Developmental changes in ERP responses to spatial frequencies.

Social interaction starts with perception of other persons. One of the first steps in perception is processing of basic information such as spatial frequencies (SF), which represent details and global information. However, although behavioural perception of SF is well investigated, the developmental trajectory of the temporal characteristics of SF processing is not yet well understood. The speed of processing of this basic visual information is crucial, as it determines the speed and possibly accuracy of subsequent visual and social processes. The current study investigated developmental changes in the temporal characteristics of selective processing of high SF (HSF; details) versus low SF (LSF; global). To this end, brain activity was measured using EEG in 108 children aged 3-15 years, while HSF or LSF grating stimuli were presented. Interest was in the temporal characteristics of brain activity related to LSF and HSF processing, specifically at early (N80) or later (P1 or N2) peaks in brain activity. Analyses revealed that from 7-8 years onwards HSF but not LSF stimuli evoked an N80 peak. In younger children, aged 3-8 years, the visual manipulation mainly affected the visual N2 peak. Selective processing of HSF versus LSF thus occurs at a rather late time-point (N2 peak) in young children. Although behavioural research previously showed that 3-6 year-olds can perceive detailed information, the current results point out that selective processing of HSF versus LSF is still delayed in these children. The delayed processing in younger children could impede the use of LSF and HSF for emotional face processing. Thus, the current study is a starting point for understanding changes in basic visual processing which underlie social development.

Neural processing of high and low spatial frequency information in faces changes across development: qualitative changes in face processing during adolescence.

Face perception in adults depends on skilled processing of interattribute distances ('configural' processing), which is disrupted for faces presented in inverted orientation (face inversion effect or FIE). Children are not proficient in configural processing, and this might relate to an underlying immaturity to use facial information in low spatial frequency (SF) ranges, which capture the coarse information needed for configural processing. We hypothesized that during adolescence a shift from use of high to low SF information takes place. Therefore, we studied the influence of SF content on neural face processing in groups of children (9-10 years), adolescents (14-15 years) and young adults (21-29 years) by measuring event-related potentials (ERPs) to upright and inverted faces which varied in SF content. Results revealed that children show a neural FIE in early processing stages (i.e. P1; generated in early visual areas), suggesting a superficial, global facial analysis. In contrast, ERPs of adults revealed an FIE at later processing stages (i.e. N170; generated in face-selective, higher visual areas). Interestingly, adolescents showed FIEs in both processing stages, suggesting a hybrid developmental stage. Furthermore, adolescents and adults showed FIEs for stimuli containing low SF information, whereas such effects were driven by both low and high SF information in children. These results indicate that face processing has a protracted maturational course into adolescence, and is dependent on changes in SF processing. During adolescence, sensitivity to configural cues is developed, which aids the fast and holistic processing that is so special for faces.

Electrophysiological correlates of automatic spreading of activation in patients with psychotic disorder and first-degree relatives.

BACKGROUND: Semantic network abnormalities in patients with psychotic disorder were examined using associative prime-target relations with two stimulus asynchronies (SOAs; -250ms and -500ms) to assess the time course of automatic and more controlled processes of semantic priming. To investigate whether an aberrant semantic network system is part of the familial liability for psychosis, healthy siblings of patients with psychotic disorder were additionally examined. The N400 event-related brain potential (ERP) was used as a probe of semantic processing. METHOD: Twenty-two patients with psychotic disorder, twenty siblings of patients with psychotic disorder and twenty controls participated in a lexical decision task and ERPs were recorded to target words that were associatively, indirectly or not related to their preceding prime word. RESULTS: Associative priming of the N400 amplitude was found across all participants and both SOAs, but no between-group differences were found for the N400 amplitude (both SOAs). The Group×Condition interaction of the indirect priming N400 latency of the three groups was just short of statistical significance (F2,59=2.7, p=.077). Patients showed an increased indirect priming effect of the N400 latency only at short SOA, with decreased latency of the indirectly related compared to the unrelated condition, while controls did not show an indirect priming N400 latency effect. No between-group differences in N400 latency of indirect priming were found at the long SOA. Only a trend towards a Group×Condition interaction of the indirect priming N400 latency between the sibling and the controls was found, but without a main effect of indirect priming in the sibling group. CONCLUSION: These preliminary results support the assumption of a hyperactive semantic network in patients with psychotic disorder, which develops under automatic processes and decreases with more controlled processes, but does not represent clear trait familial liability.

