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PubMed2006

Automatic and intrinsic auditory "what" and "where" processing in humans revealed by electrical neuroimaging.

The auditory system includes 2 parallel functional pathways-one for treating sounds' identities and another for their spatial attributes (so-called "what" and "where" pathways). We examined the spatiotemporal mechanisms along auditory "what" and "where" pathways and whether they are automatically engaged in differentially processing spatial and pitch information of identical stimuli. Electrical neuroimaging of auditory evoked potentials (i.e., statistical analyses of waveforms, field strength, topographies, and source estimations) was applied to a passive "oddball" paradigm comprising 2 varieties of blocks of trials. On "what" blocks, band-pass-filtered noises varied in pitch, independently of perceived location. On "where" blocks, the identical stimuli varied in perceived location independently of pitch. Beginning 100 ms poststimulus, the electric field topography significantly differed between conditions, indicative of the automatic recruitment of distinct intracranial generators. A distributed linear inverse solution and statistical analysis thereof revealed activations within superior temporal cortex and prefrontal cortex bilaterally that were common for both conditions, as well as regions within the right temporoparietal cortices that were selective for the "where" condition. These findings support models of automatic and intrinsic parallel processing of auditory information, such that segregated processing of spatial and pitch features may be an organizing principle of auditory function.

Acoustic Stimulation↗
PubMed2006

Acute performance evaluation of a new ventricular automatic capture algorithm.

AIMS: This study evaluated the acute clinical performance of a new ventricular automatic capture algorithm developed to work with all lead types and pacing vectors. METHODS AND RESULTS: During regular pacemaker implant or replacement, AutoThreshold and manual threshold tests were performed in ventricular unipolar (UP) and bipolar (BP, if applicable) pacing using a customized external prototype INSIGNIA pacemaker. The success rate and accuracy of two different modes (commanded and ambulatory) of the automatic capture algorithm were used to evaluate the performance. Loss-of-capture events (two consecutive non-captured beats without backup pacing) were used to assess safety. Data of 53 patients (33 DDD/20 VVI) from four medical centres were analysed. Tested leads included 43 BP and 10 UP from nine manufacturers, and seven had electrodes with low polarization. The rate of successful commanded and ambulatory AutoThreshold tests was 96 and 94%, respectively, with an average absolute threshold difference compared with manual threshold of < 0.1 V at 0.4 ms (commanded 0.07 +/- 0.07 V and ambulatory 0.08 +/- 0.07 V). There was no significant difference in performance between UP/BP pacing, polarization, and lead type. No loss-of-capture event was observed. CONCLUSION: When successful, the ventricular automatic capture algorithm accurately determined pacing thresholds in either a UP or BP pacing configuration among all leads tested.

Adult↗
PubMed1993

Automatic and effortful memory processes in depressed persons.

Clinical lore has held that depression results in memory dysfunction, particularly in older adults. Some believe that memory loss due to depression is indistinguishable from an organic dementia and label such dysfunction pseudodementia. Previous literature has inconclusively supported the relation between depression and memory deficits. This research assessed three groups of subjects: (a) 30 depressed patients, (b) 20 psychiatric controls, and (c) 30 normal controls. Dependent memory tasks were designed to vary along the automatic and effortful memory encoding continuum defined by Hasher and Zacks (1979). Two tasks were designed to be effortful (free recall and paired associates) and two tasks were designed to be automatic (memory for frequency and location). Contrary to predictions, depression was not related to memory deficits. However, post-hoc analyses indicated that psychiatric hospitalization and psychotropic medication had a greater negative impact on memory than did depression. As predicted, age resulted in effortful encoding deficits whereas age resulted in minimal deficits on the automatic tasks. There was no evidence of an interaction between depression and age that would be consistent with the descriptive label of pseudodementia.

Adolescent↗
PubMed1989

Differences between handwritten and automatic blood pressure records.

