Canonical finger-numeral configurations facilitate the processing of Arabic numerals in adults: An Event-Related Potential study.

Various studies claim that early-learned, culture-typical (canonical) finger configurations used to communicate or represent numerosity, have stronger connections to numerical concepts stored in long-term memory than cultural-unfamiliar finger configurations, thereby allowing for faster access to their numerical meaning. The current study investigated whether presentation of canonical finger configurations gesturing numerosities 1-4 or 6-9 would facilitate young adults' behavioral and neural processing of Arabic numerals. Thirty-one adults performed a number comparison task in which they had to decide whether simultaneously presented Arabic numerals and canonical or non-canonical finger configurations showed the same or a different numerosity, while measuring their performance and Event-Related Potentials (ERPs). The results showed faster responses when comparisons involved canonical (versus non-canonical) finger configurations, but only on numerosity-congruent trials where finger configuration and Arabic numeral matched in number identity. Canonical, and small-number finger configurations 1-4 in general (irrespective of their canonicity), also elicited enhanced amplitude of the early right-parietal P2p, and the later centro-parietal P3 on numerosity-congruent trials. We suggest these P2p and P3 findings respectively reflect facilitated numerical access and easier categorization of canonical finger-numeral configurations. The current results provide behavioral and neurophysiological evidence for the embodiment of culture-specific, canonical, finger-numeral configurations, and their link with other number representations in the adult brain, likely emerging from their more frequent use in daily life communication and/or in early childhood during number symbol acquisition.

The cognitive and socio-emotional development of 5-year-old children born after PGD.

STUDY QUESTION: Does PGD increase the risk on adverse cognitive and socio-emotional development? SUMMARY ANSWER: The cognitive and socio-emotional development in children born after PGD seems to be normal when compared to control groups. WHAT IS KNOWN ALREADY: A limited number of studies with small sample sizes indicate that the cognitive and socio-emotional development of (pre)school-aged children born after either PGD or PGS seem to be comparable to those of children born after IVF/ICSI and to naturally conceived (NC) children from the general population. STUDY DESIGN, SIZE, DURATION: For this study we invited 72 5-year-old PGD children, 128 5-year-old IVF/ICSI children and 108 5-year-old NC children from families with a genetic disorder. All children were invited between January 2014 and July 2016. PARTICIPANTS/MATERIALS, SETTING, METHODS: In total, 51 PGD children, 52 IVF/ICSI children and 35 NC children underwent neuropsychological testing (WPPSI-III-NL and AWMA). The children's parent(s) and teachers filled in questionnaires evaluating children's executive functioning (Behaviour Rating Inventory of Executive Functions; BRIEF) and socio-emotional development (Child Behaviour Checklist; CBCL and Caregiver-Teacher Report Form; C-TRF). MAIN RESULTS AND THE ROLE OF CHANCE: The mean full-scale intelligence quotient scores (P = 0.426) and performance on the AWMA Listening Span task (P = 0.873) and Spatial Span task (P = 0.458) were comparable between the three groups. Regarding socio-emotional development, the teachers' scores revealed more externalizing (P = 0.011) and total problem (P = 0.019) behaviour in PGD children than for IVF/ICSI children; both groups did not differ significantly from the NC children (P = 0.11). More children (13%) with an affected first-degree family member (mostly parent) were included in the PGD group than in the NC group. Scores in all groups fell within the normal population range and should be considered normal. LIMITATIONS, REASONS FOR CAUTION: The number of NC children from families with a genetic disorder was relatively small. Furthermore, the fathers' CBCL results were based on small samples. WIDER IMPLICATIONS OF THE FINDINGS: PGD children show levels of cognitive and socio-emotional development at 5 years that are within the normal range, despite the biopsy involved in PGD and the potential extra psychological burden associated with the presence of a genetic disorder in the family. STUDY FUNDING/COMPETING INTEREST(S): This study was funded by ZonMw (70-71300-98-106). None of the authors have any competing interests to declare. TRIAL REGISTRATION NUMBER: NCT02149485.

