Temporal Lobe, Autism, and Macrocephaly
Erin D. Biglera,c,
David F. Tatea,
E. Shannon Neeleyb,
Lara J. Wolfsonb,
Michael J. Millera,
Sara A. Ricea,
Howard Cleavingera,
Carol Andersona,
Hilary Coonc,
Sally Ozonoffd,
Michael Johnsonc,
Elena Dinhc,
Jeff Luc,
William Mc Mahonc and
Janet E. Lainhartc
a Department of Psychology and Neuroscience, Brigham Young University, Provo, UT
b Department of Statistics, Brigham Young University, Provo, UT
c Department of Psychiatry, University of Utah
d MIND Institute, Department of Psychiatry, University of California, Davis
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FIG 1. A, T1-weighted coronal image shows the five temporal gyri: superior temporal gyrus (A), middle temporal gyrus (B), inferior temporal gyrus (C), fusiform gyrus (D), parahippocampal gyrus (E), and hippocampus (F). The red triangle (G) defines the region of classification for determining the volume of the temporal stem, which represents the trunk of the white matter projections of the temporal lobe in the coronal plane.
B, Coregistered T2-weighted image.
C, Edited segmented image from the T1- and T2-weighted images depicts gray matter in gray, white matter in white, and CSF in blue. The Volume Render Module and region-of-interest feature in ANALYZE (54, 55) were used to identify gyral boundaries, defined by each sulcus.
D, Three-dimensional reconstruction of this subject’s brain depicts a lateral view showing the region where gyral quantification occurred (green) and the temporal pole (yellow). Anterior to the coronal sections in A and B, where the temporal horn is no longer definable, was the landmark to begin measuring the temporal pole. The red triangle (G) in A defines the region of classification for determining the volume of the temporal stem. The mesial vertical boundary was defined by connecting the inner extension of the sylvian fissure to the most lateral aspect of the temporal horn, triangulated with the gray matter extension at the innermost point of the superior temporal sulcus. CSF boundaries were defined by CSF segmented pixels in the region bounded by the inferior frontal lobe and the superior temporal gyrus for the sylvian fissure; between the superior and inferior temporal gyri for the middle temporal sulcus; between the inferior and fusiform for the inferior temporal sulcus; and the rhinal sulcus between the fusiform and parahippocampal gyrus.
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FIG 2. 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.
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FIG 3. 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.
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FIG 4. 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.
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FIG 5. Growth plots by structure and age, for amygdala, temporal lobe, white matter stem, hippocampus, area dentata, and the CAS region of the hippocampus. As with Figure 4, the fit was tested for quadratic and linear, and, in the case of these structures, several showed no superiority of one fit over the other, therefore both are presented. Legend is otherwise the same as that in Figure 4. Of interest was that as a group, the autistic subjects had smaller white matter stem volumes than those of the control subjects earlier in life (younger than 17 years), although the slopes of the regression lines were not different. Note that area dentata and CAS values are in mm2 as they represent the surface area at that level.
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