Cortical complexity estimation using fractal dimension: A systematic review of the literature on clinical and nonclinical samples

• Published in: The European journal of neuroscience Vol. 55; no. 6; pp. 1547 - 1583
• Main Authors: Meregalli, Valentina, Alberti, Francesco, Madan, Christopher R., Meneguzzo, Paolo, Miola, Alessandro, Trevisan, Nicolò, Sambataro, Fabio, Favaro, Angela, Collantoni, Enrico
• Format: Journal Article
• Language: English
• Published: France Wiley Subscription Services, Inc 01.03.2022; John Wiley and Sons Inc
• Subjects: Aging; Brain; Cognitive Neuroscience; cortical complexity; cortical structure; fractal dimension; Fractals; Literature reviews; Magnetic Resonance Imaging - methods; MRI; Nervous system; Neurological diseases; Neurosciences; Review; Systematic review; cortical complexity; fractal dimension; cortical structure; MRI
• ISSN: 0953-816X; 1460-9568; 1460-9568
• DOI: 10.1111/ejn.15631

Fractal geometry has recently been proposed as a useful tool for characterizing the complexity of the brain cortex, which is likely to derive from the recurrence of sulci–gyri convolution patterns. The index used to describe the cortical complexity is called fractal dimensional (FD) and was employed by different research exploring the neurobiological correlates of distinct pathological and nonpathological conditions. This review aims to describe the literature on the application of this index, summarize the heterogeneities between studies and inform future research on this topic. Sixty‐two studies were included in the systematic review. The main research lines concern neurodevelopment, aging and the neurobiology of specific psychiatric and neurological disorders. Overall, the included papers indicate that cortical complexity is likely to reduce during aging and in various pathological processes affecting the brain. Nevertheless, the high heterogeneity between studies strongly prevents the possibility of drawing conclusions. Further research considering this index besides other morphological values is needed to better clarify the role of FD in characterizing the cortical structure. Fractal dimension (FD) is a useful tool for the assessment of cortical complexity. In healthy controls, FD is associated with development, aging and cognition. Alterations in FD have been observed in different neurological and psychiatric disorders.