Degree Received
Ph.D., University of Texas-Austin, 1984

Research Interests

Clinical and experimental neuropsychology. Specific ongoing lines of research include:

1. Individual differences in brain organization:  investigation of the major dimensions of differences among human brains, including intelligence, sex, age, handedness and anatomical cerebral asymmetries. See publications 1, 4, 6, 9, 10, 14, 16, 20, 21, 23, 25, 26.

A key construct in much of this work is “developmental stability”. This refers to an organism’s ability to develop the appropriate species-specific phenotype, despite genetic and environmental perturbations that tend to disrupt development, such as mutations, inbreeding, toxins, pathogens, parasites, injuries, starvation, and prenatal maternal stress. Developmental stability is analogous to a builder’s ability to turn a blueprint (the genotype) into a well-constructed house (the phenotype).  A major discovery in biology and evolutionary psychology has been that individuals show differences in developmental stability: some individuals grow adaptive phenotypes under almost any conditions, whereas others show disrupted development given the slightest perturbations. These individual differences show moderate heritability. At the level of morphological development, one key manifestation of developmental stability is body symmetry.  Confusingly, this is usually operationalized as the converse of developmental stability, called developmental instability, which is indexed by a measure called fluctuating asymmetry (FA).  FA refers to deviation from perfect symmetry in bilateral traits that are symmetrical at the population level. FA negatively predicts (i.e. body symmetry positively predicts):  health, fecundity, the quality of fitness-related traits, social dominance, and mating success across many species, including humans, though there is substantial variability in the strengths of associations across studies, and the reasons for this remain poorly understood.  Another measure of developmental stability is through assessment of “minor physical anomalies” (or MPAs), various features of the face, head, hands, etc. that reflct slowed prenatal growth.

An example of this research approach is shown in the figure below.  On the X-axis is relative hand skill, with modal, moderate right-handedness as the low point in the center. On the Y-axis is a composite measure of FA and MPAs. Each dot represents a group of more tha 20 individuals.  As one deviates from normal handedness, markers of developmental instability increase.  We argue that this relationship suggests that  (1) it is the tendency to deviate from normality that is heritable, rather than any directional tendency, (2) there is a polygenic basis to individual variation in handedness, and (3) helps explain why measures of atypical lateralization, including handedness, are so often seen in neurodevelopmental disorders.

Another example of this line of work is described in the abstract below (from ref. 1).

Just as body symmetry reveals developmental stability at the morphological level, general intelligence may reveal developmental stability at the level of brain development and cognitive functioning.  These two forms of developmental stability may overlap by tapping into a “general fitness factor”.  If so, then intellectual tests with higher g-loadings should show higher correlations with a composite measure of body symmetry.  We tested this prediction in 78 young males, by measuring their left-right symmetry at 10 body points, and administering five cognitive tests with diverse g-loadings.  As predicted, we found a significant (z = 3.64, p < .003) relationship between each test’s rank order g-loading and its body-symmetry association.  We also found a substantial correlation (r = .39, p < .01) between body symmetry and our most highly g-loaded test (Ravens Advanced Progressive Matrices).  General intelligence is apparently a valid indicator of general developmental stability and heritable fitness, which may partly explain its social and sexual attractiveness.

2. Magnetic resonance spectroscopy (MRS) investigations of the neurochemical correlates of brain injury, intelligence, and mood. See publications 5, 7, 8. 11, 12, 13, 15, 17, 18.

Magnetic Resonance Spectroscopy (MRS), investigates in vivo brain chemistry using conventional MR scanners; proton MRS (¹H MRS) in particular has become widely used.

In ¹H MRS the most commonly measured neurometabolites reflect peaks arising from N-acetylaspartate and other N-acetyl groups (NAA), myo-inositol (mI), creatine-phosphocreatine (Cre) and choline (Cho) containing compounds. Other peaks arise from lactate, glutamine, glutamate, GABA, macromolecules, and lipids. NAA is the strongest peak in the adult proton MR spectrum and it is localized almost entirely to neuronal bodies and axons. Reduced NAA levels have been noted in many conditions, including normal aging and Alzheimer’s disease, suggesting neuronal injury or death. The Cre peak represents a measure of intracellular creatine and phosphocreatine, providing a measure of cellular energy currency. The Cho peak reflects all MRS visible choline moieties not bound to cell membranes, and these are thought to be involved in membrane synthesis and production of acetylcholine. Elevated Cho levels may indicate inflammation or demyelination. ¹H MRS studies vary in at least two important ways. Some studies, especially more recent ones, provide estimates of the absolute concentrations of neurometabolites, while others represent concentrations as ratios, most often with Cre as the denominator.  Studies also vary in the size, locus, and number of brain voxels assessed.

