Correction to: The disengagement of visual attention in the gap paradigm across adolescence.

In the manuscript, we write that saccadic reaction time was determined as the time between the offset of the last fixation on the central stimulus and the onset of the peripheral stimulus (the target).

The disengagement of visual attention in the gap paradigm across adolescence.

Attentional disengagement is important for successful interaction with our environment. The efficiency of attentional disengagement is commonly assessed using the gap paradigm. There is, however, a sharp contrast between the number of studies applying the gap paradigm to clinical populations and the knowledge about the underlying developmental trajectory of the gap effect. The aim of the present study was, therefore, to investigate attentional disengagement in a group of children aged 9-15. Besides the typically deployed gap and the overlap conditions, we also added a baseline condition in which the fixation point was removed at the moment that the target appeared. This allowed us to reveal the appropriate experimental conditions to unravel possible developmental differences. Correlational analyses showed that the size of the gap effect became smaller with increasing age, but only for the difference between the gap and the overlap conditions. This shows that there is a gradual increase in the capacity to disengage visual attention with increasing age, but that this effect only becomes apparent when the gap and the overlap conditions are compared. The gradual decrease of the gap effect with increasing age provides additional evidence that the attentional system becomes more efficient with increasing age and that this is a gradual process.

Slow segmentation of faces in Autism Spectrum Disorder.

Atypical visual segmentation, affecting object perception, might contribute to face processing problems in Autism Spectrum Disorder (ASD). The current study investigated impairments in visual segmentation of faces in ASD. Thirty participants (ASD: 16; Control: 14) viewed texture-defined faces, houses, and homogeneous images, while electroencephalographic and behavioral responses were recorded. The ASD group showed slower face-segmentation related brain activity and longer segmentation reaction times than the control group, but no difference in house-segmentation related activity or behavioral performance. Furthermore, individual differences in face-segmentation but not house-segmentation correlated with score on the Autism Quotient. Segmentation is thus selectively impaired for faces in ASD, and relates to the degree of ASD traits. Face segmentation relates to recurrent connectivity from the fusiform face area (FFA) to the visual cortex. These findings thus suggest that atypical connectivity from the FFA might contribute to delayed face processing in ASD.

Test-retest reliability of infant event related potentials evoked by faces.

Reliable measures are required to draw meaningful conclusions regarding developmental changes in longitudinal studies. Little is known, however, about the test-retest reliability of face-sensitive event related potentials (ERPs), a frequently used neural measure in infants. The aim of the current study is to investigate the test-retest reliability of ERPs typically evoked by faces in 9-10 month-old infants. The infants (N=31) were presented with neutral, fearful and happy faces that contained only the lower or higher spatial frequency information. They were tested twice within two weeks. The present results show that the test-retest reliability of the face-sensitive ERP components is moderate (P400 and Nc) to substantial (N290). However, there is low test-retest reliability for the effects of the specific experimental manipulations (i.e. emotion and spatial frequency) on the face-sensitive ERPs. To conclude, in infants the face-sensitive ERP components (i.e. N290, P400 and Nc) show adequate test-retest reliability, but not the effects of emotion and spatial frequency on these ERP components. We propose that further research focuses on investigating elements that might increase the test-retest reliability, as adequate test-retest reliability is necessary to draw meaningful conclusions on individual developmental trajectories of the face-sensitive ERPs in infants.

Eurosibs: Towards robust measurement of infant neurocognitive predictors of autism across Europe.

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder that affects social communication skills and flexible behaviour. Developing new treatment approaches for ASD requires early identification of the factors that influence later behavioural outcomes. One fruitful research paradigm has been the prospective study of infants with a first degree relative with ASD, who have around a 20% likelihood of developing ASD themselves. Early findings have identified a range of candidate neurocognitive markers for later ASD such as delayed attention shifting or neural responses to faces, but given the early stage of the field most sample sizes are small and replication attempts remain rare. The Eurosibs consortium is a European multisite neurocognitive study of infants with an older sibling with ASD conducted across nine sites in five European countries. In this manuscript, we describe the selection and standardization of our common neurocognitive testing protocol. We report data quality assessments across sites, showing that neurocognitive measures hold great promise for cross-site consistency in diverse populations. We discuss our approach to ensuring robust data analysis pipelines and boosting future reproducibility. Finally, we summarise challenges and opportunities for future multi-site research efforts.

Integrity of lateral and feedbackward connections in visual processing in children with pervasive developmental disorder.

