Meditation reduces brain activity in the default mode network in children with active cancer and survivors

BACKGROUND

Mounting evidence demonstrates that meditation can lower pain and emotional distress in adults, and more recently, in children. Children may benefit from meditation given its accessibility across a variety of settings (e.g., surgical preparation). Recent neuroimaging studies in adults suggest that meditation techniques are neurobiologically distinct from other forms of emotion regulation, such as distraction, that rely on prefrontal control mechanisms, which are underdeveloped in youth. Rather, meditation techniques may not rely on "top-down" prefrontal control and may therefore be utilized across the lifespan.

PROCEDURE

We examined neural activation in children with cancer, a potentially distressing diagnosis. During neuroimaging, children viewed distress-inducing video clips while using martial arts-based meditation (focused attention, mindful acceptance) or non-meditation (distraction) emotion regulation techniques. In a third condition (control), participants passively viewed the video clip.

RESULTS

We found that meditation techniques were associated with lower activation in default mode network (DMN) regions, including the medial frontal cortex, precuneus, and posterior cingulate cortex, compared to the control condition. Additionally, we found evidence that meditation techniques may be more effective for modulating DMN activity than distraction. There were no differences in self-reported distress ratings between conditions.

CONCLUSION

Together, these findings suggest that martial arts-based meditation modulates negative self-referential processing associated with the DMN, and may have implications for the management of pediatric pain and negative emotion.

Alterations in fear extinction neural circuitry and fear-related behavior linked to trauma exposure in children

Exposure to childhood trauma is extremely common (>60 %) and is a leading risk factor for fear-based disorders, including anxiety and posttraumatic stress disorder. These disorders are characterized by deficits in fear extinction and dysfunction in underlying neural circuitry. Given the strong and pervasive link between childhood trauma and the development of psychopathology, fear extinction may be a key mechanism. The present study tests the impact of childhood trauma exposure on fear extinction and underlying neural circuitry. Children (N = 44, 45 % trauma-exposed; 6-11 yrs) completed a novel two-day virtual reality fear extinction experiment. On day one, participants underwent fear conditioning and extinction. Twenty-four hours later, participants completed a test of extinction recall during fMRI. Conditioned fear was measured throughout the experiment using skin conductance and fear-related behavior, and activation in fear-related brain regions was estimated during recall. There were no group differences in conditioned fear during fear conditioning or extinction learning. During extinction recall, however, trauma-exposed children kept more distance from both the previously extinguished and the safety cue, suggesting poor differentiation between threat and safety cues. Trauma-exposed youth also failed to approach the previously extinguished cue over the course of extinction recall. The effects on fear-related behavior during extinction recall were accompanied by higher activation to the previously extinguished cue in fear-relevant brain regions, including the dorsal anterior cingulate cortex and anterior insula, in trauma-exposed relative to control children. Alterations in fear-related brain regions and fear-related behavior may be a core mechanism through which childhood trauma confers heightened vulnerability to psychopathology.

Effects of Duration and Midpoint of Sleep on Corticolimbic Circuitry in Youth

INTRODUCTION

Adequate sleep is essential for cognitive and emotion-related functioning, and 9 to 12 hr of sleep is recommended for children ages 6 to 12 years and 8 to 10 hr for children ages 13 to 18 years. However, national survey data indicate that older youth sleep for fewer hours and fall asleep later than younger youth. This shift in sleep duration and timing corresponds with a sharp increase in onset of emotion-related problems (e.g., anxiety, depression) during adolescence. Given that both sleep duration and timing have been linked to emotion-related outcomes, the present study tests the effects of sleep duration and timing, and their interaction, on resting-state functional connectivity (RS-FC) of corticolimbic emotion-related neural circuitry in children and adolescents.

METHODS

A total of 63 children and adolescents (6-17 years, 34 females) completed a weekend overnight sleep journal and a 10-min resting-state functional magnetic resonance imaging scan the next day (Sunday). Whole-brain RS-FC of the amygdala was computed, and the effects of sleep duration, timing (i.e., midpoint of sleep), and their interaction were explored using regression analyses.