Comparison of 46 handwritten and electromechanically generated blood pressure records revealed substantial differences between the recordings. The highest automated record pressures exceeded the highest pressures found in corresponding handwritten records. Similarly, the lowest pressures from automated records were lower than those from handwritten records. Seventeen records (37%) had at least three automatic blood pressure determinations with values substantially in excess of the most extreme values recorded by hand. No handwritten record contained a diastolic pressure above 110 mmHg. Discrepancies between handwritten and automatic records may arise from one or more causes. Among these are readings captured automatically but not observed by the anesthesiologist, faulty reconstruction of handwritten records from memory, and bias in favor of less controversial values.

Adult↗
PubMed2000

Automatic object identification: an fMRI study.

Boucart and Humphreys reported an automatic access to object identity when observers attend to a physical property of the form of an object (e.g. the orientation) but not to its colour. We sought evidence for automatic identification in a brain imaging study using fMRI. In an orientation decision task participants decided whether a picture was vertical or horizontal. In the colour decision task participants decided if a picture was blue or green. Activation of areas 18-19 was found for both color and orientation. Activation of the temporal area 37 occurred more frequently in the orientation than in the colour decision task. This result suggests that automatic identification activates the same brain area as overt processing of semantic information.

Adult↗
PubMed2002

Brain activity during non-automatic motor production of discrete multi-second intervals.

It has been suggested that the different patterns of brain activity observed during paced finger tapping and non-movement related timing tasks, with medial premotor cortex (supplementary motor cortex, pre and proper) and ipsilateral cerebellum dominating the former, and dorsolateral prefrontal cortex (DLPFC) the latter, might be related to differing motor demands. Since paced finger tapping often consists of automatic movement (requiring little overt attention), while non-motor timing is attentionally modulated, the difference could also be related to attentional processing. Here, we observed timing related activity in both medial premotor cortex and DLPFC, with non-timing related activity in other areas, including ipsilateral cerebellum, when subjects performed non-automatic motor timing. This result shows that, in time measurement, medial premotor activation is not specific to automatic movement, and DLPFC activity is not specific to non-motor tasks.

Adult↗
PubMed2000

Automatic and strategic processing of threat cues in patients with chronic pain: a modified stroop evaluation.

OBJECTIVE: The goal of this study was to clarify whether patients with chronic pain selectively attend to syndrome-specific (i.e., pain-related) information and, if so, to determine whether this occurs at the conscious (i.e., strategic) or unconscious (i.e., automatic) level. SETTING: This study was conducted at a tertiary care rehabilitation center. PATIENTS: Thirty-three patients with chronic back and/or neck pain and 33 healthy volunteers matched for age, sex, and education participated in this study. OUTCOME MEASURES: A computerized version of a modified Stroop color-naming task, with unmasked and masked conditions, was used to assess strategic and automatic information processing of words related to sensory pain, affect pain, physical threat, social threat, and neutral themes. RESULTS: A repeated-measures ANOVA indicated that patients with chronic pain but not healthy volunteers had delayed color-naming latencies to both sensory and affect pain words in the unmasked condition. Color-naming latency differences were not evident for other word types in the unmasked condition or for any word types in the masked condition. Correlational and regression analyses indicated that the delayed color-naming latencies to pain words in the unmasked condition observed for the chronic pain patients were, in part, associated with high pain-specific cognitive anxiety and interference and lower levels of anxiety sensitivity. CONCLUSIONS: Individuals with chronic pain selectively process pain-related cues at the strategic level but not at the automatic level. Implications of the findings and future research directions are discussed.

Adult↗
PubMed2002

Tracheal pressure control provides automatic and variable inspiratory pressure assist to decrease the imposed resistive work of breathing.

