Biomedical subjects

Vincent J Schmithorst

Publications and source records attributed to Vincent J Schmithorst.

At least 19 recordsLinked to original sources

PubMed2006

Functional MRI evidence for disparate developmental processes underlying intelligence in boys and girls.

Previous research has shown evidence for sex differences in the neuroanatomical bases for intelligence in adults. Possible differences in the neuroanatomical correlates of intelligence and their developmental trajectories between boys and girls were investigated using functional MRI (fMRI). A large cohort of over 300 children, ages 5-18, performed the semantic processing task of silent verb generation. Regions were found in the left hemisphere exhibiting positive correlations of blood-oxygenation-level-dependent (BOLD) activation with IQ, including the middle temporal gyrus, prefrontal cortex (Broca's area), medial frontal gyrus, precuneus, and cingulate gyrus, while the superior temporal gyrus in the right hemisphere displayed a negative correlation of BOLD activation with IQ. Significant sex-X-IQ and sex-X-IQ-X-age interaction effects were also seen in the left middle temporal gyrus and left inferior frontal gyrus. Using a data-driven analysis procedure, a sex-X-IQ-X-age interaction was also demonstrated in the functional connectivity between regions in the left hemisphere, parameterized as a weighted sum of pairwise covariances between fMRI time courses. While young girls (<13 years) exhibited no correlation of connectivity with intelligence, older girls (>13 years) demonstrated a positive association of functional connectivity with intelligence. Boys, however, demonstrated the opposite developmental trajectory, from a positive association of connectivity with intelligence in young boys (ages <9 years), to a negative association in older boys (ages >13 years). Our results provide evidence for disparate neuroanatomical trajectories underlying intelligence in boys and girls.

Adolescent↗

PubMed2006

A longitudinal functional magnetic resonance imaging study of language development in children 5 to 11 years old.

OBJECTIVE: Language skills continue to develop rapidly in children during the school-age years, and the "snapshot" view of the neural substrates of language provided by current neuroimaging studies cannot capture the dynamic changes associated with brain development. The aim of this study was to conduct a 5-year longitudinal investigation of language development using functional magnetic resonance imaging in healthy children. METHODS: Thirty subjects enrolled at ages 5, 6, or 7 were examined annually for 5 years using a 3-Tesla magnetic resonance imaging scanner and a verb generation task. Data analysis was conducted based on a general linear model that was modified to investigate developmental changes whereas minimizing the potential for missing data. RESULTS: With increasing age, there is progressive participation in language processing by the inferior/middle frontal, middle temporal, and angular gyri of the left hemisphere and the lingual and inferior temporal gyri of the right hemisphere and regression of participation of the left posterior insula/extrastriate cortex, left superior frontal and right anterior cingulate gyri, and left thalamus. CONCLUSION: The age-related changes observed in this study provide evidence of increased neuroplasticity of language in this age group and may have implications for further investigations of normal and aberrant language development.

Algorithms↗

PubMed2006

fMRI study of language lateralization in children and adults.

Language lateralization in the brain is dependent on family history of handedness, personal handedness, pathology, and other factors. The influence of age on language lateralization is not completely understood. Increasing left lateralization of language with age has been observed in children, while the reverse has been noted in healthy young adults. It is not known whether the trend of decreasing language lateralization with age continues in the late decades of life and at what age the inflection in language lateralization trend as a function of age occurs. In this study, we examined the effect of age on language lateralization in 170 healthy right-handed children and adults ages 5-67 using functional MRI (fMRI) and a verb generation task. Our findings indicate that language lateralization to the dominant hemisphere increases between the ages 5 and 20 years, plateaus between 20 and 25 years, and slowly decreases between 25 and 70 years.

Adolescent↗

PubMed2006

fMRI shows atypical language lateralization in pediatric epilepsy patients.

PURPOSE: The goal of this study was to compare language lateralization between pediatric epilepsy patients and healthy children. METHODS: Two groups of subjects were evaluated with functional magnetic resonance imaging (fMRI) by using a silent verb-generation task. The first group included 18 pediatric epilepsy patients, whereas the control group consisted of 18 age/gender/handedness-matched healthy subjects. RESULTS: A significant difference in hemispheric lateralization index (LI) was found between children with epilepsy (mean LI =-0.038) and the age/gender/handedness-matched healthy control subjects (mean LI=0.257; t=6.490, p<0.0001). A dramatic difference also was observed in the percentage of children with epilepsy (77.78%) who had atypical LI (right-hemispheric or bilateral, LI<0.1) when compared with the age/gender/handedness-matched group (11.11%; chi(2)=16.02, p<0.001). A linear regression analysis showed a trend toward increasing language lateralization with age in healthy controls (R(2)=0.152; p=0.108). This association was not observed in pediatric epilepsy subjects (R(2)=0.004, p=0.80). A significant association between language LI and epilepsy duration also was found (R(2)=0.234, p<0.05). CONCLUSIONS: This study shows that epilepsy during childhood is associated with neuroplasticity and reorganization of language function.

