Effects of event probability and sequence on children with attention-deficit/hyperactivity, reading, and math disorder.

BACKGROUND: We investigated the impact of stimulus probability and sequence on performance and event-related potentials of 310 children classified into 12 combinations of attention-deficit/hyperactivity disorder (Not-attention-deficit/hyperactivity disorder, Inattentive and Combined subtypes) with presence/absence of reading disorder and math disorder. METHODS: Subjects pressed buttons to displays of the letters O and X, which were presented with probabilities of either .17/.83 or .50/.50. Greater response selection was required in the .17/.83 condition. RESULTS: Stimulus probability had comparable effects on all diagnostic groups. The extent of mismatch between a stimulus and preceding events elicited less systematic increases in errors, P3b latency, and P3b amplitude among both attention-deficit/hyperactivity disorder subtypes than controls. Mismatch with preceding trials more greatly reduced math disorder and reading disorder + math disorder children's speed in the Rare task and accuracy in both conditions. Math disorder and reading disorder + math disorder subjects also registered less the effects of alternations of the infrequent O on N2 amplitude and on P3b latency. CONCLUSIONS: Math disorder and reading disorder + math disorder youngsters' lower sensitivity to sequence irregularity in their event-related potentials along with greater disruption of performance suggest working memory deficits that adversely affected response selection. Comorbidity of attention-deficit/hyperactivity disorder and reading disorder did not affect the results.     

Effects of lithium on evoked potentials and performance during sustained attention

Two versions of the continuous performance test (CPT) differing in complexity were administered to 15 patients with bipolar affective disorder, manic type before and after treatment with lithium. Reaction time, performance accuracy, and the late positive component (LPC) of the event related potential evoked by the task were measured concurrently. Lithium treatment decreased errors of commission on both CPT tasks, although the difference was significant only for the simpler task. Reaction time was significantly increased by lithium treatment on the more difficult CPT task. LPC amplitude to the target stimulus on the difficult CPT was significiantly increased by lithium. The data are interpreted as consistent with an attention-enhancing effect of lithium, coupled with a general reduction in the tendency to respond to stimuli.     

Effects of induced psychological stress on click and rhythm in mitral valve prolapse

Our clinical observations suggested that anxiety accentuated the click in patients with mitral valve prolapse. In order to evaluate this systematically, a psychological stress was administered to 30 subjects-15 patients with click murmur syndrome and 15 normal controls. The phonocardiogram was recorded and the electrocardiogram were continuously monitored to assess the effects on arrhythmias.State Anxiety Inventory scores demonstrated an increase in anxiety during the psychological stress. A change in rhythm during psychological stress was noted in five of the 15 patients. No arrhythmias occurred in the control subjects during psychological stress (p < .025). Amplitude of the click increased during psychological stress in five of the 15 patients, in four associated with arrhythmia.The only patient with auscultatory-electrocardiographic variant developed frequent, multifocal ventricular ectopics with couplets during the psychological stress.Acute psychological stress exerts important effects on the rhythm and click only in some patients with mitral valve prolapse, and may provide a mechanism for intermittence of clicks and episodes of profound unexplained arrhythmias.     

Number processing in adolescents with prenatal alcohol exposure and ADHD: differences in the neurobehavioral phenotype

Background: Poor arithmetic performance is among the most sensitive outcomes associated with prenatal alcohol exposure and is also common in individuals with attention‐deficit hyperactivity disorder (ADHD). We hypothesized that prenatal alcohol exposure would be associated with deficits in the most fundamental aspects of number processing, representation of quantity and distance, whereas ADHD would be associated with deficits in calculation, the form of number processing most dependent on attention and memory. Methods: Two hundred and sixty‐two inner‐city, African American adolescents, who had been evaluated prospectively for prenatal alcohol exposure and ADHD, were assessed on a number‐processing test comprised of 7 subtests. Results: More heavily alcohol‐exposed adolescents were 4 times more likely to meet diagnostic criteria for ADHD than those whose mothers abstained from alcohol use during pregnancy. Two dimensions of number processing were identified in a factor analysis—magnitude comparison and calculation. As hypothesized, prenatal alcohol exposure was more strongly related to the former and ADHD to the latter. Moreover, the relation of prenatal alcohol to calculation was fully mediated by magnitude comparison, whereas the relation of ADHD to calculation was mediated by IQ but not by magnitude comparison. Conclusion: These data confirm findings from previous studies identifying arithmetic as a particularly sensitive developmental endpoint for prenatal alcohol exposure. Whereas difficulties with arithmetic in ADHD are mediated by domain‐general deficits in overall cognitive ability, fetal alcohol‐related arithmetic difficulties are mediated primarily by a specific deficit in the core quantity system involving the ability to mentally represent and manipulate number. These data suggest that different interventions are likely to be effective for remediating arithmetic problems in children with prenatal alcohol exposure than in non‐exposed children with ADHD.     