Dissociating the effects of semantic grouping and rehearsal strategies on event-related brain potentials.

The application of elaborative encoding strategies during learning, such as grouping items on similar semantic categories, increases the likelihood of later recall. Previous studies have suggested that stimuli that encourage semantic grouping strategies had modulating effects on specific ERP components. However, these studies did not differentiate between ERP activation patterns evoked by elaborative working memory strategies like semantic grouping and more simple strategies like rote rehearsal. Identification of neurocognitive correlates underlying successful use of elaborative strategies is important to understand better why certain populations, like children or elderly people, have problems applying such strategies. To compare ERP activation during the application of elaborative versus more simple strategies subjects had to encode either four semantically related or unrelated pictures by respectively applying a semantic category grouping or a simple rehearsal strategy. Another goal was to investigate if maintenance of semantically grouped vs. ungrouped pictures modulated ERP-slow waves differently. At the behavioral level there was only a semantic grouping benefit in terms of faster responding on correct rejections (i.e. when the memory probe stimulus was not part of the memory set). At the neural level, during encoding semantic grouping only had a modest specific modulatory effect on a fronto-central Late Positive Component (LPC), emerging around 650 ms. Other ERP components (i.e. P200, N400 and a second Late Positive Component) that had been earlier related to semantic grouping encoding processes now showed stronger modulation by rehearsal than by semantic grouping. During maintenance semantic grouping had specific modulatory effects on left and right frontal slow wave activity. These results stress the importance of careful control of strategy use when investigating the neural correlates of elaborative encoding.

Response inhibition and attention processing in 5- to 7-year-old children with and without symptoms of ADHD: An ERP study.

OBJECTIVE: Response inhibition and attention processing in 5- to 7-year-old children with or without symptoms of attention-deficit hyperactivity disorder (ADHD) were examined. METHODS: Twelve children with ADHD symptoms and 15 control children performed a CPT-AX task. Behavioral measures of inattention and impulsivity and ERP measures of conflict monitoring and inhibition (Nogo-N2 and Nogo-P3), cue-orientation and prestimulus target expectation (Cue-P2 and P3) and response preparation (CNV) were collected. RESULTS: ADHD children detected fewer targets and had higher Inattention scores accompanied by reduced centro-parietal Cue- and Go-P3 activity. Occipital CNV amplitude was larger in ADHD children. At fronto-central leads, strong and comparable fronto-parietal Nogo-N2 effects were found in both groups, whereas the Nogo-P3 was only marginally significant in both groups. CONCLUSIONS: The attenuated Cue- and Go-P3 effects in the ADHD-symptom group are interpreted as early signs of delayed attention development, resulting in less preparation and less alertness to detect significant events. Whereas the Nogo-N2 effects were interpreted as signs of comparable levels of conflict processing in both groups, the small Nogo-P3 suggests that inhibitory processing is still immature at this age. SIGNIFICANCE: The present study shows that specific attention problems can already be detected in the behavior and brain activity of 5- to 7-year-old children with symptoms of ADHD performing a CPT-AX task, and might be better indicators for the risk of developing ADHD than impulsivity measures.

Source localization of the Nogo-N2: a developmental study.

OBJECTIVE: The aim of the present study was to investigate whether similar neural sources are involved in generating Nogo-N2 scalp topography in children and adults. METHODS: Source analysis was performed on the Nogo-N2 data from two groups of children (sixteen 6/7 year-olds and seventeen 9/10 year-olds) and seventeen young adults (aged 19-23 years) that were obtained in a prior study by Jonkman LM. The development of preparation, conflict monitoring and inhibition from early childhood to young adulthood; a go/nogo ERP study. Brain Res 2006;1097:181-93. RESULTS: In both children and adults a bilateral source pair in the medial frontal cortex (near ACC) was involved in the generation of Nogo-N2 activity. However, children needed an additional, posteriorly located source pair to adequately explain the Nogo-N2 distribution. In 6/7 year-olds this posterior source was localized in occipito-temporal areas, whereas in 9/10 year-olds the posterior sources shifted to parietal locations. CONCLUSIONS: Although children recruit similar frontal regions as adults in the Nogo-N2 time window, the additional activation of posterior sources might indicate that early executive control performance is less automatic or requires more effortful control in children. This in turn might cause them to rely on more basic stimulus processing or to activate additional attention-related areas. SIGNIFICANCE: Results from the present study show that in children, a more diffuse brain network is involved in executive control processing (conflict monitoring) in the Nogo-N2 time window than in adults.

