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Dyslexia, dyscalculia and their comorbid manifestation are prevalent disorders associated with well-documented behavioral manifestations. However, attempts to relate these manifestations to abnormalities in brain structure have yielded mixed results, with no clear consistency across a range of measures. In this study, we used a unique design including adults with dyslexia, dyscalculia, both disorders and controls, to explore differences in gray matter characteristics across groups. Specifically, we examined whether dyslexia, dyscalculia, or their comorbid manifestation could be related to volumetric and surface characteristics of gray matter, using voxel-based and surface-based morphometry. We demonstrate with Bayesian analyses that the present data favor the null model of no differences between groups across the brain, a result that is in line with recent findings in this field of research. Importantly, we provide detailed statistical maps to enable robust assessment of our findings, and to promote cumulative evaluation of the evidence. Together, these findings suggest that gray matter differences associated with dyslexia and dyscalculia might not be as reliable as suggested by previous literature, with important implications for our understanding of these disorders.

Learning disabilities such as dyslexia, dyscalculia and their comorbid manifestation are prevalent, affecting as much as 15% of the population. Structural neuroimaging studies have indicated that these disorders can be related to differences in white matter integrity, although findings remain disparate. In this study, we used a unique design composed of individuals with dyslexia, dyscalculia, both disorders and controls, to systematically explore differences in fractional anisotropy across groups using diffusion tensor imaging. Specifically, we focused on the corona radiata and the arcuate fasciculus, two tracts associated with reading and mathematics in a number of previous studies. Using Bayesian hypothesis testing, we show that the present data favor the null model of no differences between groups for these particular tracts—a finding that seems to go against the current view but might be representative of the disparities within this field of research. Together, these findings suggest that structural differences associated with dyslexia and dyscalculia might not be as reliable as previously thought, with potential ramifications in terms of remediation., Highlights • Previous literature indicates important discrepancies in structural differences associated with dyslexia and dyscalculia • We explore the relationship between these disorders and fractional anisotropy, a measure of white matter integrity • We show support for the null model in the corona radiata and the arcuate fasciculus • This suggests that structural differences associated with these disorders are not as reliable as previously thought

A key difficulty in assessing cognitive development in early childhood lies in the necessity of using different measures for age groups over time. We report on the development of cognitive composite indices (CCIs) at 9 months, 2 years and 4.5 years in children enrolled in the Growing Up in New Zealand study. Data was collected from 6074 children comprising 21 age-adjusted cognitive outcomes. Factor analysis was performed, identifying one factor at 9 months and two factors at 2 years and 4.5 years, respectively. Only the CCIs identified at 4.5 years were significantly related to cognitive outcomes at 8 years. The scores identified in this study can potentially be used to observe rank order changes or movement of general cognitive abilities.

Dyslexia is a developmental disorder characterized by reading and phonological difficulties, yet important questions remain regarding its underlying neural correlates. In this study, we used partial least squares (PLS), a multivariate analytic technique, to investigate the neural networks used by dyslexics while performing a word-rhyming task. Although the overall reading network was largely similar in dyslexics and typical readers, it did not correlate with behavior in the same way in the two groups. In particular, there was a positive association between reading performance and both right superior temporal gyrus and bilateral insula activation in dyslexic readers but a negative correlation in typical readers. Together with differences in lateralization unique to dyslexics, this suggests that the combination of poor reading performance with high insula activity and atypical laterality is a consistent marker of dyslexia. These findings emphasize the importance of understanding right-hemisphere activation in dyslexia and provide promising directions for the remediation of reading disorders.