Individual Differences in Fear and Autonomic Reactions to Affective Stimulation

Klorman et al. (1975) found that mutilation-fearful persons reacted with heart rate speeding to mutilation slides and to neutral stimuli. The within-subject design of that study suggested that these paradoxical reactions to neutral slides may have been due to subjects' anticipation of phobic materials. In the present work, 84 female subjects, categorized by a standardized questionnaire as high or low in fear of mutilation, viewed one of three types of slides: 1) mutilated bodies; 2) persons and objects in incongruous or humorous poses; or 3) standard photographs of persons, objects, and landscapes. Mutilation materials evoked cardiac acceleration and high subjective tension in fearful subjects vs bradycardia and moderate tension in low-fear subjects. Neutral and incongruous slides prompted similar reactions from both fear groups: heart rate deceleration and low tension. Low-fear subjects shown mutilation slides tended to exceed the groups receiving nonaversive stimulation in magnitude of cardiac deceleration. Extensive analyses of respiratory activity showed that these differential heart rate reactions were not attributable to breathing. Mutilation stimuli evoked greater skin conductance responses than nonaversive slides, but there were no electrodermal differences as a function of fear relevance. The lawful relationship uncovered in the present research between cardiac reactions and individual differences in fear supports our suggestion that anticipation may have played a role in our earlier work.     

Habituation of Fear: Effects of Intensity and Stimulus Order

This study investigated snake-fearful subjects' skin conductance, heart rate, and fear ratings to repeated presentations of seascape and snake films (10–13 sec duration). The films sampled three levels of fear intensity and were displayed in ascending, descending, or nonsystematic orders; additional Ss viewed only high-fear material. A linear relationship with fear intensity emerged for fear ratings, but not for physiological measures. Differences found between orders in patterns of habituation were concordant for cardiac rate and fear ratings; relative to the other orders, the ascending sequence habituated less and displayed sensitization to material of higher fear levels. In all orders, there was marked habituation of physiological responses, especially in the first session. The possible role of adaptation level and implications of the data for desensitization and flooding were noted.     

The functional neural architecture of components of attention in language-processing tasks

Using functional magnetic resonance imaging we examined three important dimensions of attentional control (selective attention, divided attention, and executive function) in 25 neurologically normal, right-handed men and women, using tasks involving the perception and processing of printed words, spoken words, or both. In the context of language-processing manipulations: selective attention resulted in increased activation at left hemisphere parietal sites as well as at inferior frontal sites, divided attention resulted in additional increases in activation at these same left hemisphere sites and was also uniquely associated with increased activation of homologous sites in the right hemisphere, and executive function (measured during a complex task requiring sequential decision-making) resulted in increased activation at frontal sites relative to all other conditions. Our findings provide support for the belief that specific functional aspects of attentional control in language processing involve widely distributed but distinctive cortical systems, with mechanisms associated with the control of perceptual selectivity involving primarily parietal and inferior frontal sites and executive function engaging specific sites in frontal cortex.     

Contingent Negative Variation and Cardiac Deceleration in a Long Preparatory Interval: A Developmental Study

Ten-, 14-, and 19-yr-olds participated in a simple RT task with 5-sec foreperiod. CNV waveforms contained an early and a late negative component, and comparable deceleratory limbs characterized the cardiac waveforms. The 19-yr-oldsapos; early cardiac deceleration underwent intersession habituation and the analogous CNV response intra-session diminution; both processes were absent in younger subjects. Only young adults exhibited steady growth of late cardiac and CNV waves across both sessions. There were no developmental differences in basal body movement or anticipatory slowing of somatic activity or cardiac rate. However, 10-yr-olds had faster basal heart rates and larger acceleratory cardiac responses within the foreperiod than either older group. The results demonstrated partial dissociation of somatic and cardiac activity under the present experimental conditions. The overall results underscore the need for developmental psychophysiological research including childhood and adolescence.     

Effects of Methylphenidate on Processing Negativities in Patients With Attention-deficit Hyperactivity Disorder

This study compared the impact of methylphenidate on patients with Attention-deficit Hyperactivity Disorder (ADHD) with and without aggressive/noncompliant features in an oddball test consisting of a randomly ordered series of loud (frequent) tones, soft (rare) tones, bright (frequent) lights, and dim (rare) lights. In alternate conditions, subjects were required to respond to either the rare tones or the rare lights. These tasks were administered in a drug-free baseline session and after a counterbalanced treatment of 14 days each of methylphenidate (0.3 mg/Kg b.i.d.) and placebo (lactose b.i.d.). In comparison with placebo, methylphenidate resulted in greater accuracy and speed of reactions to targets of both modalities. The amplitude of N1 to auditory nontargets was larger when the target was a rare tone as opposed to a rare light, and this attention-related effect was increased by methylphenidate. The same differential amplitude enhancement by stimulant treatment was found for an early area measure of difference ERPs. In contrast, for N1 to visual nontargets the effect of selective attention (larger amplitude when the target was a rare light vs. a rare tone) was not significant and was not affected by stimulant medication. All these findings were comparable for the three ADHD subgroups, a result attesting to the generality of stimulant effects on information processing.