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PubMed1988

Effect of auditory masking on lingual vibrotactile thresholds and magnitude estimation scaling responses.

Auditory masking has become a frequently employed part of the procedure used in vibrotactile research. Research investigating the effect of auditory masking on lingual vibrotactile thresholds of sensitivity has shown that there is little difference between lingual vibrotactile thresholds under masking and no masking conditions. The purpose of the present study was to extend the investigation of the effect of auditory masking to include lingual vibrotactile suprathreshold scaling responses. 20 young adult subjects of mean age 19 yr. completed lingual vibrotactile-threshold and magnitude-estimation scaling tasks under conditions of bilateral auditory masking and no masking. Similar lingual vibrotactile-threshold values and magnitude-estimation power-function exponents for the conditions of masking and no masking were noted.

Acoustic Stimulation↗
PubMed1992

Behaviour of delayed evoked otoacoustic emission under forward masking paradigm.

The behaviour of delayed evoked otoacoustic emission (DEOAE) has been studied in normally hearing adults under a conventional forward-masking paradigm, and subjective measurements were carried out additionally for comparison. The clicks served as signals and the noise bursts were used as masker. In different experimental sets, signal and masker intensity, masker duration, and the interval between masker and maskee were altered. At masker levels corresponding to the subjective post-masking threshold of the clicks, the DEOAE was unaffected, i.e. had no noticeable alteration, compared with click stimulation without masking. Even at higher masker levels the inaudible clicks elicited clearly discernible DEOAEs. The forward-masking detection threshold of DEOAE ('DEOAE post-masking threshold') was reached at masker levels approximately 35 dB above the subjective post-masking threshold. The gap between subjective and DEOAE post-masking threshold vis-à-vis the masker level was also evident at different masker durations and different time intervals between masker and maskee. Central neural and peripheral receptor mechanisms are suggested to be the constituents of the masking phenomenon. The neural mechanism is involved at low masker levels. The receptor mechanism effectively joins the neural one at masker levels exceeding the threshold of psychoacoustic masking. The progressive increase in the number of auditory units from the periphery to the centre in the hearing system, linked with an increase in inhibition, can help to explain these effects.

Acoustic Stimulation↗
PubMed2004

Warning: attending to a mask may be hazardous to your perception.

Object substitution is a type of backward masking that occurs when a mask appears during visual search for a target. We tested the hypothesis that object substitution is an overwriting process triggered by attentional selection of the mask. Impeding attentional selection of a mask by embedding it in an array of distractors eliminated object substitution. Similarly, object substitution did not occur when the mask appeared in advance of the target and, therefore, could not capture attention during search for the target. However, masking was reinstated when the mask was revealed from background contours at the moment of target onset and could therefore capture attention during search. These observations demonstrate that attentional selection of the mask is a necessary step in this type of masking and suggest that object substitution is active overwriting of unattended information triggered by selection of other visual information at a nearby location.

Attention↗
PubMed1999

Visual masking plays two roles in the attentional blink.

When two targets are displayed in rapid visual sequence and masked by trailing patterns, identification accuracy is nearly perfect for the first target but follows a U-shaped pattern over temporal lag for the second target. Three experiments examined the role of visual masking in this attentional blink. Experiment 1 compared integration and interruption masks for both targets. Although either mask was effective in producing the blink when applied to the first target, only the interruption mask was effective when applied to the second target. Experiment 2 showed that integration masking of the second target was ineffective over a wide range of accuracy levels. Combining the two forms of masking in Experiment 3 confirmed the dissociation: A combined mask and only a main effect on accuracy for the first target, whereas it produced a qualitatively different pattern over temporal lag for the second target. These results suggest that representations of the target are substituted in consciousness by that of the interruption mask when visual attention is preoccupied.

Adolescent↗
PubMed1989

Evaluation of mouth-to-mask ventilation devices.

