Neocortical maturation during adolescence: change in neuronal soma dimension

During adolescence, cognitive abilities increase robustly. To search for possible related structural alterations of the cerebral cortex, we measured neuronal soma dimension (NSD = width times height), cortical thickness and neuronal densities in different types of neocortex in post-mortem brains of five 12-16 and five 17-24 year-olds (each 2F, 3M). Using a generalized mixed model analysis, mean normalized NSD comparing the age groups shows layer-specific change for layer 2 (p < .0001) and age-related differences between categorized type of cortex: primary/primary association cortex (BA 1, 3, 4, and 44) shows a generalized increase; higher-order regions (BA 9, 21, 39, and 45) also show increase in layers 2 and 5 but decrease in layers 3, 4, and 6 while limbic/orbital cortex (BA 23, 24, and 47) undergoes minor decrease (BA 1, 3, 4, and 44 vs. BA 9, 21, 39, and 45: p = .036 and BA 1, 3, 4, and 44 vs. BA 23, 24, and 47: p = .004). These data imply the operation of cortical layer- and type-specific processes of growth and regression adding new evidence that the human brain matures during adolescence not only functionally but also structurally.     

Personal and impersonal stimuli differentially engage brain networks during moral reasoning

Moral decision making has recently attracted considerable attention as a core feature of all human endeavors. Previous functional magnetic resonance imaging studies about moral judgment have identified brain areas associated with cognitive or emotional engagement. Here, we applied graph theory-based network analysis of event-related potentials during moral decision making to reveal the personal/impersonal distinction in the organization of functional connectivity. Our results indicated that the personal task had more larger long-range connections involved in frontal regions and the right hemisphere, and higher network efficiency of some frontal electrodes such as F2 than the impersonal. These might be related to brain resource reorganization contributing to efficient conflict resolution. These findings provide new insights into neural mechanisms of moral dilemmas.     

Semantic relations differentially impact associative recognition memory: Electrophysiological evidence

Though associative recognition memory is thought to rely primarily on recollection, recent research indicates that familiarity might also make a substantial contribution when to-be-learned items are integrated into a coherent structure by means of an existing semantic relation. It remains unclear how different types of semantic relations, such as categorical (e.g., dancer–singer) and thematic (e.g., dancer–stage) relations might affect associative recognition, however. Using event-related potentials (ERPs), we addressed this question by manipulating the type of semantic link between paired words in an associative recognition memory experiment. An early midfrontal old/new effect, typically linked to familiarity, was observed across the relation types. In contrast, a robust left parietal old/new effect was found in the categorical condition only, suggesting a clear contribution of recollection to associative recognition for this kind of pairs. One interpretation of this pattern is that familiarity was sufficiently diagnostic for associative recognition of thematic relations, which could result from the integrative nature of the thematic relatedness compared to the similarity-based nature of categorical pairs. The present study suggests that the extent to which recollection and familiarity are involved in associative recognition is at least in part determined by the properties of semantic relations between the paired associates.     

My face or yours? Event-related potential correlates of self-face processing

The neural basis of self-recognition is mainly studied using brain-imaging techniques which reveal much about the localization of self-processing in the brain. There are comparatively few studies using EEG which allow us to study the time course of self-recognition. In this study, participants monitored a sequence of images, including 20 distinct images of their own face, a friend’s face and a stranger’s face articulating different speech sounds, while EEG was recorded from 64 scalp electrodes. Differences in the ERP waveforms were observed very early on, with increased N170 and VPP amplitude to self relative to both friend and stranger measured over posterior and fronto-central sites, respectively. This ‘self effect’ was also marked at ∼250 ms where P2/N2 amplitude was significantly reduced for self-faces. By comparison, differences between friend and stranger faces did not emerge until 250 ms and beyond, where a more conventional ‘familiarity effect’ was observed. The data also point to a ‘less lateralized’ representation of self over posterior sites. These findings are consistent with both behavioral and fMRI studies which suggest that self-face processing is ‘special’ and are discussed with reference to EEG studies of face processing.     

Electrophysiological correlates of processes supporting memory for faces

The retrieval processes supporting recognition memory for faces were investigated using event-related potentials (ERPs). The focus for analyses was ERP old/new effects, which are the differences between neural activities associated with correct judgments to old (studied) and new (unstudied) test stimuli. In two experiments it was possible to identify three old/new effects that behaved as neural indices of the process of recollection. In both experiments there was one old/new effect that behaved as an index of the process of familiarity. These outcomes are relevant to the ongoing debate about the functional significance of ERP old/new effects and the implications that scalp-recorded electrophysiological data have for theories of the processes supporting long-term memory judgments.     

