Global and local cortical folding alterations are associated with neurodevelopmental subtype in bipolar disorders: a sulcal pits analysis

Refining Criteria for a Neurodevelopmental Subphenotype of Bipolar Disorders: A FondaMental Advanced Centers of Expertise for Bipolar Disorders Study

BACKGROUND

Bipolar disorder (BD) is a complex and heterogeneous psychiatric disorder. It has been suggested that neurodevelopmental factors contribute to the etiology of BD, but a specific neurodevelopmental phenotype (NDP) of the disorder has not been identified. Our objective was to define and characterize an NDP in BD and validate its associations with clinical outcomes, polygenic risk scores, and treatment responses.

METHODS

We analyzed the FondaMental Advanced Centers of Expertise for Bipolar Disorders cohort of 4468 patients with BD, a validation cohort of 101 patients with BD, and 2 independent replication datasets of 274 and 89 patients with BD. Using factor analyses, we identified a set of criteria for defining NDP. Next, we developed a scoring system for NDP load and assessed its association with prognosis, neurological soft signs, polygenic risk scores for neurodevelopmental disorders, and responses to treatment using multiple regressions, adjusted for age and gender with bootstrap replications.

RESULTS

Our study established an NDP in BD consisting of 9 clinical features: advanced paternal age, advanced maternal age, childhood maltreatment, attention-deficit/hyperactivity disorder, early onset of BD, early onset of substance use disorders, early onset of anxiety disorders, early onset of eating disorders, and specific learning disorders. Patients with higher NDP load showed a worse prognosis and increased neurological soft signs. Notably, these individuals exhibited a poorer response to lithium treatment. Furthermore, a significant positive correlation was observed between NDP load and polygenic risk score for attention-deficit/hyperactivity disorder, suggesting potential overlapping genetic factors or pathophysiological mechanisms between BD and attention-deficit/hyperactivity disorder.

CONCLUSIONS

The proposed NDP constitutes a promising clinical tool for patient stratification in BD.

The sulcal pits as neurodevelopmental markers: A systematic review about their potential use in clinical practice

Sulcal pits, defined as the deepest points of the cortical surface and identified as stable landmarks, exhibit a consistent emergence sequence that aligns with established gyrification patterns, underscoring their potential as markers for early neurodevelopmental trajectories. Here, we investigate the potential of sulcal pits in characterizing the etiological roots of neurodevelopmental traits and disorders. This systematic review (PROSPERO register: CRD42022347303) was conducted according to PRISMA guidelines. Searches were performed in PubMed, Web of Science (WOS), and Scopus, initially identifying 102 articles, from which 53 were screened and 19 finally included. The articles were categorized into two main groups: those exploring the ontogenetic processes of sulcal pits and those investigating their relationship with neurodevelopmental phenotypes in health and disease. The review findings indicate that individuals with congenital conditions or neurodevelopmental disorders exhibit distinct patterns of sulcal pits that correlate with cognitive traits. Additionally, graph analyses consistently show lower mean similarity within individuals from affected groups, suggesting that variations in sulcal pit patterns reflect the impact of neurodevelopmental disturbances. These results highlight the potential of sulcal pits to capture instabilities in early brain development. However, they also point to a lack of comprehensive biological interpretation in the current literature. Further research is needed to enhance our understanding of the significance of sulcal pits in neurodevelopmental outcomes and to advance their use as diagnostic tools.

Towards a neurodevelopmental model of bipolar disorder: a critical review of trait- and state-related functional neuroimaging in adolescents and young adults

Neurodevelopmental mechanisms are increasingly implicated in bipolar disorder (BD), highlighting the importance of their study in young persons. Neuroimaging studies have demonstrated a central role for frontotemporal corticolimbic brain systems that subserve processing and regulation of emotions, and processing of reward in adults with BD. As adolescence and young adulthood (AYA) is a time when fully syndromal BD often emerges, and when these brain systems undergo dynamic maturational changes, the AYA epoch is implicated as a critical period in the neurodevelopment of BD. Functional magnetic resonance imaging (fMRI) studies can be especially informative in identifying the functional neuroanatomy in adolescents and young adults with BD (BDAYA) and at high risk for BD (HR-BDAYA) that is related to acute mood states and trait vulnerability to the disorder. The identification of early emerging brain differences, trait- and state-based, can contribute to the elucidation of the developmental neuropathophysiology of BD, and to the generation of treatment and prevention targets. In this critical review, fMRI studies of BDAYA and HR-BDAYA are discussed, and a preliminary neurodevelopmental model is presented based on a convergence of literature that suggests early emerging dysfunction in subcortical (e.g., amygdalar, striatal, thalamic) and caudal and ventral cortical regions, especially ventral prefrontal cortex (vPFC) and insula, and connections among them, persisting as trait-related features. More rostral and dorsal cortical alterations, and bilaterality progress later, with lateralization, and direction of functional imaging findings differing by mood state. Altered functioning of these brain regions, and regions they are strongly connected to, are implicated in the range of symptoms seen in BD, such as the insula in interoception, precentral gyrus in motor changes, and prefrontal cortex in cognition. Current limitations, and outlook on the future use of neuroimaging evidence to inform interventions and prevent the onset of mood episodes in BDAYA, are outlined.