Enhanced visual detail processing in subjects with pervasive developmental disorder (PDD) has been related to impairments in feature integration. The functional integrity of two types of neuronal connections involved in visual feature integration, namely horizontal and feedbackward connections, were tested. Sixteen children with PDD and 17 age- and IQ-matched control children (mean age 13.3 years) were included. In a texture segregation task the difference in ERP response to homogeneous and checkered visual stimuli was determined. Additionally, in a contour integration task subjects had to point out a contour consisting of colinearly aligned Gabor signals in backgrounds increasing in noise. Children with PDD showed a normal performance on the contour integration task, suggesting that neurons in the primary visual cortex of children with PDD can effectively integrate the activity of local detectors that process different aspects of the same object information by making use of long-range lateral connections. The amplitude of ERP activity related to texture segregation was also not different between the PDD and control groups, indicating functional visual feedback mechanisms between V1 and higher order areas in subjects with PDD. However, a difference in latency of texture-segmentation related activity between the groups was noted. This effect did not reach significance, which could be due to the small N of the study. Therefore, the data need replication in a study with larger samples before more definitive conclusions can be drawn.

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.

Abnormal spatial frequency processing in high-functioning children with pervasive developmental disorder (PDD).

OBJECTIVE: Basic abnormalities in visual information processing could be associated with the local visual bias often found in subjects with PDD. Therefore, the present study investigated the existence of deficits in spatial frequency processing at an early sensory level in children with PDD. METHODS: Visual evoked potentials (VEPs) and VEP dipole sources elicited by high and low spatial frequency gratings were analyzed in high-functioning children with PDD and matched controls. RESULTS: Around 80 ms (N80-latency) children with PDD did not show the same robust differences between high and low spatial frequencies in VEP amplitude and VEP brain sources as controls, because of atypical processing of high frequencies. Analyses at the P1-latency (130 ms) revealed that, although similar inferior-medial brain sources were activated for the processing of both spatial frequencies in the PDD and control group, source strength in response to both frequencies was weaker in the PDD compared to control group. Moreover, additional superior-lateral brain sources were activated during the processing of both frequencies in the PDD group. CONCLUSIONS: Decreased specialized processing of high and low spatial frequencies might be a robust characteristic of PDD. Early in processing abnormalities in high spatial frequency processing seem to occur in PDD. At a later phase in processing there seems to be both atypical high and low spatial frequency processing. Considering that the processing of specific spatial frequencies plays an important role in the processing of global and local aspects of hierarchical stimuli and faces and of emotions, present data suggest that peculiarities in PDD subjects with respect to these stimuli might be related to an abnormality in more fundamental visual processes. SIGNIFICANCE: A basic abnormality in visual frequency processing is established in children with PDD.

Visual information processing in high-functioning individuals with autism spectrum disorders and their parents.

The authors assessed visual information processing in high-functioning individuals with pervasive developmental disorders (PDD) and their parents. The authors used tasks for contrast sensitivity, motion, and form perception to test visual processing occurring relatively early and late in the magnocellular-dorsal and parvocellular-ventral pathways. No deficits were found in contrast sensitivity for low or high spatial frequencies or for motion or form perception between individuals with PDD in comparison with a matched control group. Individuals with PDD performed equally with or better than controls on motion detection tasks. In addition, the authors did not find differences on any of the tasks between parents of the PDD group and matched control parents. These results indicate that high-functioning individuals with PDD and their parents are able to process visual stimuli that rely on early or late processing in the magnocellular-dorsal and parvocellular-ventral pathways as well as controls.

No effects of l-dopa and bromocriptine on psychophysiological parameters of human selective attention.

Patients with schizophrenia exhibit diverse cognitive deficits, one of which is a loss of the ability to focus attention. According to the revised dopamine hypothesis of schizophrenia both an increased mesolimbic and a decreased prefrontal dopaminergic activity is suggested to be involved in schizophrenia. The current study was designed to explore the relationship between dopamine and two psychophysiological parameters of selective attention, i.e. P300 amplitude and processing negativity (PN) in healthy volunteers. In two separate experiments, with a double-blind, balanced and placebo-controlled crossover design, 18 healthy male volunteers were orally administered either 300 mg l-dopa (precursor of dopamine) or placebo (experiment I), or 1.25mg bromocriptine (D2 agonist) or placebo (experiment II). Following this treatment they were tested in an auditory, dichotic selective attention paradigm. An increase in P300 amplitude was found following deviant stimuli when compared to standard stimuli and following attended stimuli when compared to unattended stimuli, regardless of treatment. Similarly, PN was found regardless of treatment. Neither l-dopa nor bromocriptine affected task performance or the amplitudes of PN or P300. In the present study neither l-dopa nor bromocriptine affected PN, P300 amplitude or task performance in healthy controls, phenomena which are usually found to be disrupted in schizophrenia. This indicates that P300 amplitude and PN are neither affected by a global (l-dopa) increased dopaminergic activity, nor by a more selectively towards striatal areas targeted (bromocriptine) increase in dopaminergic activity.

