Jakub Szewczyk

Response inhibition of children with ADHD in the stop-signal task: an event-related potential study.

The Stop-Signal Task (SST) is a procedure that can provide a measure of inhibitory control of an ongoing motor response. We used the stop-signal paradigm to determine whether deficient inhibitory control distinguishes children with a diagnosis of attention deficit hyperactivity disorder combined type (ADHD-Com) from normally developing children, matched on age and sex. Participants performed a standard visual two-choice task with an auditory stop-signal stimulus, while an EEG was recorded. The behavioral results indicated that the ADHD group had significantly impaired inhibitory control compared to the performance of normal children. Relative to controls, the go stimulus reaction time (RT) and the stop-signal reaction time (SSRT) were prolonged in children with ADHD. The amplitudes of P2 and P3 components to the auditory stop-signal were more pronounced for successful than for unsuccessful stop-signal trials in both groups. However, the successful-unsuccessful difference was larger in control subjects. In contrast, the amplitude of the N2 component to auditory stop-signal was more pronounced for unsuccessful than for successful stop-signal trials in both groups. The comparison of the N2 component between control and ADHD groups revealed a greater amplitude and longer latency in the latter group, in successful stop-signal trials only. Additionally, the amplitude of response-locked ERPs, containing the ERN-Pe complex related to error-detection, was smaller in ADHD children. These results support the hypothesis of a complex deficit of inhibitory control, conflict monitoring, and error recognition mechanisms in ADHD and corroborate the utility of the stop-signal task in distinguishing hyperactive from normal children.

Event-related potentials in children with attention deficit hyperactivity disorder: An investigation using an auditory oddball task

The aim of the study was to investigate differences in electrophysiological brain activity between children diagnosed with attention deficit hyperactivity disorder combined type (ADHD-Com) and normally developing children, using the auditory 2-tone oddball paradigm. Forty right-handed subjects aged between 6.9 and 12.3 years participated in the present study, with 16 boys and 4 girls in each of the control and ADHD-Com groups. Children were individually age- and gender-matched. The auditory oddball task consisted of 155 standards (1 KHz, p=.66) and 80 targets (1.5 KHz, p=.34), presented randomly one at a time. Subjects were instructed to listen to the sounds and count the rare tones. Task performance in ADHD children did not differ compared to that in the control group. Event-related potentials (ERPs) elicited to target and standard stimuli were analyzed for between-group differences. The ADHD group showed enhanced P2 and reduced N2 component to both oddball stimuli, followed by reduced P3 component to attended targets compared with controls. The difference in the P3 amplitude between targets and standards was smaller in the ADHD group, particularly over the right hemisphere. These results suggest deficiencies in both automatic and controlled processing in children with ADHD. Enhanced amplitude of the P2 in ADHD children may reflect an early orienting deficit which affects later processing stages in the oddball task. Reduced amplitude of the N2 in the clinical group may be associated with stimulus discrimination impairment and inappropriate conflict monitoring. Reduced amplitude of target P3 and its asymmetrical distribution in ADHD children may reflect a deficit in higher-level executive functions, such as attention allocation and stimulus evaluation, accompanied by an impairment of global aspects of attentional processing that are under right hemisphere control.

Is animacy special? ERP correlates of semantic violations and animacy violations in sentence processing

Animacy is often conceived as a special semantic feature because of its relevance to thematic and syntactic processing. This study uses event-related brain potentials to investigate whether violations of the expected animacy value of a noun are processed differently from semantic violations which preserve the expected animacy value in a situation in which the animate/inanimate distinction has no consequences for thematic or syntactic processing. The language under test is Polish, a language in which the animate-inanimate distinction is reflected in the inflection of nouns. We constructed short stories such that either an animate direct object noun is highly expected in the storys final sentence, or an inanimate direct object. This noun appears in one of three conditions: (a) congruent, i.e. fitting the preceding context, (b) semantic violation without a violation of the expected animacy value, or (c) animacy violation, i.e. a violation of the expected animacy value. Semantic violations and animacy violations elicited a biphasic N400/P600 pattern. The N400 effect had the same amplitude for the two types of violation, while the P600 elicited by animacy violations had a significantly higher amplitude than the P600 elicited by semantic violations. These results indicate that animacy is processed differently from other semantic features even in syntactically and thematically unambiguous positions in a sentence.