OBJECTIVE: To evaluate the operation of a continuous positive airway pressure system by using tracheal airway pressure (PT) as the control signal for system operation (i.e., tracheal pressure control). DESIGN: Repeated measures. SETTING: University research laboratory. SUBJECTS: Twelve anesthetized, spontaneously breathing swine. INTERVENTIONS: Subjects were intubated and connected to a tracheal pressure control system (5 cm H2O continuous positive airway pressure). Varying inspiratory flow demands and degrees of partial endotracheal tube occlusion (25%, 50%, and 75%) were studied. Tracheal pressure control was compared with a conventionally controlled system (pressure from breathing circuit Y-piece [PY] used as control signal) during endotracheal tube occlusion. MEASUREMENTS AND RESULTS: Imposed resistive work of breathing (work to spontaneously inhale through endotracheal tube and ventilator circuit), work by ventilation system assisting inhalation, PT, PY, tidal volume, and inspiratory flow demands were measured. As inspiratory flow demands increased (range, 0.2-2.3 L/sec), pressure assist increased automatically (range, 5-40 cm H2O) as well as work of breathing by ventilation system assisting inhalation (range, 0.2-2.5 J/L). Imposed resistive work of breathing was nullified at the lower and was negligible at the higher flow demands. During endotracheal tube occlusion with a conventionally controlled system, PY was unchanged, whereas PT decreased (up to -15 cm H2O) and imposed resistive work of breathing increased (up to 1.05 J/L). With tracheal pressure control, PY increased automatically (range, 8-52 cm H2O), whereas PT varied slightly (range, 2 to -4.6 cm H2O). Imposed resistive work of breathing was negligible (range, 0-0.2 J/L). Breathing circuit pressure (PY), not pulmonary airway pressure (PT), increased significantly during tracheal pressure control. CONCLUSIONS: Tracheal pressure control results in automatic and variable levels of pressure assist to decrease imposed resistive work of breathing under conditions of varying spontaneous inspiratory flow demands and endotracheal tube occlusion. Conventional systems are potentially flawed when PY is used as the control signal because they do not function in this manner and do not accurately assess pulmonary airway pressure.

Animals↗
PubMed1994

A method for automatic edge detection and volume computation of the left ventricle from ultrafast computed tomographic images.

RATIONALE AND OBJECTIVES: Detection of endocardial and epicardial borders of the left ventricle (LV) using various imaging modalities is time-consuming and prone to interpretive error. An automatic border detection algorithm is presented that is used with ultrafast computed tomographic images of the heart to compute cavity volumes. METHODS: The basal-level slice is identified, and the algorithm automatically detects the endocardial and epicardial borders of images from the basal to the apical levels. From these, the ventricular areas and chamber volumes are computed. The algorithm uses the Fuzzy Hough Transform, region-growing schemes, and optimal border-detection techniques. The cross-sectional areas and the chamber volumes computed with this technique were compared with those from manually traced images using canine hearts in vitro (n = 8) and studies in clinical patients (n = 27). RESULTS: Though the correlation was good (r = .88), the algorithm overestimated the LV epicardial area by 4.8 +/- 6.4 cm2, though this error was not statistically different from zero (P > .05). There was no difference in endocardial areas (r = .95, P > .05). The algorithm tended to underestimate the end-diastolic volume (r = .94) and the end-systolic volume (r = .94), although these errors were not statistically different from zero (P > .05). The algorithm tended to underestimate the ejection fraction (r = .80), although this error was not statistically different from zero (P > .05). CONCLUSIONS: Automatic detection of myocardial borders provides the clinician with a useful tool for calculating chamber volumes and ejection fractions. The algorithm, with the corrections suggested, provides an accurate estimation of areas and volumes. This algorithm may be useful for contour border identification with ultrasound, positron-emission tomography, magnetic resonance imaging, and other imaging modalities in the heart, as well as other structures.

Algorithms↗
PubMed2002

Automatic determination of aortic compliance with cine-magnetic resonance imaging: an application of fuzzy logic theory.

RATIONALE AND OBJECTIVES: Aortic compliance is defined as the relative change in aortic cross-sectional area divided by the change in arterial pressure. Magnetic resonance imaging (MRI) is a useful imaging modality for the noninvasive evaluation of aortic compliance. However, manual tracing of the aortic contour is subject to important interobserver variations. To estimate the aortic compliance from cine-MRI, a method based on fuzzy logic theory was elaborated. MATERIALS AND METHODS: Seven healthy volunteers and eight patients with Marfan syndrome were examined using an ECG gated cine-MRI sequence. The aorta was imaged in the transverse plane at the level of the pulmonary trunk. A method based on fuzzy logic was developed to automatically detect the aortic contour. RESULTS: Through our robust automatic contouring method, the calculation of aortic cross-sectional areas allows an estimation of the aortic compliance. CONCLUSION: The aortic compliance can be obtained from a fuzzy logic based automatic contouring method, thereby avoiding the important interobserver variation often associated with manual tracing.

