Temporal Lobe, Autism, and Macrocephaly

Parenchymal gyral volumes of the temporal lobe, volume of the temporal lobe tip, and white matter stem. Each box contains the actual data point representing the uncorrected volume for each structure. The five groups are represented on the y axis. The x axis is in cm³. Colored asterisks indicate where significance (P < .05) is present and between which groups the significance resides (ie, same color). For example, in the superior temporal gyrus panel in the upper left, the two blue asterisks indicate that subjects with reading disorder had smaller volume than that of the control subjects with benign macrocephaly (Macro). Note that there are basically no significant differences between autistic and control subjects with normal head size or between autistic and control subjects with large head size. The only comparisons that were significant were between one of the macrocephalic groups and the normocephalic groups.

Volumetric comparisons of subcortical regions of the temporal lobe including the amygdala, total hippocampal volume, area dentata (AD), and the CA1-CA3 region plus subiculum (CAS) of the hippocampus. Legend is otherwise the same as that in Figure 2. Note that AD and CAS values are in mm² as they represent the surface area at that level.

Growth plots by age for total temporal lobe white matter and gray matter, fusiform gyrus white and gray matter, and parahippocampal gyrus white and gray matter. Controls include typically developing subjects with or without macrocephaly, and subjects with reading disorder. The nature of the relationship of structure, development, and age was tested by either a linear or quadratic fit. As can be seen for all white matter structures, the better fit was linear. For gray matter structures, the fit was quadratic. The dash-line represents the extension of the quadratic for the autistic subjects older than 23 years. Since there were no controls to compare beyond that age, the actual regression line stops with the solid line and the projected regression is represented by the dash. None of these growth plots were significantly different, indicating generally similar growth patterns between autistic and control subjects, even though the curves showed some differences. Large blue ‘bulls eye’ points denote macrocephalic (both selected and unselected) autistic subjects, and the large red diamonds indicate macrocephalic control subjects. Age is shown on the x axis and volume (cm³) on the y axis.