Dose-related effect of methylphenidate on stopping and changing in children with attention-deficit/hyperactivity disorder.

PURPOSE: The effect of methylphenidate (MPH) on inhibitory control as assessed by the stop task in children with attention-deficit/hyperactivity disorder (ADHD) could be influenced by task difficulty and may be mediated by attention. SUBJECTS AND METHODS: Fifteen children with ADHD performed the stop and the change task after placebo, 0.5 and 1.0 mg/kg MPH in a within-subject design. RESULTS: Linear-trend analysis showed a similar effect of MPH in both tasks and a stronger effect for inhibitory control than for attention. Furthermore, a correlation was found between blood serum metabolites of norepinephrine and dopamine for attentional measures and inhibitory control measures, respectively. DISCUSSION AND CONCLUSION: In children with ADHD MPH could act primarily on inhibitory control, and is not influenced by task difficulty. Also, attention and inhibitory control could have differential pharmacological profiles.

The relationship between local and global processing and the processing of high and low spatial frequencies studied by event-related potentials and source modeling.

The processing of global and local elements and of low- and high-spatial frequencies are thought to be interrelated. Evidence for this stems from findings showing that brain localizations for global/local elements and for low/high spatial frequencies seem to overlap. The present study aimed to provide direct evidence that topographical differences between the processing of global and local visual elements can directly be explained by their spatial frequency content, and to study at which point in time this relation is present. This was done by studying the event-related potentials (ERPs) and source models elicited by unfiltered, low- or high-pass filtered hierarchical stimuli. Results showed that performance for global and local targets was affected by removing low and high spatial frequencies, respectively. ERP data indicated that at 250 ms, there was an interaction between the processing of global/local targets and of spatial frequencies because at this time-point removal of low spatial frequencies decreased activity associated with the processing of global targets. When localizing this effect, we found evidence implying that spatial frequency content indeed affected the brain region in which local/global targets were processed. Results implicated that the processing of global information depended on its low spatial frequency content, which was processed more laterally. Instead, processing of local information seemed to depend on its high spatial frequency content, which was processed more medially. Thereby, present results extend former results showing that global and local processing is dependent on spatial frequency and mapped retinotopically in the visual cortex.

Time-varying differences in evoked potentials elicited by high versus low spatial frequencies: a topographical and source analysis.

OBJECTIVE: To investigate time-varying differences in visual-evoked potentials (VEPs) and dipoles elicited by high versus low spatial frequencies. The main question was whether different spatial frequencies are processed in distinct cortical areas, especially after 100 ms. An additional question was whether and how a hemispheric balance in spatial frequency processing develops over time. METHODS: Stimuli were square-wave gratings, with spatial frequencies of 0.75, 1.5, and 6 c/d. VEPs and dipole models were analyzed at various latencies. RESULTS: For the time-window of 80-100 ms, spatial frequency-related differences in VEPs and dipoles in posterior regions as reported previously were replicated: lower spatial frequencies were associated with more positivity in the VEP and with more anterior and radial sources than high frequencies. However, after 100 ms differences in amplitude, but not in topography and dipoles, were found between the different spatial frequencies. Between 180-200 ms a right hemisphere dominance was found for all frequencies. CONCLUSIONS: After 100 ms, VEPs in response to different spatial frequencies seem to be generated in the same cortical areas. Also, no evidence for frequency-related hemispheric lateralization was found. SIGNIFICANCE: Insight is provided into the functional-anatomical basis of longer-latency frequency-related differences in processing.

ERP differences among subtypes of pervasive developmental disorders.

BACKGROUND: Children with multiple complex developmental disorder (MCDD) have been distinguished from autistic children on the basis of chart reviews. It was questioned whether it is possible to find other, e.g., event-related potential (ERP), evidence for this assertion. METHODS: ERPs were measured in response to stimuli in a visual oddball task in autistic, MCDD, attention deficit disorder, dyslexic, and normal control children, to study whether ERP peaks can be used to distinguish autistic and MCDD children, and to classify the aforementioned groups. RESULTS: It was found that the P3 at four different leads and the frontal Nc showed differences among the groups, and that the autistic and MCDD groups differed from each other as well as from the other groups. Also, it was found that, using discriminant analyses in which these parameters were included, children were classified above chance level. Especially in the MCDD group, a high percentage of correct classification was seen. CONCLUSIONS: ERP parameters indicate that autistic and MCDD children might differ in underlying pathology and might therefore, better be regarded as two separate diagnostic entities.