Basic abnormalities in visual processing affect face processing at an early age in autism spectrum disorder.

BACKGROUND: A detailed visual processing style has been noted in autism spectrum disorder (ASD); this contributes to problems in face processing and has been directly related to abnormal processing of spatial frequencies (SFs). Little is known about the early development of face processing in ASD and the relation with abnormal SF processing. We investigated whether young ASD children show abnormalities in low spatial frequency (LSF, global) and high spatial frequency (HSF, detailed) processing and explored whether these are crucially involved in the early development of face processing. METHODS: Three- to 4-year-old children with ASD (n = 22) were compared with developmentally delayed children without ASD (n = 17). Spatial frequency processing was studied by recording visual evoked potentials from visual brain areas while children passively viewed gratings (HSF/LSF). In addition, children watched face stimuli with different expressions, filtered to include only HSF or LSF. RESULTS: Enhanced activity in visual brain areas was found in response to HSF versus LSF information in children with ASD, in contrast to control subjects. Furthermore, facial-expression processing was also primarily driven by detail in ASD. CONCLUSIONS: Enhanced visual processing of detailed (HSF) information is present early in ASD and occurs for neutral (gratings), as well as for socially relevant stimuli (facial expressions). These data indicate that there is a general abnormality in visual SF processing in early ASD and are in agreement with suggestions that a fast LSF subcortical face processing route might be affected in ASD. This could suggest that abnormal visual processing is causative in the development of social problems in ASD.

An eye for detail: an event-related potential study of the rapid processing of fearful facial expressions in children.

There is converging evidence for the presence of a fast subcortical face-processing route that operates on global face characteristics in the mature brain. Until now, little has been known about the development of such a route, which is surprising given suggestions that this fast subcortical face-processing route might be affected in neurodevelopmental disorders such as autism. To address this, early visual event-related potentials to pictures of fearful and neutral faces containing detailed or global information in 3- to 4-year-old (n = 20), 5- to 6-year-old (n = 25), and 7- to 8-year-old (n = 25) children were compared. In children, emotional processing was driven by detailed information. Developmental effects are discussed in terms of maturation of the fast subcortical face-processing route as well as an increase in experience with facial expressions with age.

Reaching around barriers: the performance of the great apes and 3-5-year-old children.

Inhibitory control has been suggested as a key predictive measure of problem-solving skills in human and nonhuman animals. However, there has yet to be a direct comparison of the inhibitory skills of the nonhuman apes and their development in human children. We compared the inhibitory skills of all great ape species, including 3-5-year-old children in a detour-reaching task, which required subjects to avoid reaching directly for food and instead use an indirect reaching method to successfully obtain the food. We tested 22 chimpanzees, 18 bonobos, 18 orangutans, 6 gorillas and 42 children. Our sample included chimpanzees, bonobos and orangutans housed in zoos (N = 27) and others housed in sanctuaries in their native habitats (N = 37). Overall, orangutans were the most skilful apes, including human children. As expected older children outperformed younger children. Sanctuary chimpanzees and bonobos outperformed their zoo counterparts whereas there was no difference between the two orangutan samples. Most zoo chimpanzees and bonobos failed to solve the original task, but improved their performance with additional training, although the training method determined to a considerable extent the level of success that the apes achieved in a transfer phase. In general, the performance of the older children was far from perfect and comparable to some of the nonhuman apes tested.

Is the early modulation of brain activity by fearful facial expressions primarily mediated by coarse low spatial frequency information?

