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An improved neuroanatomical model of the default-mode network reconciles previous neuroimaging and neuropathological findings.
The brain is constituted of multiple networks of functionally correlated brain areas, out of which the default-mode network (DMN) is the largest. Most existing research into the DMN has taken a corticocentric approach. Despite its resemblance with the unitary model of the limbic system, the contribution of subcortical structures to the DMN may be underappreciated. Here, we propose a more comprehensive neuroanatomical model of the DMN including subcortical structures such as the basal forebrain, cholinergic nuclei, anterior and mediodorsal thalamic nuclei. Additionally, tractography of diffusion-weighted imaging was employed to explore the structural connectivity, which revealed that the thalamus and basal forebrain are of central importance for the functioning of the DMN. The contribution of these neurochemically diverse brain nuclei reconciles previous neuroimaging with neuropathological findings in diseased brains and offers the potential for identifying a conserved homologue of the DMN in other mammalian species.
Altered resting-state functional connectivity in emotion-processing brain regions in adults who were born very preterm
<jats:sec id="S0033291716001604_sec_a1"><jats:title>Background</jats:title><jats:p>Very preterm birth (VPT; <32 weeks of gestation) has been associated with impairments in emotion regulation, social competence and communicative skills. However, the neuroanatomical mechanisms underlying such impairments have not been systematically studied. Here we investigated the functional integrity of the amygdala connectivity network in relation to the ability to recognize emotions from facial expressions in VPT adults.</jats:p></jats:sec><jats:sec id="S0033291716001604_sec_a2" sec-type="methods"><jats:title>Method</jats:title><jats:p>Thirty-six VPT-born adults and 38 age-matched controls were scanned at rest in a 3-T MRI scanner. Resting-state functional connectivity (rs-fc) was assessed with SPM8. A seed-based analysis focusing on three amygdalar subregions (centro-medial/latero-basal/superficial) was performed. Participants’ ability to recognize emotions was assessed using dynamic stimuli of human faces expressing six emotions at different intensities with the Emotion Recognition Task (ERT).</jats:p></jats:sec><jats:sec id="S0033291716001604_sec_a3" sec-type="results"><jats:title>Results</jats:title><jats:p>VPT individuals compared to controls showed reduced rs-fc between the superficial subregion of the left amygdala, and the right posterior cingulate cortex (<jats:italic>p</jats:italic> = 0.017) and the left precuneus (<jats:italic>p</jats:italic> = 0.002). The VPT group further showed elevated rs-fc between the left superficial amygdala and the superior temporal sulcus (<jats:italic>p</jats:italic> = 0.008). Performance on the ERT showed that the VPT group was less able than controls to recognize anger at low levels of intensity. Anger scores were significantly associated with rs-fc between the superficial amygdala and the posterior cingulate cortex in controls but not in VPT individuals.</jats:p></jats:sec><jats:sec id="S0033291716001604_sec_a4" sec-type="conclusion"><jats:title>Conclusions</jats:title><jats:p>These findings suggest that alterations in rs-fc between the amygdala, parietal and temporal cortices could represent the mechanism linking VPT birth and deficits in emotion processing.</jats:p></jats:sec>
<jats:title>Abstract</jats:title><jats:p><jats:bold>Objectives:</jats:bold> Children and adolescents who were born very preterm (≤32 weeks’ gestation) are vulnerable to experiencing cognitive problems, including in executive function. However, it remains to be established whether cognitive deficits are evident in adulthood and whether these exert a significant effect on an individual’s real-lifeachievement. <jats:bold>Methods:</jats:bold> Using a cross-sectional design, we tested a range of neurocognitive abilities, with a focus on executive function, in a sample of 122 very preterm individuals and 89 term-born controls born between 1979 and 1984. Associations between executive function and a range of achievement measures, indicative of a successful transition to adulthood, were examined. <jats:bold>Results:</jats:bold> Very preterm adults performed worse compared to controls on measures of intellectual ability and executive function with moderate to large effect sizes. They also demonstrated significantly lower achievement levels in terms of years spent in education, employment status, and on a measure of functioning in work and social domains. Results of regression analysis indicated a stronger positive association between executive function and real-life achievement in the very preterm group compared to controls. <jats:bold>Conclusions:</jats:bold> Very preterm born adults demonstrate executive function impairments compared to full-term controls, and these are associated with lower achievement in several real-life domains. (<jats:italic>JINS</jats:italic>, 2017, <jats:italic>23</jats:italic>, 381–389)</jats:p>
<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>Individuals who were born very preterm have higher rates of psychiatric diagnoses compared to term-born controls; however, it remains unclear whether they also display increased sub-clinical psychiatric symptomatology. Hence our objective is to utilise a dimensional approach to assess psychiatric symptomatology in adults who were born very preterm.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>152 adults who were born very preterm (before 33 weeks’ gestation; gestational range 24–32 weeks) and 96 term-born controls. We examined participants’ clinical profile using the Comprehensive Assessment of At-Risk Mental States (CAARMS), a measure of sub-clinical symptomatology that yields seven subscales including general psychopathology, positive, negative, cognitive, behavioural, motor and emotional symptoms, in addition to a total psychopathology score. Intellectual abilities were examined using the Wechsler Abbreviated Scale of Intelligence.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Between-group differences on the CAARMS showed elevated symptomatology in very preterm participants compared to controls in positive, negative, cognitive and behavioural symptoms. Total psychopathology scores were significantly correlated with IQ in the very preterm group only. In order to examine the characteristics of participants’ clinical profile a principal component analysis was conducted. This revealed two components, one reflecting a non-specific psychopathology dimension, and the other indicating a variance in symptomatology along a positive-to-negative symptom axis. K-means (k=4) were used to further separate the study sample into clusters. Very preterm adults were more likely to belong to the high non-specific psychopathology cluster compared to controls.</jats:p></jats:sec><jats:sec><jats:title>Conclusion and Relevance</jats:title><jats:p>Very preterm individuals demonstrated elevated psychopathology compared to full-term controls. Psychiatric risk was characterised by a non-specific clinical profile and was associated with lower IQ.</jats:p></jats:sec>