Biomedical subjects

Rex E Jung

Publications and source records attributed to Rex E Jung.

8 recordsLinked to original sources

PubMed2005

Sex differences in N-acetylaspartate correlates of general intelligence: an 1H-MRS study of normal human brain.

Researchers have long attempted to determine brain correlates of intelligence using available neuroimaging technology including CT, MRI, PET, and fMRI. Although structural and functional imaging techniques are well suited to assess gross cortical regions associated with intelligence, the integrity and functioning of underlying white matter networks critical to coordinated cortical integration remain comparatively understudied. A relatively recent neuroimaging advance is magnetic resonance spectroscopy (MRS) which allows for interrogation of biochemical substrates of brain structure and function in vivo. In this study, we examined twenty-seven normal control subjects (17 male, 10 female) to determine whether N-acetylaspartate (NAA), a metabolite found primarily within neurons, is related to intelligence as assessed by the Wechsler Adult Intelligence Scale-III. Of the three white matter regions studied (i.e., left frontal, right frontal, left occipito-parietal), we found that a model including only left occipito-parietal white matter predicted intellectual performance [F(1,25) = 8.65, P = .007; r2 = .26], providing regional specificity to our previous findings of NAA-IQ relationships. Moreover, we found that a complex combination of left frontal and left occipito-parietal NAA strongly predicted performance in women, but not men [F(2,7) = 21.84, P < .001; adjusted r2 = .82]. Our results highlight a biochemical substrate of normal intellectual performance, mediated by sex, within white matter association fibers linking posterior to frontal brain regions.

Adolescent↗

PubMed2005

The neuroanatomy of general intelligence: sex matters.

We examined the relationship between structural brain variation and general intelligence using voxel-based morphometric analysis of MRI data in men and women with equivalent IQ scores. Compared to men, women show more white matter and fewer gray matter areas related to intelligence. In men IQ/gray matter correlations are strongest in frontal and parietal lobes (BA 8, 9, 39, 40), whereas the strongest correlations in women are in the frontal lobe (BA10) along with Broca's area. Men and women apparently achieve similar IQ results with different brain regions, suggesting that there is no singular underlying neuroanatomical structure to general intelligence and that different types of brain designs may manifest equivalent intellectual performance.

Adolescent↗

PubMed2005

A novel technique to study the brain's response to pain: proton magnetic resonance spectroscopy.

Glutamate, a major excitatory neurotransmitter, has been implicated as an important mediator in the neurotransmission, potentiation, and negative affect associated with pain. We present results showing that a painful stimulus elicits a dynamic increase in glutamate (9.3% from baseline) concentrations in the anterior cingulate cortex, detectable using proton Magnetic Resonance Spectroscopy ((1)H-MRS). Increases in glutamine levels were also seen, which correlate strongly with the subjective level of pain experienced by participants (r(2) = 0.58, P < 0.01). These novel findings are the first time a dynamic change in glutamate and glutamine levels from baseline in response to an external stimuli has been measured in a single proton MRS scanning session. As such, this report demonstrates the efficacy of (1)H-MRS as a non-invasive tool for the study of neural responses to pain in vivo. The paradigm used in this study demonstrates that dynamic glutamate/glutamine changes due to stimulation are measurable by proton MRS, and could provide a means of testing novel pharmaceutical agents and other treatments for chronic pain.

Adult↗

PubMed2005

Selective cognitive impairments associated with NMDA receptor blockade in humans.

Hypofunction of the N-methyl-D-aspartate receptor (NMDAR) may be involved in the pathophysiology of schizophrenia. NMDAR antagonists like ketamine induce schizophrenia-like features in humans. In rodent studies, NMDAR antagonism impairs learning by disrupting long-term potentiation (LTP) in the hippocampus. This study investigated the effects of ketamine on spatial learning (acquisition) vs retrieval in a virtual Morris water task in humans. Verbal fluency, working memory, and learning and memory of verbal information were also assessed. Healthy human subjects participated in this double-blinded, placebo-controlled study. On two separate occasions, ketamine/placebo was administered and cognitive tasks were assessed in association with behavioral ratings. Ketamine impaired learning of spatial and verbal information but retrieval of information learned prior to drug administration was preserved. Schizophrenia-like symptoms were significantly related to spatial and verbal learning performance. Ketamine did not significantly impair attention, verbal fluency, or verbal working memory task performance. Spatial working memory was slightly impaired. In conclusion, these results provide evidence for ketamine's differential impairment of verbal and spatial learning vs retrieval. By using the Morris water task, which is hippocampal-dependent, this study helps bridge the gap between nonhuman animal and human NMDAR antagonism research. Impaired cognition is a core feature of schizophrenia. A better understanding of NMDA antagonism, its physiological and cognitive consequences, may provide improved models of psychosis and cognitive therapeutics.