Interference and Inhibition in Bilingual Language Comprehension: Evidence from Polish-English Interlingual Homographs

The main goal of the present study was to explore the involvement of inhibition in resolution of cross-language activation in bilingual comprehension and a possible modulatory effect of L2 proficiency. We used a semantic relatedness judgment task in L2 English that included Polish-English interlingual homographs and English translations of the Polish homographs’ meanings. Based on previous studies using the same paradigm, we expected a strong homograph interference and inhibition of the homographs’ Polish meanings translations. In addition, we predicted that participants with lower L2 proficiency would experience greater interference and stronger inhibitory effects. The reported results confirm a strong homograph interference effect. In addition, our results indicate that the scope of inhibition generalized from the homograph’s irrelevant meaning to a whole semantic category, indicating the flexibility of the inhibitory mechanisms. Contrary to our expectations, L2 proficiency did not modulate the effects of interference and inhibition, possibly due to a relatively low variability in proficiency within our participant sample.

Cognitive functions in patients with liver cirrhosis: A tendency to commit more memory errors

Background Minimal hepatic encephalopathy (MHE) is the mildest form of hepatic encephalopathy (HE). For diagnostic purposes, 2 alternative batteries of psychometric screening tests are recommended. They differ from each other in terms of the cognitive domains assessed. The research was designed to provide a profile of cognitive functioning in patients with liver cirrhosis, using an assessment that covers a wider range of cognitive functions than the usual screening battery. Material/Methods We examined 138 persons, including 88 with liver cirrhosis and 50 healthy volunteers. The Mini Mental State Examination (MMSE) was used for screening and excluding advanced cognitive impairment. Then, to assess cognitive functions in more detail, the following tests were used: Auditory Verbal Learning Test (AVLT), Letter and Semantic Fluency Tests (LF and SF), Trail Making Test (TMT A&B), Digit Symbol Test (DST), Block Design Test (BDT), and Mental Rotation Test (MRT). The MRT task has not been used in MHE diagnosis so far. Finally, 57 patients and 48 controls took part in the entire study. Results Patients with liver cirrhosis commit significantly more errors of intrusions in the AVLT during the delayed free recall trial. Results significantly deviating from the norm in at least 2 tests were found only in 7 cirrhosis patients. Conclusions The results do not provide any specific profile of cognitive disturbances in MHE, but suggest that cirrhosis patients have a tendency to commit more memory errors, probably due to subtle impairments of executive function.

Flanker task with equiprobable congruent and incongruent conditions does not elicit the conflict N2

In many published studies, various modifications of the flanker task have been used. Regardless of the flanker task version, the conflict N2 component has been consistently reported and interpreted as evidence for the resolution of conflict introduced by incongruent flankers. However, ERP studies that used the most basic flanker task (i.e., a version with equiprobable congruent and incongruent conditions in which only congruency between the target and flankers is manipulated) have not provided compelling evidence for the conflict N2 component. We report the results of a large-sample ERP study employing a basic flanker task that allowed us to revisit the mechanism underlying the resolution of conflict introduced by incongruent flankers. In the behavioral data, we observed the classic effect of congruency. In the ERP data, we found three conflict-sensitive components: (a) an early frontal component, presumably corresponding to P2, (b) P300 for congruent trials, followed by (c) P300 for incongruent trials. We did not find evidence for the conflict N2 component. Based on a review of literature, we propose that the conflict N2 component observed in a basic flanker task might be a frontal aspect of the P300 component. Given previous attempts to attribute the functional role of the ERP components, the absence of the conflict N2 in the basic flanker task suggests that response inhibition may not be crucial for the resolution of conflict induced by incongruent flankers. Instead, the P2 component appears to indicate that selective attention might play an important role in resolving the flanker conflict.

Different phonological mechanisms facilitate vocabulary learning at early and late stages of language acquisition: Evidence from Polish 9-year-olds learning English

To acquire a new word, learners need to create its representation in phonological short-term memory (STM) and then encode it in their long-term memory. Two strategies can enable word representation in STM: universal segmentation and phonological mapping. Universal segmentation is language universal and thus should predict word learning in any language, while phonological mapping is language specific. This study investigates the mechanisms of vocabulary learning through a comparison of vocabulary learning task results in multiple languages. We tested 44 Polish third graders learning English on phonological STM, phonological awareness in Polish and in English, and on three tasks, which involved learning novel word forms in Polish (first language), in English (second language), and in a language that did not resemble any language known to participants (an unknown language). Participants’ English proficiency was controlled through a vocabulary task. The results suggest that word learning engages different mechanisms for familiar and unfamiliar languages. Phonological awareness in English predicted learning second language and unknown language words, and phonological STM predicted learning words of the unknown language. We propose that universal segmentation facilitates word learning only in an unfamiliar language, while in familiar languages speakers use phonological mapping in order to learn new words.