Adolescent↗

PubMed2006

Making memories: a cross-sectional investigation of episodic memory encoding in childhood using FMRI.

In adults, the neural substrate associated with encoding memories connected to a specific time and place include the prefrontal cortex and medial temporal lobe (MTL). Using functional magnetic resonance imaging, this research studied the developmental trajectory of this frontal-MTL system by comparing 7- and 8-year-old children to those who were 10 or older in conditions that promoted episodic encoding. In 1 condition, participants generated verbs from nouns heard; in another, they listened to short stories for comprehension. Regions in which brain activation predicted subsequent recognition memory performance were identified. These included the left prefrontal cortex, but not MTL, in the verb generation condition for both age groups. In the story comprehension condition, activation in left posterior MTL predicted subsequent memory performance in both age groups, and activation in left anterior MTL (including the hippocampus proper) and left prefrontal cortex predicted subsequent memory only for the older children. These results illustrate both similarities and differences in how brain systems interact in development to mediate the formation of episodic memories.

Adolescent↗

PubMed2006

Cerebral ischemia-hypoxia induces intravascular coagulation and autophagy.

Hypoxia is a critical factor for cell death or survival in ischemic stroke, but the pathological consequences of combined ischemia-hypoxia are not fully understood. Here we examine this issue using a modified Levine/Vannucci procedure in adult mice that consists of unilateral common carotid artery occlusion and hypoxia with tightly regulated body temperature. At the cellular level, ischemia-hypoxia produced proinflammatory cytokines and simultaneously activated both prosurvival (eg, synthesis of heat shock 70 protein, phosphorylation of ERK and AKT) and proapoptosis signaling pathways (eg, release of cytochrome c and AIF from mitochondria, cleavage of caspase-9 and -8). However, caspase-3 was not activated, and very few cells completed the apoptosis process. Instead, many damaged neurons showed features of autophagic/lysosomal cell death. At the tissue level, ischemia-hypoxia caused persistent cerebral perfusion deficits even after release of the carotid artery occlusion. These changes were associated with both platelet deposition and fibrin accumulation within the cerebral circulation and would be expected to contribute to infarction. Complementary studies in fibrinogen-deficient mice revealed that the absence of fibrin and/or secondary fibrin-mediated inflammatory processes significantly attenuated brain damage. Together, these results suggest that ischemia-hypoxia is a powerful stimulus for spontaneous coagulation leading to reperfusion deficits and autophagic/lysosomal cell death in brain.

Animals↗

PubMed2005

Cognitive modules utilized for narrative comprehension in children: a functional magnetic resonance imaging study.

The ability to comprehend narratives constitutes an important component of human development and experience. The neural correlates of auditory narrative comprehension in children were investigated in a large-scale functional magnetic resonance imaging (fMRI) study involving 313 subjects ages 5-18. Using group independent component analysis (ICA), bilateral task-related components were found comprising the primary auditory cortex, the mid-superior temporal gyrus, the hippocampus, the angular gyrus, and medial aspect of the parietal lobule (precuneus/posterior cingulate). In addition, a right-lateralized component was found involving the most posterior aspect of the superior temporal gyrus, and a left-lateralized component was found comprising the inferior frontal gyrus (including Broca's area), the inferior parietal lobule, and the medial temporal gyrus. Using a novel data-driven analysis technique, increased task-related activity related to age was found in the components comprising the mid-superior temporal gyrus (Wernicke's area) and the posterior aspect of the superior temporal gyrus, while decreased activity related to age was found in the component comprising the angular gyrus. The results are discussed in light of recent hypotheses involving the functional segregation of Wernicke's area and the specific role of the mid-superior temporal gyrus in speech comprehension.

Adolescent↗

PubMed2005

Sound blending in the brain: a functional magnetic resonance imaging investigation.

The presence of high levels of background noise is a serious concern for functional magnetic resonance imaging studies of phonological processing using conventional methods. As a result, many such studies have focused on phonological units larger than phonemes (e.g. syllables) or used stimuli presented in the visual (e.g. printed letters) rather than the auditory domain. We used a recently developed functional magnetic resonance imaging method to present spoken stimuli without the scanner's background noise. Young adult participants mentally blended phonemes in a series (e.g. /b/, /ae/, /t/), counted the number of discrete tones, or rested. Relative to tone counting, sound blending elicited activation in bilateral temporal and prefrontal cortices with left asymmetry. Activation within the dorsoposterior inferior frontal gyrus, a subregion of Broca's area, was negatively correlated with sound-blending accuracy. Our findings are consistent with prior studies ascribing a role of general sequencing, motor and articulatory programming, and vocal or subvocal articulatory rehearsal to this brain region.