Attention deficit and impulsivity: selecting, shifting, and stopping.

The present selective review addresses attention, inhibition, and their underlying brain mechanisms, especially in relation to attention deficit/hyperactivity disorders (AD/HD), and the effects of methylphenidate. In particular, event-related potential (ERP) studies suggest a deficit in the early-filtering aspect of selective attention in children with AD/HD. Results from stop tasks are consistent with impairments in stopping performance in AD/HD, but in children (as opposed to adults) these effects cannot be easily dissociated from more general impairments in attention to the task, and therefore an interpretation in terms of inhibitory control is not straightforward. On the other hand, the beneficial effects of methylphenidate are more specific to stopping, and there are no clearcut effects of methylphenidate on measures of selective attention. Even when group differences pertain specifically to stopping performance (as with adults with AD/HD), ERP evidence suggests at least a partial contribution of differences in switching attention to the stop signal, as revealed in measures of sensory cortex activation. ERP evidence from cued go/nogo tasks underlines the importance of taking into account the contribution of higher order control processes involved in anticipation of and preparation for task stimuli. It suggests that in certain conditions, expectancy, rather than response bias, contributes to increased behavioral response tendencies, and that a presumed index of response inhibition, the nogo N2, may rather reflect conflict monitoring. In sum, direct reflections of brain activity suggest that mechanisms of expectation and attention, rather than of response bias or inhibitory control, govern behavioral manifestations of impulsivity.

Dipole source localization of event-related brain activity indicative of an early visual selective attention deficit in ADHD children.

OBJECTIVE: This study was aimed at investigating whether attention-deficit hyperactivity disorder (ADHD) children suffer from specific early selective attention deficits in the visual modality with the aid of event-related brain potentials (ERPs). Furthermore, brain source localization was applied to identify brain areas underlying possible deficits in selective visual processing in ADHD children. METHODS: A two-channel visual color selection task was administered to 18 ADHD and 18 control subjects in the age range of 7-13 years and ERP activity was derived from 30 electrodes. RESULTS: ADHD children exhibited lower perceptual sensitivity scores resulting in poorer target selection. The ERP data suggested an early selective-attention deficit as manifested in smaller frontal positive activity (frontal selection positivity; FSP) in ADHD children around 200 ms whereas later occipital and fronto-central negative activity (OSN and N2b; 200-400 ms latency) appeared to be unaffected. Source localization explained the FSP by posterior-medial equivalent dipoles in control subjects, which may reflect the contribution of numerous surrounding areas. CONCLUSIONS: ADHD children have problems with selective visual processing that might be caused by a specific early filtering deficit (absent FSP) occurring around 200 ms. The neural sources underlying these problems have to be further identified. Source localization also suggested abnormalities in the 200-400 ms time range, pertaining to the distribution of attention-modulated activity in lateral frontal areas.

Developmental differences in behavioral and event-related brain responses associated with response preparation and inhibition in a go/nogo task.

The present study investigated developmental trends in response inhibition and preparation by studying behavior and event-related brain activity in a cued go/nogo task, administered to nine-year-old children and young adults. Hits, false alarms, inattention, and impulsivity scores and ERP measures of inhibition (fronto-central nogo-N2 and P3), target selection (parietal go-nogo P3 difference), and response preparation (contingent negative variation; CNV) were collected. Higher false alarm and impulsivity scores and the absence of the fronto-central nogo P3 all suggest a developmental lag in response inhibition in children. A developmental lag in sustained attention processes was suggested by worse target detection and larger parietal target/nontarget P3 effects in children. Cue orientation and response preparation processes were respectively measured by early and late CNV activity. Children displayed smaller early CNV amplitudes at fronto-central locations, but mature late CNV. The smaller early CNV activity might indicate inefficient cue-orientation processes caused by incomplete frontal lobe development.

