Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Automatism”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 847 records · Page 47Linked to original sources
PubMed2001

[Automatic definition of prescription isodose for stereotaxic radiation of arteriovenous malformations].

PURPOSE: To evaluate dosimetric consequences generated by the automatic definition based on lesion coverage of prescription isodose. A clinical series of 124 arteriovenous malformations was analysed. Plan quality was quantified by the standard deviation of the differential dose volume histogram calculated in the lesion. MATERIAL AND METHODS: We define two quantitative protocols based on lesion coverage for the automatic definition of prescription isodose using a volumetric definition of coverage (90% of lesion volume), and an isodose-based definition proposed by RTOG (prescription isodose equals minimum isodose in the lesion divided by 0.9). RESULTS: We have evaluated the plans obtained for these two protocols, calculating several dose-volume indices. These indices are presented as a function of dose-volume histogram standard deviation in order to quantify the consequences of their variations for this representative series of plans. The margin our team tolerates is such that the sum of underdosed lesion and overdosed healthy tissues factors remains lower than one. Protocol based on volumetric coverage gives results situated within this margin. Protocol based on RTOG definition produces conformation indices that could be greater than 1. CONCLUSION: The absolute dose would be decided taking into account examined dose-volume indices and clinical data. A protocol for automatic definition of prescription isodose using volumetric lesion coverage seems to be more judiciously adapted to arteriovenous malformation conformal plans in stereotactic conditions because of variations observed in the overdosage of healthy tissues.

Algorithms↗
PubMedDate not supplied

The single-isocentre treatment of head and neck cancer: time gain using MLC and automatic set-up.

PURPOSE: In this manuscript, we studied the difference in the treatment time required to execute a single-isocentre three-field irradiation of the head and neck, using either tray-mounted cerrobend blocks or a multileaf collimator (MLC) for field shaping and automatic set-up. MATERIALS AND METHODS: A total of twenty consecutive, unselected patients (16 males, four females), were eligible for this study because the dose they were to received was 44 Gy (2 Gy/fraction) to the head, neck and supraclavicular regions. Patients were randomly allocated to one of two treatment groups. The first group (n = 11) was treated on a Philips SL-75 linear accelerator (SL-75), using 5 MV photons and tray-mounted cerrobend blocks. The second group (n = 9) was treated on a Philips SL-25 linear accelerator (SL-25-MLC), using 6 MV photons and a MLC. Patients of the second group were treated using the automatic set-up facility of the SL-25-MLC, without entering the treatment room between consecutive fields. RESULTS: Overall treatment time was significantly shorter on the SL-25-MLC than on the SL-75 (P < 0.0001). The difference in total treatment-execution time was in the range of 157 s per treatment session. The largest difference was observed in the set-up time. There was an average of a 125 s time gain per treatment day (P < 0.0001) in favour of the SL-25-MLC. CONCLUSIONS: Compared to tray-mounted cerrobend blocks, a MLC and automatic set-up results in a significant time advantage when a single isocentre technique is used to treat head and neck cancer.

Computer Simulation↗
PubMed2003

Development of the automatic mismatch response: from frontal positivity in kindergarten children to the mismatch negativity.

OBJECTIVE: The automatic event-related potential (ERP) response to auditory deviance typically consists of a frontocentral mismatch negativity (MMN), which has been shown to be quite stable during development. Whereas in some infant studies, positive frontal mismatch responses have been reported instead of a MMN; to date, such positivities have not been reported for older children. METHODS: Oddball sequences with small frequency and phoneme deviance (standard: 1000 Hz, 'ba'; larger deviance: 1060 Hz, 'ta'; smaller deviance: 1030 Hz, 'da') and short intervals (every 0.38 s) were presented to 6-7-year-old children and adults during 43-channel ERP recordings. RESULTS: Children showed a consistent frontal positive mismatch response with posterior negativity (179-207 ms), and adults a frontocentral MMN with mastoid positivity (129-199 ms). This map polarity reversal was reflected by significantly different 3D centroid distributions. Low-resolution electromagnetic tomography (LORETA) revealed temporal mismatch response sources for both age groups and conditions. CONCLUSIONS: Major developmental changes characterise the automatic mismatch response for the small deviances and short intervals used. Source localisation suggests that children's and adults' mismatch responses originated from superior temporal plane generators with similar localisation but opposite polarity. This indicates qualitatively different neurophysiological functioning of the automatic bi-temporal auditory change detectors in children and adults.