In diverse studies greater NAA concentrations have predicted better cognitive performance. For example, we have shown that NAA is strongly correlated with neurocognitive function in patient populations, such as traumatic brain injury and neuropsychiatric lupus erythematosus. Moreover, findings in normal control population also reveal substantial correlations between NAA and neurocognitive function (including IQ) and between Cho and mood.

Below is a figure from ongoing research. The brain of a child with traumatic brain injury is displayed, with color-coded intensity maps for concentrations of the rations of Cho/Cre and NAA/Cre. This young man suffered a left hemisphere injury. Note the asymmetry of concentrations shown in panels B and C. The injured hemisphere is characterized by higher Cho/Cre and lower NAA/Cre.

3. Biological bases of neurodevelopmental disorders: schizophrenia, dyslexia, attention deficit/hyperactivity disorder. See publications 2, 3, 9, 16, 19, 22, 24.

Below are a couple figures from our recent studies of ADHD. We observed smaller superior prefrontal volumes in ADHD children, but no difference in inferior frontal volumes. We also found that girls with ADHD, but not boys with ADHD had reduced right prefrontal NAA.

List of Recent Publications

• Yeo, R.A., Gangestad, S.W., & Thoma, R.J. (2007). Developmental instability and individual variation in brain development: Implicatios for the etiology of neurodevelopmental disorders. Current Directions in Psychological Science, 16, 245-249.
• Edgar, C., Yeo, R. A., Canive, J., Miller, G. Reduced auditory M100. (2006). Asymmetry in schizophrenia and dyslexia: Applying a developmental instability approach to assess atypical brain asymmetry. Neuropsychologia, 44, 289-299.
• Yeo, R. A., Brooks, W. M., Jung, R. E. (2006). NAA and Higher Cognitive Function in Humans. Advanced Experimental Medicine and Biology, 576: 215-26, 2006.
• Hanlon, F. M., Weisend, M., Hamilton, D. A., Jones, A. P., Thoma, R. J., Huang, M., Martin, K., Yeo, R. Ac, Miller, G.A., & Cañive, J. M. (2006). Impairment on the Hippocampal-Dependent Virtual Morris Water Task in Schizophrenia. Schizophrenia Research, 87, 67-80.
• Gangestad, S. W., & Yeo, R. A. (2006). Mutations, developmental instability, and the Red Queen. Brain and Behavioral Sciences, 29, 412-413.
• Thoma, R. J., Yeo, R. A., Gangestad, S. W., Halgren, E., Davis, J., Paulson, K. M., & Lewine, J. D. (2006). Developmental instability and the neural dynamics of the speed-intelligence relationship. NeuroImage, 32(3), 1456-1464.
• Yeo, R. A., Phillips., J. P., Jung, R. E., Brown,. A. J., Campbell, R. C., & Brooks, W. M. (2006). Magnetic resonance spectroscopy detects brain injury and predicts cognitive functioning in children with brain injuries. Journal of Neurotrauma, 23 (10), 427-1435.
• Thoma, R. J., Yeo, R. A., Gangestad, S. W., Halgren, E., Sanchez, NM, & Lewine, J. D. (2005). Cortical Volume and Developmental Instability are Independent Predictors of General Intellectual Ability. Intelligence, 33, 27-38.
• Rowland, L. M., Bustillo, J. R., Mullins, P. G., Jung, R. E., Lenroot, R., Landgraf, E., Barrow, R., Yeo, R. A., Lauriello, J., Brooks, W. M. (2005). Effects of ketamine on anterior cingulated glutamate metabolism in healthy humans: A 4-T proton MRS study. American Journal of Psychiatry, 162, 394-396.
