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Blaine Hart

Publications and source records attributed to Blaine Hart.

9 recordsLinked to original sources
PubMed2006

Aging: compensation or maturation?

Neuroimaging studies of healthy aging often reveal differences in neural activation patterns between young and elderly groups for episodic memory tasks, even though there are no differences in behavioral performance. One explanation typically offered is that the elderly compensate for their memory deficiencies through the recruitment of additional prefrontal regions. The present study of healthy aging compared magnetoencephalographic (MEG) time-courses localized to specific cortical regions in two groups of subjects (20-29 years and >or=65 years) during a visual delayed-match-to-sample (DMS) task. MR morphometrics and neuropsychological test results were also examined with the hope of providing insight into the nature of the age-related differences. The behavioral results indicated no differences in performance between young and elderly groups. Although there was a main effect of age on the latency of the initial peak in primary/secondary visual cortex, these longer latencies were not correlated with the performance of elderly on the DMS task. The lateral occipital gyrus (LOG) revealed qualitatively different patterns of activity for the two age groups corroborated by neuropsychological test results. Morphometric results for the young versus elderly groups revealed less white (WM) and gray matter (GM) volumes in the frontal lobes of the elderly. When a group of middle-aged subjects (33-43 years) was included in the morphometric analyses, the middle-aged subjects revealed statistically greater WM volumes in frontal and parietal cortex suggesting immature WM tracts in the young. Perhaps our elderly utilized a different strategy compared to the young due to the different brain maturation levels of these groups.

Adult↗
PubMed2005

Aging changes and gender differences in response to median nerve stimulation measured with MEG.

OBJECTIVE: The current study uses magnetoencephalography (MEG) to characterize age-related changes and gender differences in the amplitudes and timing of cortical sources evoked by median nerve stimulation. METHODS: Thirty-four healthy subjects from two age groups: 20-29 and >64 years of age were examined. After measuring the MEG responses, we modeled the data using a spatio-temporal multi-dipole modeling approach to determine the source locations and their associated timecourses. RESULTS: We found early, large amplitude responses in the elderly in primary somatosensory (approximately 20 ms) and pre-central sulcus timecourses (approximately 22 ms) and lower amplitude responses in the elderly later in primary somatosensory (approximately 32 ms) and contralateral secondary somatosensory timecourses (approximately 90 ms). In addition, females had larger peak amplitude responses than males in the contralateral secondary somatosensory timecourse (approximately 28 and 51 ms). CONCLUSIONS: These results show that the median nerve stimulation paradigm provides considerable sensitivity to age- and gender-related differences. The results are consistent with the theory that increased amplitudes identified in the elderly may be associated with decreased inhibition. SIGNIFICANCE: The results emphasize that an examination of two discrete age groups, collapsed across gender, cannot provide a complete understanding of the fundamental changes that occur in the brain across the lifetime.

Adult↗
PubMed2005

Osmotic myelinolysis following chronic hyponatremia corrected at an overall rate consistent with current recommendations.

Rapid correction of chronic hyponatremia (CH) may lead to the development of osmotic myelinolysis (OM), a condition with high mortality and high incidence of devastating neurological sequelae. Treatment guidelines suggest "safe" overall rates of correction of serum sodium concentration ([Na](s)) over the first 24 and 48 hours of treatment of CH. We report a patient with CH who developed fatal OM despite overall rates of correction of [Na](s) that were within the recommended rates. The potential risk factors for the development of OM in this patient included short (within a few hours) rises in [Na](s) exceeding 0.5 mmol/l per hour and the presence of severe protein malnutrition. We suggest that the rate of correction of [Na](s) in CH should be uniformly slow and that the overall rate of correction should be slower than the currently recommended rate in severely malnourished patients.

Aged↗
PubMed2003

Magnetic resonance imaging correlates of attention-deficit/hyperactivity disorder in children.

This study compared magnetic resonance imaging size differences in several brain regions and neurocognitive function in a group of male and female children with attention-deficit/hyperactivity disorder (ADHD) with no comorbid learning disorders with a normal control group of children. The ADHD group demonstrated smaller total brain, superior prefrontal, and right superior prefrontal volumes, as well as significantly smaller areas for cerebellar lobules I-V and VIII-X, total corpus callosum area, and splenium. No group differences were observed for the inferior prefrontal, caudate, or cerebellar volumes, or for the area of cerebellar lobules VI-VII. In the ADHD group but not in the control group, greater right superior prefrontal volume predicted poorer performance on a test of sustained attention. Patterns of brain abnormality did not differ in male and female children with ADHD.

Attention Deficit Disorder with Hyperactivity↗
PubMed2003

Proton magnetic resonance spectroscopy investigation of the right frontal lobe in children with attention-deficit/hyperactivity disorder.