Acoustic Stimulation↗
PubMed2003

Myocardial tissue characterization in echocardiography with videodensitometry: evaluation of a new semi-automatic software applied on a population of hypertensive patients.

BACKGROUND: The interactions between ultrasound and cardiac muscle can be exploited to characterize abnormalities of myocardial structure in echocardiography. Two different methods permit an objective assessment of myocardial tissue characterization: analysis of the radiofrequency signal and videodensitometry. We conducted a videodensitometric study using a new practical semi-automatic software applied on digital signal to evaluate gray level cyclic variations of myocardial walls. The aim was to determine parameters differentiating healthy and hypertrophic myocardium in hypertensive patients. METHODS AND RESULTS: Echocardiographic examinations were performed on 30 hypertensives vs 30 healthy controls using second harmonic imaging. Dynamic 2D sequences were recorded in digital form and transferred on computer. Region of interest (ROI) was selected on interventricular septum (IVS) and the software automatically analyzed its systolo-diastolic displacements. ROI echo intensity and its cyclic variations were computed. Values were normalized with blood backscatter. The hypertensives had a smaller amplitude of gray level cyclic variation than did the controls (22+/-6 vs 27+/-11; P=0.02), and this parameter was correlated in multivariate analysis with left ventricle fractional shortening (P=0.032) and diastolic pressure(P=0.014). CONCLUSIONS: Magnitude of gray level cyclic variation of IVS can be studied easily with this new semi-automatic software, is altered in hypertensives and correlated with parameters of systolic function.

Cardiomegaly↗
PubMed1997

Application of automatic image segmentation to tibiae and vertebrae from ovariectomized rats.

Automatic contextual segmentation algorithms were developed to objectively identify bone compartments in pQCT images of tibiae, femora, and vertebrae. Principal advantages of this approach over existing techniques such as histomorphometry are as follows: (a) the algorithms can be implemented in a fast, uniform, nonsubjective manner across many images, allowing unbiased comparisons of therapeutic efficacy; (b) much larger volumes in the region of interest can be analyzed to derive true volumetric parameters for trabecular and cortical bone compartments; and (c) pQCT can be used to quantitate bone effects longitudinally in vivo. An automatic contextual segmentation algorithm was used to analyze over 600 scans of proximal tibiae, distal femora, and L-4 vertebrae from studies with ovariectomized rats. Accuracy and precision analyses were performed, and correlation to histomorphometry parameters showed that pQCT trabecular bone density correlates to Tb.N with r = 0.93, while BV/TV correlates to Tb.N with r = 0.95. In other words, pQCT correlates as well to histomorphometry as histomorphometry does to itself. We conclude that the developed automatic segmentation algorithm provides fast, precise, and objective quantitation of bone compartments that are highly correlated with histomorphometry measurements.

Absorptiometry, Photon↗
PubMed1999

Increased automatic spreading activation in healthy subjects with elevated scores in a scale assessing schizophrenic language disturbances.

BACKGROUND: Previous studies on semantic priming have suggested that schizophrenic patients with language disturbances demonstrate enhanced semantic and indirect semantic priming effects relative to controls. However, the interpretation of semantic priming studies in schizophrenic patients is obscured by methological problems and several artefacts (such as length of illness). We, therefore, used a psychometric high-risk approach to test whether healthy subjects reporting language disturbances resembling those of schizophrenics (as measured by the Frankfurt Complaint Questionnaire subscale 'language') display increased priming effects. In addition, the Schizotypal Personality Questionnaire was used to cover symptoms of schizotypal personality. Enhanced priming was expected to occur under conditions favouring automatic processes. METHODS: One hundred and sixty healthy subjects performed a lexical decision semantic priming task containing two different stimulus onset asynchronicities (200 ms and 700 ms) with two experimental conditions (semantic priming and indirect semantic priming) each. RESULTS: Analyses of variance revealed that the Frankfurt Complaint Questionnaire-' language' high scorers significantly differed from low scorers in three of the four priming conditions indicating increased automatic spreading activation. No significant results were obtained for the Schizotypal Personality Questionnaire total and subscales scores. CONCLUSIONS: In line with Maher and Spitzer it is suggested that increased automatic spreading activation underlies schizophrenia-typical language disturbances which in our study cannot be attributed to confounding variables such as different reaction time baselines, medication or length of illness. Finally, results confirm that the psychometric high-risk approach is an important tool for investigating issues relevant to schizophrenia.