Attentional capacity, a probe ERP study: differences between children with attention-deficit hyperactivity disorder and normal control children and effects of methylphenidate.

In the present study it was investigated whether the smaller P3s in attention-deficit hyperactivity disorder (ADHD) children are caused by a shortage of capacity underlying P3 processes or whether they are due to a capacity allocation problem. Also, effects of methylphenidate on these processes were investigated. Performance and event-related potentials (ERPs) of 14 ADHD and 14 control children were measured using an irrelevant-probe technique. Three types of task irrelevant visual probes (standards, deviants, and novels) were presented against the background of two visual tasks that varied in task difficulty. The parietal P3 wave was measured in response to task stimuli and probes. ADHD subjects made significantly fewer correct detections than normal controls in both the easy and the hard tasks. Controls showed an enhanced P3 to task-relevant stimuli in the hard task, whereas ADHD children did not. Probe (novel) P3 amplitudes decreased from the easy to the hard task to the same extent in both groups. Methylphenidate enhanced the percentage of correct responses and task P3 amplitudes in both the easy and the hard task but probe P3 amplitudes were not influenced by methylphenidate. It was concluded that ADHD children do not suffer from a shortage in attentional capacity; rather, the evidence is in favor of a problem with capacity allocation. Furthermore, methylphenidate had enhancing effects on performance and ERPs, but did not improve the capacity-allocation deficit.

Perceptual and response interference in children with attention-deficit hyperactivity disorder, and the effects of methylphenidate.

Fourteen children with attention-deficit hyperactivity disorder (ADHD) and 14 normal control children were compared with respect to stimulus- and response-related processes. Subjects with ADHD took part in two additional sessions under methylphenidate or placebo. In both experiments, performance and electrophysiological measures such as the P2, N2, and P3 components of event-related potential and electromyogram (EMG) activity were measured during an Eriksen flanker task. In both groups of children, reaction times (RTs) to arrow stimuli incongruent with the target were longer than those to neutral stimuli (response interference), which were again slower than RTs to target-alone stimuli (perceptual interference). Children with ADHD made more errors to incongruent stimuli and showed more response interference. For correct responses, no differences between the groups in response interference effects on reaction time, P2, N2, and P3 latency, or EMG onset were found. Methylphenidate had a general enhancing effect on accuracy but did not specifically reduce interference from the flanking stimuli. Methylphenidate had no effects on RT, N2 and P2 latency, P3 amplitude or latency, or EMG activity. The conclusion that methylphenidate did not influence response processes contrasts sharply with findings reported by authors using the Sternberg memory search task.

Carbohydrate intake improves cognitive performance of stress-prone individuals under controllable laboratory stress.

Cognitive performance has been found to decline after exposure to stress, particularly in stress-prone subjects. The present study investigated whether a carbohydrate-rich, protein-poor (CR/PP) diet, which may enhance cerebral serotonin function in stress-prone subjects due to increases in the available tryptophan, improves the performance of stress-prone subjects after exposure to acute laboratory stress. Twenty-two high-stress-prone (HS) subjects and twenty-one low-stress-prone (LS) subjects aged between 19 and 26 years performed a memory scanning task after controllable and uncontrollable stress, following either a CR/PP diet or a protein-rich, carbohydrate-poor (PR/CP) isoenergetic diet. Uncontrollable stress reduced feelings of control (F(1,38) 9.30; P = 0.004), whereas pulse rate and skin conductance increased after both stress tasks (F(1,38) 78.34; P = 0.0005 and F(1,37) 83.16; P = 0.0004). Diet, stress-proneness and stress-controllability interacted (F(1,36) 9.46; P = 0.004) in such a way that performance in HS subjects was better with the CR/PP diet than with the PR/CP diet, but only after controllable stress. As the CR/PP diet has been found to increase the plasma tryptophan:large neutral amino acids ratio, indicating an increased availability of cerebral tryptophan and, thus, higher serotonin levels, it appears that there may be an increased availability of brain serotonin in HS subjects after controllable laboratory stress.

