[Age-dependent features of the readiness potential during performance of simple voluntary movement].
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Adult↗
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Results for “Contingent Negative Variation”
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[Electrophysiologic correlates of selective attention in children and adolescents at increased risk of schizophrenia].
Electrophysiological correlates of selective attention in children and adolescents at high risk for schizophrenia. As part of a research project on electrophysiological correlates of attention in young subjects at high genetic risk for schizophrenia, auditory event-related potentials (ERPs) associated with selective attention and automatic information processing were recorded in 21 adolescent (offspring of at least one parent with schizophrenia) and 21 control subjects matched for age, sex and socioeconomic status. The experimental task was a dichotic listening task, and accuracy of counting target pips served as a psychometric control variable. The results showed group-related differences in the ERPs, with a significant reduction being present in the high-risk group concerning the amplitude of the fronto-precentrally located negative difference (Nd) wave and the F3 component elicited by selectively attended stimuli. Comparison of individual matched pairs showed that reduced Nds, characterized 14/21 high-risk individuals and reduced P3s 16/21. Moreover, there were significant correlations between ERP reductions and psychometric deficit (counting accuracy). Finally, 13 latencies tended to be prolonged in the high-risk group. Mismatch negativity (MMN), an ERP correlate of automatic information processing, did not differ significantly in the two groups, although there was a marked reduction in amplitude in the high-risk group. The ERP alterations point to impaired selective attention in a considerable proportion of subjects at high genetic risk for schizophrenia.
Adolescent↗
[Use of jerk-locked back averaging for detecting the epileptiform discharge in a patient with supplementary motor seizure].
A 23-year-old, right handed women has suffered from supplementary motor seizures manifesting tonic followed by clonic contractions of the left foot, occasionally spreading to the left hand and trunk, since the age of 7 years. The mean frequency of seizures on admission was about 10 times per day. A brain MRI showed an abnormal intensity area about 3 cm in diameter in the right mesial frontal lobe involving the superior frontal and cingulate gyri. Six habitual seizures were recorded during long-term monitoring with digital EEG segments time-locked to the clonic contractions of the left foot, a negative spike was detected about 50 ms before the EMG onset at the midline fronto-central area slightly lateralized to the left. In the focal motor seizure arising from the mesial frontal lobe like in the present case, jerk-locked back averaging helps detecting the epileptiform activity which is otherwise undetectable.
Adult↗
[llocalization of grouping effect in overlapping tasks].
In certain kinds of overlapping tasks subjects have to respond to two stimuli (S1 and S2), presented in close succession with variable onset asynchrony (SOA), carrying out two different responses (R1 and R2). When responding to S1 is given priority over S2 processing, reaction time (RT) to the first stimulus is unaffected by SOA. However, sometimes subjects adopt, either spontaneously or because of instruction, a different processing strategy called grouping. In this case R1 is postponed until R2 has been determined too. The present study addresses the localization of the postponed processing stage by means of the lateralized readiness potential (LRP). One group of subjects was instructed to group responses and a second group was to give priority to S1 processing. The adherence to instructions was verified by subjects' reaction times. In case of grouping the interval between LRP onset and overt reaction increased proportionally to the postponement caused by SOA. In contrast, the interval between stimulus and LRP onset was unaffected by SOA. These findings speak against assumptions that grouping causes response activation postponement; rather, the corresponding reaction is already selected and activated prior to postponement.
Adult↗
[EEG correlates of different methods of information processing in response selection].
The lateralized readiness potential as a measure of response tendencies has become a relevant method in experimental psychology within the last decade. This measure delivers information about response preparation long before the overt response. Applying the method of measuring event-related lateralizations (ERL) of the EEG to posterior sites, correlates of processing of spatial information and of response selection have been found. The present study investigated the topographical distribution of asymmetries at the moment of response selection. Response selection was assumed to be reflected in a discrete peak of parietal asymmetries. At this time point two distinct topographies were found that might reflect two different types of information processing. If response selection was based on spatial information a parieto-occipital maximum was found. In contrast, if centrally presented symbolic stimuli were used for response selection, lateralizations were largest at central (motor areas) and at parietal sites.