White matter development during adolescence as shown by diffusion MRI

Previous volumetric developmental MRI studies of the brain have shown white matter development continuing through adolescence and into adulthood. This review presents current findings regarding white matter development and organization from diffusion MRI studies. The general trend during adolescence (age 12–18 years) is towards increasing fractional anisotropy (FA) with age and decreasing mean diffusivity (MD) with age, findings primarily due to decreasing radial diffusivity with age. However, results of studies vary as to the regional specificity of such age-related changes, likely due in part to methodological issues. Another general trend is for FA to positively correlate and MD to negatively correlate with cognitive function. This trend is however region-specific, task-specific, and population-specific; some studies have in fact found negative correlations of FA and positive correlations of MD in specific regions with specific measures of cognitive performance. There are also published reports of sexual dimorphism in white matter development, indicating differing developmental trajectories between males and females as well as differing relationships developmentally between white matter architecture and cognitive function. There is a need for more research to further elucidate the development of white matter and its relation to cognitive function during this critical developmental period.     

Sleep EEG changes during adolescence: An index of a fundamental brain reorganization

Delta (1–4 Hz) EEG power in non-rapid eye movement (NREM) sleep declines massively during adolescence. This observation stimulated the hypothesis that during adolescence the human brain undergoes an extensive reorganization driven by synaptic elimination. The parallel declines in synaptic density, delta wave amplitude and cortical metabolic rate during adolescence further support this model. These late brain changes probably represent the final ontogenetic manifestation of nature’s strategy for constructing nervous systems: an initial overproduction of neural elements followed by elimination. Errors in adolescent brain reorganization may cause mental illness; this could explain the typical age of onset of schizophrenia. Longitudinal studies of sleep EEG are enhancing our knowledge of adolescent brain maturation. Our longitudinal study of sleep EEG changes in adolescence showed that delta power, which may reflect frontal cortex maturation, begins its decline between ages 11 and 12 years and falls by 65% by age 17 years. In contrast, NREM theta power begins its decline much earlier. Delta and theta EEG frequencies are important to sleep theory because they behave homeostatically. Surprisingly, these brain changes are unrelated to pubertal maturation but are strongly linked to age. In addition to these (and other) maturational EEG changes, sleep schedules in adolescence change in response to a complex interaction of circadian, social and other influences. Our data demonstrate that the daytime sleepiness that emerges in adolescence is related to the decline in NREM delta as well as to altered sleep schedules. These longitudinal sleep data provide guideposts for studying cognitive and behavioral correlates of adolescent brain reorganization.     

Developmental changes in dopamine neurotransmission in adolescence: Behavioral implications and issues in assessment

Adolescence is characterized by increased risk-taking, novelty-seeking, and locomotor activity, all of which suggest a heightened appetitive drive. The neurotransmitter dopamine is typically associated with behavioral activation and heightened forms of appetitive behavior in mammalian species, and this pattern of activation has been described in terms of a neurobehavioral system that underlies incentive-motivated behavior. Adolescence may be a time of elevated activity within this system. This review provides a summary of changes within cortical and subcortical dopaminergic systems that may account for changes in cognition and affect that characterize adolescent behavior. Because there is a dearth of information regarding neurochemical changes in human adolescents, models for assessing links between neurochemical activity and behavior in human adolescents will be described using molecular genetic techniques. Furthermore, we will suggest how these techniques can be combined with other methods such as pharmacology to measure the impact of dopamine activity on behavior and how this relation changes through the lifespan.     

Fairness considerations: Increasing understanding of intentionality during adolescence

The development of fairness considerations in decision making is not well understood. Here we tested the hypothesis that increased understanding of intentionality during adolescence underlies increased fairness considerations in social decision making. We conducted three experiments using an adapted version of the Ultimatum Game with participants during four stages of adolescence: 9, 12, 15, and 18 years of age. Participants made or evaluated monetary offers, and we manipulated the intentionality context of offers. Results show that strategic thinking is already present at 9 years of age. There was no age difference in fairness of offers when the responder could not reject an offer (Experiment 1), but when they could reject an offer there was an age-related increase in taking into account the perspective and intentionality of other players when making offers (Experiment 2) and evaluating offers (Experiment 3). Taken together, the results demonstrate a linear developmental transition in fairness considerations that may have important implications for our understanding of social interactions during adolescence.     