Acoustic Stimulation↗

PubMed2005

Cortical reorganization in children with unilateral sensorineural hearing loss.

Previous studies have shown evidence of cortical reorganization following unilateral sensorineural hearing loss (USNHL). In addition, study participants with right USNHL have shown greater deficits in academic and language performance compared with those with left USNHL. A preliminary functional magnetic resonance imaging investigation was performed on a small cohort of participants, four with left USNHL and four with right USNHL, using the paradigm of listening to random tones. While the participants with left USNHL displayed greater activation in the right superior temporal gyrus, those with right USNHL displayed greater activation in the left inferior frontal area immediately anterior to the superior temporal gyrus. The results provide preliminary evidence of disparate neural circuitry supporting auditory processing in participants with left and right USNHL.

Acoustic Stimulation↗

PubMed2005

Separate cortical networks involved in music perception: preliminary functional MRI evidence for modularity of music processing.

Music perception is a quite complex cognitive task, involving the perception and integration of various elements including melody, harmony, pitch, rhythm, and timbre. A preliminary functional MRI investigation of music perception was performed, using a simplified passive listening task. Group independent component analysis (ICA) was used to separate out various components involved in music processing, as the hemodynamic responses are not known a priori. Various components consistent with auditory processing, expressive language, syntactic processing, and visual association were found. The results are discussed in light of various hypotheses regarding modularity of music processing and its overlap with language processing. The results suggest that, while some networks overlap with ones used for language processing, music processing may involve its own domain-specific processing subsystems.

Adult↗

PubMed2005

Cognitive functions correlate with white matter architecture in a normal pediatric population: a diffusion tensor MRI study.

A possible relationship between cognitive abilities and white matter structure as assessed by magnetic resonance diffusion tensor imaging (DTI) was investigated in the pediatric population. DTI was performed on 47 normal children ages 5-18. Using a voxelwise analysis technique, the fractional anisotropy (FA) and mean diffusivity (MD) were tested for significant correlations with Wechsler full-scale IQ scores, with subject age and gender used as covariates. Regions displaying significant positive correlations of IQ scores with FA were found bilaterally in white matter association areas, including frontal and occipito-parietal areas. No regions were found exhibiting correlations of IQ with MD except for one frontal area significantly overlapping a region containing a significant correlation with FA. The positive direction of the correlation with FA is the same as that found previously with age, and indicates a positive relationship between fiber organization and/or density with cognitive function. The results are consistent with the hypothesis that regionally specific increased fiber organization is a mechanism responsible for the normal development of white matter tracts.

Adolescent↗

PubMed2004

The effect of musical training on the neural correlates of math processing: a functional magnetic resonance imaging study in humans.

The neural correlates of the previously hypothesized link between formal musical training and mathematics performance are investigated using functional magnetic resonance imaging (fMRI). FMRI was performed on fifteen normal adults, seven with musical training since early childhood, and eight without, while they mentally added and subtracted fractions. Musical training was associated with increased activation in the left fusiform gyrus and prefrontal cortex, and decreased activation in visual association areas and the left inferior parietal lobule during the mathematical task. We hypothesize that the correlation between musical training and math proficiency may be associated with improved working memory performance and an increased abstract representation of numerical quantities.

Adult↗

PubMed2004

Comparison of three methods for generating group statistical inferences from independent component analysis of functional magnetic resonance imaging data.

PURPOSE: To evaluate the relative effectiveness of three previously proposed methods of performing group independent component analysis (ICA) of functional magnetic resonance imaging (fMRI) data. MATERIALS AND METHODS: Data were generated via computer simulation. Components were added to a varying number of subjects between 1 and 20, and intersubject variability was simulated for both the added sources and their associated time courses. Three methods of group ICA analyses were performed: across-subject averaging, subject-wise concatenation, and row-wise concatenation (e.g., across time courses). RESULTS: Concatenating across subjects provided the best overall performance in terms of accurate estimation of the sources and associated time courses. Averaging across subjects provided accurate estimation (R > 0.9) of the time courses when the sources were present in a sufficient fraction (about 15%) of 100 subjects. Concatenating across time courses was shown not to be a feasible method when unique sources were added to the data from each subject, simulating the effects of motion and susceptibility artifacts. CONCLUSION: Subject-wise concatenation should be used when computationally feasible. For studies involving a large number of subjects, across-subject averaging provides an acceptable alternative and reduces the computational load.

Computer Simulation↗

PubMed2004

A STAP algorithm approach to fMRI: a simulation study.