UNLABELLED: A number of mouth-to-mask ventilation devices have become commercially available in the past several years. In this study, we compared the volumes delivered by eight of these devices to the volumes delivered by mouth-to-mouth ventilation. METHOD: Fourteen respiratory care practitioners participated in the study. Ventilation was delivered to an adult resuscitation manikin. Each subject ventilated the manikin using mouth-to-mouth technique and each of the following mouth-to-mask devices: Boehringer EVA, Hospitak, Hudson, Intertech Safe Response, Laerdal Pocket Mask, Life Design Systems (LDS), Respironics SealEasy, and Vital Signs. Evaluation periods of 1 minute were used, minute ventilation and respiratory rate were measured, and tidal volume was calculated. RESULTS: There was a significant difference between the volumes delivered by the masks (p less than 0.001). The volumes delivered by each mask were less than mouth-to-mouth volumes (p less than 0.05 in each case). The mean +/- SD mouth-to-mouth volume was 1.04 +/- 0.32 L. The mean +/- SD volumes for each of the devices was 0.54 +/- 0.34 L for the EVA, 0.77 +/- 0.21 L for the Hospitak, 0.51 +/- 0.26 L for the Hudson, 0.81 +/- 0.35 L for the Safe Response, 0.65 +/- 0.25 L for the Pocket Mask, 0.82 +/- 0.27 L for the LDS, 0.79 +/- 0.32 L for the SealEasy, and 0.76 +/- 0.21 L for the Vital Signs. CONCLUSIONS: We found considerable variability between the volumes delivered with commercially available mouth-to-mask ventilation devices. Although the volumes delivered during mouth-to-mask technique were less than those delivered with mouth-to-mouth technique, the volumes delivered by some of the mouth-to-mask devices were large enough to allow them to be substituted for mouth-to-mouth technique.

Equipment Design↗
PubMed2001

Asymmetric object substitution masking.

Object substitution masking occurs when a lateral mask persists beyond the duration of a target, reflecting reentrant processes in vision (V. Di Lollo, J. Enns, & R. Rensink, 2000). The authors studied whether substitution masking is location specific and whether it is symmetric around the target. A brief circular display of letters was presented along with a mask that designated the target. The mask was centered on the target or 1.1 degrees to the central or to the peripheral side. Substitution masking was found even when the target and the mask were at different locations. It was asymmetric and stronger when the mask was to the peripheral side of the target than to the central side. Asymmetric substitution was observed using various masks. It could not be explained by retina acuity gradients and was not attenuated by focused attention. The authors propose that target selection triggers an asymmetric inhibitory surround that is stronger toward the central side of the target.

Adolescent↗
PubMed2005

[The application of the same frequency tone masking test in forensic identification].

OBJECTIVE: To investigate the relationship between minimum contralateral masking level (MCML) and pure tone threshold of the masking ears by the same frequency tone masking test. METHODS: The pure tone thresholds of 30 subjects (60 ears) were measured by pure tone audiometry and MCML was obtained by means of the same frequency tone masking test. RESULTS: When the stimulus was at the threshold of masked ears, the differences between MCML and pure tone threshold of masking ears were among 0-30 dBHL. 82.4 percent of results showed the differences not higher than 10 dBHL, 97.1 percent of results showed the differences not higher than 15 dBHL. When the stimulus was at 10 dBHL above the threshold of masked ears, the differences between MCML and pure tone threshold of masking ears were among 0-35 dBHL. 90.5 percent of results showed the differences not higher than 25 dBHL, 98.1 percent of results showed the differences not higher than 30 dBHL. CONCLUSION: The real thresholds can be deduced correctly by the same frequency tone masking test.

Acoustic Stimulation↗
PubMed1978

Tuning curves and masking functions of auditory-nerve fibers in cat.