Adult↗
PubMed1997

An automatic approach to the analysis, quantitation and review of perfusion and function from myocardial perfusion SPECT images.

UNLABELLED: We have developed a software suite that automatically selects, analyses, quantitates and displays all the key image data in a myocardial perfusion SPECT study. METHODS: The files automatically selected (upon specification of the patient name) are rest and stress projections, rest and stress short axis and gated short axis files, and all 'snapshot' files. The projection data sets are presented in cine mode for evaluation of patient motion, while the lung/heart ratio at rest and stress is calculated from regions of interest (ROIs) that are automatically derived and overlayed on the LAO 45 images. Left ventricular (LV) cavity volumes at rest and stress are calculated from the short axis data sets, and the related transient ischemic dilation (TID) ratio derived and displayed. Quantitative measurements of global (ejection fraction) and regional function parameters are performed from the gated short axis dataset. All algorithms use the C++, X-Windows and OSF-Motif standards. The overall suite executes in less than 1 minute on a SunSPARC5 with 32 Mb of RAM and no proprietary hardware. RESULTS: The software was validated on 144 patients (118 rest 201T1/post-stress 99mTc-sestamibi, 18 post-stress 99mTC-sestamibi, 8 rest 201Tl) acquired on a 90 degrees dual detector (ADAC Vertex, 91 patients) and a triple detector camera (Picker Prism 3000, 53 patients). Overall, the individual algorithms for the analysis of projection, short axis and gated short axis images were successful in 622/660 (94.2%) of the images. In 80.5% of the patients (73/91 + 43/53) all algorithms executed successfully, without significant difference in success rates for 201Tl versus 99mTc-sestamibi images. CONCLUSION: Our automated approach to myocardial perfusion SPECT analysis and review is highly successful, intrinsically reproducible, and can produce time and cost savings while improving accuracy in a clinical or teleradiology-type environment.

Algorithms↗
PubMed2001

Automatic mass-rearing of Amblyseius womersleyi (Acari: Phytoseiidae).

Using incorporated devices, Tetranychus urticae spider mites were rinsed from hydroponically-grown lima bean plants, collected, separated and blow-dried. This yielded a reliable and large volume of eggs and larvae, which were fed to Amblyseius womersleyi rearings on 15 x 5 cm2 polyethylene arenas. Of several feeding regimes tested, daily feeding of 10 mg T. urticae eggs and larvae resulted in the highest predator population levels. The best harvest period was between 15 and 27 days, when predator density exceeded 600 mites per arena. A preliminary automatic mass-rearing device was tested for A. womerslyi. This incorporated both rearing and harvesting procedures. A micro-feeder was developed to supply the required volume of spider mites and maize pollen (1:1 mixture) to the predators. A Bakelite rearing arena reduced the space requirements of a polyethylene arena, was more durable and an essential component in the automatic mass-rearing and harvesting. Mite harvesting is carried out through the use of a vacuum-head harvester. Supplements of (sterilized) spider mites, pollen, vermiculite and wheat bran are automatically added to the predators. The devices for harvesting, filling and packing are incorporated and synchronized and the entire system is controlled by a single slide-switch. The design and system can be expanded without changing the basic processes and program, for example to adopt it for other species of predaceous mites.

Animal Husbandry↗
PubMed2000

Beta,gamma-methylene ATP but not alpha,beta-methylene ATP mimics the inhibitory effect of ATP on ventricular automaticity.

The effects of alpha,beta- and beta,gamma-methylene ATP on ventricular automaticity induced by local injury in the right ventricle of rats pretreated with reserpine, were investigated and compared with the effects of ATP and adenosine. Beta,gamma-methylene ATP but not alpha,beta-methylene ATP mimicked the inhibitory effect of both ATP and adenosine on the spontaneous automaticity In low concentrations, adenosine was more effective than ATP. Alpha,beta-methylene ATP caused little or no effect on ventricular automaticity. The results suggest that the effect of ATP might depend on its hydrolysis into AMP/adenosine.