The relationships between screen media use and hot and cool executive functioning (EF) and inattention/hyperactivity during the preschool years were assessed using data from mothers, fathers and children (N = 3787) participating in the Growing Up in New Zealand study. Patterns of screen time (i.e., whether children exceeded 2 hr of screen time at 2 and 4 years), content of screen media (adult-directed vs child-directed), total exposure of child to weekday TV (background and foreground), allowing meals in front of TV, having restrictive rules about TV, and frequency of co-viewing were examined. Binomial logistic regression analyses revealed a relationship between total exposure to TV on a weekday at age 2 and poorer performance on a hot EF task at 4.5 years of age. A relationship between eating meals in front of TV at 4 years and poorer performance on a cool EF task at 4.5 years was also identified.

Neuroimaging research into the brain structure of schizophrenia patients has shown consistent reductions in grey matter volume relative to healthy controls. Examining structural differences in individuals with high levels of schizotypy may help elucidate the course of disorder progression, and provide further support for the schizotypy-schizophrenia continuum. Thus far, the few studies investigating grey matter differences in schizotypy have produced inconsistent results. In the current study, we used a multivariate partial least squares (PLS) approach to clarify the relationship between psychometric schizotypy (measured by the Oxford-Liverpool Inventory of Feelings and Experiences) and grey matter volume in 49 healthy adults. We found a negative association between all schizotypy dimensions and grey matter volume in the frontal and temporal lobes, as well as the insula. We also found a positive association between all schizotypy dimensions and grey matter volume in the parietal and temporal lobes, and in subcortical regions. Further correlational analyses revealed that positive and disorganised schizotypy were strongly associated with key regions (left superior temporal gyrus and insula) most consistently reported to be affected in schizophrenia and schizotypy. We also compared PLS with the typically used General Linear Model (GLM) and demonstrate that PLS can be reliably used as an extension to voxel-based morphometry (VBM) data. This may be particularly valuable for schizotypy research due to PLS' ability to detect small, but reliable effects. Together, the findings indicate that healthy schizotypal individuals exhibit structural changes in regions associated with schizophrenia. This adds to the evidence of an overlap of phenotypic expression between schizotypy and schizophrenia, and may help establish biological endophenotypes for the disorder.

Research on adolescent and adult populations has linked depression to variation in several monoaminergic genes, but genetic association studies on depression in children are limited. Additionally, few studies have investigated whether stressors occurring very early in development moderate the influence of certain genes on depression. The aim of this study was to investigate whether single nucleotide polymorphisms (SNPs) from monoaminergic genes interacted with measures of early life stress to influence depressive symptoms in children. Participants were members of the Auckland Birthweight Collaborative cohort. Small for gestational age (SGA) and maternal stress during pregnancy were measured at birth and used as indicators of early life stress. At age 11, depressive symptoms were measured using the Centre for Epidemiological Studies Depression Scale for Children (CES-DC) and DNA samples were collected for genotyping. A two-way ANOVA revealed that SGA and a SNP from the dopamine transporter gene DAT1 had an interactive effect on children's depressive symptoms. Specifically, symptoms were greater in children born SGA who are T homozygous for the rs1042098 SNP. These findings suggest that adverse intrauterine environments leading to low birth weight also seem to exacerbate the effects of certain DAT1 variants on depression.

Sensory gating is the ability to filter out irrelevant stimuli from the environment. Individuals with schizophrenia consistently demonstrate deficits in this ability leading to sensory overload and cognitive fragmentation. This dysfunction has also been found in schizotypy, which is defined as a manifestation of nonclinical symptoms qualitatively similar to those found in schizophrenia. In the present study, auditory sensory gating was assessed in healthy individuals by testing the attenuation of the P50 event-related potential. The degree of suppression was then correlated with schizotypy by using the O-LIFE questionnaire. Relative to the low-scoring individuals, P50 suppression was significantly reduced in those with high levels of schizotypy. Furthermore, the degree of deficit in P50 gating correlated with both cognitive disorganisation and impulsive nonconformity dimensions of schizotypy. These results suggest that schizotypal individuals may have early sensory gating deficits similar to schizophrenia patients, especially if they display a disorganised or impulsive profile. As they do not exhibit overt psychotic symptoms, it is likely that such deficits represent an underlying core cognitive dysfunction within the schizophrenia spectrum.