RESULTS

Overall, we found that older youth tended to sleep later and for fewer hours than younger youth. Controlling for age, shorter sleep duration was associated with lower RS-FC between the amygdala and regions implicated in emotion regulation, including ventral anterior cingulate cortex, precentral gyrus, and superior temporal gyrus. Interestingly, midpoint of sleep was associated with altered connectivity in a distinct set of brain regions involved in interoception and sensory processing, including insula, supramarginal gyrus, and postcentral gyrus. Our data also indicate widespread interactive effects of sleep duration and midpoint on brain regions implicated in emotion regulation, sensory processing, and motor control.

CONCLUSION

These results suggest that both sleep duration and midpoint of sleep are associated with next-day RS-FC within corticolimbic emotion-related neural circuitry in children and adolescents. The observed interactive effects of sleep duration and timing on RS-FC may reflect how homeostatic and circadian process interact in the brain and explain the complex patterns observed with respect to emotional health when considering sleep duration and timing. Sleep-related changes in corticolimbic circuitry may contribute to the onset of emotion-related problems during adolescence.

Poor between-session recall of extinction learning and hippocampal activation and connectivity in children

BACKGROUND

In healthy adults, successful between-session recall of extinction learning depends on the hippocampus and ventromedial prefrontal cortex (vmPFC), especially when tested in the extinction context. Poor extinction recall and dysfunction within hippocampal-vmPFC circuitry are associated with fear-based disorders (e.g., anxiety, posttraumatic stress disorder). Despite the early age of onset of virtually all fear-based disorders and the protracted development of the hippocampus and vmPFC across the first two decades of life, little is known about extinction recall and the underlying neural correlates in children.

METHODS

Here, we tested extinction recall in 43 pre-adolescent children (ages 6-11 yrs) by coupling functional magnetic resonance imaging and virtual reality with a novel interpersonal threat-related two-day (ABBA) fear-extinction paradigm. Conditioned fear responding was assessed at behavioral, subjective, physiological, and neural levels.

RESULTS

Although children demonstrated intact within-session extinction, there was poor between-session recall of extinction learning (retention index: 13.56%), evidenced by elevations in skin conductance, avoidant behavioral responses, and subjective ratings. Elevations in conditioning fear responding were accompanied by activation in the hippocampus and insula, and increased connectivity of the hippocampus with the insula and dorsal anterior cingulate cortex - regions implicated in the return of fear in adult studies. Children who kept more distance from the extinguished cue during extinction subsequently demonstrated heightened hippocampal-cingulate coupling during recall, suggesting that avoidant behavior interferes with extinction retention.

CONCLUSIONS

Poor extinction recall in children may have implications for developmental vulnerability to fear-based disorders, and for the application of therapeutic strategies that rely on principles of extinction (e.g., exposure therapy) to pediatric samples.

Location and type of mutation in the LIS1 gene do not predict phenotypic severity

BACKGROUND

Lissencephaly is a neuronal migration disorder leading to absent or reduced gyration and a broadened but poorly organized cortex. The most common form of lissencephaly is isolated, referred as classic or type 1 lissencephaly. Type 1 lissencephaly is mostly associated with a heterozygous deletion of the entire LIS1 gene, whereas intragenic heterozygous LIS1 mutations or hemizygous DCX mutations in males are less common.

METHODS

Eighteen unrelated patients with type 1 lissencephaly were clinically and genetically assessed. In addition, patients with subcortical band heterotopia (n = 1) or lissencephaly with cerebellar hypoplasia (n = 2) were included.