OBJECTIVE: To investigate neurometabolite concentrations in right prefrontal white matter in children with attention-deficit/hyperactivity disorder (ADHD) and relations of neurometabolites with attention skill and frontal anatomy. METHOD: Single voxel proton magnetic resonance spectroscopy ( H-MRS), quantitative morphometric analysis of left and right dorsolateral frontal volumes, and assessment of attentional problems with the Conners Continuous Performance Test were undertaken in 23 children (17 male) with ADHD (with no comorbid learning disabilities) and 24 matched controls (16 male). RESULTS: No overall group differences were found for any neurometabolite. However, a group by sex interaction was noted for -acetylaspartate, such that girls with ADHD had especially low concentrations. Morphological analyses revealed smaller right (but not left) dorsolateral volumes in children with ADHD, and in the ADHD group this volume correlated with neurometabolite concentrations. In the ADHD group Continuous Performance Test performance was related to both dorsolateral volume and the creatine-phosphocreatine peak from H-MRS. CONCLUSIONS: These results add to a growing body of evidence suggesting sex-specific neurobiological differences in ADHD and draw attention to relationships between neurochemistry, neuroanatomy, and performance in children with ADHD. Study limitations include small sample size and clinical heterogeneity among the children with ADHD.

Aspartic Acid↗
PubMed2003

Severity of cervical spine ligamentous injury correlates with mechanism of injury, not with severity of blunt head trauma.

Clearance of the cervical spine (CS) in obtunded trauma patients in an intensive care unit is problematic. Patients with no osseous injuries have potential unstable extradural supportive soft tissue injury. Evaluation of the supporting structures involves dynamic fluoroscopy or MRI both of which have inherent risks and convenience issues. Defining which of these patients are at highest risk for severe supportive structure injury may improve resource utilization for CS clearance. The purpose of this study was to evaluate clinical factors that may predict the probability of CS supportive soft tissue injury in patients with traumatic brain injury. Patients who sustained traumatic brain injury with intracranial pathology, absence of CS osseous injury, and a limited cervical spine MRI within 72 hours of injury were included. Potential clinical predictors included the severity of the traumatic brain injury defined by the Abbreviated Injury Severity Score for the cerebrum and initial Glasgow Coma Scale, the Injury Severity Score (ISS), mechanism of injury, and high versus low-velocity mechanism. Severity of soft tissue/ligament injury was graded by MRI findings. One hundred twenty-five patients met the study criteria; 81 had negative MRI findings and in 44 the MRI study was positive for potentially unstable injuries. High-velocity mechanisms of injury and ISS--not the severity of the traumatic brain injury or initial Glasgow Coma Scale score--were statistically significant predictors of severe CS supportive soft tissue injuries. Obtunded blunt trauma patients who have been involved in high-velocity-mechanism incidents and have high ISS are at greatest risk for extradural supportive soft tissue CS injuries. These patients should either remain in CS immobilization until clinical evaluation can be completed or undergo further evaluation of their supportive soft tissue structures by MRI or fluoroscopic flexion/extension.

Adult↗
PubMed2002

Longitudinal follow-up of neurochemical changes during the first year of antipsychotic treatment in schizophrenia patients with minimal previous medication exposure.

Reduced frontal N-acetylaspartate (NAA) has been repeatedly found in chronic schizophrenia and suggests neuronal loss or dysfunction. However, the potential confounding effect of antipsychotic drugs on NAA has not been resolved. The few studies of antipsychotic-nai;ve patients are inconclusive. A recent report suggests that antipsychotic drugs may increase NAA in the dorsolateral prefrontal cortex (DLPFC). We studied 10 minimally treated (less than 3 weeks lifetime exposure) schizophrenia patients and 10 normal controls with single-voxel proton magnetic resonance spectroscopy (1H-MRS) of the left frontal and occipital lobes. Concentrations of NAA, Cho, and Cre were determined and corrected for the proportion of cerebrospinal fluid (CSF) in the voxel. Patients were treated in a randomized-controlled double-blind design with either haloperidol or quetiapine. 1H-MRS was repeated within a year. There were no differences in frontal or occipital NAA between patients and controls at baseline. However, frontal NAA was reduced in the schizophrenia group within the first year of treatment. Patients had a clear clinical response to treatment but changes in frontal NAA were not correlated with symptom improvement. The well-described reduced frontal NAA in schizophrenia may not be a trait of the illness but may represent medication effect or progression of the disease.

Adult↗
PubMed2002

High choline concentrations in the caudate nucleus in antipsychotic-naive patients with schizophrenia.

OBJECTIVE: Proton magnetic resonance spectroscopy ((1)H-MRS) studies of medicated patients with schizophrenia suggest high choline levels in the caudate nucleus. However, assessments of antipsychotic-naive patients are needed. METHOD: The authors studied 11 antipsychotic-naive schizophrenia patients and 11 normal comparison subjects with single-voxel (1)H-MRS of the left caudate nucleus. Concentrations of N-acetylaspartate, choline, and creatine were determined and corrected for the proportion of cerebrospinal fluid in the voxel. RESULTS: The patients with schizophrenia had significantly higher levels of choline than the comparison subjects, while the other two metabolites did not differ between groups. CONCLUSIONS: High caudate choline levels in schizophrenia are not secondary to antipsychotic treatment.

Adult↗