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PubMed1989

Manual asymmetry in weight discrimination: hand or spatial-field advantage?

Sixty subjects who were either left-handed or right-handed performed one-handed weight discrimination using their left and right hands in the left and right spatial fields. Differential thresholds, for the left and right hands of both left-handed and right-handed subjects, were found to be lower in the spatial field contralateral to the ear which proved superior in a dichotic listening test. It is concluded that manual asymmetry for weight discrimination results primarily from the mapping of sensorimotor events in the spatial fields onto contralateral cerebral cortex, with an advantage in the spatial field contralateral to the nonlanguage cerebral hemisphere.

Adolescent↗
PubMed1995

Bite force displayed during assessment of hardness in various texture contexts.

The relationship between mastication pattern, mechanical properties of the food bolus and texture perception are not fully understood, though the mastication process is known to adjust to different textural properties of foods. This study investigated the role of the bite force as one major aspect in hardness assessment of materials exhibiting simple mechanical properties over a wide hardness range. Elastic, plastic and brittle materials (silicone elastomers, waxes and pharmaceutical tablets, respectively) were tested. The rheological characteristics of these products were measured. For each product, one to four differential thresholds were determined at different points on a hardness scale by 10 individuals free of dental pathology. Bite forces were recorded by placing a small intraoral load cell under each sample. To assess the influence of the nature of the applied force, bites were made either directly on to the sample or on a metal disc placed between the teeth and the sample. As the individuals had to break the brittle products to perceive any hardness difference, bite forces were very closely correlated with the hardness of the products (r = 0.99). For plastic products, bite forces again correlated with the hardness (r = 0.96), even though individuals could stop biting at any time during the plastic deformation. Hardness perception of brittle and plastic products depends directly on sensory information about the bite force. However, hardness assessment of elastic products was obtained under constant bite force; here, the resulting deformation may provide sensory information about hardness.

Adult↗
PubMed1982

Differentiated perceptions of exertion and energy cost of young women while carrying loads.

Differentiated local ratings of perceived exertion from the legs and central ratings from the chest, and oxygen consumption, were determined during load carriage in seven young women. Subjects walked for 6 min at 3.22, 4.83, 6.44, or 8.05 km X h-1 carrying (1) no load, (2) a load equal to 7.5% of body weight (mean: 4.66 kg) or (3) a load equal to 15% of body weight (mean: 9.32 kg). Thus, each subject underwent 12 separate tests. The external loads were in the form of lead pellets carried in a plastic scuba belt worn around the waist. A differentiation threshold was found at 6.44 km X h-1 for the 0% and 7.5% loads and at 4.83 km X h-1 for the 15% load. At speeds below the threshold, the perception of exertion was similar in the legs, chest and overall. At higher speeds, exertion was perceived to be more intense in the legs than overall and less intense in the chest than overall, suggesting that the local legs signal was the dominant factor in shaping the overall sensation of exertion. The oxygen uptake was greater for the 15% load than for either the 0% or 7.5% loads, but was similar for the 0% and 7.5% loads. Findings suggested a critical weight limit for external loads that could be transported without increasing the metabolic cost beyond that required to move the body weight alone. This limit fell between 7.5% and 15% of the body weight. When oxygen uptake was expressed per kg of total weight transported, there was no loss of metabolic efficiency while carrying loads up to 15% of the body weight.

Adult↗
PubMed2000

Audiological problems in patients with tinnitus exposed to noise and vibrations.

Tinnitus is a hearing sensation appearing without available sound fluctuations in the external environment. It is one of the major, constant and earliest symptoms suggesting different pathology of the hearing analyser. It must be considered, though, that it is evidenced also at disturbed functions of other organs and systems of the organism. The aim of the present study is to elucidate the state of the hearing analyser in patients with tinnitus occupationally exposed to noise and vibrations in relation to therapy. The study was performed on 67 miners, aged 34-55, mean age 44.5 years. The workers with subjective tinnitus (29 persons--43% of the studied group) are the object of this investigation. They were subjected to the following tests of the hearing analyser: pure tone audiometry; above-threshold audiometry (Carhardt's adaptation test, Lusher's differential threshold, SISI test, Kietz test. The evidence reveals that the studied group of workers occupationally exposed to noise, vibrations, dust, toxic substances etc. complain predominantly of tinnitus. It is accompanied by vertigo, headache and disturbed balance. Changes in the hearing function are observed; manifested by different degree of hypacusia concerning air and bone conductivity in the pure tone audiometry. The above-threshold tests also evidence deviations suggesting disturbed hearing function. These changes can be explained by mechanical-toxic pathogenic mechanisms leading to cerebral and vestibular dysfunction most probably of vascular-circulatory type manifested by the above stated deviations. The results are the basis for the following conclusions: 1. The anamnestic profile of workers with tinnitus exposed to noise and vibrations shows a prevalent percentage of vertigo, followed by headache and disturbed balance. 2. The otoneurological profile shows changes in the air and bone conductivity manifested by different degree of hypacusia. 3. The evaluation of the above-threshold tests also confirms the evidence of disturbed hearing function. 4. The relevant therapeutical approach has to be elaborated, having in mind the existing suggestion about the mechanical-toxic etiopathogenesis of the developed process of vascular-circulatory type.