Empirical studies indicate a link between creativity and schizotypal personality traits, where individuals who score highly on schizotypy measures also display greater levels of creative behaviour. However, the exact nature of this relationship is not yet clear, with only a few studies examining this association using neuroimaging methods. In the present study, the neural substrates of creative thinking were assessed with a drawing task paradigm in healthy individuals using fMRI. These regions were then statistically correlated with the participants' level of schizotypy as measured by the Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE), which is a questionnaire consisting of four dimensions. Neural activations associated with the creativity task were observed in bilateral inferior temporal gyri, left insula, left parietal lobule, right angular gyrus, as well as regions in the prefrontal cortex. This widespread pattern of activation suggests that creative thinking utilises multiple neurocognitive networks, with creative production being the result of collaboration between these regions. Furthermore, the correlational analyses found the Unusual Experiences factor of the O-LIFE to be the most common dimension associated with these areas, followed by the Impulsive Nonconformity dimension. These correlations were negative, indicating that individuals who scored the highest in these factors displayed the least amount of activation when performing the creative task. This is in line with the idea that 'less is more' for creativity, where the deactivation of specific cortical areas may facilitate creativity. Thus, these findings contribute to the evidence of a common neural basis between creativity and schizotypy.

The developmental learning disabilities dyscalculia and dyslexia have a combined prevalence of 10% or more, and a co-occurrence (comorbidity) rate of around 40%. The causes and consequences of this comorbidity are poorly understood, despite implications for identification and remediation. We examined the cognitive bases of MDRD comorbidity in four groups of 85 adults (dyscalculia only, dyslexia only, comorbid and control), controlling for IQ and attentional difficulties. We used a computerized testing battery including core components of mathematics and reading, plus domain general capacities. Our results provide one of the first descriptions of dyscalculia symptoms in adults, showing that impairment on core numerical tasks continues into adulthood. Dyscalculia and dyslexia showed independent domain specific deficits, however we also found evidence for domain general symptoms associated with both disorders. We argue that the presence of multiple underlying and additive impairments supports complex multifactorial models of comorbidity.

Maternal smoking in pregnancy has been separately linked with both lower IQ scores and epigenetic modifications of the brain-derived neurotrophic factor (BDNF) gene in offspring. The purpose of this study was to investigate whether maternal smoking exposure interacts with the BDNF single nucleotide polymorphism (SNP) rs6265 to affect offspring IQ across multiple ages during childhood. Participants are 546 members of a longitudinal study of 871 Caucasian infants sampled disproportionately for small for gestational age: approximately half had birthweight p = 0.052).

Despite the wealth of literature examining long term outcomes of preterm low birthweight children, few studies have directly assessed the developmental impact of being born full term but small for gestational age (SGA). We aim to determine whether (i) being SGA increases preschool behavioural problems and (ii) other risk factors operate differently in SGA and appropriate for gestational age (AGA) controls. 550 New Zealand European mothers and their 3.5 year old children participated in this study. All children were born at full term (>37 weeks' gestation) and approximately half were SGA (≤sex specific 10th percentile for gestation) the remainder were AGA controls. Extensive data were collected at the child's birth, 1 year and 3.5 years. Behavioural problems were measured when children were 3.5 years, using the Strengths and Difficulties Questionnaire (SDQ). Multiple regression analyses were used to examine the associations between risk factors and behavioural problems; statistical weighting was used for analyses of the total study group. There was no significant difference in behavioural problems between SGA and AGA groups. In the total sample the significant predictors of behavioural problems included: mothers' school leaving age; smoking during pregnancy; maternal alcohol use during pregnancy; and absence of the father. Predictors of behavioural problems were found to be the same for SGA and AGA groups. These results do not support the view that SGA is a risk for behavioural preschool difficulties or that SGA children are sensitised to risks known to be associated with such difficulties in the preschool years.

