a perceptual constancy model for odor strength: the effects of sniff pressure and resistance to sniffing.

The rate at which odorous vapor flows over the receptor surface is reflected in olfactory nerve activity, but the evidence for a corresponding effect on odor strength is scant and inconsistent. A perceptual constancy model for odor strength resolves this apparent contradiction: The effect of flow rate at the receptor site may be perceptually discounted when there is sensory feedback, in the form of perceived effort, from the action of sniffing responsible for changes in flow rate. Previous evidence shows that observers experience change in perceived effort when sniffing at various pressures against fixed resistance but not when sniffing with fixed pressure against varying resistance. Thus the model predicts both that odor strength varies when flow rate is manipulated by changes in olfactory resistance and that odor strength is invariant when flow rate is manipulated by changes in sniff pressure. In the present study, in which subjects made magnitude estimates of the odor strength of pyridine and n-butanol, an earlier finding for the effects of resistance change was confirmed and extended. Further, within the framework of a single experiment in which both pressure and resistance were independently manipulated, the odor strength of n-butanol conformed to the predictions of the constancy model.

1-Butanol↗
PubMed1978

Invariance of odor strength with sniff vigor: an olfactory analogue to size constancy.

Previous evidence has shown that detection threshold in humans and olfactory neural discharge rate in animal preparations both depend on flow rate of odorous vapor. But no data have been reported that show the effects of flow rate in humans on perceived odor strength at suprathreshold intensities. Subjects learned to inspire at two flow rates, one twice as great as the other, by adjusting (on a cathode ray tube) the transduced trace of a sniff-produced pressure change to match either of two target contours. They then made magnitude estimations of odor strength, while producing either weak or strong sniffs, for odorants presented over a wide range of concentrations via a specially designed sniff-bottle system. The odorant, diluted in diethyl phthalate, was n-butanol in two experiments and n-amyl acetate in two others. Subject-controlled flow rate had no effect on odor strength for either odorant. There was an apparent contradiction between these data and those on neural discharge rate that may, however, be resolved by adopting an odor constancy model: When sniff intensity varies during the olfactory exploration of an odor source, information about the rate at which odorant molecules are established at the receptor site is combined with information about sniff vigor so that the resulting percept is of invariant odor strength.

Acetates↗