Adult↗
Response variables and the CNV revisited.
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Adult↗
Mismatch negativity in dichotic listening: evidence for interhemispheric differences and multiple generators.
The characteristics of mismatch negativity (MMN) elicited by dichotic stimulation were examined using frequency-deviant stimuli presented to the right, to the left, or to both sides. The experiment was run twice, once using earphones and once using loudspeakers in free field. With both modes of stimulation, deviants presented in the left, right, or both ears, or tones that were switched between ears, elicited comparable MMNs, with a peak latency of about 180 ms. With earphones, the amplitude of the MMN was bigger at the frontal-lateral right hemisphere sites than at the homologous left-hemisphere sites for all deviance conditions. Scalp current density analysis revealed that deviance in the right side elicited bilaterally equivalent frontal current sinks and a trend towards stronger contralateral current sources at the mastoid sites. In contrast, left side deviance elicited frontal sinks and temporal current sources stronger over the right hemiscalp. These results are compatible with the multiple-generator model of MMN. The attention-related role of the MMN is discussed, suggesting comparable attention mechanisms for vision and audition.
Adult↗
On the automaticity of ipsilateral response activation in the Simon effect.
The effects on performance of unattended stimulus-response spatial relationships in choice reaction time tasks (i.e., the Simon effect) have been attributed to automatic activation of the response ipsilateral to stimulus location. We tested this assumption using the lateralized readiness potential (LRP). The response key labels changed randomly from trial to trial and were presented either 400 ms before (immediate-reaction trials) or 400 ms after (delayed-reaction trials) stimulus. The critical test for the automatic activation hypothesis was on delayed-reaction trials, in which LRP deflections were expected in the interval between stimulus and response-key labels. Contrary to this prediction, there were no LRP signs of response activation within that interval.
Adult↗
Automatic change detection: does the auditory system use representations of individual stimulus features or gestalts?
The effects of global and feature-specific probabilities of auditory stimuli were manipulated to determine their effects on the mismatch negativity (MMN) of the human event-related potential. The question of interest was whether the automatic comparison of stimuli indexed by the MMN was performed on representations of individual stimulus features or on gestalt representations of their combined attributes. The design of the study was such that both feature and gestalt representations could have been available to the comparator mechanism generating the MMN. The data were consistent with the interpretation that the MMN was generated following an analysis of stimulus features.
Adult↗
Variable cerebral responses to equally distinct deviance in four auditory dimensions: a mismatch negativity study.
In this study we compared the amplitude, latency, and spatial distribution of the mismatch negativity (MMN), elicited by tones deviating in either frequency, intensity, stimulus-onset asynchrony (SOA) or location, and assessed inter- and intra-subject variability. Cross-dimensional comparisons were facilitated by adjusting the magnitude of deviance individually, so that the detection rates were similar, both across dimensions (within subject) and across subjects (within dimension). Despite similar detection rates, the MMN elicited by frequency deviance was larger, and the MMN elicited by SOA deviance was earlier than the other types of MMN. The reliability of frequency-related MMN was better than that of the other types of MMN. The results highlight the problems of comparing MMN across dimensions, especially in clinical populations.
Adult↗
[Sensorimotor transpositions and cerebral activities evoked in aphasia].
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Acoustic Stimulation↗
Spontaneous sequence duplication within an open reading frame of the pneumococcal type 3 capsule locus causes high-frequency phase variation.
The molecular genetic basis of high-frequency serotype 3 capsule phase variation in Streptococcus pneumoniae (the pneumococcus) was investigated. Pneumococci were grown in sorbarod biofilms at 34 degrees C to mimic nasopharyngeal carriage. Different type 3 pneumococci commonly associated with invasive disease generated apparently random tandem duplications of 11-239 bp segments within the cap3A gene of the type 3 capsule locus. These duplications alone were found to be responsible for high-frequency capsule phase variation, in which (phase off) acapsular variants possessed duplications within cap3A, and (phase on) capsular revertants possessed wild-type cap3A genes, indicating the precise excision of the duplication. Additionally, the frequency of phase reversion (off to on) was found to exhibit a linear relationship between (log) frequency of reversion and (log) length of duplication. This apparently random duplication giving rise to phase variation is in stark contrast to the 'preprogrammed' contingency genes in many Gram-negative organisms that possess homopolymeric sequence repeats or motifs for site-specific recombination.