• Rowland, L. M. Astur, R. S., Jung, R. E. Bustillo, J. B., Lauriello, J., & Yeo, R. A. (2005). Selective Cognitive Impairments Associated with NMDA Receptor Blockade in Humans. Neuropsychopharmacology, 30, 633-639.
• Driscoll I, Hamilton DA, Yeo RA, Brooks WM, and Sutherland RJ (2005). Virtual Navigation in Humans: The Impact of Age, Sex, and Hormones on Place Learning. Hormones and Behavior, 47, 326-335.
• Haier, R. J., Jung, R. E., Yeo, R. A., Head, K., Alkire, M. (2005) The neuroanatomy of general intelligence: Sex matters. NeuroImage, 25, 320-327.
• Jung, R. E. Haier, R. J., Yeo, R. A., Rowland, M., Petropoulos, H., Levine, A. S., Sibbitt, W. S., & Brooks, W. M. (2005). Sex differences in N-acetylaspartate correlates of general intelligence: A 1H-MRS study of normal human brain. NeuroImage, 26, 965-972.
• Hanlon, F. M., Weisend, M. P., Yeo, R. A. , Huang, M., Lee, R. R., Thoma, R. J.,Moses, S. N., Paulson, K. M., Miller, G. A., & Cañive, J. (2005). A Specific Test of Hippocampal Deficit in Schizophrenia. Behavioral Neuroscience, 119(4), 863-875.
• Prokosch, M. D., Yeo, R. A., & Miller, G. F. (2005). Intelligence tests with higher g-loadings show higher correlations with body symmetry: Evidence for a general fitness factor mediated by developmental stability. Intelligence, 33, 203-213
• Yeo, R. A., Hill, D. E., Campbell, R. A., Brooks, W. M., Vigil, J., Hart, B., & Zamora, L. (2003). A proton magnetic resonance spectroscopy investigation of the right frontal lobe in children with attention deficit hyperactivity disorder. Journal of the American Academy of Child and Adolescent Psychiatry, 42, 303-310.
• Hill, D. E., Yeo, R. A., Campbell, R. A., Hart, B., Vigil, J., & Brooks, W. M. (2003). MRI Correlates of Attention Deficit/Hyperactivity Disorder (ADHD) in Children. Neuropsychology, 17, 496-506.
• Yeo, R. A., Thoma, R., & Gangestad, S. W. (2002). Human handedness: A biological perspective. In I. Rapin & S. Segalowitz (Eds.), Handbook of Neuropsychology, Amsterdam: Elsevier Science, pp. 329-364.
• Jung, R. E., Yeo, R. A., Love, T. M., Petropoulos, H., Sibbitt, W. M., & Brooks, W. M. (2002). Biochemical markers of mood: A proton MR spectroscopy study of normal human brain. Biological Psychiatry, 51, 224-229.
• Thoma, R., Yeo, R. A., Gangestad, S. W., Lewine, J. D., & Davis, J. (2002). Fluctuating asymmetry and the human brain. Laterality, 7, 45-58.
• Jung, R. E., Yeo, R. A., Love, T. M., Petropoulos, H., Sibbitt, W. M., & Brooks, W. M. (2002). Biochemical markers of mood: A proton MR spectroscopy study of normal human brain. Biological Psychiatry, 51, 224-229.
• Jung, R. E., Yeo, R. A. , Sibbitt, W. L. , Ford, C. C., Hart, B. L., & Brooks, W. M. (2001). Gerstmann Syndrome in Systemic Lupus Erythematosus: Neuropsychological, Neuroimaging and Spectroscopic Findings. Neurocase, 7, 515-521.
• Yeo, R. A., Hill, D. E., Campbell, R., Vigil, J., & Brooks, W. M. (2000). Developmental instability and working memory ability in children: A magnetic resonance spectroscopy investigation. Developmental Neuropsychology, 17, 143-159.
• Jung, R., Yeo, R. A., & Gangestad, S. W. (2000). Developmental instability predicts individual variation in verbal memory skill following caffeine ingestion. Behavioral Neurology, Neuropsychology, and Neuropsychiatry, 13, 195-198.
