Structural diverseness of neurons between brain areas and between cases (2007.00212v1)

Abstract: The cerebral cortex is composed of multiple cortical areas that exert a wide variety of brain functions. Although human brain neurons are genetically and areally mosaic, the three-dimensional structural differences between neurons in different brain areas or between the neurons of different individuals have not been delineated. Here, we report a nanometer-scale geometric analysis of brain tissues of the superior temporal gyrus of 4 schizophrenia and 4 control cases by using synchrotron radiation nanotomography. The results of the analysis and a comparison with results for the anterior cingulate cortex indicated that 1) neuron structures are dissimilar between brain areas and that 2) the dissimilarity varies from case to case. The structural diverseness was mainly observed in terms of the neurite curvature that inversely correlates with the diameters of the neurites and spines. The analysis also revealed the geometric differences between the neurons of the schizophrenia and control cases, suggesting that neuron structure is associated with brain function. The area dependency of the neuron structure and its diverseness between individuals should represent the individuality of brain functions.

• The paper demonstrates that neurons in schizophrenia cases exhibit higher neurite curvature revealed through three-dimensional nanotomography analysis.
• The methodology combined Golgi impregnation and synchrotron radiation imaging to precisely quantify microstructural differences between brain regions.
• The study links variations in neuronal structure to potential alterations in brain microcircuit function, highlighting implications for schizophrenia.

Structural Diverseness of Neurons Between Brain Areas and Between Cases

Introduction

The paper explores the microscopic structural variations of neurons within distinct areas of the brain and compares these differences across individual cases, with a specific focus on schizophrenia. Utilizing synchrotron radiation nanotomography, researchers performed a detailed three-dimensional structural analysis of neurons in the superior temporal gyrus (Brodmann area 22) in both schizophrenia and control cases, further building on previous studies of the anterior cingulate cortex (Brodmann area 24).

Methodology

The paper analyzed brain tissues using synchrotron radiation nanotomography, which allows for nanometer-scale visualization of neuronal structures. Brain samples from Brodmann areas 22 and 24 were extracted from the left hemisphere of post-mortem brains. The tissues underwent Golgi impregnation to visualize neurons and were then imaged. A total of 34 three-dimensional image datasets originating from four schizophrenia and four control cases were processed, with neuronal network structures established through sophisticated image analysis methods.

Results

The paper revealed several significant findings regarding the structural diversity of neurons:

1. Neurite Curvature and Geometric Parameters: Neurons exhibited varying degrees of neurite curvature and torsion depending on the brain area and the individual case. In general, neurons from schizophrenia cases have higher neurite curvature compared to controls.
2. Area-Dependent and Individual Differences: The geometric parameters displayed substantial differences not only between individuals but also between brain areas, underscoring individual-specific neuronal architectures.
3. Correlations with Schizophrenia: Neurons in schizophrenia cases were generally thinner and more tortuous than those in controls, suggesting a correlation between structural properties and the disorder.
4. Potential Impact on Brain Function: The paper indicated that structural properties such as neurite curvature and spine dimensions could impact microcircuit functionality in the brain, possibly influencing individual abilities and characteristics.

Discussion

The findings underscore the critical role of neuronal microstructure in brain function and its variability across different brain areas and between individuals. The pronounced differences in neurite curvature and structural parameters may contribute to the large-scale functional heterogeneities observed in neuroanatomical studies of schizophrenia. This paper adds to the understanding of the neuropathology of schizophrenia, suggesting that these structural deviations could underlie functional imbalances.

Limitations and Future Research

A primary limitation is the small sample size, constrained by the availability of synchrotron radiation beamtime. There is also an inherent limitation in the Golgi staining technique that selectively visualizes a subset of neurons. Future research should involve a larger cohort to validate these findings and investigate the potential impact of genetic mosaicism and pharmacotherapy on neuronal structure.

Conclusion

This paper offers a detailed quantification of structural neuron diversity within the human brain. By providing insights into the microstructural variations of neurons, particularly in the context of schizophrenia, it lays the groundwork for deeper investigations into the individuality of brain functions and the potential for targeted therapeutic interventions. The correlations between neuron structure and function suggest further studies on neuronal geometry could illuminate the basis of behavioral and cognitive individuality.