Bacterial Capsules↗
Family affiliation and prostitution in a cultural context: career onsets of Taiwanese prostitutes.
American researchers emphasize family disaffiliation resulting from negative experiences as an important career contingency for prostitutes. They suggest that cohesive families insulate daughters from entering prostitution, an implication that ignores cultural variations within the United States and worldwide. This study examined the nature of family affiliations among prostitutes in Taiwan, a nation characterized by strong family cohesion and widespread prostitution. The traditional status and role of daughters in Taiwanese families is described. A sample of 89 prostitutes were interviewed in Taipei. The majority had good or very good relationships with their parents before the women left home and continued to maintain such relationships. Only 10% mentioned negative family experiences as precipitating factors in the decision to enter prostitution. A typology of career onsets was drafted. About one third of the sample entered the occupation out of a sense of filial obligation toward their families of origin. Other precipitating factors included paying off their own or husbands' debts, upgrading their financial status, deriving other satisfactions from the life-style, escaping from difficulties with parents or husbands, and being victimized by force or fraud. Several social changes are likely to lessen the importance of filial obligation as a career contingency of prostitution. Speculations about the future of Taiwanese prostitution are offered.
Adolescent↗
Patch testing with nickel sulfate: comparison between 2 nickel sulfate preparations and 2 different test sites on the back.
Among patients routinely undergoing patch testing for suspected allergic contact dermatitis (ACD), nickel is the most frequently sensitizing hapten, with a clear predominance in the female population. However, some patients who report the appearance of dermatitis upon exposure to metal objects show negative patch test results to a nickel sulfate 5% pet. application. In some cases, a positive response to nickel can be observed simply by repeating the patch test. The objective of our study was to assess if, during routine patch testing, positive responses to nickel sulfate are missed owing to contingent problems, referring to application site, patch test execution or variations in skin reactivity. To this end, we applied 2 different patch test materials containing nickel sulfate 5% pet. to 3040 consecutive patients, undergoing patch testing for suspected allergic contact dermatitis, during the same session. The rôle of the test site was also investigated by applying the preparation on 2 different sites of the back in 30 patients. Of the whole, 612 patients (20%) showed positive patch test responses. The 2 nickel materials were almost equivalent: 78% of nickel-sensitive patients had positive reactions to both, whereas 11% showed a positive response to 1 preparation alone. No variations in patch test responses in relation to application site were observed. Our data show that false-negative patch test responses to nickel are frequent. The use of 2 different preparations during the same patch test session increases the response rate by 10%.
Adolescent↗
What makes extinction work: an analysis of procedural form and function.
We examined methods for determining how extinction should be applied to different functions of self-injurious behavior (SIB). Assessment data indicated that the head banging of 3 children with developmental disabilities was maintained by different reinforcement contingencies: One subject's SIB was positively reinforced by attention from adults, the 2nd subjects SIB was negatively reinforced by escape from educational tasks, and the 3rd subject's SIB appeared to be automatically reinforced or "self-stimulatory" in nature. Three functional variations of extinction--EXT (attention), EXT (escape), and EXT (sensory)--were evaluated, and each subject was exposed to at least two of these variations in reversal or multiple baseline designs. Reductions in SIB were observed only when implementation of "extinction" involved the discontinuation of reinforcement previously shown to be responsible for maintaining the behavior. These results highlight important differences among treatment techniques based on the same behavioral principle (extinction) when applied to topographically similar but functionally dissimilar responses, and further illustrate the practical implications of a functional analysis of behavior disorders for designing, selecting, and classifying therapeutic interventions.
Attention↗
Reversed circadian blood pressure rhythm preserves fetal growth in preeclamptic pregnancy.