Cognition Disorders↗

PubMed2005

Effects of ketamine on anterior cingulate glutamate metabolism in healthy humans: a 4-T proton MRS study.

OBJECTIVE: The authors' goal was to test in humans the hypothesis that N-methyl-d-aspartate receptor (NMDAR) antagonism results in increased cortical glutamate activity, as proposed by the NMDAR hypofunction model of schizophrenia. METHOD: 4-T 1H proton magnetic resonance spectroscopy (1H-MRS) was used to acquire in vivo spectra from the bilateral anterior cingulate of 10 healthy subjects while they received a subanesthetic dose of either placebo or ketamine, an NMDAR antagonist. Assessments given before and after ketamine or placebo administration included the Brief Rating Psychiatric Rating Scale, the Scale for the Assessment of Negative Symptoms, the Clinician-Administered Dissociative States Scale, and the Stroop task. RESULTS: As predicted, there was a significant increase in anterior cingulate glutamine, a putative marker of glutamate neurotransmitter release, with ketamine administration. This increase was not related to schizophrenia-like positive or negative symptoms but was marginally related to Stroop performance. CONCLUSIONS: In humans as in animals, an acute hypofunctional NMDAR state is associated with increased glutamatergic activity in the anterior cingulate.

Adult↗

PubMed2004

MRI morphometric and neuropsychological correlates of long-term memory in survivors of childhood leukemia.

BACKGROUND: Long-term survivors of acute lymphoblastic leukemia (ALL) are reported to have post-treatment neurological changes as well as neuropsychological changes. Few studies have investigated the relationship between magnetic resonance imaging (MRI) volumetric measurements of brain regions of interest and cognitive functioning. This study examined the relationship between hippocampal volumes and long-term memory abilities in survivors of ALL. PROCEDURE: Ten survivors of ALL and ten matched controls underwent MRI acquisition. The participants completed a battery of tests measuring both visual and verbal long-term memory. Volumetric measurements of the hippocampus were obtained by consecutive manual tracing using the NIH Image 1.52 program. Estimates of whole brain volume were also obtained. RESULTS: No significant group differences were found in right or left hippocampi. Nor were there significant differences between the two groups on measures of long-term memory. Correlations between volumetric measurements of the hippocampus and measures of long-term memory were non-significant. CONCLUSIONS: Our hypothesis of deficits in both long-term memory and its neural substrates was not supported. It was concluded that the hippocampus, as an early developing structure, may be less vulnerable to chemotherapy treatment. Children surviving ALL are able to retain and retrieve once learned information comparable with peers.

Adolescent↗

PubMed2004

Structural brain variation and general intelligence.

Total brain volume accounts for about 16% of the variance in general intelligence scores (IQ), but how volumes of specific regions-of-interest (ROIs) relate to IQ is not known. We used voxel-based morphometry (VBM) in two independent samples to identify substantial gray matter (GM) correlates of IQ. Based on statistical conjunction of both samples (N = 47; P < 0.05 corrected for multiple comparisons), more gray matter is associated with higher IQ in discrete Brodmann areas (BA) including frontal (BA 10, 46, 9), temporal (BA 21, 37, 22, 42), parietal (BA 43 and 3), and occipital (BA 19) lobes and near BA 39 for white matter (WM). These results underscore the distributed neural basis of intelligence and suggest a developmental course for volume--IQ relationships in adulthood.

Adult↗

PubMed2002

Biochemical markers of mood: a proton magnetic resonance spectroscopy study of normal human brain.

BACKGROUND: Elevated brain Cho has been shown within the basal ganglia and frontal (i.e., orbitofrontal and cingulate) cortices in patients with mood disorders utilizing Proton Magnetic Resonance Spectroscopy (1H-MRS). We sought to determine the relationship between Cho and mood in a cohort of healthy young subjects. METHODS: Twenty-seven subjects without neurologic or psychiatric disorders were evaluated with the Positive and Negative Affect Scale and underwent 1H-MRS of bilateral frontal and occipito-parietal white matter. RESULTS: We found that Cho in the left frontal lobe was inversely correlated with Positive Affect [F(1,24) = 19.2, p <.001, r(2) =.45]. CONCLUSIONS: Our results highlight the important involvement of Cho underlying the integration of affective processing within prefrontal circuitry, and may indicate increased myelin turnover in subjects with lower Positive Affect. Further efforts will be necessary to determine if high Cho is associated with increased incidence of mood disorders throughout life.

Adult↗