Adenosine Triphosphate↗
PubMed1985

How automatic are social judgments?

Do people infer personality dispositions automatically when they encode behavior? Tulving's encoding-specificity paradigm was adapted to test three operational indicants of automatism: absence of intention, of interference from other mental activity, and of awareness. Recruited for a digit-recall study, subjects read sentences describing actions during the retention interval of either an easy or a difficult digit recall task. Later, sentence recall was cued by (a) disposition cues, (b) strong semantic associates to the sentence actor, or (c) words representing the gist of the sentence, or (d) sentence recall was not cued. Awareness was measured immediately after the last sentence was read. Disposition-cued recall was higher than (b) or (d) and was unaffected by digit recall difficulty. Awareness of making dispositional inferences was only weakly correlated with disposition-cued recall. Results suggest that disposition inferences occurred at encoding, without intention, without interference by differential drain on processing capacity, and with little awareness. Thus, making dispositional inferences seems to be largely, but not entirely, automatic.

Awareness↗
PubMed1986

On the automatic activation of attitudes.

We hypothesized that attitudes characterized by a strong association between the attitude object and an evaluation of that object are capable of being activated from memory automatically upon mere presentation of the attitude object. We used a priming procedure to examine the extent to which the mere presentation of an attitude object would facilitate the latency with which subjects could indicate whether a subsequently presented target adjective had a positive or a negative connotation. Across three experiments, facilitation was observed on trials involving evaluatively congruent primes (attitude objects) and targets, provided that the attitude object possessed a strong evaluative association. In Experiments 1 and 2, preexperimentally strong and weak associations were identified via a measurement procedure. In Experiment 3, the strength of the object-evaluation association was manipulated. The results indicated that attitudes can be automatically activated and that the strength of the object-evaluation association determines the likelihood of such automatic activation. The implications of these findings for a variety of issues regarding attitudes--including their functional value, stability, effects on later behavior, and measurement--are discussed.

Arousal↗
PubMed1988

Context-dependent automatic processing in depression: accessibility of negative constructs with regard to self but not others.

The existence of automatic negative self-referential thought in depression was examined by using the concurrent memory load paradigm. Depressed and nondepressed subjects judged each of a series of depressed- and nondepressed-content adjectives as to its descriptiveness of the self or of the average other person. While making each judgment, some subjects held six digits in working memory, whereas the remaining subjects had no concurrent memory load. We found that the memory load manipulation resulted in a reliably smaller increase in depressed subjects' self-referential judgment latencies for depressed content than for nondepressed content, with the reverse being true of nondepressed subjects. For all subjects, however, the load effect on other-referential judgment latencies was smaller for nondepressed-content adjectives than for depressed-content adjectives. The results suggest an automatic, unintentional component in the depressed person's use of negative social constructs in self-perception but not in other-perception, indicating a context-dependent form of automatic processing.

Adult↗
PubMed1991

Automatic vigilance: the attention-grabbing power of negative social information.

One of the functions of automatic stimulus evaluation is to direct attention toward events that may have undesirable consequences for the perceiver's well-being. To test whether attentional resources are automatically directed away from an attended task to undesirable stimuli, Ss named the colors in which desirable and undesirable traits (e.g., honest, sadistic) appeared. Across 3 experiments, color-naming latencies were consistently longer for undesirable traits but did not differ within the desirable and undesirable categories. In Experiment 2, Ss also showed more incidental learning for undesirable traits, as predicted by the automatic vigilance (but not a perceptual defense) hypothesis. In Experiment 3, a diagnosticity (or base-rate) explanation of the vigilance effect was ruled out. The implications for deliberate processing in person perception and stereotyping are discussed.

Adult↗
PubMed1990

Abrupt visual onsets and selective attention: voluntary versus automatic allocation.