The form of the structural asymmetries across the cerebral hemispheres, that support well-established functional asymmetries, are not well understood. Although, many previous studies have investigated structural differences in areas associated with strong functional asymmetries, such as language processes, regions of the brain with less well established functional laterality have received less attention. The current study aims to address this by exploring global white matter asymmetries of the healthy human brain using diffusion tensor imaging (DTI) and tractography. DTI was conducted on twenty-nine healthy right-handed males, and pathways from the four major lobes were reconstructed using probabilistic tractography. Mean FA, parallel and perpendicular diffusion values were calculated and compared across hemispheres for each pathway generated. Significant asymmetries in the parietal (rightward asymmetry) and occipital (leftward asymmetry) pathways were found in FA measures. However, asymmetric patterns in parallel and/or perpendicular diffusion were observed in all four lobes, even in pathways with symmetrical FA. For instance, significant rightward asymmetry in parallel diffusion was found in the parietal and frontal lobes, whereas significant leftward asymmetry was found in the temporal and occipital lobes. We suggest that these different patterns of diffusion asymmetry reflect differences in microanatomy that support the known patterns of differential functional asymmetry. The different directions of anatomical asymmetry support the notion that there may be a number of different lateralising influences operating in the brain.

The association between intelligence and diet at 3.5 and 7 years was examined in 591 children of European descent. Approximately half of the children were born small-for-gestational age (birth weight ≤ 10th percentile). The relationship between IQ and diet (measured by food frequency) was investigated using multiple regression analyses. Eating margarine at least daily was associated with significantly lower IQ scores at 3.5 years in the total sample and at 7 years in SGA children. For all children, eating the recommended daily number of breads and cereals was associated with significantly higher IQ scores at 3.5 years, and those who ate fish at least weekly had significantly higher IQ scores at 7 years than those who did not. The consumption of fish, breads and cereals commeasurable with nutritional guidelines may be beneficial to children's cognitive development. In contrast, consuming margarine daily was associated with poorer cognitive functioning. Further research is needed to identify the nutrients that may underlie this association.

The majority of studies support a role of the anterior cingulate cortex (ACC) in the attentional control necessary for conflict resolution in the Stroop task; however, the time course of activation and the neural substrates underlying the Stroop task remain contentious. We used high-density EEG to record visual-evoked potentials from 16 healthy subjects while performing a manual version of the traditional Stroop colour-word task. Difference waveforms for congruent-control and incongruent-control conditions were similar in amplitude and had a similar spatial distribution in the time window of 260-430 ms post stimulus onset. Source estimation indicated particularly middle cingulate involvement in congruent-control and incongruent-control difference waveforms. In contrast, the difference waveform for the incongruent-congruent contrast was observed later (in the time window of 370-480 ms), had a different spatial distribution, and source estimation indicated that the anterior cingulate underlies this difference waveform. As congruent-control and incongruent-control differences have a similar timeframe and cingulate source, we propose that this indicates early attentional allocation processes. That is, the identification of two sources of information (the word and the colour it is printed in) and the selective attention to one. The later peak in the incongruent-congruent difference wave, originating in anterior cingulate, likely reflects identification (and subsequent resolution) of conflict in the two sources of information.

Two versions of the line bisection task, paper-and-pencil and computerized, were administered to non-medicated children (5-12 years) with and without Attention-Deficit/Hyperactivity Disorder (ADHD). Fifteen children were classified with ADHD-Inattentive type (ADHD-I), 15 were classified with ADHD-Combined or Hyperactive-Impulsive type (ADHD-C), and 15 children served as controls. During the paper-and-pencil task, and irrespective of hand-use, participants with ADHD-C bisected lines with a right bias, whereas participants with ADHD-I showed a leftwards bias. Interestingly, during the computerized version, an opposite pattern of hemineglect was observed with a leftwards bias for participants with ADHD-C and a rightwards bias for participants with ADHD-I. These findings suggest that different task demands are associated with the paper-and-pencil and computerized tasks. The findings also suggest that the two subtypes differ according to their cognitive profile, and possibly differ as to their underlying neural impairment.