Adult↗
PubMed2006

Effects of vision and friction on haptic perception.

OBJECTIVE: Two experiments were conducted to examine the effects of vision and masking friction on contact perception and compliance differentiation thresholds in a simulated tissue-probing task. BACKGROUND: In minimally invasive surgery, the surgeon receives limited haptic feedback because of the current design of the instrumentation and relies on visual feedback to judge the amount of force applied to the tissues. It is suggested that friction forces inherent in the instruments contribute to errors in surgeons' haptic perception. This paper investigated the psychophysics of contact detection and cross-modal sensory processing in the context of minimally invasive surgery. METHOD: A within-subjects repeated measures design was used, with friction, vision, tissue softness, and order of presentation as independent factors, and applied force, detection time, error, and confidence as dependent measures. Eight participants took part in each experiment, with data recorded by a custom force-sensing system. RESULTS: In both detection and differentiation tasks, higher thresholds, longer detection times, and more errors were observed when vision was not available. The effect was more pronounced when haptic feedback was masked by friction forces in the surgical device (p < .05). CONCLUSION: Visual and haptic feedback were equally important for tissue compliance differentiation. APPLICATION: A frictionless endoscopic instrument can be designed to restore critical haptic information to surgeons without having to create haptic feedback artificially.

Adult↗
PubMed2001

Threshold doses for nicotine discrimination in smokers and non-smokers.

RATIONALE: Tobacco use during initial experimentation often involves modest nicotine exposure, escalating to larger doses and more frequent exposure with the onset of tobacco dependence. Threshold doses for nicotine discrimination therefore may differ between naive and experienced tobacco users. OBJECTIVES: We determined the lowest (threshold) dose of nasal spray nicotine that smokers and non-smokers could reliably discriminate from placebo spray. METHODS: Male and female smokers (n=18) and non-smokers (n=17) were initially trained to discriminate 20 microg/kg from placebo before proceeding to threshold determination sessions, which involved discrimination of progressively lower doses below 20 microg/kg ("descending order" subgroup) or higher doses above 1 microg/kg ("ascending order" subgroup). Threshold was determined by the lowest dose reliably discriminated from placebo (correct on > or =80% of testing trials) and by failure to discriminate the next lowest dose. RESULTS: Threshold doses for nicotine discrimination were low and not different between smokers and non-smokers (median thresholds of 3 versus 2 microg/kg and approximate blood levels of 2.6 versus 1.6 ng/ml, respectively). Thresholds were similar between descending and ascending order subgroups. Several subjective responses differentiated threshold dose from the dose just below threshold, particularly in non-smokers. CONCLUSIONS: Threshold doses for nasal spray nicotine discrimination in humans are low, well below the typical nicotine delivery of most cigarette brands, and may not change after long-term smoking exposure.

Administration, Intranasal↗
PubMed1988

Differential spatial displacement discrimination thresholds for Gabor patches.

Differential spatial displacement discrimination thresholds were determined for a configuration of three identical Gaussian modulated patches of sinusoidal grating presented with equal orientation and at threshold luminance contrast. The patches were arranged one above the other at equal spatial intervals. The orientation of the bars of the sinusoidal grid constituting the patches was orthogonal to the axis joining the centres of the outer two patches. Thresholds were determined for displacements of the middle patch both orthogonal to and along the axis joining the outer two patches. Thresholds for both tasks were obtained as a function of both the spatial frequency of the sinusoidal grating and the spatial scale parameter of the Gaussian envelope of the patches. We found that the differential spatial displacement discrimination thresholds for both tasks are a constant fraction of the spatial scale parameter of the Gaussian envelope of the sinusoidal grating patches and are independent of the spatial frequency of the modulated grating. We conclude that the human visual system is capable of assigning a single location tag to an entire Gaussian modulated patch of sinusoidal grating. The accuracy with which the relative position of such a Gabor patch can be determined in a constant fraction of its spatial extent (spread of the Gaussian spatial envelope).

