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PubMed2002

Attend to it now or lose it forever: selective attention, metacontrast masking, and object substitution.

Metacontrast masking occurs when the visibility of a brief target stimulus is decreased by the subsequent appearance of another nearby visual stimulus. Early explanations of the phenomenon involved low-level mechanisms, but subsequent studies have suggested a role for selective attention. The results of three experiments presented here extend previous findings to the metacontrast paradigm. It is shown that the strength of metacontrast masking increases with the number of distractor items in a display, decreases when the target location is validly but not invalidly precued, and is eliminated when search for the target is efficient (pop-out search) but not when search is inefficient (serial search). A connection between metacontrast masking and object substitution masking is considered.

Attention↗
PubMed2001

Orthographic and phonological computation in visual word recognition: evidence from backward masking in Hebrew.

We employed the backward masking paradigm to map the early computation involved in the perception of printed words in Hebrew. By independently manipulating orthographic and phonological overlap between targets and masks, we examined whether orthographic and phonological structure imposes late or early constraints on lexical access. The results demonstrated that the probability of reinstating a masked target depended on both the orthographic and the phonological overlap between the target and the mask. However, whereas phonemic structure seems to constrain lexical access only at short exposure durations, orthographic overlap also exerts its influence at longer durations.

Adult↗
PubMed1991

Sources of auditory masking in infants: distraction effects.

Previous work has demonstrated that infants' thresholds for a pure tone are elevated by a masker more than would be predicted from their critical bandwidths. The present studies explored the nature of this additional masking. In Experiment 1, detection thresholds of 6-month-old infants and of adults for a 1-kHz tone were estimated under three conditions: in quiet, in the presence of a 4- to 10-kHz bandpass noise at 40 dB SPL, and in the presence of the same noise at 50 dB SPL. The noise was gated on at the beginning of each trial. Adult thresholds were the same in all three conditions, indicating that little or no sensory masking took place in the presence of the noise. Infant thresholds were about 10 dB higher in the presence of the noise. We term this effect distraction masking. In Experiment 2, the effect of gating the noise on at trial onset was examined. Thresholds for the same tone were estimated in quiet and in the presence of the band-pass noise at 40 dB SPL, but the noise was presented continuously during the session. Under these conditions, distraction masking was still observed for infants. These findings suggest that a masker can have nonsensory effects on infants' performance in a psychoacoustic task.

Attention↗
PubMed1991

Informational masking and auditory attention.

Informational masking is broadly defined as a degradation of auditory detection or discrimination of a signal embedded in a context of other similar sounds; it is not related to energetic masking caused by physical interactions between signal and masker. In this paper, we report a systematic release from informational masking of a target tone in a nine-tone rapid auditory sequence as the target is increasingly isolated in frequency or intensity from the remaining sequence components. Improved target-tone frequency difference limens as isolation increases are interpreted as a reflection of increasingly focused auditory attention. The change from diffuse to highly focused attention is gradual over the frequency and intensity ranges examined, with each 1-dB increment in target intensity relative to the remaining components producing performance improvements equivalent to those produced by a 2% increase in frequency isolation. The results are modeled as bands of attention in the frequency and intensity domains. For attention directed by frequency isolation, there is a strong correspondence with auditory filters predicted by the power spectrum model of masking. These data also support the existence of an attention band of intensity, with a bandwidth of about 5-7 dB at the moderate levels used in this experiment.

Adult↗
PubMed1999

The roles of location specificity and masking mechanisms in the attentional blink.

In a series of four experiments using rapid serial visual presentations of two target letters embedded in numeral distractors, with different numbers of display positions and with or without masking, we show that (1) the nonmonotonic, U-shaped attentional blink (AB) function, which occurs when all items are presented at the same display location, is eliminated in favor of a monotonic function when targets and distractors are presented randomly dispersed over four or nine adjacent positions; (2) the AB monotonicity is maintained with the spatially distributed presentation even when backward masks are used in all possible stimulus positions and when the location of the next item in sequence is predictable; and (3) the U-shaped AB is not due to position-specific forward or backward masking effects occurring at early levels of visual processing. We tentatively conclude that the U-shaped AB is primarily a function of the interruption of late visual processing produced when the item following the first target occurs at the same location. In order for the AB to severely disrupt performance, the item following the first target must be presented at the same location as the target so that it can serve both as a distractor and as a mask interrupting of interfering with subsequent visual processing.

Adult↗
PubMed1989

Partial masking in electrocutaneous sensation: a model for sensation matching, with applications to loudness recruitment.