RESULTS

Fourteen new and seven previously described LIS1 mutations were identified. We observed nine truncating mutations (nonsense, n = 2; frameshift, n = 7), six splice site mutations, five missense mutations, and one in-frame deletion. Somatic mosaicism was assumed in three patients with partial subcortical band heterotopia in the occipital-parietal lobes or mild pachygyria. We report three mutations in exon 11, including a frameshift which extends the LIS1 protein, leading to type 1 lissencephaly and illustrating the functional importance of the WD domains at the C terminus. Furthermore, we present two patients with novel LIS1 mutations in exon 10 associated with lissencephaly with cerebellar hypoplasia type a.

CONCLUSION

In contrast to previous reports, our data suggest that neither type nor position of intragenic mutations in the LIS1 gene allows an unambiguous prediction of the phenotypic severity. Furthermore, patients presenting with mild cerebral malformations such as subcortical band heterotopia or cerebellar hypoplasia should be considered for genetic analysis of the LIS1 gene.

A filamin A splice mutation resulting in a syndrome of facial dysmorphism, periventricular nodular heterotopia, and severe constipation reminiscent of cerebro-fronto-facial syndrome

BACKGROUND

Mutations of the filamin A locus (FLNA) on Xq28 have been established in girls with periventricular nodular heterotopia and in patients with otopalatodigital and overlapping phenotypes, the pathogenesis of these phenotypes being thought to be quite distinct. To date only six male cases of periventricular nodular heterotopia (PVNH) have been reported and these almost invariably associated with severe neurological signs.

METHODS AND RESULTS

We report a new phenotype of male PVNH, with relatively normal development, no epilepsy or other neurological abnormality, severe constipation, and facial dysmorphism and without a discernible skeletal phenotype. This phenotype is associated with a splice site mutation in FLNA c.1923C>T, resulting in the generation of both normal and aberrant mRNA.

CONCLUSIONS

We postulate that the patient retains enough FLNA function to avoid the usual lethality associated with loss of function mutations in males and suggest that the severe constipation may be a clue to the molecular aetiology of other X linked conditions associated with severe constipation.

Molecular basis for the stereoselective interactions of catecholamines with alpha-adrenoceptors

The catecholamines were found to inhibit the binding of the alpha 2-adrenoceptor agonist, [3H]-clonidine, to the recombinant wild type alpha 2a-adrenoceptor (Table 1) with potencies that are consistent with their functional activity in alpha 2-adrenoceptor test systems [6,7]. Mutation of Ser165 to alanine had no significant effect (less than 2-fold) on the affinity of any of the catecholamines for the alpha 2a-adrenoceptor, and in particular, the ratios of affinities between the corresponding (-)- and (+)-enantiomers of the catecholamines were not altered by the point mutation at Ser165. These findings indicate clearly that Ser165, in contrast to predictions made by molecular modeling, plays little if any role in the binding of the catecholamines in general, and cannot be involved in the attachment of the beta-hydroxyl group to the alpha 2a-adrenoceptor. Mutation of either Ser90 on transmembrane helix II or Ser419 on transmembrane helix VII to alanine produced dramatic and selective reductions in the affinity of the (-)-enantiomers of the catecholamines for the alpha 2a-adrenoceptor, with no changes occurring in affinities of the (+)-enantiomers. Thus, the affinities of (-)-norepinephrine and (-)-epinephrine for the Ser90 and Ser419 mutants of the alpha 2a-adrenoceptor were 35-75 fold lower than their affinities for the wild type receptor (Table 1), suggesting that Ser90 and/or Ser419 are involved in the attachment of the beta-hydroxyl groups of the catecholamines to the receptor. Similarly, the affinity of (+/-)-6-fluoronorepinephrine was reduced by 100-fold for the Ser90 mutant receptor (Table 1). Importantly, the affinities of the (+)-enantiomers of the catecholamines, as well as dopamine and epinine, which are the corresponding analogs of norepinephrine and epinephrine which lack the beta-hydroxyl group, were not affected by mutation of Ser90 or Ser419 to alanine (Table 1). Asn293 in transmembrane helix VI has also been proposed to be involved in the interaction of the beta-hydroxyl group of isoproterenol with the beta 2-adrenoceptor [4]. The alpha 2a-adrenoceptor contains three hydroxyl bearing amino acids at a position corresponding to this site (Thr393-Tyr394-Thr395). These amino acids could theoretically form a hydrogen bond with the beta-hydroxyl group of a catecholamine, and therefore could serve as a potential point of attachment. Simultaneous mutation of all three of these amino acids to Ala-Phe-Ala reduced the affinity of the (-)-enantiomers of the catecholamines by 12-20 fold, which is somewhat less than what was observed for mutation of either Ser90 or Ser419 (Table 1). However, in contrast to mutation of Ser90 or Ser419, which had no effect on the affinity of the (+)-enantiomers, mutation of the three residues in transmembrane helix VI did significantly reduce the affinities of the (+)-enantiomers of the catecholamines by approximately 5- to 9-fold, indicating that mutations at these points of the receptor are not selective for the (-)-enantiomers, and are therefore not likely to be involved in the attachment of the beta-hydroxyl group of the catecholamines.