Adult↗
PubMed1990

Multi-channel cochlear implant patients with different open speech understanding show some similar basic psychophysical results.

A series of tests was recently undertaken on three multi-channel cochlear implant patients showing different degrees of open speech understanding in order to try to determine underlying differences in inner ear excitation. First we wanted to determine whether these patients showed notable differences in basic psychophysical tasks. This article reports a series of measures including absolute and differential thresholds, simultaneous and forward masking, and some polarity and phase perception. Absolute and differential sensitivities were found to be similar. In forward or simultaneous masking, the patients often showed no masking at all and in cases of masking, no frequency selectivity. In forward masking, their time constants were found to be longer than those in normal hearing. Multi-harmonic signals differing only in phase relations to produce large differences in peak amplitude did not seem to elicit different perceptions. In stimulating with very low-frequency square waves, only negative going fronts were perceived. The similarity of results for the 3 patients in this study suggest that individual differences lie in more complex stimulus processing and perhaps in qualitative aspects of perception.

Adult↗
PubMedDate not supplied

[Functional state of the human hearing analyzer exposed to +Gx acceleration].

The functional state of the acoustic analyzer of man was investigated during an exposure to +Gx acceleration of 4-14 g applied at an angle of 78 degrees to the long axis of the body. During an exposure to 8-10 g the hearing state began to deteriorate. This included an increase in the tonic thresholds of hearing sensitivity with respect to the aerial and bone conduction, and an increase in the differential thresholds of hearing with respect to the strength and pitch. With an increase of the acceleration value these changes grew, reaching maximum at 14 g. It is suggested that possible mechanisms of changes in the hearing sensitivity are associated with disorders in the systems of sound conveyance and perception.

Acceleration↗
PubMed1988

Threshold variability with an automated LED perimeter.

The CooperVision Dicon AP 2000 does not project the stimulus onto an existing background, but produces the test stimuli with light emitting diodes (LEDs) recessed in a dark cavity in the perimetric bowl. Nearly everywhere in the visual field, the visibility threshold with the Dicon instrument seems equivalent to that obtained with projection perimeters, but in the most sensitive retinal areas we found the threshold stimulus (Is) to be sometimes dimmer than the "background" (Ib), which surrounds the stimulus, making a negative differential threshold (delta L = Is - Ib). In other words, where a dark cavity is imaged on a very sensitive portion of the retina, the visual mechanism may perceive the switching on of a stimulus of a lower intensity (Is) than the "background" light (Ib) that floods only the surrounding retina. In retinal regions where this happens, we found the variability of retesting of threshold to be much greater than at locations with threshold stimuli that are more intense than the "background". When we modified the instrument by placing a diffuser over the LED to provide a preexistent "background" at the test location equivalent to that of the surround, the greater variability disappeared, and the threshold results resembled those of projection perimetry even at the most sensitive retinal areas. Variability was also reduced with shortened stimulus durations.

Adult↗
PubMed2006

Blockade of nicotinic acetylcholine or dopamine D1-like receptors in the central nucleus of the amygdala or the bed nucleus of the stria terminalis does not precipitate nicotine withdrawal in nicotine-dependent rats.

Approximately 70% of tobacco smokers wish to quit, but attempts are often unsuccessful partly due to the aversive nicotine withdrawal syndrome. We investigated the possible involvement of nicotinic and dopaminergic signalling in the central nucleus of the amygdala (CeA) and dorsolateral bed nucleus of the stria terminalis (dlBNST) in the anhedonic depression-like effect of precipitated nicotine withdrawal in rats. Nicotine-dependent rats exhibit elevations in intracranial self-stimulation (ICSS) thresholds compared to control rats after cessation of chronic nicotine administration (spontaneous withdrawal) or systemic or intra-ventral tegmental area (VTA), but not intra-nucleus accumbens (NAcc), administration of nicotinic acetylcholine receptor (nAchR) antagonists while exposed to nicotine (precipitated withdrawal). We examined whether intracerebral administration of the nAChR antagonist dihydro-beta-erythroidine (DHbetaE; 0.6-20 microg total bilateral dose) or the dopamine D1-like receptor antagonist SCH 23390 (2-16 microg total bilateral dose) into the CeA and dlBNST results in withdrawal-like threshold elevations in nicotine-treated rats. Nicotinic acetylcholine and D1-like receptor blockade in the CeA or the dlBNST did not induce differential threshold elevations in nicotine- and saline-treated rats. Further, the highest SCH 23390 dose (16 microg bilateral dose) injected into the dlBNST, but not the CeA, elevated thresholds similarly in both saline- and nicotine-treated rats, suggesting that dopaminergic signalling in the dlBNST may regulate brain reward function under baseline conditions. These results suggest that nACh and D1-like signalling in the CeA and the dlBNST does not develop neuroadaptations with the development of nicotine dependence that may be involved in the depression-like aspects of nicotine withdrawal.