Single units of the auditory nerve are maximally sensitive to a given frequency, the so-called characteristic frequency (CF). Tuning curves (functions relating the "threshold" for such units to the frequency of a sinusoidal stimulus) have inspired psychophysical measurements of masked thresholds in humans. At low levels, the results bear a striking resemblance to neural tuning curves, suggesting that a small, homogeneous group of units determine the so-called psychophysical tuning curves. This paper describes physiological measurements modeled after the psychophysical forward-masking paradigm. A masking tone was used to reduce the response in auditory-nerve fibers elicited by a probe tone that followed the masker. The level of the masking tone was varied to maintain a criterion level of responding to the probe. Plotting level of the masker as a function of its frequency yields a fiber-masking function. For low probe-tone levels, fiber-masking functions of low CF fibers and the tips of functions from high CF fibers were similar in shape to tuning curves obtained with single tone bursts. The fiber-masking function depends upon the response criterion and upon the level, duration, and frequency of the probe. Varying the level of the probe can also alter the shape of the fiber-masking function. These results have implications for interpreting psychophysical masking functions.

Acoustic Stimulation↗
PubMed1983

The choice of a masking agent in the histochemical staining of metals.

The masking effects of standard masking agents (aminopolycarboxylic acids, carboxylic acids and phosphates) have been investigated in both test-tube experiments and tissue sections in order to ascertain the factors which must be considered when choosing a masking agent for the histochemical staining of a metal. The masking effects in vitro were determined by spectrophotometry through the complexing of the dye Chrome Azurol S with aluminium, beryllium, and iron at pH 5 and 7. The effects were also examined by staining metal-containing tissue sections in a Chrome Azurol S masking agent system at the same pH values. In many cases, the masking effects observed in sections did not agree with those obtained in the test-tube experiments. This means that the published values of stability constants are not a sufficient guide for choosing a suitable masking agent for the staining of metals. The discrepancy is mainly attributable to the presence of protein in a solid state when metals are stained in sections. Therefore, in the future, consideration should be given to a metal-protein or masking agent-protein interaction using a model compound such as a chelate resin. The polyphosphates are among the most useful masking agents for metal staining in acidic solutions from a practical standpoint.

Animals↗
PubMed1985

Internal interactions within the human circadian system: the masking effect.

In the realm of human circadian rhythms, the masking effect is defined as the change in the course of deep body temperature induced by changes in the degree of physical activity, or by the alteration between sleep and wake. This effect is particularly obvious during internal desynchronization where the rhythms of deep body temperature, and the sleep-wake sleep cycle - i.e. one of the masking factors - run with different periods. Every sleep onset is accompanied by a rapid drop, and wake onset by a rapid rise in deep body temperature, each one with an overshoot of about 50% of the steady state variations. When rhythms are calculated, with the dominant temperature period as the screening period, exclusively from data obtained during sleep episodes, on the one hand, and from those obtained exclusively during wake, on the other, two average cycles emerge: the 'sleep temperature curve' and the 'wake temperature curve'. Both run in parallel but are separated by the 'masking effect'. As derived from many experiments, the mean masking effect amounts to 0.28 +/- 0.06 degree C. The masking effect also depends to some extent on the phase of the temperature rhythm; it is larger than average around the temperature maximum and during the descending phase of the temperature cycle, where the alertness commonly is highest and the probability to sleep, in general, and the REM sleep propensity, in particular, are smaller than average. This also can be interpreted to indicate that the sleep temperature curve is phase advanced relative to the wake temperature curve; this, on the average, by 0.9 +/- 0.3 h. If the individually determined amount of masking is added to the temperature data obtained during sleep, or subtracted from the temperature data obtained during wake, a temperature curve emerges that can be thought of as being 'purified' of the masking effect. Analyses of this artificial curve allow estimation of that part of the internal interactions uninfluenced by the masking effect. On the average, about half of the amount of interaction between the rhythm of sleep-wake and that of deep body temperature is explained by the masking effect, whereas the other half is 'oscillatory interaction'. Both types of interaction are inherent and inseparable parts of the circadian clock mechanism, as can be deduced from model considerations.

Body Temperature↗
PubMed2005

White-coat and masked hypertension in children: association with target-organ damage.

