FIG 5. Scatterplots show total temporal gyral and sulcal volumes, hippocampal volumes, and temporal stem measurements, fitted with linear and quadratic functions. Note the greater variability in sulcal volume compared with the parenchymal measures. At statistical analysis, degrees of freedom for regression and residuals, respectively, were 2 and 251 for the linear function and 1 and 252 for the quadratic function. For each structure, values with the functions were as follows: total gyral volume, quadratic F = 4.35 and P 
.014, linear F = 7.97 and P .005; total sulcal volume, quadratic F = 14.09 and P .00001, linear F = 24.06 and P .00001; total hippocampal volume, quadratic F = 3.65 and P .03, linear F = 7.14 and P .008; and total WM, quadratic F = 1.2 and P .29, linear F = 1.41 and P .24. In each case, head size (total intracranial volume) and sex were used as covariates.