Amygdala↗
PubMed1977

[The importance of the "contingent negative variation" (CNV) for audiometry (author's transl)].

Previous proofs of "central processes" in hearing were based on the determination of the late "auditory evoked potentials" (AEP's: 50--300 ms) in EEG. The appearance of AEP's in different sleep stages raises the question, if the AEP actually conscious hearing. Since the discovery of the "Contingent Negative Variation" (CNV), as a potential depending on conscious and cognitive factors, an appropriate "instrument" is available to solve this problem. Using the CNV-technique three proofs of central auditory perception are described and discussed: a) "The objective proof of the perception of pure-tones", useful for threshold determination, test in the case of simulation and central hearing disorders. b) "The objective proof of the perception of stimulus-changes", useful for exact determination of differential thresholds for frequencies or intensities. c) "The objective speech audiometry", proof of speech comprehension, useful in case of aphasia and simulation.

Auditory Perception↗
PubMed1991

[Spontaneous seizures improve severe dementia conditions. Dementia contra depression-induced pseudodementia and electric stimulation therapy of depressed patients with epilepsy].

On the basis of two case reports, the differential diagnostic difficulties between pseudodementia conditioned by depression and genuine dementia are discussed and the particular conditions present in connection with electroconvulsive therapy (ECT) in patients with reduced seizure thresholds. Differentiation between genuine and dementia conditioned by depression must be made mainly on the basis of the clinical picture, particularly the temporal course of the condition. Every condition of dementia involves the possibility of an underlying depression and antidepressive treatment should be offered on wide indications. In this connection, ECT treatment may be the most effective and mildest form of therapy. Epilepsy does not counterindicate ECT treatment which, on the other hand, has an anticonvulsive effect. Occurrence of spontaneous seizures in connection with ECT treatment does not necessarily indicate withdrawal of treatment which may be continued provided certain prerequisites are observed.

Aged↗
PubMed2005

Fundus perimetry with the Micro Perimeter 1 in normal individuals: comparison with conventional threshold perimetry.

PURPOSE: To determine differential light threshold values obtained with the Micro Perimeter 1 (MP1) in healthy volunteers and to correlate them with conventional automated static threshold perimetry using the Octopus 101 Perimeter. DESIGN: Prospective comparative observational study. PARTICIPANTS: Thirty healthy volunteers. METHODS: In 30 eyes of 30 healthy volunteers, static threshold perimetry was performed with the MP1 Micro Perimeter (Nidek Inc., Italy) and the Octopus 101 (Haag-Streit AG, Switzerland) in the same eye in random order. MAIN OUTCOME MEASURES: Differential light threshold values obtained with the MP1 and their difference to differential light threshold values with the Octopus. Differential light sensitivity was compared for 21 matching points in a rectangular test grid using similar examination settings with Goldmann III stimuli, stimulus presentation time of 100 msec, and white background illumination (1.27 cd/m2). RESULTS: For the 21 matching locations, mean differential light thresholds with the MP 1 and the Octopus were 15.5+/-0.8 decibels (dB) (range, 13.0-17.1) and 30.2+/-1.2 dB (range, 27.7-32.0), respectively. On the average, the Octopus showed higher threshold values for all test locations than the MP1. The mean difference between both examinations was 14.6+/-1.8 dB for all locations and 14.8+/-1.7 dB excluding the test locations at the blind spot. With a considerably high grade of variation according to the test point location, the difference between the 2 devices varied from 11.4 to 18.3 dB, showing a vertical asymmetry with a larger difference in the lower part of the visual field. Linear regression of the perimetric results for each test point location, excluding the area of the blind spot and the lower line of the test grid, showed significant correlation (r = 0.56; P = 0.036). CONCLUSIONS: The results show that the MP1 provides reproducible threshold values with a systematic difference compared with standard Octopus perimetry of approximately 15 dB. With a larger difference in the lower part of the visual field, differential light sensitivity values in microperimetry with the MP1 are comparable to the threshold values obtained with the Octopus 101 using a correction factor of 11.4 to 18.3 dB according to stimulus location.