A model for partial masking and other threshold-elevation effects is presented in the context of a sensation-matching paradigm. The model is applied to an electrocutaneous experiment in which the subjects adjusted stimulus intensity on the right-hand fingertip to match sensation levels of standard stimuli presented to the left fingertip. Concurrent mechanical stimulation on the right fingertip masked sensation magnitude in a way consistent with the model. Similarities between this tactile masking effect and analogous auditory phenomena are explored. When applied to loudness matching, the model describes the general shape of loudness contours and it shows that the steep slopes observed in auditory masking and "recruitment" can be a consequence of a threshold shift alone, without a supranormal growth in loudness. The model also shows that a small response bias can distort plots of sensation matching, leading to the suggestion that some varieties of loudness recruitment may not have a sensory basis.

Discrimination Learning↗
PubMed2000

The left-to-right nature of the masked onset priming effect in naming.

Two experiments were performed to investigate the nature of the masked onset priming effect in naming, that is, the facilitation in naming latency that is observed when a target shares the initial grapheme/phoneme with a masked prime. Experiment 1 showed that the effect is not due to position-independent letter priming, since the naming of nonword targets preceded by masked primes was facilitated only if the prime shared the initial letter with the target (e.g., suf-SIB) and not if the prime shared the final letter (e.g., mub-SIB). Experiment 2 showed that the effect reflects the sharing of onsets rather than the initial letter, since facilitation due to an overlap of the initial letter was observed only for the simple onset target (e.g., penny-PASTE) for which the letter corresponded to the onset, and not for complex onset targets (e.g., bingo-BLISS). It is argued that the serial nature of the masked onset priming effect is best interpreted as the planning of articulation, rather than as the computation of phonology from orthography.

Cognition↗
PubMed1991

Apparent reversals of a rotating mask: a new demonstration of cognition in perception.

A mask of a face rotated about its vertical axis of symmetry can appear to oscillate rather than rotate. Do stimulus features (e.g., shape) or cognitive factors (e.g., differential familiarity with convex and concave views of faces) explain this new illusion? In Experiment 1, differential familiarity was varied across stimuli by using familiar and unfamiliar objects rotating at 4 rpm and within stimuli by showing the objects upright and inverted. True motion was seen more with unfamiliar objects than with familiar objects and more with an inverted mask than with an upright mask. The results of Experiment 2, which was done with static views, suggest that the upright and inverted masks present similar structure to the visual system. In Experiment 3, the objects were shown rotating at 8 rpm; the results are similar to those of Experiment 1. These experiments favor a differential familiarity account of this illusory motion. Cognitive constraints on perceived motion and perceived rigidity are discussed.

Cognition↗
PubMed1995

Tactile selective attention and temporal masking.

The presentation of a nontarget stimulus to one fingerpad interferes with the identification of a target stimulus presented to a second fingerpad. This interference has been attributed to a failure of selective attention and, more specifically, to the nontarget's eliciting a competing response. In the present study, the temporal interval between the target and nontarget was varied to determine the extent to which a nontarget primes a competing response. The results showed more interference when the nontarget was presented after the target than when it was presented before the target. Although still consistent with a response-competition explanation, this result offered no support for a priming explanation. The function relating the amount of interference to the temporal separation between the target and nontarget was similar to the functions obtained in studies of temporal masking, and this prompted a second experiment in which temporal masking was examined. These results, obtained with stimuli presented to the same fingerpad, indicate that response competition may be a major factor in temporal masking and that similar processes are involved in temporal masking and selective attention.

Adult↗
PubMed2006

Comparison of armoured laryngeal mask airway with endotracheal tube for adenotonsillectomy.

OBJECTIVE: To assess the reliability of armoured laryngeal mask airway for adenotonsillectomy and to compare the haemodynamic changes during anaesthesia with those of endotracheal tube. DESIGN: A prospective comparative study. PLACE AND DURATION OF STUDY: Services Hospital Lahore/ Services Institute of Medical Sciences from April to September 2003. PATIENTS AND METHODS: A total of 100 patients undergoing adenotonsillectomy between ages 10-35 years and ASA I status were enrolled for the study. Two groups with 50 patients in each group were formed. Group I patients underwent surgery with armoured laryngeal mask airway while group II underwent surgery with endotracheal intubation. Baseline heart rate, systolic blood pressure and diastolic blood pressure were noted pre-operatively, one minute after insertion and every five minutes after induction in both the groups. A change in all these haemodynamic parameters from the baseline was noted. The effect of Boyle Davis Gag and adequacy of surgical access were also noted. Occurrence of cough, laryngospasm and stridor were noted at the time of recovery in both the groups. RESULTS: Baseline variables in both groups were identical. Surgical access was adequate in 48/50 patients in group I while it was adequate in 49/50 patients in group II. The frequencies of cough, laryngeal spasm and stridor were lower in group I. In group I, there was insignificant change from baseline in heart rate, systolic and diastolic blood pressure at one, five and ten minutes after induction. In group II, significant change from baseline was observed in heart rate (p < 0.01), systolic blood pressure (p < 0.05) and diastolic blood pressure (p < 0.05). CONCLUSIONS: Armoured laryngeal mask is reliable for performing adenotonsillectomies. It provides adequate surgical access for adenotonsillectomy. It is also associated with lower occurrence of cough, bronchospasm and stridor at recovery. Use of armoured laryngeal mask is associated with fewer haemodynamic changes compared with those of endotracheal tube.

