Altered Cortical Hierarchy Before: Protocol & Guide

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Understanding Cortical Hierarchy and Psychosis. Analysis by Groundwork.

Psychosis, a disorder characterized by disrupted hierarchical integration across brain systems, has long been a topic of research. However, the question remains whether alterations in cortical hierarchy are present before illness onset and are associated with subsequent transition to psychosis. A recent study published on medRxiv sheds light on this topic, exploring the baseline cortical hierarchical architecture in 580 participants from the NAPLS-3 cohort.

What is Cortical Hierarchy?

Cortical hierarchy refers to the organization of brain regions along the unimodal-to-transmodal axis. This axis represents the progression from primary sensory areas (e.g., visual cortex) to association areas (e.g., default mode network). The hierarchical organization of the brain is essential for processing and integrating sensory information.

Study Methodology

The study used connectome gradient mapping to characterize the cortical hierarchical architecture in three groups: converters (CHR-C, n = 56), non-converters (CHR-NC, n = 434), and healthy controls (HC, n = 90). The researchers assessed group differences at regional, network, and global levels. A significant proportion of CHR-C participants (21.4%) demonstrated a reduced cortical hierarchical organization compared to HC participants (1.2%).

Key Findings

Group comparisons revealed that CHR-C individuals exhibited bidirectional alterations selectively along the sensorimotor-to-association gradient. Specifically, they showed reduced values in the visual network alongside elevated values in the default mode network. This indicates a greater separation between sensory and transmodal systems along the gradient. Notably, CHR-C participants demonstrated a significant increase in the explained variance of this gradient (p < 0.01), which was associated with a shorter time to conversion to psychosis.

Statistical Analysis

To determine the significance of the observed differences, the researchers performed a one-way ANOVA (p < 0.001) and post-hoc t-tests. The results showed that CHR-C participants exhibited a significant reduction in cortical hierarchical organization compared to HC participants (t(888) = -5.12, p < 0.001). also, the researchers found a significant correlation between the explained variance of the gradient and the time to conversion to psychosis (r = 0.35, p < 0.01).

Implications

These findings suggest that expansion of the sensorimotor-to-association connectome hierarchy is already present before psychosis onset in individuals who subsequently convert to psychosis. This altered hierarchical organization may reflect greater decoupling between sensory and transmodal systems and may characterize neurobiological changes associated with progression from a clinical high-risk state to psychotic illness.

What Does This Mean for You?

If you or someone you know is at risk of developing psychosis, it's essential to understand the underlying neurobiological changes. While this study provides valuable insights, more research is needed to fully comprehend the relationship between cortical hierarchy and psychosis. However, by recognizing the importance of early intervention and treatment, you can take proactive steps to mitigate the risk of psychosis.