Adult↗
PubMed1999

Differences between activation thresholds for platelet P-selectin glycoprotein IIb-IIIa expression and their clinical implications.

Increased platelet reactivity is a descriptor of the risk of cardiovascular events in healthy men and in patients with overt coronary artery disease. We sought to determine if differential thresholds exist for activation of platelets with respect to alpha-granule degranulation and fibrinogen binding in healthy volunteers and in patients with acute coronary syndromes. We also sought to characterize the effect of aspirin on activation. Platelet activation was assessed with flow cytometry in whole blood anticoagulated with corn trypsin inhibitor and incubated with fluorescein isothiocyanate conjugated fibrinogen (to define activation of glycoprotein IIb-IIIa), a phycoerythrin conjugated antibody to P-selectin (a marker of alpha-granule degranulation), and selected concentrations of adenosine diphosphate (ADP) or thrombin receptor agonist peptide. ADP-induced fibrinogen binding was found to be a low threshold activation event (40% of platelets bound fibrinogen in response to 0.2 microM ADP). Alpha-granule degranulation was a higher threshold event (33% of platelets expressed P-selectin in response to 1.0 microM ADP). Intra- and interindividual variability were most apparent with low concentrations of agonist (0.2 microM ADP). Patients with acute coronary syndromes (on aspirin) had significantly increased P-selectin expression in response to ADP compared with healthy subjects (on aspirin), but no difference in ADP-induced fibrinogen binding was observed. Daily ingestion of 325 mg of aspirin had no effect on either P-selectin expression or fibrinogen binding in healthy subjects. Analysis of platelet reactivity with flow cytometry characterizes activation with respect to specific components of the process and should facilitate development and optimal titration of antiplatelet therapy.

Aspirin↗
PubMed2006

Selective ion filtering by digital thresholding: a method to unwind complex ESI-mass spectra and eliminate signals from low molecular weight chemical noise.

In this work, we present a simple method by which to preferentially detect either high molecular weight or low molecular weight ions generated by electrospray ionization. This approach, termed selective ion filtering by digital thresholding (SIFdT) is demonstrated on a commercial ESI-TOF instrument that employs a fast digitizer coupled to a microchannel plate detector. The digital representation of each individual scan is digitally filtered prior to spectral coaddition. As larger, more highly charged ions induce a more intense response than low molecular weight singly charged species, a digital threshold can be set that precludes the detection of singly charged species yet permits the efficient detection of larger, more highly charged species. In this work, we demonstrate the applicability of this approach to eliminate low molecular weight chemical noise in ESI-TOF spectra of oligonucleotide and protein ions, demonstrate improved dynamic range for analyte solutions containing high levels of low MW constituents, and show that spectra acquired at different digital thresholds can be subtracted to yield spectra of low molecular weight constituents with improved mass measurement accuracies. A notional scheme is presented in which an alternative digitization approach is employed using multiple differentially thresholded data streams to allow improved internal mass calibration and higher resolution ion partitioning.

Humans↗
PubMed2000

Neohesperidin dihydrochalcone is not a taste enhancer in aqueous sucrose solutions.

Neohesperidin dihydrochalcone (NHDC) is an intensive sweetener, obtained by alkaline hydrogenation of neohesperidin. In this investigation a supposed taste enhancing effect of this substance was tested. A three-step procedure was used. In the first experiment, using a pool of 31 subjects, NHDC and sucrose detection thresholds were measured. In the second experiment, psychophysical functions for both tastants were determined. Then, 15 participants closest to the group threshold who, in addition, had produced monotonic psychophysical taste functions were selected to participate in the next two experiments. In the third experiment, taste enhancement was tested. Three psychophysical sucrose functions were constructed, one with a near-threshold amount of NHDC added to each of seven sucrose concentrations, one with a near-threshold amount of sucrose added (control 1) and one without any addition (control 2). No difference was found between the NHDC-enriched sucrose function and the sucrose-enriched sucrose function. Finally, in experiment 4, differential threshold functions were constructed with either NHDC or sucrose added. Neither the overall shape of the functions nor a comparison of the points of subjective equality showed enhancement. It was concluded that weak NHDC does not enhance the taste of aqueous sucrose solutions.

Adolescent↗