Rapidly decoding the emotional content of a face is an important skill for successful social behavior. Several Event Related brain Potential (ERP) have indicated that emotional expressions already influence brain activity as early as 100 ms. Some studies hypothesized that this early brain response to fear depends on coarse-magnocellular inputs, which are primarily driven by Low Spatial Frequency (LSF) cues. Until now however, evidence is inconclusive probably due to the divergent methods used to match luminance and contrast across spatial frequencies and emotional stimuli. In the present study, we measured ERPs to LSF and HSF faces with fearful or neutral expressions when contrast and luminance was matched across SF or not. Our findings clearly show that fearful facial expressions increases the amplitude of P1 (only for contrast-luminance equated images) and N170 in comparison to neutral faces but only in LSF faces, irrespective of contrast or luminance equalization, further suggesting that LSF information plays a crucial role in the early brain responses to fear. Furthermore, we found that, irrespective of luminance or contrast equalization, N170 occurred faster when perceiving LSF faces than HSF faces, again emphasizing the primacy of LSF processing in early face perception.

Reduced error monitoring in children with autism spectrum disorder: an ERP study.

This study investigated self-monitoring in children with autism spectrum disorder (ASD) with event-related potentials looking at both the error-related negativity (ERN) and error-related positivity (Pe). The ERN is related to early error/conflict detection, and the Pe has been associated with conscious error evaluation or attention allocation. In addition, post-error slowing in reaction times (RTs) was measured. Children with ASD and age- and IQ- matched controls were administered an easy and a hard version of an auditory decision task. Results showed that the ERN was smaller in children with ASD but localized in the anterior cingulate cortex (ACC) in both groups. In addition we found a negativity on correct trials (CRN) that did not differ between the groups. Furthermore, a reduced Pe and a lack of post-error slowing in RTs were found in children with ASD. The reduced ERN in children with ASD, in the presence of an intact CRN, might suggest a specific insensitivity to detect situations in which the chance of making errors is enhanced. This might in turn lead to reduced error awareness/attention allocation to the erroneous event (reduced Pe) and eventually in a failure in change of strategy to deal with a situation, as becomes evident from the lack of post-error slowing in the ASD group. This relates well to the perseverative behaviour that is seen in children with ASD. We discuss these results in terms of a general deficit in self-monitoring, underlying social disturbance in ASD and the involvement of the ACC.

How the great apes (Pan troglodytes, Pongo pygmaeus, Pan paniscus, and Gorilla gorilla) perform on the reversed contingency task: the effects of food quantity and food visibility.

S. T. Boysen and G. G. Berntson (1995) found that chimpanzees performed poorly on a reversed contingency task in which they had to point to the smaller of 2 food quantities to acquire the larger quantity. The authors compared the performance of 4 great ape species (Pan troglodytes, Pongo pygmaeus, Pan paniscus, and Gorilla gorilla) on the reversed contingency task while manipulating food quantity (0-4 or 1-4) and food visibility (visible pairs or covered pairs). Results showed no systematic species differences but large individual differences. Some individuals of each species were able to solve the reversed contingency task. Both quantity and visibility of the food items had a significant effect on performance. Subjects performed better when the disparity between quantities was smaller and the quantities were not directly visible.

Atypical visual orienting to gaze- and arrow-cues in adults with high functioning autism.

The present study investigates visual orienting to directional cues (arrow or eyes) in adults with high functioning autism (n = 19) and age matched controls (n = 19). A choice reaction time paradigm is used in which eye- or arrow direction correctly (congruent) or incorrectly (incongruent) cues target location. In typically developing participants, the visual orienting reflex is longer for eyes than for arrows. Right side cueing, but not left side cueing, induced a congruence effect for eyes, while this effect was evident for right as well as for left side arrow cues. In participants with autism the overall visual orienting reflex was not different between arrows and eyes and no laterality effect was found for eyes cueing. These findings suggest that, instead of a specific Eye Direction Detector persons with autism might have a general 'Symbol Direction Detector'.