OBJECTIVE: To determine the clinical trait of hypertension in pregnant women with a reversed circadian blood pressure (BP) rhythm. STUDY DESIGN: 24-h BP monitoring was performed in 56 hypertensive pregnant women, of whom 12 had a reversed systolic BP (SBP) rhythm (day/night mean BP ratio < 1.0). Clinical data, ultrasound fetometry and umbilical artery velocimetry were compared to that in women with a normal rhythm. Statistical analyses were performed with simple linear regression, Mann-Whitney U test, analysis of variance, contingency table analysis and Fisher's test. A two-tailed P value of < 0.05 was considered significant. RESULTS: In the reversed SBP group, the nighttime BP, fetal weight, albuminuria and S-urate were higher, and the BP variations smaller. The birthweight correlated negatively to the SBP day/night ratio. Higher SBP day/night ratios and larger BP variations were associated with an increased vascular resistance in the umbilical artery and an impaired growth. CONCLUSION: A reversed SBP rhythm was associated with a more severe degree of preeclampsia, but also with a smaller BP variation, maintenance of fetal growth, and higher birthweight. A sustained high nighttime BP preserved fetal growth. These novel observations challenge the opinion that a reversed circadian BP rhythm is merely an ominous sign.
Adolescent↗
E-wave and heart rate responses during anticipation of nonmotor events.
This study concentrated on three main questions: 1) can anticipatory late negative shift (expectancy wave, E-wave) be elicited in nonmotor S1-S2 paradigm, 2) is it sensitive to variation of emotional aspects of the task and 3) is there a connection between heart rate (HR) responses and E-wave. S1 was a letter row that was replaced tachistoscopically by another letter row (S2). The task of the subjects (n = 12) was to detect if the critical aspects of S2 were similar to S1. After their delayed response they received feedback of their performance. The emotional aspects of the task were varied by presenting aversive noise bursts at the end of the feedback period either always, contingently to their performance or not at all. A negative shift was present both before S2 and aversive noise (when presented). Varying the emotional aspects of the task had an effect on the amplitude of the E-wave. There was also a connection between E-wave and heart rate responses: heart rate response seemed to be a precondition for E-wave elicitation. The results support Simons's conclusion that nonmotor E-wave reflects specifically emotional anticipation.
Acoustic Stimulation↗
Genetic analysis of virulence factors of Mannheimia (Pasteurella) haemolytica A1.
Using a molecular genetic approach, the genes that code for the various virulence factors of Mannheimia haemolytica A1 have been cloned for detailed characterizations. These included analysis of the encoded proteins, their biological activities, secretion of the molecules from the bacterium as well as their use in a vaccine component. Two newly characterized antigens of M. haemolytica A1 have been identified. The first one is a TonB-dependent iron regulated outer-membrane receptor that is distinct from the transferrin binding proteins. The 84kDa Irp protein exhibits features including a TonB box and a 50 amino acid region that can adopt occluded beta-barrel structures similar to the "plug" domain of the Escherichia coli FhuA and FepA crystal structures. Homologues of Irp were identified by analysis of the genome sequences of a number of Gram negative mucosal pathogens, including Neisseria meningitidis and N. gonorrhoeae. The Neisserial irp genes were cloned by PCR and expressed the 84kDa protein as expected, demonstrating that they are functional genes. In addition to being regulated by iron and Fur, irp(Mh) undergoes phase variation by a slipped-strand mispairing mechanism and may represent a contingency locus for iron acquisition during an infection. Another locus that codes for a putative adhesin molecule has also been partially characterized. This putative adhesin protein is highly homologous with the high-molecular-weight adhesin proteins of non-piliated non-typable strains of Haemophilus influenzae (NTHi) including Hia, Hsf, HMW1, HMW2. Currently, we have cloned the DNA that codes for 2223 amino acids (225kDa) and is still missing the stop codon. It is anticipated that when complete, the protein could be close to 240kDa, similar to the molecular mass of Hsf. Though incomplete, analysis of the adhesin showed that it exhibits characteristics of autotransporter (AT) proteins. The role of this high-molecular-weight adhesin in infection is being investigated.
Adhesins, Bacterial↗