Ser165 of transmembrane helix IV is not involved in the interaction of catecholamines with the alpha-2a-adrenoceptor

Molecular modeling studies have predicted that the beta-hydroxyl group of the catecholamines interacts with the beta 2-adrenoceptor at the serine residue at position 165 (Ser165) located on transmembrane helix IV; however, this has not been confirmed by site-directed mutagenesis. It has been inferred that this site, which is conserved in all of the nine known alpha- and beta-adrenoceptor subtypes, is also involved in the interaction of catecholamines with the alpha 2a-adrenoceptor. To test the hypothesis that the beta-hydroxyl group of the catecholamines interacts with Ser165 of the alpha 2a-adrenoceptor, we prepared a mutant alpha 2a-adrenoceptor where Ser165 was mutated to alanine. Mutation of Ser165 of the alpha 2a-adrenoceptor to alanine had no effect on the affinity of dopamine (which lacks the beta-hydroxyl group) or either enantiomer of norepinephrine or epinephrine (both of which possess the beta-hydroxyl group), indicating that Ser165 is not involved in the interaction of the catecholamines with the alpha 2a-adrenoceptor. We have previously shown that mutation of Ser90, located in transmembrane helix II, to either alanine or cysteine produces a selective reduction in the affinity of the (-)-enantiomers of the catecholamines for the alpha 2a-adrenoceptor, with no effect on the (+)-enantiomers or the corresponding beta-desoxy analogs. This is consistent with the known stereoselectivity involved in the interactions of catecholamines with the alpha 2a-adrenoceptor. The results of the present investigation indicate that Ser165 is not involved in the interaction of catecholamines with the alpha 2a-adrenoceptor. Because all known alpha-adrenoceptor subtypes have a serine residue at a position corresponding to Ser90 of the alpha 2a-adrenoceptor, it would appear that this site represents an important point for attachment of the beta-hydroxyl group of catecholamines.

Metabolic requirements for induction of contact hypersensitivity to immunotoxic polyaromatic hydrocarbons

Experiments were performed to define the metabolic requirements for induction of contact hypersensitivity to polyaromatic hydrocarbons (PAHs), environmental xenobiotics that are both immunotoxic and carcinogenic. Evidence that conversion of the parent compound to a reactive metabolite was necessary for the development of contact hypersensitivity included the fact 1) that contact hypersensitivity to the polyaromatic hydrocarbon dimethylbenz(a)anthracene (DMBA) only occurred in strains of mice that could metabolize the compound, 2) that among the PAHs, only those that could induce aryl hydrocarbon hydroxylase, the rate-limiting enzyme in the PAH metabolic pathway, were immunogenic, and 3) that inhibitors of PAH metabolism reduced DMBA contact hypersensitivity. Cells from the XS52 Langerhans cell-like dendritic cell line were able to metabolize the PAH benzo(a)pyrene to its diol, quinone, and phenol metabolites. GM-CSF augmented benzo(a)pyrene metabolism in XS52 cells. Finally, in vivo depletion of CD8+, but not CD4+, T cell populations inhibited contact hypersensitivity to DMBA. The implications of these experiments are that at least for some contact allergens, the metabolic status of the host is a key determinant of individual susceptibility to the development of allergic contact dermatitis, and the metabolic pathway of an individual hapten may have ramifications for the T cell subpopulation-CD4 or CD8-that is activated.