• Brooks, W. M., Stidely, C. A., Petropoulos, H., Jung, R. E., Weers, D, C., Friedman, S. D., Barlow, M. A., Sibbitt, W. L., & Yeo, R. A. (2000). Metabolic and cognitive response to trumatic brain injury: A proton magnetic resonance study in humans. Journal of Neurotrauma, 17, 629-640.
• Jung, R. E., Yeo, R. A., Chuilli, S. J., Sibbitt, W. L., & Brooks, W. M. (2000). Myths of neuropsychology: Intelligence, neurometabolism, and cognitive ability. The Clinical Neuropsychologist, 14, 535-545.
• Jung, R. E., Brooks, W. M., Yeo, R. A., Weers. D., Hart, B., & Sibbitt, W.L. (1999). Biochemical markers of intelligence: A proton MR spectroscopy study of the normal human brain. Proceedings of the Royal Society B, 266, 1375-1379.
• Yeo, R. A. (1999). Asymmetry, developmental stability, and evolution. Laterality, 4, 389-394.
• Jung, R. E., Yeo, R. A., Weers. D., Hart, B., & Sibbitt, W. L., Brooks, W. M. (1999). Biochemical markers of neuropsychological performance: A proton MR spectroscopy study of the normal human brain. Neuroreport, 10, 1-5.
• Yeo, R. A., Gangestad, S. W., Edgar, C., & Thoma, R. (1999). The evolutionary-genetic underpinnings of schizophrenia: The Developmental Instability model. Schizophrenia Research, 39, 197-206.
• Friedman, S. D., Brooks, W. M., Jung, R. E., Hart, B. L., & Yeo, R. A. (1998). Proton MR spectroscopic findings correspond to diffuse neuropsychological function in truamtic brain injury. The American Journal of Neuroradiology, 19, 1879-1885.
• Friedman, S. F., Brooks, W. M., Jung, R. E., Chuilli, S. J., Sloan, J. H., Montoya, B. T., Hart, B. L., & Yeo, R. A. (1999). Quantitative 1H-MRS predicts outcome following traumatic brain injury. Neurology, 52, 1384-1396.
• Brooks, W.M., Hodde-Vargas, J., Vargas, L., Yeo, R.A., Ford, C.C., & Hendren, R. (1998). Frontal lobe of adolescents with schizotypal signs: A 1H- MRS study. Biological Psychiatry, 43, 263-269.
• Gangestad, S. W., & Yeo, R. A. (1997). Behavioral genetic variation, adaptation and maladaptation: An evolutionary perspective. Trends in Cognitive Science, 1, 103-108.
• Yeo, R. A., Gangestad, S. W., Thoma, R. A., Shaw, P., & Repa, K. (1997). Developmental instability and cerebral lateralization. Neuropsychology, 11, 552-561.
• Yeo, R. A., Hodde-Vargas, J., Hendren, R. L., Vargas, L. A., Brooks, W. M., Ford, C. C., Gangestad, S. W., Hart, B. F. (1997). Brain abnormalities in schizophrenia-spectrum children: Implications for a neurodevelopmental perspective. Psychiatry Research, 76, 1-13.
• Gangestad, S. W., Yeo, R. A., Shaw, P. K., Thoma, R., Daniel, W. F., & Korthank, A. J. (1996). Human leukocyte antigens and hand preference: A Preliminary analysis. Neuropsychology, 10, 423-428.
• Hendren, R. L., Hodde-Vargas, J., Yeo, R. A., Vargas, L. A., Brooks, W. M., & Ford, C. (1995). Neuropsychophysiologic study of children at risk for schizophrenia: A
  preliminary report. Journal of Child and Adolescent Psychiatry, 10, 1284-1291.
• Yeo, R. A., Gangestad, S. W., & Daniel, W. F. (1993). Hand preference and developmental instability. Psychobiology, 21, 161-168.
• Yeo, R. A., Gangestad, S. W. (1993). Developmental origins of variation in human hand preference. Genetica, 89, 281-296.

Current Graduate Lab Members

	Student/Research Interests
	Lauren Parks
	Matthew Euler Neuroimaging, clinical neuropsychology, schizophrenia
	Per Lysne Functional neuroimaging of neural correlates of psychological disorders, particularly those related to anxiety, depression, and disorders invloving social cognition.
	Maco Stewart