Adenoidectomy↗
PubMed1999

[Use of the intubating laryngeal mask for tracheal intubation in three patients with difficult airways].

The intubating laryngeal mask has a potential role for tracheal intubation in patients with difficult airways, but there have been only reports of the techniques of blind tracheal intubation through the intubating laryngeal mask. The success rate of blind intubation at the first attempt may be merely 50-60% even in patients with normal airways. We report the use of the intubating laryngeal mask for tracheal intubation in three patients with difficult airways, in whom a tube was easily inserted through the laryngeal mask into the trachea either blindly, using a fiberoptic bronchoscope or using a lighted stylet.

Adult↗
PubMed1999

[Properties of the derived cochlear action potential during tonal forward masking in guinea pigs].

In awake preimplanted guinea pigs, characteristics of auditory nerve and derived action potentials were investigated using a pure-tone forward masking paradigm. Auditory nerve action potentials are recorded from round window. The derived potential was obtained by subtracting the masked action potential from unmasked response. The results show that the derived potential is more sensitive to changes in auditory nerve action potential during masking than widely used indicator of masking--the decrement in auditory nerve action potential. Derived response reflects the response changes both in amplitude and waveform induced by masker. The differences between the auditory nerve and derived action potentials suggest that the amplitude and time changes in the derived potential give a more detailed information on the characteristics of the auditory nerve fibers responses.

Action Potentials↗
PubMedDate not supplied

[Laryngeal mask vs tracheal intubation during mechanical ventilation in pediatric anesthesia].

AIM: The aim of this study was to evaluate and compare the parameters for mechanical respiration in pediatric patients undergoing controlled ventilation with a laryngeal mask (LM) and an uncuffed orotracheal tube. METHODS: The study examined 100 ASA 1 patients undergoing general anesthesia with myoresolution and mechanical ventilation using a Servo Ventilator 900 (constant flow, 25% insufflation, 10% teleinspiratory pause, tidal volume 10 ml/kg). All patients were divided into 2 groups matched for age and weight. An uncuffed orotracheal tube was used in one group (Group T) and a laryngeal mask (LM) in the other (Group M). The following parameters were measured: peak and pause pressure in the respiratory passage (Paw), total inspiratory resistance (R tot), compliance (C) and air loss expressed as a fraction of inspired volume (Vi-Ve/Vi). The statistical analysis of results was performed using Student's "t"-test and the level of significance was p < 0.05. RESULTS: Peak pressures were comparable in the two groups and were lower than the pressure needed to open the lower esophageal sphincter. These values could be further reduced by the extension of insufflation time achieved by abolishing the teleinspiratory pause included in the study to measure air resistances and compliance. Air losses were also similar in both groups, being respectively 13 and 11%. This means that environmental pollution using LM was not greater than with the uncuffed tube and confirms that, even with the latter, the protection of the airways cannot be regarded as absolute. Total inspiratory resistances were respectively 16.1 cm H2O/l/sec in group T and 15.1 cm H2O/l/sec in group M. This occurred in spite of the fact that the latter showed an in vitro capacity to oppose lower resistances compared to the corresponding tubes given that it was shorter with a larger diameter. Studies using the mechanical model did not include the laryngeal mask--larynx connection which may cause increased resistance owing to the variable position of the epiglottis, although this cannot be identified clinically. CONCLUSIONS: The laryngeal mask allows mechanical ventilation with low pressure in the respiratory passage and reduced air losses compared to the uncuffed tracheal tube. The risk of gastroesophageal insufflation is therefore minimal and artificial ventilation is reliable, if correctly performed. Lower levels of inspiratory resistance might be an advantage in spontaneous breathing owing to the consequent reduction of respiratory effort, but they do not appear to be significantly lower than with the tracheal tube.

Adolescent↗
PubMed2000

[Effect of gargling the throat with Panaxylocaine as a lubricant for the laryngeal mask airway].