Developmental changes in infants' processing of happy and angry facial expressions: a neurobehavioral study

Event-related brain potentials were measured in 7- and 12-month-old infants to examine the development of processing happy and angry facial expressions. In 7-month-olds a larger negativity to happy faces was observed at frontal, central, temporal and parietal sites (Experiment 1), whereas 12-month-olds showed a larger negativity to angry faces at occipital sites (Experiment 2). These data suggest that processing of these facial expressions undergoes development between 7 and 12 months: while 7-month-olds exhibit heightened sensitivity to happy faces, 12-month-olds resemble adults in their heightened sensitivity to angry faces. In Experiment 3 infants' visual preference was assessed behaviorally, revealing that the differences in ERPs observed at 7 and 12 months do not simply reflect differences in visual preference.     

Attachment representations and characteristics of friendship relations during adolescence

Attachment theory proposes that experiences with the primary caregivers are an important basis for the development of close social relationships outside the parent-child relationship. This study examined the association between representations of attachment, as assessed with the Adult Attachment Interview (AAI), representations of friendship and peer relations, as assessed with an interview in a sample of 43 adolescents. Secure attachment representations were significantly related to interview-based assessments of close friendships, friendship concept, integration in a peer group, and emotion regulation within close friendships. Attachment experiences reported during the AAI, their integration, and their coherency were related to friendship quality and friendship concept. Results show the close associations between attachment representations and friendship relationships during adolescence. The associations between peer relations and attachment representations differed depending on whether an interview approach or a questionnaire approach was used.     

Developmental changes in neural activity to familiar words and gestures

Infants younger than 20 months of age interpret both words and symbolic gestures as object names. Later in development words and gestures take on divergent communicative functions. Here, we examined patterns of brain activity to words and gestures in typically developing infants at 18 and 26 months of age. Event-related potentials (ERPs) were recorded during a match/mismatch task. At 18 months, an N400 mismatch effect was observed for pictures preceded by both words and gestures. At 26 months the N400 effect was limited to words. The results provide the first neurobiological evidence showing developmental changes in semantic processing of gestures.     

Electrophysiological evidence for size invariance in masked picture repetition priming

This experiment examined invariance in object representations through measuring event-related potentials (ERPs) to pictures in a masked repetition priming paradigm. Pairs of pictures were presented where the prime was either the same size or half the size of the target object and the target was either presented in a normal orientation or was a normal sized mirror reflection of the prime object. Previous masked repetition priming studies have found a cascade of priming effect sensitive to perceptual (N190/P190) and semantic (N400) properties of the stimulus. This experiment found that both early (N190/P190 effects) and later effects (N400) were invariant to size, whereas only the N190/P190 effect was invariant to mirror reflection. The combination of a small prime and a mirror reflected target led to no significant priming effects. Taken together, the results of this set of experiments suggests that object recognition, more specifically, activating an object representation, occurs in a hierarchical fashion where overlapping perceptual information between the prime and target is necessary, although not always sufficient, to activate a higher level semantic representation.     

The longitudinal links between shame and increasing hostility during adolescence

Little research has examined changes in emotional experience in adolescents. We hypothesized that the experience of shame would lead adolescents to become increasingly hostile. We report a one-year longitudinal study involving 765 high school students (392 males and 373 females; mean age = 14.41 yrs) in Grade 9 at Time 1 and 670 students (335 males and 335 females) in Grade 10 at Time 2. Shame and hostility showed high levels of stability over one-year. Structural equation modelling showed that higher shame in Grade 9 was predictive of increases in hostility in Grade 10, whereas hostility was not predictive of increases in shame. These results are discussed with reference to the nature of shame and its potential to provoke antisocial behaviour.     

Development of sex stereotypes relative to sport competence and value during adolescence

ObjectivesSex stereotypes adoption is presumed to impact one's perceived competence and value and to ultimately lead to dropout of certain activities. Adolescence is deemed to represent a period during which sex stereotypes are reinforced. The purpose of this study was to examine through a longitudinal design how sex stereotypes concerning athletic competence and value differ across adolescence.DesignA three-wave longitudinal follow-up within five cohorts of adolescents (N = 718) was realized.MethodThe participants completed a questionnaire assessing indirectly sport value and sport competence sex stereotypes.ResultsMultilevel growth curve analyses indicated that (i) boys report higher levels of stereotypes, (ii) the level of stereotypes endorsement increases with age, (iii) the rate of change of stereotypes endorsement decreases, and (iv) its increase is more pronounced among girls.ConclusionsThe hypothesis of an increase of sex stereotypes attached to sport is confirmed among girls. Methodological shortcomings are underlined and research perspectives are advanced.     