Adolescent↗
PubMedDate not supplied

An automatic medical equipment test system.

Routine testing of medical instrumentation, for purposes of increased reliability and safety, is becoming a part of standard practice in hospitals. As many test procedures are standardized and large classes of similar equipment are often involved, a need exists for automatic testing. Automatic testing can result in increased standardization, saving of time, and reduction of tedium associated with repetitive work. A description is given of a system implementing principles of automatic testing. The system was designed, constructed, and deployed within a program of routine hospital equipment testing.

Electricity↗
PubMedDate not supplied

Automatic bone segmentation technique for CT angiographic studies.

PURPOSE: The purpose of this work was to develop and evaluate an automatic bone segmentation technique for CT angiographic studies. METHOD: An automatic bone segmentation scheme was developed and applied to 40 CT examinations. The results of the segmentation were evaluated subjectively by two radiologists. RESULTS: The bone segmentation was, on average, rated between excellent and good. Automatic segmentation required approximately 25 s/case. CONCLUSION: With this high quality technique, bone can be segmented easily and accurately and subsequently can be removed from CT data sets for further 3D visualization and analysis of various organs.

Angiography↗
PubMedDate not supplied

Increased automaticity and decreased inotropism of ouabain in dogs with furosemide-induced hypomagnesemia.

Unusual cardiac glycoside toxicity has been reported during hypomagnesemia, but the underlying cause remains unexplained. Therefore, we characterized and compared the effects of ouabain in normo- and hypomagnesemic dogs with and without induced heart block. Hypomagnesemia (30% reduction in plasma magnesium) was induced with 7 days of furosemide treatment (20 mg/kg, p.o.). Following potassium replacement, ouabain was infused at 1 microgram/kg/min and changes in contractile force (strain gauge), electrocardiogram (ECG), ventricular automaticity, and cardiac conduction were monitored. The inotropic response, sustained ventricular arrhythmias, and death all occurred at significantly lower ouabain doses in hypomagnesemic dogs with and without heart block. The changes observed were specifically related to magnesium depletion, and not to potassium depletion. Ouabain activity was not different from control when both magnesium and potassium were replaced. Ouabain-induced increases in automaticity were enhanced during hypomagnesemia and contributed to the development of sustained ventricular arrhythmias at lower ouabain doses. Although the inotropic response occurred at smaller ouabain doses in hypomagnesemia, the overall increase in contractile force was diminished. Thus, increased glycoside toxicity appears related to enhanced automaticity development at doses which are normally subtoxic.

Animals↗
PubMedDate not supplied

Effects of timolol on action potential characteristics and automaticity in barium-depolarized canine cardiac Purkinje fibers.

To evaluate timolol's ability to antagonize the "slow response" in cardiac tissues, isolated canine cardiac Purkinje fibers were exposed to 0.25 mM barium chloride to induce membrane depolarization, spontaneous automaticity, and slow response action potentials. The effects of timolol on action potential parameters and the cycle length of spontaneous automaticity were tested at concentrations of 10, 100, and 500 micrograms/ml. Timolol significantly depressed the action potential and slowed automaticity only at 100 and 500 micrograms/ml but not at 10 micrograms/ml. Since verapamil and nifedipine have been reported to completely suppress activity in this model at concentrations of 0.2-2.0 micrograms/ml, we conclude that timolol has little direct slow response blocking potency.

Action Potentials↗
PubMed1994

Action of ATP on ventricular automaticity.