Measurement of residual stress in the brain

Mechanical stress in brain tissue is an important feature of the brain, likely to play key roles in brain development and brain injury. Here, we characterize residual stresses in grey matter and white matter from the deformed shape of tissue cylinders extracted from the brain using a biopsy needle and imaged with high-resolution magnetic resonance imaging (MRI). We use finite element simulations to reconstruct the stress state of tissue sections in the intact brain from images of corresponding sections of the deformed excised tissue. In both adult mouse and Yucatan minipig brains, cortical grey matter exhibited predominantly compressive stresses, while white matter exhibited strongly anisotropic tensile stresses. The direction of maximum tension in white matter generally aligns with axon orientation as observed with diffusion MRI in the minipig. These stress patterns (compressive in cortical grey matter, tensile along axons) are consistent with constrained cortical expansion and tension-induced axonal growth during brain development. These findings offer new insights into the biomechanical factors underlying brain morphogenesis, with implications for understanding neurodevelopmental disorders, brain injuries, and neurosurgical interventions.

Sulcal pits of the superior temporal sulcus in schizophrenia patients with auditory verbal hallucinations

Auditory verbal hallucinations (AVHs) are among the most common and disabling symptoms of schizophrenia. They involve the superior temporal sulcus (STS), which is associated with language processing; specific STS patterns may reflect vulnerability to auditory hallucinations in schizophrenia. STS sulcal pits are the deepest points of the folds in this region and were investigated here as an anatomical landmark of AVHs. This study included 53 patients diagnosed with schizophrenia and past or present AVHs, as well as 100 healthy control volunteers. All participants underwent a 3-T magnetic resonance imaging T1 brain scan, and sulcal pit differences were compared between the two groups. Compared with controls, patients with AVHs had a significantly different distributions for the number of sulcal pits in the left STS, indicating a less complex morphological pattern. The association of STS sulcal morphology with AVH suggests an early neurodevelopmental process in the pathophysiology of schizophrenia with AVHs.

Population-wise labeling of sulcal graphs using multi-graph matching

Population-wise matching of the cortical folds is necessary to compute statistics, a required step for e.g. identifying biomarkers of neurological or psychiatric disorders. The difficulty arises from the massive inter-individual variations in the morphology and spatial organization of the folds. The task is challenging both methodologically and conceptually. In the widely used registration-based techniques, these variations are considered as noise and the matching of folds is only implicit. Alternative approaches are based on the extraction and explicit identification of the cortical folds. In particular, representing cortical folding patterns as graphs of sulcal basins-termed sulcal graphs-enables to formalize the task as a graph-matching problem. In this paper, we propose to address the problem of sulcal graph matching directly at the population level using multi-graph matching techniques. First, we motivate the relevance of the multi-graph matching framework in this context. We then present a procedure for generating populations of artificial sulcal graphs, which allows us to benchmark several state-of-the-art multi-graph matching methods. Our results on both artificial and real data demonstrate the effectiveness of multi-graph matching techniques in obtaining a population-wise consistent labeling of cortical folds at the sulcal basin level.

On presentation of the human cerebral sulci from inside of the cerebrum

The human cerebral cortex is highly convoluted forming patterns of gyri separated by sulci. The cerebral sulci and gyri are fundamental in cortical anatomy as well as neuroimage processing and analysis. Narrow and deep cerebral sulci are not fully discernible either on the cortical or white matter surface. To cope with this limitation, I propose a new sulci presentation method that employs the inner cortical surface for sulci examination from the inside of the cerebrum. The method has four steps, construct the cortical surface, segment and label the sulci, dissect (open) the cortical surface, and explore the fully exposed sulci from the inside. The inside sulcal maps are created for the left and right lateral, left and right medial, and basal hemispheric surfaces with the sulci parcellated by color and labeled. These three-dimensional sulcal maps presented here are probably the first of this kind created. The proposed method demonstrates the full course and depths of sulci, including narrow, deep, and/or convoluted sulci, which has an educational value and facilitates their quantification. In particular, it provides a straightforward identification of sulcal pits which are valuable markers in studying neurologic disorders. It enhances the visibility of sulci variations by exposing branches, segments, and inter-sulcal continuity. The inside view also clearly demonstrates the sulcal wall skewness along with its variability and enables its assessment. Lastly, this method exposes the sulcal 3-hinges introduced here.