Auditory event-related brain potentials in autistic children and three different control groups.

ERPs to auditory stimuli, generated during an oddball task, were obtained in a group of autistic children and three control groups (normal, ADDH, and dyslectic children, respectively). The task included the presentation of standards, deviants, and novels and had a (between-group) passive vs. active (counting) condition. It was examined whether 1) it was possible to replicate several earlier findings, 2) autistics manifest an abnormal lateralization pattern of ERPs, 3) autistics have an abnormal mismatch negativity (MMN), and 4) differences between autistics and normals are really specific to the autistic group. The only finding that could be replicated was that autistics have a smaller A/Pcz/300. There was no evidence for abnormal lateralization or abnormal MMN; however, there was an unexpected effect of the task manipulation on the amplitude of the P3: in autistics, the occipital P3 to deviant stimuli was significantly larger in the active than in the passive condition, a finding, like the replication of the smaller A/Pcz/300, specific to the autistic group. It was suggested that the auditory occipital task effect is related to understimulation of the occipital lobe by visual stimuli in autistic children.

Eye movements, visual attention, and autism: a saccadic reaction time study using the gap and overlap paradigm.

BACKGROUND: On the basis of the literature on autism, it was hypothesized that children with autism have deficits in attentional (dis-)engagement mechanisms. METHODS: A saccadic gap-overlap task was used to study visual engagement and disengagement in 16 high-functioning autistic children of about 10 years of age and 15 age- and IQ-matched normal control children. Subjects were asked to make saccadic eye movements from a fixation point to a suddenly appearing target as fast as possible. The saccadic reaction time was compared in two conditions: 1) the overlap condition, in which the fixation point was continuously visible, and 2) the gap condition, in which the fixation point was turned off 200 msec before the target appeared. RESULTS: Although no differences between the groups in either condition was observed, the gap effect (i.e., the difference in saccadic reaction time between the overlap condition and the gap condition) was smaller in the autistic group than in the control group. CONCLUSIONS: We concluded that autistic children show a lower level of attentional engagement.

Event-related brain potentials in children with attention-deficit and hyperactivity disorder: effects of stimulus deviancy and task relevance in the visual and auditory modality.

It has frequently been reported that in so-called oddball tasks, children with attention-deficit and hyperactivity disorder (ADDH) show small P3 peaks of the event-related potential (ERP) in response to "targets" (task-relevant deviant stimuli) than normal children. It is not clear, however, whether this smaller P3 is due to abnormal processing of infrequent stimuli per se and/or of task-relevant stimuli and whether it is preceded by abnormalities in earlier peaks, especially those thought to be related to automatic deviancy detection [mismatch negativity (MMN) in the auditory modality and P2N2 in the visual modality]. ERPs of ADDH and normal children in response to visual and auditory stimuli were studied in a condition without task relevance as well as in a task-relevant condition. ADDH children showed smaller P3 amplitudes and (marginally) smaller MMN to auditory deviant stimuli, irrespective of task relevance, so smaller P3s in ADDH children are due to stimulus deviancy per se. In the visual modality the P3 effect failed to reach significance. Because the smaller P3s were also found in a condition not requiring task-related motivation, recent motivational interpretations of differences with normal children are not supported. ADDH children also showed smaller P1 amplitudes than normal children to all stimuli except visual novels. The ERP differences were unrelated to performance, since both groups performed equally well.

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.

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.

P50 suppression and prepulse inhibition of the startle reflex in humans: a correlational study.

BACKGROUND: Sensory gating is an important feature of the normally functioning brain. When not operating correctly, it can contribute to different kinds of psychiatric illnesses by flooding the higher brain functions with useless information. Over the years, two paradigms have evolved to quantify the amount of sensory gating: the prepulse inhibition (PPI) of the startle reflex and the suppression of the P50 evoked potential. To enable comparison across studies it is important to find out to what extent these paradigms reflect the same processes. In the present study, this relationship was explored. METHODS: Thirty-one healthy male volunteers with no personal or family history of mental illness were tested on their ability to suppress the P50 wave and to inhibit the startle reflex. RESULTS: A significant positive correlation was found between PPI and P50 suppression mainly early in testing, when habituation of the startle reflex is taking place. Furthermore, a significant negative correlation was found between P50 suppression in the second half of testing and the habituation of the startle reflex. CONCLUSIONS: PPI and P50 suppression are correlated at an early stage of testing, when the process of habituation of the startle reflex is active. The role of the habituation in the correlation between these two measures needs to be further explored.