ATP is an effective treatment of supraventricular tachycardia when the atrioventricular (AV) node is part of the reentrant circuit. However, the lower a pace-maker in the pacemaker hierarchy, the more sensitive it is to adenosine. Therefore, we investigated the effects of ATP on ventricular automaticity in in vivo and in vitro conditions. Wide and narrow QRS complex tachycardia in 46 patients was treated with 6, 12, and 18 mg ATP as sequential intravenous (i.v.) bolus. ATP terminated tachycardias in 67%. Bolus infusion ATP caused < or = 6.4-s asystole that was self-limited. Perfusion of isolated spontaneously beating guinea pig heart with 100 microM ATP completely suppressed ventricular automaticity. After ATP-infusion was discontinued, the first ventricular beat was evident after 3.1 +/- 0.9 s and sinus node activity recovered with a time constant of 3.0 +/- 1.1 s. Because sinus node and ventricular automaticity recovered within seconds after ATP infusion was discontinued in vitro, recovery in vivo is also likely to be determined by the short half-life (+1/2) of ATP.

Adenosine Triphosphate↗
PubMed1995

Comparative study of three automatic programs of left ventricular ejection fraction evaluation.

The aim of this study was to compare three automatic programs (P1, P2, P3) for evaluating radionuclide left ventricular ejection fraction (LVEF) and to emphasize the clinical consequences. Gated radionuclide ventriculography was performed in 73 subjects, 15 of whom were healthy and 58 of whom had experienced heart failure. All scintigraphic data were processed with the three programs. Good inter-observer, intra-observer and automatic-manual reproducibility were observed using each of the three programs. On the other hand, in the normal subjects, the three mean normal LVEF values were significantly different from each other (P1 = 77 +/- 5%, P2 = 63 +/- 7%, P3 = 68 +/- 8%; P < 0.0001) In the pathological patients, the values obtained with P2 were significantly different from those obtained using P1 and P3 (P1= 32 +/- 15%, P2 = 26 +/- 13%; P < 0.0001), Moreover, the linear regression studies between the three automatic programs were always significantly different from the identity line equation (y = x). This study shows that LVEF criteria for normality depend on the program used, and inter-program measurement of LVEF is poorly reproducible. Caution is recommended when comparing data obtained from different centres (or different computers), either in the follow-up of a given patient or in gathering results from patient groups.

Adult↗
PubMed1999

Reductions in finger doses for radiopharmaceutical dispensing afforded by a syringe shield and an automatic dose dispenser.

A gamma extremity monitoring system (GEMS) has been used to measure finger doses during radio-nuclide dispensing procedures. GEMS uses a small semi-conductor probe that can be attached to a finger from which a continuous read-out can be obtained that is related to dose rate. The pattern of dose accumulation can be analysed to allow doses received from individual operations within a procedure to be evaluated. GEMS has been used to compare the radiation dose reduction afforded by a syringe shield and an automatic dose dispenser. Dispensing procedures were simulated using 10% of the activity normally administered in order to avoid problems with detector saturation. Results show that the syringe shield and the automatic dose dispenser reduced finger doses by more than a factor of 10 for the procedures tested. The disadvantages of the automatic dispenser tested were a failure to transfer activity in 10% of cases and a longer time taken for the dispensing process. GEMS has the potential to facilitate greater optimization of finger doses through analysis of finger dose patterns.

Dispensatories as Topic↗
PubMed1987

Automatic infrared refractors--a comparative study.

In order to determine the performance of seven automatic infrared (IR) eye refractors, measurements have been conducted on a model eye as well as on normal subjects and patients under standardized conditions. Concerning the model eye, a range of measurement slightly smaller than specified and linearity errors have been detected on several instruments. Using a group of 55 normal ametropic subjects, the results of the automatic refraction were compared to the results of a conventional subjective examination. The spherical equivalent differed by less than 0.51 D in more than 80% of all cases on all instruments. The error of the cylinder power was smaller than 0.51 D in more than 90% of all cases. Larger errors were found on patients with intra ocular lenses, aphakic eyes, or scattering eye media. In each of these groups the automatic refraction was at times either impossible or yielded a wrong result.

Aphakia↗