Differences in plasma concentrations of the D- and L-threo methylphenidate enantiomers in responding and non-responding children with attention-deficit hyperactivity disorder.

Children with attention-deficit hyperactivity disorder who are categorized as responders or non-responders to methylphenidate (MPH) on the basis of their electrophysiological P3 response in a selective attention task differ in metabolic patterns of the D- and L-threo MPH enantiomers. Non-responders showed significantly higher plasma concentrations of both D- and L-threo MPH enantiomers.

Event-related potentials and performance of attention-deficit hyperactivity disorder: children and normal controls in auditory and visual selective attention tasks.

Attention-deficit hyperactivity disorder (ADHD) children and normal controls (7-13 yrs old) performed an auditory and visual selective attention task. Subjects were instructed to respond to the infrequent (10%) stimuli in the relevant channel. Processing negativity (PN) and several other ERP peaks were scored at the midline electrodes. In the auditory task, controls had more correct detections (hits), less false alarms, larger P3b amplitudes to nontarget stimuli (but not to hits), a larger central PN and larger early frontal positivity (100-250 ms) to target stimuli than ADHD subjects. In the visual modality, controls had more correct detections, less false alarms, larger P3b amplitudes to nontarget stimuli (but not to hits), and larger frontal P3(1) amplitudes to infrequent than to frequent stimuli. It was hypothesized that in ADHD children in both the auditory and the visual task, there is a deficit in the activation of the P3b process. Incorrect triggering of the P3b process might be caused by disturbances in other aspects of the attention process, preceding the P3b.

The effects of sleep loss on task performance and the electroencephalogram in young and elderly subjects.

The effects of 28-h sleep loss on performance, reaction time (RT) distribution functions, and spectral composition of the EEG were evaluated in three choice-RT tasks for young (N = 12, aged 18-24 years) and old (N = 12, aged 62-73 years) subjects. Manipulations of stimulus degradation, stimulus-response compatibility, and interstimulus interval variability were to affect encoding, response selection, and motor adjustment stages, respectively. In order to discriminate between independent variables that were presumed to be computational or energetical in nature, effects on EEG spectra and RT-distributions were studied. Spectra of the EEG indicated higher cortical arousal levels for the elderly than for the young. The most dramatic effect of sleep loss on performance was a marked increase in the number of omitted responses. This effect was smaller for the elderly than for the young. The results suggest that the detrimental effects of sleep loss are smaller in the elderly, which is consistent with an inverted-U relationship between arousal and performance. The age effects on the processing stages were mainly limited to response selection.

Effects of methylphenidate on event-related potentials and performance of attention-deficit hyperactivity disorder children in auditory and visual selective attention tasks.

Attention-deficit hyperactivity disorder (ADHD) children participated in a double-blind placebo-controlled study in which the effects of a dosage of 15 mg methylphenidate (MPH) on auditory and visual selective attention tasks was determined by presenting frequent (90%) and infrequent (10%) stimuli in both relevant and irrelevant input channels. The subject's task was to respond to the infrequent tones in the relevant input channel. Processing activity (negativity and positivity) was assessed for both tasks. N1, P2, N2, and P3b peaks were scored in the auditory task and N1, P1, N2, P2, P3(1), and P3b peaks were scored in the visual task. Effects of MPH were more prevalent in the visual than in the auditory condition. In the visual condition MPH enhanced the percentage of hits, caused higher central, parietal, and occipital P3b amplitudes to attended stimuli (both standards and deviants), and also enhanced the frontal processing negativity (PN). In the auditory task MPH did not influence performance, but it enhanced the frontal PN as well as the parietal and occipital P3b amplitudes to all stimulus types. In ADHD children, MPH ameliorates some, but not all, deficits and also improves processing where no differences with normal children are present.