Metabolic requirements for induction of contact hypersensitivity to immunotoxic polyaromatic hydrocarbons

Experiments were performed to define the metabolic requirements for induction of contact hypersensitivity to polyaromatic hydrocarbons (PAHs), environmental xenobiotics that are both immunotoxic and carcinogenic. Evidence that conversion of the parent compound to a reactive metabolite was necessary for the development of contact hypersensitivity included the fact 1) that contact hypersensitivity to the polyaromatic hydrocarbon dimethylbenz(a)anthracene (DMBA) only occurred in strains of mice that could metabolize the compound, 2) that among the PAHs, only those that could induce aryl hydrocarbon hydroxylase, the rate-limiting enzyme in the PAH metabolic pathway, were immunogenic, and 3) that inhibitors of PAH metabolism reduced DMBA contact hypersensitivity. Cells from the XS52 Langerhans cell-like dendritic cell line were able to metabolize the PAH benzo(a)pyrene to its diol, quinone, and phenol metabolites. GM-CSF augmented benzo(a)pyrene metabolism in XS52 cells. Finally, in vivo depletion of CD8+, but not CD4+, T cell populations inhibited contact hypersensitivity to DMBA. The implications of these experiments are that at least for some contact allergens, the metabolic status of the host is a key determinant of individual susceptibility to the development of allergic contact dermatitis, and the metabolic pathway of an individual hapten may have ramifications for the T cell subpopulation-CD4 or CD8-that is activated.

Mutations in FGFR1 and FGFR2 cause familial and sporadic Pfeiffer syndrome

Pfeiffer syndrome (PS) is an autosomal dominant skeletal disorder which affects the bones of the skull, hands and feet. Previously, we have mapped PS in a subset of families to chromosome 8cen by linkage analysis and demonstrated a common mutation in the fibroblast growth factor receptor-1 (FGFR1) gene in the linked families. Here we report a second locus for PS on chromosome 10q25, and present evidence that mutations in the fibroblast growth factor receptor-2 (FGFR2) gene on 10q25 cause PS in an additional subset of familial and sporadic cases. Three different point mutations in FGFR2, which alter the same acceptor splice site of exon B, were observed in both sporadic and familial PS. In addition, a T to C transition in exon B predicting a cysteine to arginine substitution was identified in three sporadic PS individuals. Interestingly, this T to C change is identical to a mutation in FGFR2 previously reported in Crouzon syndrome, a phenotypically similar disorder but one lacking the hand and foot anomalies seen in PS. Our results highlight the genetic heterogeneity in PS and suggest that the molecular data will be an important complement to the clinical phenotype in defining craniosynostosis syndromes.

A common mutation in the fibroblast growth factor receptor 1 gene in Pfeiffer syndrome

Pfeiffer syndrome (PS) is one of the classic autosomal dominant craniosynostosis syndromes with craniofacial anomalies and characteristic broad thumbs and big toes. We have previously mapped one of the genes for PS to the centromeric region of chromosome 8 by linkage analysis. Here we present evidence that mutations in the fibroblast growth factor receptor-1 (FGFR1) gene, which maps to 8p, cause one form of familial Pfeiffer syndrome. A C to G transversion in exon 5, predicting a proline to arginine substitution in the putative extracellular domain, was identified in all affected members of five unrelated PS families but not in any unaffected individuals. FGFR1 therefore becomes the third fibroblast growth factor receptor to be associated with an autosomal dominant skeletal disorder.