The hypothesis that abrupt visual onsets capture attention automatically, as suggested by Yantis and Jonides (1984) was tested in four experiments. A centrally located cue directed attention to one of several stimulus positions in preparation for the identification of a target letter embedded in an array of distractor letters. In all experiments, one stimulus (either the target or one of the distractors) had an abrupt onset; the remaining letters did not. The effectiveness of the cue was manipulated (varying either its duration or its predictive validity) to test whether abrupt onsets capture attention even when subjects are in a highly focused attentional state. Results showed that onsets do not necessarily capture attention in violation of an observer's intentions. A mechanism for partially automatic attentional capture by abrupt onset is proposed, and the diagnosticity of the intentionality criterion for automaticity is discussed.

Adult↗
PubMed1991

Automatic processing, code dissimilarity, and the efficiency of successive memory searches.

Two experiments examined the effects of automatic processing and code dissimilarity on the performance of successive memory searches through a single memory set having the same or different kinds of information (i.e., verbal and spatial). The results of both experiments showed that the total time to complete the successive searches was less when automatic processing was involved compared with when both searches required controlled processing. Performance of the successive searches improved substantially with practice. Both experiments also showed an asymmetrical temporal interference between the two searches. Aspects of the to-be-performed second search did not affect first-search reaction times (RTs), but performing the first search did affect the second-search RTs. The interfering effect of the first search was greatest when controlled processes that used the same code were required for both searches, whether the code was verbal or spatial. Several interpretations are offered for the interference generated by the first search. The joint effects of automatic processing and code dissimilarity are also discussed.

Adult↗
PubMed1992

Automatic and attentional priming in young and older adults: reevaluation of the two-process model.

Three experiments addressed the distinction between automatic and attentional mechanisms underlying semantic priming effects by factorially crossing prime-target relatedness, expectancy, and SOA in a task (pronunciation) that minimized postlexical checking processes. Also, possible age-related (young vs. older adults) differences in the automatic and attentional mechanisms were addressed. Across all experiments there was evidence of a Relatedness x Expectancy x SOA interaction, which is inconsistent with the notion of independent automatic and attentional mechanisms in semantic priming and the notion of a self-encapsulated modular lexicon. The results also indicated age-related differences in the build-up of the expectancy effect across SOAs when the prime was visually available for only 200 ms, independently of the prime-target SOA (Experiments 1 and 3), but not when the prime was visually available throughout the SOA (Experiment 2).

Adolescent↗
PubMed1982

Words, pictures, and priming: on semantic activation, conscious identification, and the automaticity of information processing.

We investigated the encoding mechanisms involved in the perceptual recognition of words and pictures. Latencies in naming word and picture targets were analyzed as a function of several characteristics of a preceding prime, including whether it was a word or a picture, its duration of exposure, the interval between the prime and target onset, and whether or not the prime was consciously identified and reported by the subject. Results indicated that a common semantic code is available that can represent the meaning of either a word or a picture. This semantic representation, however, appears to be more easily activated by picture primes than by word primes and seems to benefit the naming of picture targets more than the naming of word targets. Despite the advantage for pictures with respect to semantic activation, overall processing in the naming task was slower and more attention demanding for pictures than for words. Comparison of our data with data on classification, in which an opposite pattern occurs (overall processing appears to be slower and more attention demanding for words than for pictures), suggests that, on the average, pictures have faster and more automatic access to their meanings than to their names but that words have faster and more automatic access to their names than to their meanings. This conclusion concerning the relative ability of stimuli to activate different kinds of internal representations has implications for a theory of the basis and development of automaticity.

Discrimination Learning↗
PubMed2000

Not evidence for separable controlled and automatic influences in artificial grammar learning: comment on Higham, Vokey, and Pritchard (2000).

P. A. Higham, J. R. Vokey, and J. L. Pritchard (2000) claimed to provide evidence for separable controlled and automatic processes in artificial grammar learning. It is argued that their results are compatible with a single controlled influence: Participants might mistakenly identify more grammatical items than nongrammatical items as belonging to the other grammar, because the grammars are very similar to each other, and the nongrammatical items are relatively highly dissimilar. Participants' knowledge may be ambiguous, rather than automatic. It is further argued that even if Higham et al.'s data do support automatic effects, opposition logic, in this case, cannot be said to have succeeded where dissociation logic has failed, because it is used to address the issue of whether participants have conscious control over the knowledge they acquire, rather than whether they possess conscious awareness of that knowledge.

Humans↗