We used Panaxylocaine as a suitable lubricant with gargling before insertion of laryngeal mask for twenty preoperative breast cancer patients. Patients were divided into two groups; Control group (N = 10) received water-based lidocaine gel just before insertion of laryngeal mask, and Panaxylocaine group (N = 10) received Panaxylocaine as a premedication for breast cancer operation. Compared to water-based lidocaine gel, Panaxylocaine was more effective for oral discomfort after insertion of laryngeal mask. But there was no difference between two groups about oral paresthesia. We conclude that Panaxylocaine is a good premedication before insertion of laryngeal mask preventing oral and pharyngeal complications.

Anesthetics, Local↗
PubMed2000

[Visual backward masking in schizophrenia].

Visual backward masking is used to investigate the function of attention as the initial stage of visual information processing by measuring the shortest stimulus presentation time for accurate cognition. This is achieved by applying a masking stimulus after target stimulus presentation. In this study, 50 controls and 50 schizophrenics (paranoid type) were examined by this method. In the control group, 1) there was a significant decline in correct answers to the target stimulus with age; and 2) there was a significant increase in correct answers with repetition. However, in the schizophrenic group, 1) there was a significantly lower number of correct answers in all age groups compared to that in the controls, along with a greater decline in correct answers with age; and 2) there was no increase in correct answers with repetition; 3) good performers among the schizophrenic patients were young with a short duration of illness and on a low dose of medication. Poor performers showed numerous positive and negative psychotic symptoms, were not on medication, or had positive findings on CTscan; furthermore, 4) longitudinal re-examination of the same subjects showed that even when psychotic symptoms improved and the subjects were able to return to society, their ability to give correct answers remained significantly different compared to that of the controls. These findings seem to reflect the trait-dependence aspect of schizophrenia (paranoid type) on a visual backward masking task. Furthermore, visual backward masking seems to be a convenient and useful measure for this aspect of attention and its trait-dependence in schizophrenia.

Adult↗
PubMed2001

[Fastrach laryngeal mask, sevoflurane and remifentanil: an anesthetic alternative for the myasthenic patient].

A 46-year-old myasthenic man diagnosed two months earlier and experiencing nocturnal dyspnea was scheduled for transsternal thymectomy. The patient was premedicated with midazolam in the operating room. Anesthetic induction and maintenance were with inhaled sevoflurane and an intravenous infusion of remifentanil, with no need for neuromuscular relaxants. Airway management was achieved by inserting a Fastrach laryngeal mask (LM-Fastrach), through which an endotracheal tube could be inserted easily. The tube was withdrawn through the mask at the end of surgery and the mask was removed in the operating room 6 minutes later. Anesthesia in patients with myasthenia gravis is one of the greatest challenges in clinical anesthesiology. The interest of this case lies mainly in that the anesthetic technique chosen allows neuromuscular relaxants to be avoided. Moreover, airway access through the Fastrach laryngeal mask is highly useful for transsternal thymectomy of the patient with myasthenia gravis, providing immobility and adequate hemodynamic stability during sternotomy as well as facilitating safe and rapid postanesthetic recovery.

Anesthetics, Inhalation↗
PubMed2001

[A new bite block for laryngeal mask].

We devised a new bite block made of a used connector of anesthesia machine (ACOMA medical industry CO., LTD.) for laryngeal mask. Fitness for laryngeal mask and strength against patient's biting are the key for its use. Cutting lengthwise the connector (the outside diameter 22 mm, inside diameter 15-19 mm, 55 mm in length) we made a bite block for laryngeal mask. We studied the strength of a new bite block experimentally and recognized its ability to bear the human biting. We conclude a new bite block for laryngeal mask is clinically useful and can be used during anesthesia for its fitness and safety.

Evaluation Studies as Topic↗
PubMed2002

Experience in the use of laryngeal mask airway in Tikur Anbessa Hospital.

The study was designed to make an initial observation in the use of laryngeal mask airway with the only existing drug, i.e., ketamine, for induction of anaesthesia. Its effective use should be determined to maintain patients airway following induction of anaesthesia with the only available drug for induction than the drug that is commonly used for its insertion. There were a total of 64 patients included in the study in a period of seven weeks with a male to a female ratio of 1 to 1.33 and age range of 6-70 years. A successful insertion following induction of anaesthesia with ketamine was achieved in 40 patients at the 1st attempt and in 23 patients at the 2nd attempt. Successful insertion of laryngeal mask airway was considered when it was achieved on the first attempt. Deepening anaesthesia with halothane/O2 by mask or adding small dose of relaxant (Succinylcholine) was necessary in 33 patients. The fact that a second insertion attempt was necessary and a large number of cases needed additional anaesthesia or relaxation indicated ketamine alone was not a good drug as an induction agent for laryngeal mask airway insertion.

Adolescent↗