White-coat hypertension (WCH) and masked hypertension have been associated with increased cardiovascular risk in adults. In the current study, we investigated: (a) the prevalence of WCH and masked hypertension in pediatric patients and (b) the association of these conditions with target organ damage. A total of 85 children underwent office blood pressure measurements, 24-h ambulatory blood pressure monitoring, echocardiography and ultrasonography of the carotid arteries. Subjects with both office and ambulatory normotension or hypertension were characterized as confirmed normotensives or hypertensives, respectively; WCH was defined as office hypertension with ambulatory normotension and masked hypertension as office normotension and ambulatory hypertension. WCH was found in 12.9% and masked hypertension in 9.4% of the subjects. WCH was significantly more prevalent in obese subjects, while masked hypertension was only present in non-obese ones. Confirmed and masked hypertensives had significantly higher left ventricular mass index than confirmed normotensives (34.0+/-5.8 g/m(2.7), 31.9+/-2.9 g/m(2.7) and 25.3+/-5.6 g/m(2.7), respectively, P<0.05). White-coat hypertensives tended to have higher left ventricular mass index than confirmed normotensives, but the difference was not statistically significant (27.8+/-5.1 g/m(2.7) versus 25.3+/-5.6 g/m(2.7)). No significant differences were found in the intima-media thickness of the carotid arteries between confirmed normotensives, white-coat hypertensives, masked hypertensives and confirmed hypertensives. WCH and masked hypertension are common conditions in children. Confirmed and masked hypertension in pediatric patients are accompanied by increased left ventricular mass index.

Adolescent↗
PubMed1991

Mechanical masking of neurosensory pathways at the calf-teat interface: endocrine, reproductive and lactational features of the suckled anestrous cow.

A mammary somatosensory mask was employed in suckled anestrous beef cows to attenuate signals that were hypothesized to play a direct regulatory role in postpartum anestrus. Cows (n = 20) were randomly assigned to one of three treatment groups on Days 15 to 20 postcalving. The three treatments were: 1) masked (n = 7); 2) suckled (negative control, n = 6); and 3) weaned (positive control, n = 7). Four layers of surgical glove latex were used to cover the teats and ventro-lateral prominence of the udder of masked cows with a nonhardening, nontoxic adhesive (Day 0). Masks were designed to prevent direct contact between the skin of the teat/udder and the mouth of the calf and to allow normal suckling and milk removal. Masks were left in place for 7 d, with calves in the weaned group removed to a remote location for 7 d. Calves in the suckled group were allowed ad libitum suckling. Calves in the masked group tended (P < 0.1) to suckle longer than calves in the suckled control group (11.3 +/- 1.3 vs. 7.8 +/- 1.3 min/suckle) posttreatment; however, suckling frequency and calf weight gains did not differ due to treatment. Weaned cows exhibited a four-fold increase (P < 0.01) in the frequency of luteinizing hormone (LH) pulses on Day 2 relative to suckled and masked cows. The percentage of animals ovulating within 12 d after treatment differed (P < 0.05) and was 100, 50 and 0% for weaned, suckled and masked cows, respectively. Presence of the latex mask allowed essentially normal suckling and lactation, but failed to attenuate (and may have potentiated) the negative effects of suckling on secretory patterns of LH, ovulation and estrus.

Journal Article↗
PubMed2005

In clinical practice, masked hypertension is as common as isolated clinic hypertension: predominance of younger men.

BACKGROUND: The prevalence and implications of masked hypertension are under investigation. The aim of this study was to investigate the clinical characteristics associated with masked hypertension in subjects referred for ambulatory blood pressure (BP) monitoring. METHODS: We analyzed 1494 BP monitoring sessions. A subject was considered to have isolated clinic hypertension if clinic BP was > or =140/90 mmHg and awake BP was <135/85 mmHg. Masked hypertension was diagnosed when clinic BP was <140/90 mmHg and awake BP was > or =135/85 mmHg. RESULTS: Of 1494 individuals, 16% had normal BP, 11% had isolated clinic hypertension, 61% had hypertension, and 11% had masked hypertension. Subjects with masked hypertension were younger and more likely to be male than subjects with isolated clinic hypertension, and their awake heart rate was significantly higher. A negative correlation was found between the awake-clinic systolic BP difference and clinic systolic BP (r = -0.7, P < .0001). The reproducibility of the masking phenomenon was comparable to that of other variables. CONCLUSIONS: In a group of consecutive subjects referred for ambulatory BP monitoring, masked hypertension was found to be as common as isolated clinic hypertension. Masking was correlated with male sex, young age, and higher awake heart rate, thus suggesting a causal relationship with greater daytime physical activity. The linear association of the masking and the white-coat effects to clinic BP suggests that regression toward the mean may partially explain these phenomena.

