Bio

Clinical Focus


  • Neurology

Academic Appointments


Professional Education


  • Fellowship:Stanford University - Dept of Neurology (2012) CA
  • Residency:Stanford University - Dept of Neurology (2011) CA
  • Medical Education:University of California Irvine School of Medicine (2006) CA
  • Board Certification: Neurology, American Board of Psychiatry and Neurology (2011)
  • Residency:Kaiser Permanente Los Angeles Medical Center - Department of Radiation Oncology (2008) CA

Publications

Journal Articles


  • Here's looking at you, kid - Neural systems underlying face and gaze processing in fragile X syndrome ARCHIVES OF GENERAL PSYCHIATRY Garrett, A. S., Menon, V., MacKenzie, K., Reiss, A. L. 2004; 61 (3): 281-288

    Abstract

    Children with fragile X syndrome (fraX) are at risk for manifesting abnormalities in social function that overlap with features of autism and social anxiety disorder. In this study, we analyzed brain activation in response to face and gaze stimuli to better understand neural functioning associated with social perception in fraX.Eleven female subjects with fraX, aged 10 to 22 years, were compared with age-matched female control subjects. Photographs of forward-facing and angled faces, each having direct and averted gaze (4 types of stimuli), were presented in an event-related design during functional magnetic resonance imaging. Subjects were instructed to determine the direction of gaze for each photograph. Activation in brain regions known to respond to face and gaze stimuli, the fusiform gyrus (FG) and superior temporal sulcus (STS), were compared between groups to isolate neural abnormalities in the perception of directed social stimuli.The fraX subjects had decreased accuracy in determining the direction of gaze compared with controls. Region of interest analysis of the FG revealed a significant interaction between diagnostic group and face orientation. Specifically, control subjects had greater FG activation to forward than to angled faces, whereas fraX subjects had no difference in FG activation to forward and angled faces. Controls showed greater left STS activation to all stimuli compared with fraX subjects.Our results suggest that gaze aversion in fraX subjects is related to decreased specialization of the FG in the perception of face orientation. Decreased STS activation in fraX suggests aberrant processing of gaze. These data suggest that gaze aversion in fraX may be related to dysfunction of neural systems underlying both face and gaze processing.

    View details for Web of Science ID 000220064800009

    View details for PubMedID 14993116

  • Prefrontal cortex involvement in processing incorrect arithmetic equations: Evidence from event-related fMRI HUMAN BRAIN MAPPING Menon, V., MacKenzie, K., Rivera, S. M., Reiss, A. L. 2002; 16 (2): 119-130

    Abstract

    The main aim of this study was to investigate the differential processing of correct and incorrect equations to gain further insight into the neural processes involved in arithmetic reasoning. Electrophysiological studies in humans have demonstrated that processing incorrect arithmetic equations (e.g., 2 + 2 = 5) elicits a prominent event-related potential (ERP) compared to processing correct equations (e.g., 2 + 2 = 4). In the present study, we investigated the neural substrates of this process using event-related functional magnetic resonance imaging (fMRI). Subjects were presented with arithmetic equations and asked to indicate whether the solution displayed was correct or incorrect. We found greater activation to incorrect, compared to correct equations, in the left dorsolateral prefrontal cortex (DLPFC, BA 46) and the left ventrolateral prefrontal cortex (VLPFC, BA 47). Our results provide the first brain imaging evidence for differential processing of incorrect vs. correct equations. The prefrontal cortex activation observed in processing incorrect equations overlaps with brain areas known to be involved in working memory and interference processing. The DLPFC region differentially activated by incorrect equations was also involved in overall arithmetic processing, whereas the VLPFC was activated only during the differential processing of incorrect equations. Differential response to correct and incorrect arithmetic equations was not observed in parietal cortex regions such as the angular gyrus and intra-parietal sulcus, which are known to play a specific role in performing arithmetic computations. The pattern of brain response observed is consistent with the hypothesis that processing incorrect equations involves detection of an incorrect answer and resolution of the interference between the internally computed and externally presented incorrect answer. More specifically, greater activation during processing of incorrect equations appears to reflect additional operations involved in maintaining the results in working memory, while subjects attempt to resolve the conflict and select a response. These findings allow us to further delineate and dissociate the contributions of prefrontal and parietal cortices to arithmetic reasoning.

    View details for DOI 10.1002/hbm.10035

    View details for Web of Science ID 000175972400006

    View details for PubMedID 11954061

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