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We present a new subcortical structure shape modeling framework using heat kernel smoothing constructed with the Laplace-Beltrami eigenfunctions. The cotan discretization is used to numerically obtain the eigenfunctions of the Laplace-Beltrami operator along the surface of subcortical structures of the brain. The eigenfunctions are then used to construct the heat kernel and used in smoothing out measurements noise along the surface. The proposed framework is applied in investigating the influence of age (38-79 years) and gender on amygdala and hippocampus shape. We detected a significant age effect on hippocampus in accordance with the previous studies. In addition, we also detected a significant gender effect on amygdala. Since we did not find any such differences in the traditional volumetric methods, our results demonstrate the benefit of the current framework over traditional volumetric methods.
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This experiment was designed to test whether reading disabled boys differ from matched controls on behavioral measures of interhemispheric transfer time (IHTT). Specifically, we proposed that language-disordered reading disabled children who had deficits in naming would show either faster or slower IHTTs compared with controls. From an initial group of 118 right-handed males, we selected a group of 25 disabled and 25 normal readers, matched on age. All subjects had to obtain a full scale IQ of 90 or above, a PIQ score of 85 or above, and a scaled score of 7 or above on the Block Design Subtest of the WISC-R. After meeting additional criteria for group assignment, manual reaction time (RT) measures of IHTT were obtained in response to simple visual and tactile stimuli during two laboratory testing sessions. Half the trials were conducted with the hands in an uncrossed orientation and half with the hands crossed in order to examine the effects of spatial compatibility on estimates of IHTT. The results revealed no overall group differences in IHTT for any of the conditions. However, correlations between IHTT measures and indices of cognitive performance indicated that faster IHTTs were significantly correlated with poorer performance on measures of reading and language function in the dyslexic group. These data are discussed within the context of a model of interhemispheric transfer deficits in disabled readers.
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