Adult↗
PubMed2001

Cloning of MASK, a novel member of the mammalian germinal center kinase III subfamily, with apoptosis-inducing properties.

We have cloned a novel human GCK family kinase that has been designated as MASK (Mst3 and SOK1-related kinase). MASK is widely expressed and encodes a protein of 416 amino acid residues, with an N-terminal kinase domain and a unique C-terminal region. Like other GCK-III subfamily kinases, MASK does not activate any mitogen-activated protein kinase pathways. Wild type MASK, but not a form lacking the C terminus, exhibits homophilic binding in the yeast two-hybrid system and in coimmunoprecipitation experiments. Additionally, deletion of this C-terminal region of MASK leads to an increased kinase activity toward itself as well as toward an exogenous substrate, myelin basic protein. A potential caspase 3 cleavage site (DESDS) is present in the C-terminal region of MASK, and we show that MASK is cleaved in vitro by caspase 3. Finally, wild type and C-terminally truncated forms of MASK can both induce apoptosis upon overexpression in mammalian cells that is abrogated by CrmA, suggesting involvement of MASK in the apoptotic machinery in mammalian cells.

Amino Acid Motifs↗
PubMed2005

An ERP indicator of processing relevant gestalts in masked priming.

Briefly presented arrows, made indistinguishable by masks that contain arrows, inversely prime responses to following visible arrows. This inverse effect might reflect general regularities of masked priming or be either due to the task-relevant elements of the mask or to special features of arrows. Here we report a slow negative EEG potential recorded from the scalp above the visual cortex, which is evoked by masks that contain arrows. Even being evoked when arrows masks were presented in isolation, this "Nd-mask" appeared to be an obligatory response. Yet Nd-mask was enhanced when primes and targets were arrows and was reduced in the other cases, and even reversed its polarity with appropriate control stimuli. These findings provide support both for the special status of arrows and for the notion of mask relevance. Nd-mask might be one instance of negative EEG potentials evoked by stimuli with familiar gestalts.

Adult↗
PubMed2002

Tissue counter analysis of histologic sections of melanoma: influence of mask size and shape, feature selection, statistical methods and tissue preparation.

BACKGROUND: Tissue counter analysis is an image analysis tool designed for the detection of structures in complex images at the macroscopic or microscopic scale. As a basic principle, small square or circular measuring masks are randomly placed across the image and image analysis parameters are obtained for each mask. Based on learning sets, statistical classification procedures are generated which facilitate an automated classification of new data sets. OBJECTIVE: To evaluate the influence of the size and shape of the measuring masks as well as the importance of feature selection, statistical procedures and technical preparation of slides on the performance of tissue counter analysis in microscopic images. As main quality measure of the final classification procedure, the percentage of elements that were correctly classified was used. STUDY DESIGN: HE-stained slides of 25 primary cutaneous melanomas were evaluated by tissue counter analysis for the recognition of melanoma elements (section area occupied by tumour cells) in contrast to other tissue elements and background elements. Circular and square measuring masks, various subsets of image analysis features and classification and regression trees compared with linear discriminant analysis as statistical alternatives were used. The percentage of elements that were correctly classified by the various classification procedures was assessed. In order to evaluate the applicability to slides obtained from different laboratories, the best procedure was automatically applied in a test set of another 50 cases of primary melanoma derived from the same laboratory as the learning set and two test sets of 20 cases each derived from two different laboratories, and the measurements of melanoma area in these cases were compared with conventional assessment of vertical tumour thickness. RESULTS: Square measuring masks were slightly superior to circular masks, and larger masks (64 or 128 pixels in diameter) were superior to smaller masks (8 to 32 pixels in diameter). As far as the subsets of image analysis features were concerned, colour features were superior to densitometric and Haralick texture features. Statistical moments of the grey level distribution were of least significance. CART (classification and regression tree) analysis turned out to be superior to linear discriminant analysis. In the best setting, 95% of melanoma tissue elements were correctly recognized. Automated measurement of melanoma area in the independent test sets yielded a correlation of r=0.846 with vertical tumour thickness (p<0.001), similar to the relationship reported for manual measurements. The test sets obtained from different laboratories yielded comparable results. CONCLUSIONS: Large, square measuring masks, colour features and CART analysis provide a useful setting for the automated measurement of melanoma tissue in tissue counter analysis, which can also be used for slides derived from different laboratories.