PURPOSE: To adapt the space-time adaptive processing (STAP) algorithm, previously developed in the field of sensor array processing and applied to radar signal processing, for use in construction of brain activation maps in functional magnetic resonance imaging (fMRI). MATERIALS AND METHODS: STAP is a two-dimensional filter in which both the spatial and temporal responses are controlled adaptively. It processes space-time data as a complete spatiotemporal set. Unlike presently used fMRI techniques, STAP locates activated regions both spatially and in frequency. RESULTS: Computer simulations incorporating actual MRI noise indicate that STAP exhibits a high degree of accuracy in detecting the small signal intensity changes inherent in fMRI. CONCLUSION: Because STAP processes space-time data as a single data matrix, it exhibits potential over currently available fMRI methods in providing a measure of the full spatiotemporal extent of a task-related activity.

Algorithms↗

PubMed2004

Event-related fMRI technique for auditory processing with hemodynamics unrelated to acoustic gradient noise.

Acoustic noise from the imaging gradients presents a major difficulty in functional MRI (fMRI) studies of auditory cortical function. For studies involving hearing-impaired pediatric subjects, the auditory stimuli should be presented during completely silent gradient intervals. In addition, the scan time is limited by constraints involving subject motion and subject compliance. A novel event-related method for conducting fMRI studies of auditory function is proposed. Auditory stimuli are presented during completely silent gradient intervals, but using a variable TR. A general nonlinear model (GNLM) is proposed as a postprocessing methodology for the data. The technique increases the flexibility of the experimental design, with minimal loss of sensitivity compared to standard fMRI acquisition techniques, and may therefore be useful for fMRI studies of auditory function in hearing-impaired pediatric subjects.

Adult↗

PubMed2004

Empirical validation of the triple-code model of numerical processing for complex math operations using functional MRI and group Independent Component Analysis of the mental addition and subtraction of fractions.

The suitability of a previously hypothesized triple-code model of numerical processing, involving analog magnitude, auditory verbal, and visual Arabic codes of representation, was investigated for the complex mathematical task of the mental addition and subtraction of fractions. Functional magnetic resonance imaging (fMRI) data from 15 normal adult subjects were processed using exploratory group Independent Component Analysis (ICA). Separate task-related components were found with activation in bilateral inferior parietal, left perisylvian, and ventral occipitotemporal areas. These results support the hypothesized triple-code model corresponding to the activated regions found in the individual components and indicate that the triple-code model may be a suitable framework for analyzing the neuropsychological bases of the performance of complex mathematical tasks.

Adult↗

PubMed2004

High-resolution functional MRI at 3T in healthy and epilepsy subjects: hippocampal activation with picture encoding task.

Functional MRI (fMRI) studies of memory with coarse resolution of 4 x 4 x 5 mm often fail to demonstrate blood oxygenation level-dependent (BOLD) activation in the hippocampal formation. This failure occurs when nonactivating white matter is averaged with the signal from hippocampal gray matter, attenuating the total BOLD signal from a single voxel due to the "partial volume effect." In this study, we evaluated the suitability of high-resolution fMRI at 3T (voxel size 2 x 2 x 3 mm) for improved visualization of hippocampal activation during memory encoding in 21 healthy and 6 epilepsy subjects. We used a picture encoding task (block design) that involved memorization of indoor and outdoor scenes along with an appropriate resting task. Region-of-interest (ROI) analysis was performed; laterality indices (LIs) were calculated based on hippocampal ROIs (hROIs) or on global medial temporal ROIs (mtROIs). In 19 healthy subjects, robust bilateral BOLD signal changes within both ROIs were noted. The mean LI+/-SD for the hROIs is -0.12+/-0.06 and that for the medial temporal ROIs -0.12+/-0.05, with correlation between the LIs (r = 0.59, P = 0.009). Good concordance was noted between the surgical outcome and memory lateralization with the fMRI task employed in this study. The preliminary results are encouraging, and with continuing improvements in MRI scanner technology, we expect fMRI of the hippocampal formation at higher resolution to be possible and preferable. Furthermore, these results suggest that a larger study to test the utility of high-resolution fMRI in epilepsy presurgical evaluation is needed.

Adult↗

PubMed2003

The effect of musical training on music processing: a functional magnetic resonance imaging study in humans.

Previous studies have demonstrated changes in neuronal activity in trained musicians relative to controls while performing various music processing tasks. In this study the neural correlates of the effect of music training on two aspects of music processing, melody and harmony, are investigated using functional magnetic resonance imaging (fMRI). Fifteen subjects, seven with continuous musical training from early childhood to adulthood and eight without, underwent a passive fMRI listening paradigm designed to test the effects of melodic and harmonic processing. Melodic processing activated the most anterior part of the superior temporal gyrus for both musicians and non-musicians, while harmonic processing activated different visual association areas for musicians relative to non-musicians. The inferior parietal lobules were recruited only by musicians for both tasks. We conclude that musical training results in the recruitment of different neural networks for these aspects of music processing.

Acoustic Stimulation↗