Browsing by Subject "Corpus callosum"

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The corpus callosum and reading : an MRI volumetric study
(2006-08) Fine, Jodene Goldenring; Semrud-Clikeman, Margaret; Keith, Timothy, 1952-
Researchers have long been interested in the role of the corpus callosum in reading disorder, but existing studies have yielded inconsistent results. Some have found larger corpus callosa in those with reading disorder, others have found smaller corpus callosa, and some have found no differences in the corpus callosa of persons with and without reading disability. Some possible problems with past studies include failure to control for whole brain size, intelligence, gender, lateral dominance, and the presence of other syndromes such as Attention Deficit Hyperactivity Disorder. The current study is an examination of the corpus callosum in 68 readers nested in 24 families. Data were centered around the family mean so that the variance within families could be determined. Corpus callosum volumes were measured and controlled for whole brain volume, intelligence, and gender. A series of regressions were used to determine whether the volume of the corpus callosum significantly contributed to the variance in oral reading, phonological processing, and rapid naming. The midsagittal slice was segmented into fifths, and similar regressions were performed. A logistic regression was used to determine whether variation in corpus callosum volume could predict RD and no RD group membership. Finally, left and right volumes were compared and a correlation between corpus callosum volume and area at the midsagittal slice were conducted. Results suggest that better readers within families have larger corpus callosum areas in the midsagittal slice at the midbody. Better phonological processors within families had smaller corpus callosum volumes, but a problem with restricted range for phonological processing scores renders this finding unreliable. Rapid naming scores appear to be unrelated to the corpus callosum in this sample. Differences in the corpus callosum are not robust enough to predict diagnostic group and there appears to be no differences between left and right hemisphere volumes of the corpus callosum. Measurements of area at the midsagittal slice are highly correlated with the volumetric measurements suggesting that for subsequent studies, area at the midsagittal slice may be sufficient.
Functional significance of corpus callosum anatomy in chronically treated and treatment naïve ADHD
(2005) Schnoebelen, Sarah Sue; Semrud-Clikeman, Margaret
Neuroimaging has revealed differences between control and ADHD groups in corpus callsoum (CC) size, although the reported findings have been somewhat variable. Since ADHD is commonly treated with stimulants, concerns have been raised about the long-term neurological consequences of chronic stimulant treatment, yet this has not been controlled for in previous studies. Furthermore, since all previous studies have utilized the mid-sagittal area of the CC as the unit of measurement, additional objectives of this investigation were to determine 1) whether CC volume could be reliably measured and 2) whether using mid-sagittal CC area provides a valid estimation of CC volume. Anatomical MRI’s were obtained from children aged 9-15 in three diagnostic groups 1) chronically-treated ADHD (n=12), 2) stimulant-naïve ADHD (n=13), and 3) a control group (n=15) to determine whether differences in CC size existed. These children also completed a battery of neuropsychological tests to determine whether the functions of sustained attention, speed of information processing, planning, and inhibitory control were related to CC size. Parental ratings of hyperactive and impulsive behavior were also collected. The three groups did not differ in overall CC volume. Differences between the groups in the area of the splenium were approaching significance, with the treatment-naïve group exhibiting the smallest splenium area. Therefore, the results of this investigation do not indicate maladaptive structural changes in the CC associated with chronic (at least one year) stimulant use. It was also found that volume of the CC can be reliably obtained when strict definitional criteria are applied. However, mid sagittal area is highly related to CC volume and therefore is likely an accurate estimate, an important finding given the significant time required to obtain volumetric measures. Finally, smaller splenium size was found to be related to higher levels of hyperactivity and restlessness; however, no associations between measures of CC size and neuropsychological measures were found.