Two left- and right-hemispherectomized patients with contralateral hemianopia and 20 normal controls were administered a line bisection task. All hemispherectomized patients showed a strong bisection bias towards their blind visual field. This contralateral bias persisted when patients were forced to start scanning within their blind hemifield, supporting the idea of a strategic adaptation of attention towards the blind visual field. In all patients the hemispherectomy was performed as a result of cortical abnormality (congenital or acquired) and therefore early changes in functional cerebral organization may have occurred in these patients. The absence of a neglect-like ipsilateral bias and the presence of a hemianopic-like contralateral bias in line may represent a functional deficit or suggest that plastic changes following hemispherectomy induced an adaptive functional re-organization of spatial attention in both left- and right-hemispherectomized patients.

A longitudinal investigation of risk factors for early- and late-onset dental fear was conducted. Early-onset dental fear was related to conditioning experiences (indexed via caries level and tooth loss), service use patterns, stress reactive personality and specific beliefs about health professionals. Late-onset dental fear was related to aversive conditioning experiences, irregular service use and an external locus of control. In contrast to recent findings for dental anxiety, personality factors were not strongly related to the onset of dental fear in young adulthood. The key role played by conditioning events in the development of both early- and late-onset dental fear was confirmed. Conditioning events appear to play a different role in the development of dental fear vs dental anxiety. This may reflect important, but largely ignored differences between these two closely-related constructs. Interventions for early-onset dental fear should aim to modify both the dental fear and the personality vulnerabilities that may contribute to the development of dental fear early in the life-course.

The non-associative, Darwinian theory of fear acquisition proposes that some individuals fail to overcome biologically-relevant fears (e.g. height) because they (1) do not have sufficient safe exposure to the relevant stimuli early in life or (2) are poor habituators who have difficulty 'learning not to fear'. These two hypotheses were tested in a longitudinal birth cohort study. Study 1 found evidence for reduced exposure to height stimuli in childhood for individuals with a fear of heights compared to study members without fear. Study 2 found evidence for higher levels of stress reactivity (a proxy for habituation) in childhood and adolescence among 18-year-old height phobics compared to study members with dental phobia and those with no fear. The results were discussed in relation to recent findings suggesting that some evolutionary-relevant fears may appear in the absence of traumatic 'learning' experiences. The merits of adding a fourth, non-associative pathway to Rachman's [Rachman, S. (1977)]. The conditioning theory of fear acquisition: a critical examination. Behaviour Research and Therapy, 15, 375-387) three pathways model of fear acquisition were briefly considered.

Several recent studies have reported a causal association between stature and month of birth. Perinatal exposure to sunlight has been suggested as the principal factor underlying this relationship, although the mechanisms involved remain a matter of debate. The longitudinal design of the present study allowed us to directly test the influence of perinatal sunlight exposure (and other meteorological and behavioural factors) on body size at birth and at regular intervals up to age 26. The findings confirmed that pre-natal sunlight is one of the most significant determinants of height. However, the trimester of greatest influence differs depending on the age at which study members were measured.

Behavioral laterality tasks assessed the differential processing efficiencies of the cerebral hemispheres in younger and older reading-age children. Lateralized lexical decision task findings supported a "direct access" model of hemispheric processing for the younger children whereas the older children demonstrated a "callosal relay" pattern. A dual-task with oral and silent reading indicated that the right hand was significantly more disrupted than the left during unimanual finger tapping. The findings suggest that although the left hemisphere's involvement during reading is developmentally stable, the involvement of the right hemisphere appears to change dynamically as reading experience increases.