How Does L1 and L2 Exposure Impact L1 Performance in Bilingual Children? Evidence from Polish-English Migrants to the United Kingdom

Most studies on bilingual language development focus on children’s second language (L2). Here, we investigated first language (L1) development of Polish-English early migrant bilinguals in four domains: vocabulary, grammar, phonological processing, and discourse. We first compared Polish language skills between bilinguals and their Polish non-migrant monolingual peers, and then investigated the influence of the cumulative exposure to L1 and L2 on bilinguals’ performance. We then examined whether high exposure to L1 could possibly minimize the gap between monolinguals and bilinguals. We analyzed data from 233 typically developing children (88 bilingual and 145 monolingual) aged 4;0 to 7;5 (years;months) on six language measures in Polish: receptive vocabulary, productive vocabulary, receptive grammar, productive grammar (sentence repetition), phonological processing (non-word repetition), and discourse abilities (narration). Information about language exposure was obtained via parental questionnaires. For each language task, we analyzed the data from the subsample of bilinguals who had completed all the tasks in question and from monolinguals matched one-on-one to the bilingual group on age, SES (measured by years of mother’s education), gender, non-verbal IQ, and short-term memory. The bilingual children scored lower than monolinguals in all language domains, except discourse. The group differences were more pronounced on the productive tasks (vocabulary, grammar, and phonological processing) and moderate on the receptive tasks (vocabulary and grammar). L1 exposure correlated positively with the vocabulary size and phonological processing. Grammar scores were not related to the levels of L1 exposure, but were predicted by general cognitive abilities. L2 exposure negatively influenced productive grammar in L1, suggesting possible L2 transfer effects on L1 grammatical performance. Children’s narrative skills benefitted from exposure to two languages: both L1 and L2 exposure influenced story structure scores in L1. Importantly, we did not find any evidence (in any of the tasks in which the gap was present) that the performance gap between monolinguals and bilinguals could be fully closed with high amounts of L1 input.

Neither action nor phonological video games make dyslexic children read better

The prevalence and long-term consequences of dyslexia make it crucial to look for effective and efficient ways of its therapy. Action video games (AVG) were implied as a possible remedy for difficulties in reading in Italian and English-speaking children. However, the studies examining the effectiveness of AVG application in dyslexia suffered from significant methodological weaknesses such as small sample sizes and lack of a control group with no intervention. In our study, we tested how two forms of training: based on AVG and on phonological non-action video games (PNAVG), affect reading in a group of fifty-four Polish children with dyslexia. Both speed and accuracy of reading increased in AVG as much as in PNAVG group. Moreover, both groups improved in phonological awareness, selective attention and rapid naming. Critically, the reading progress in the two groups did not differ from a dyslexic control group which did not participate in any training. Thus, the observed improvement in reading in AVG and PNAVG can be attributed either to the normal reading development related to schooling or to test practice effect. Overall, we failed to replicate previous studies: Neither AVG nor PNAVG remedy difficulties in reading in school children.

Individual differences in decisiveness: ERP correlates of response inhibition and error monitoring

The aim of the current study was to examine whether and how self-reported decisiveness is associated with response inhibition and performance monitoring. We hypothesized that these two cognitive control mechanisms, both of which are often associated with decision making, would differ in individuals varying in decisiveness. We focused on ERP correlates and behavioral measures of inhibition and error processing in the stop-signal task. We expected a negative relationship between decisiveness and behavioral measures of inhibitory control. We also hypothesized that stop-signal-locked N1 and P3 components and response-locked error-related negativity (ERN) would be less pronounced when participants self-reported higher levels of decisiveness. Correlation analysis identified an association between high decisiveness, long stop-signal reaction time, and low inhibition rate. Analysis with mixed-effects linear models revealed that stop signals evoked less pronounced N1 and P3 in individuals scoring higher on decisiveness in both successfully and unsuccessfully inhibited trials. Additionally, high decisiveness was linked to reduced error monitoring, as indicated by decreased ERNs. Importantly, we also found positive association between P3 onset latency and decisiveness, suggesting that individuals scoring higher on this measure have relatively less ability to rapidly engage the stopping process. Thus, our findings primarily indicate that decisiveness is negatively associated with the efficiency of both response inhibition and error monitoring. They also suggest that highly decisive people may share some characteristics of diminished cognitive control with impulsive individuals.