Relationships in Ongoing Structural Maintenances of the Two Cerebral Cortices of an Individual Brain

Abstract

A human brain has separate left and right cerebral cortices, each of which must be continuously structurally maintained during adulthood. There is no understanding of how ongoing structural maintenances of separate parts of a mature individual brain, including the 2 cortices, are related. To explore this issue, this study used an unconventional N-of-1 magnetic resonance imaging time-series paradigm to identify relationships between maintenances of structural thicknesses of the 2 cortices in an adult human brain over week intervals for 6 months. The results suggest that maintenances of left and right cortical thicknesses were symmetrically related in some, but asymmetrically related in other, respects. For matched times, thickness magnitudes and variations on the 2 sides were positively correlated and appeared to reflect maintenance symmetry. Maintenance relationships also extended from earlier to later times with temporal continuity and apparent "if-then" contingencies which were reflected in symmetry and asymmetry dynamics spanning 1- to 2-week periods. The findings suggest concepts of individual brain cortical maintenance symmetry, asymmetry, and temporal continuity dynamics that have not been previously recognized. They have implications for defining cortical maintenance traits or states and for development of N-of-1 precision medicine paradigms that can contribute to understanding individual brain health.

Keywords: Brain maintenance; MRI N-of-1 time series; cortical symmetry/asymmetry; cortical thickness; precision medicine.

Figure 1.

Thicknesses of left and right cortices for (A) scan A and (B) scan B over the 6-month study period. Right thickness was consistently larger than left thickness at each week for both scan series.

Figure 2.

Thickness magnitude (mm) analyses. For A to E, upper part indicates matched or shifted time relationship that was tested and lower part indicates corresponding scatterplot and linear regression line for that relationship. (A) Matched time analysis 2. (B, C) Shifted time analysis 3. (D, E) Shifted time analysis 4. See text for findings.

Figure 3.

Thickness maintenance variation (%) analyses. Conventions for upper and lower parts of A to E as in Figure 2. (A) Matched time analysis 5. (B, C) Shifted time analysis 6. (D, E) Shifted time analysis 7. See text for findings.

Figure 4.

Summary of relationships in maintenance of thickness magnitudes (top) and thickness maintenance variations (bottom) that reached significant (A, C, D, and E) and trend (B and F) levels of significance.