Work values system development during adolescence

Work values stability, change, and development can be appreciably reduced to a living system model [Ford, D. H. (1994). Humans as self-constructing living systems: A developmental perspective on behavior and personality (2nd ed.). Hillsdale, NJ: Lawrence Erlbaum Associates]. This theoretical model includes discrepancy-reducing and cohesion-amplifying mechanisms that interact to govern the change in standard- and goal-oriented work values over time [Boldero, J., & Francis, J. (2002). Goals, standards, and the self: reference values serving different functions. Personality and Social Psychology Review, 6(3), 232-241]. Employing longitudinal data from a sample of adolescents (n = 1010) spanning the 9th through the 12th grades, the results demonstrate that the value system develops in a theoretically predictable fashion during the adolescent period. Discrepancy reduction and cohesion mechanisms interact to either maintain or increase the integrity of and harmony between standard-oriented values associated with high school part-time work experiences and goal-oriented work values related to anticipated career-oriented work during adulthood. Exploratory analyses suggest that adolescents’ educational expectations influence the relative salience of standard- and goal-oriented work values and the discrepancy reduction process linking the two over time.     

Individual differences in ERPs during mental rotation of characters: Lateralization,and performance level

The cognitive process of imaging an object turning around is called mental rotation. Many studies have been put forward analyzing mental rotation by means of event-related potentials (ERPs). Event-related potentials (ERPs) were measured during mental rotation of characters in a sample (N = 82) with a sufficient size to obtain even small effects. A bilateral ERP amplitude modulation as a function of angular displacement was observed at parietal leads without any lateralization. Sex had no effect on mental rotation of characters, neither with respect to performance nor with respect to brain potentials. When the sample was split into groups of high- and low-performers, however, the results indicated (a) in line with the idea of neural efficiency substantially larger amplitudes for low-performers; (b) that the smaller amplitudes of the high-performers involved larger parietal networks; and (c) a left-parietal disengagement of neural activity for high-performers but a right-parietal disengagement for low-performers. The latter finding became evident through an analysis of internal consistencies of ERP amplitudes across conditions and performance levels, showing that internal consistencies were reduced at all three leads in the high-performance group for the biggest rotation angle, relative the other conditions and the low-performing group.     

Loneliness and solitude in adolescence: A confirmatory factor analysis of alternative models

The present study tested a four-factor model of adolescent loneliness and solitude that comprises peer-related loneliness, family loneliness, negative attitude toward solitude, and positive attitude toward solitude. Nine different instruments for a total of 14 scales and derivative subscales were completed by a sample of mid-adolescents (N = 534) from Grades 10 through 12 (aged 15–18 years) in the Dutch-speaking part of Belgium. As expected, the four-factor solution provided a better fit to the data than did alternative models that comprised just a single factor, or two and three factors. Use of the Loneliness and Aloneness Scale for Children and Adolescents (LACA) is recommended, because the instrument measures all four aspects of the model. Implications for current theories on adolescent loneliness and associated phenomena, such as adolescents’ attitude toward being on their own, are briefly discussed.     

ERP correlates of language-specific processing of auditory pitch feedback during self-vocalization

The present study investigated whether the neural correlates for auditory feedback control of vocal pitch can be shaped by tone language experience. Event-related potentials (P2/N1) were recorded from adult native speakers of Mandarin and Cantonese who heard their voice auditory feedback shifted in pitch by −50, −100, −200, or −500 cents when they sustained the vowel sound /u/. Cantonese speakers produced larger P2 amplitudes to −200 or −500 cents stimuli than Mandarin speakers, but this language effect failed to reach significance in the case of −50 or −100 cents. Moreover, Mandarin speakers produced shorter N1 latencies over the left hemisphere than the right hemisphere, whereas Cantonese speakers did not. These findings demonstrate that neural processing of auditory pitch feedback in vocal motor control is subject to language-dependent neural plasticity, suggesting that cortical mechanisms of auditory-vocal integration can be shaped by tone language experience.     

Evidence for specificity of ERP abnormalities during response inhibition in ADHD children: A comparison with reading disorder children without ADHD

Executive function and working memory deficits are not only present in ADHD, but also in reading disorder (RD). Here, high-density ERPs were recorded during the Stop Signal Task in 53 children and adolescents: An ADHD-combined type group, a group with RD, and a healthy control group. The ADHD-C group displayed unique abnormalities of the frontal N200. Both healthy controls and RD groups showed a success-related right frontal N200 modulation, which was absent in the ADHD group. Second, for Success Inhibition trials, the ADHD-C had smaller right frontal N200 waves relative to healthy controls, while the RD group did not. In contrast, NoGo-P3 abnormalities were present both in the ADHD-C and RD groups. Impaired early response inhibition mechanisms, indexed by the frontal N200, appear to be limited to ADHD-C. In contrast, deficits in later cognitive control and error monitoring mechanisms, indexed by the NoGo-P3, appear to be present in both conditions.