Atypical connectivity in the cortico-striatal network in NF1 children and its relationship with procedural perceptual-motor learning and motor skills

Social Communication in Ras Pathway Disorders: A Comprehensive Review from Genetics to Behavior in Neurofibromatosis Type 1 and Noonan Syndrome

Neurofibromatosis type 1 (NF1) and Noonan syndrome (NS) are neurogenetic syndromes caused by pathogenetic variants encoding components of the Ras-ERK-MAPK signaling pathway (Ras pathway). NF1 and NS are associated with differences in social communication and related neuropsychiatric risks. During the last decade, there has been growing interest in Ras-linked syndromes as models to understand social communication deficits and autism spectrum disorders. We systematically review the literature between 2010-2023 focusing on the social communication construct of the RDoC framework. We provide an integrative summary of the research on facial and non-facial social communication processes in NF1 and NS across molecular, cellular, neural circuitry, and behavioral domains. At the molecular and cellular levels, dysregulation in the Ras pathway is intricately tied to variations in social communication through changes in GABAergic, glutamatergic, and serotonergic transmission, as well as inhibitory/excitatory imbalance. Neural circuitry typically associated with learning, attention, and memory in NF1 and NS (e.g., cortico-striatal connectivity), is also implicated in social communication. We highlight less researched, potential mechanisms for social communication, such as white matter connectivity and the default mode network. Finally, key gaps in NF1 and NS literature are identified and a roadmap for future research is provided. By leveraging genetic syndromes research, we can understand the mechanisms associated with behaviors and psychiatric disorders.

Unraveling neuronal and metabolic alterations in neurofibromatosis type 1

Neurofibromatosis type 1 (OMIM 162200) affects ~ 1 in 3,000 individuals worldwide and is one of the most common monogenetic neurogenetic disorders that impacts brain function. The disorder affects various organ systems, including the central nervous system, resulting in a spectrum of clinical manifestations. Significant progress has been made in understanding the disorder's pathophysiology, yet gaps persist in understanding how the complex signaling and systemic interactions affect the disorder. Two features of the disorder are alterations in neuronal function and metabolism, and emerging evidence suggests a potential relationship between them. This review summarizes neurofibromatosis type 1 features and recent research findings on disease mechanisms, with an emphasis on neuronal and metabolic features.

Distinct attentional and executive profiles in neurofibromatosis type 1: Is there difference with primary attention deficit-hyperactivity disorder?

PURPOSE

Attentional and executive dysfunctions are the most frequent cognitive disorders in neurofibromatosis type 1 (NF1), with a high prevalence of attention deficit-hyperactivity disorder (ADHD). We (i) compared attentional profiles between NF1 children with and without ADHD and children with primary ADHD criteria and (ii) investigated the possible relationship between attentional disorders and "unidentified bright objects" (UBOs) in NF1.

METHODS

This retrospective study included 47 NF1 children, 25 with ADHD criteria (NF1+adhd group), matched for age, sex, and cognitive level with 47 children with primary ADHD (ADHD group). We collected computer task (sustained-attention, visuomotor-decision, inhibition, and cognitive-flexibility tasks) scores normalized for age and sex, and brain magnetic resonance imaging data.

RESULTS

(i) Working memory was impaired in all groups. (ii) Omissions (p < 0.002) and response-time variability (p < 0.05) in sustained-attention and visuomotor-decision tasks and errors (p < 0.02) in the cognitive-flexibility task were lower for the NFI+adhd and ADHD groups than for the NF1-no-adhd group. (iii) The NF1+adhd group had slower response times (p ≤ 0.02) for inhibition and visuomotor-decision tasks than the other groups. (iv) We found no relevant association between cognitive performance and UBOs.

CONCLUSIONS

NF1 children with ADHD have an attentional and executive functions deficit profile similar to that of children with primary ADHD, but with a slower response-time, increasing learning difficulties. The atypical connectivity of fronto-striatal pathways, poorer dopamine homeostasis, and increased GABA inhibition observed in NF1 renders vulnerable the development of the widely distributed neural networks that support attentional, working-memory, and executive functions.

The long-term impact of irradiation on functional connectivity in brain circuits involved in memory processes after pediatric posterior fossa tumor

PURPOSE

Memory is one of the main specific cognitive domains impaired with attention and processing speed after a pediatric brain tumor. This work explored the long-term impact of radiotherapy in children with posterior fossa tumor (PFT) on brain connectivity in neural circuits involved in memory using resting-state functional magnetic resonance imaging (rs-fMRI).

METHODS

A total of 20 irradiated and 15 non-irradiated PFT survivors, and 21 healthy controls, prospectively included in the IMPALA study (NCT04324450), performed memory tests assessing episodic, procedural, and working memories and were subjected to an rs-fMRI. We manually contoured main structures involved in memory to explore connectivity at rest in a seed-to-voxel analysis. The groups were compared and differences in connectivity were correlated with behavioral scores and irradiation doses.

RESULTS

The performance of all mnesic tasks was lower in PFT survivors with a greater alteration in working and episodic memory in irradiated patients. Irradiated survivors had atypical connectivities in all memory circuits compared to controls and in cortico-caudate and cortico-cerebellar circuits compared to non-irradiated survivors. Non-irradiated survivors had only atypical connectivities in the cortico-cerebellar circuits compared to controls. In irradiated survivors, atypical connectivities in cortico-hippocampal circuits were linked with episodic memory scores and dose of irradiation to the left hippocampus and in cortico-striatal circuits with procedural memory scores and dose of irradiation to the striatum.

CONCLUSION

The results of this study highlight that irradiation has a long-term impact on brain connectivity in brain circuits involved in memory after pediatric PFT with a specific radiation-dose effect in supratentorial structures.