Adult↗
PubMed1983

Simultaneous masking interactions between chromatic and luminance gratings.

Simultaneous masking using test and mask gratings composed of isochromatic luminance variations and isoluminant chromatic variations was studied. Masking of chromatic gratings by chromatic gratings shows less spatial-frequency specificity than does masking of luminance gratings by luminance gratings. Luminance gratings mask chromatic gratings of identical space-average luminance and chromaticity little and only when the spatial frequencies of the test and mask gratings are similar. Chromatic gratings, however, profoundly mask luminance gratings with a degree of spatial-frequency specificity akin to that of luminance-luminance masking. The insensitivity of the luminance-color masking results to the relative phase of the chromatic and luminance gratings indicates that the observed asymmetry is not due to local interactions.

Color Perception↗
PubMedDate not supplied

Football face-mask removal with a cordless screwdriver on helmets used for at least one season of play.

CONTEXT: The Inter-Association Task Force for the Appropriate Care of the Spine-Injured Athlete recommends leaving a football player's helmet in place and removing the face mask from the helmet "as quickly as possible and with as little movement of the head and neck as possible." Although 2 groups have studied face-mask removal from new equipment, to our knowledge no researchers have investigated equipment that has been previously used. A full season of play may have a significant effect on football equipment and its associated hardware. Countless impacts, weather, playing surfaces, sweat, and other unforeseen or unknown variables might make the face-mask removal process more difficult on equipment that has been used. OBJECTIVE: To determine the percentage of face masks that we could unscrew, with a cordless screwdriver, from football helmets used for a full season. DESIGN: Cross-sectional. SETTING: Three New England high schools. PATIENTS OR OTHER PARTICIPANTS: All football helmets used at 3 local high schools were tested (n = 222, mean games, 9.7 +/- 1.2; mean practice weeks, 13.7 +/- 1.2). INTERVENTION(S): Each helmet was secured to a board, and a cordless screwdriver was used to attempt to remove all 4 screws attaching the face mask to the helmet. MAIN OUTCOME MEASURE(S): Variables included overall success or failure, time required for face-mask removal, and success by screw location. Data were analyzed with chi2, analysis of variance, and Tamhane post hoc tests. RESULTS: Overall, 832 (94%) of 885 screws were unscrewed, and 183 (82.4%) of 222 face masks were removed. Mean removal time was 26.9 +/- 5.83 seconds. Face-mask removal success was significantly different between school 1 (24 [52.2%] of 46) and schools 2 (84 [91.3%] of 92) and 3 (75 [89.3%] of 84; F(2,219) = 24.608; P < .001). The removal success rate was significantly higher at top screws (98%) than at screws adjacent to ear holes (90%) (P < .001). CONCLUSIONS: Based on our results and previous findings that demonstrated quicker access time and reduced head movement associated with the use of the screwdriver compared with cutting tools, the former may be a good tool for face-mask removal. However, an appropriate cutting tool must be immediately available should the screwdriver fail. Helmet hardware adjacent to ear holes was more vulnerable to failure, perhaps because it is protected by less padding than the top hardware. Possible causes of the higher failure rate at school 1 are the use of hardware materials subject to rust and corrosion and differences in helmet brand; these areas warrant future research and rules consideration.

Journal Article↗