Master of Arts, San Diego State University (2010)
Doctor of Philosophy, University of Missouri Columbia (2015)
Bachelor of Science, Clemson University (2006)
Antonio Hardan, Postdoctoral Faculty Sponsor
Cerebro-Cerebellar Functional Connectivity is Associated with Cerebellar Excitation-Inhibition Balance in Autism Spectrum Disorder.
Journal of autism and developmental disorders
Atypical functional connectivity (FC) and an imbalance of excitation-to-inhibition (E/I) have been previously reported in cerebro-cerebellar circuits in autism spectrum disorder (ASD). The current investigation used resting state fMRI and proton magnetic resonance spectroscopy (1H-MRS) to examine the relationships between E/I (glutamate+glutamine/GABA) and FC of the dorsolateral prefrontal cortex and posterolateral cerebellar hemisphere from 14 adolescents/adults with ASD and 12 age/sex/IQ-matched controls. In this pilot sample, cerebro-cerebellar FC was positively associated with cerebellar E/I and listening comprehension abilities in individuals with ASD but not controls. Additionally, a subgroup of individuals with ASD and low FC (n=5) exhibited reduced E/I and impaired listening comprehension. Thus, altered functional coherence of cerebro-cerebellar circuits in ASD may be related with a cerebellar E/I imbalance.
View details for DOI 10.1007/s10803-018-3613-y
View details for PubMedID 29796960
Beta-adrenergic antagonism modulates functional connectivity in the default mode network of individuals with and without autism spectrum disorder.
Brain imaging and behavior
The beta-adrenergic antagonist propranolol benefits some social and communication domains affected in autism spectrum disorder (ASD), and these benefits appear to be associated with increased functional connectivity (FC) in the brain during task performance. FC is implicated in ASD, with the majority of studies suggesting long distance hypo-connectivity combined with regionally specific local hyper-connectivity. The objective in the current investigation was to examine the effect of propranolol on FC at rest and determine whether ASD-specific effects exist. Participants with and without ASD attended three sessions in which propranolol, nadolol (a beta-adrenergic antagonist that does not cross the blood-brain barrier), or placebo were administered. Resting-state fMRI data were acquired, and graph theory techniques were utilized to assess additional aspects of FC. Compared to placebo, propranolol administration was associated with decreased FC in the dorsal medial prefrontal cortex subnetwork of the default mode network and increased FC in the medial temporal lobe subnetwork, regardless of diagnosis. These effects were not seen with nadolol suggesting that the alterations in FC following propranolol administration were not exclusively due to peripheral cardiovascular effects. Thus, beta-adrenergic antagonism can up- or down- regulate FC, depending on the network, and alter coordinated functional activation in the brain. These changes in information processing, as demonstrated by FC, may mediate some of the clinical and behavioral effects of beta-adrenergic antagonism previously reported in patients with ASD.
View details for PubMedID 27714553
Morphological differences in the lateral geniculate nucleus associated with dyslexia
2015; 7: 830-836
Developmental dyslexia is a common learning disability characterized by normal intelligence but difficulty in skills associated with reading, writing and spelling. One of the most prominent, albeit controversial, theories of dyslexia is the magnocellular theory, which suggests that malfunction of the magnocellular system in the brain is responsible for the behavioral deficits. We sought to test the basis of this theory by directly measuring the lateral geniculate nucleus (LGN), the only location in the brain where the magnocellular and parvocellular streams are spatially disjoint. Using high-resolution proton-density weighted MRI scans, we precisely measured the anatomical boundaries of the LGN in 13 subjects with dyslexia (five female) and 13 controls (three female), all 22-26 years old. The left LGN was significantly smaller in volume in subjects with dyslexia and also differed in shape; no differences were observed in the right LGN. The functional significance of this asymmetry is unknown, but these results are consistent with the magnocellular theory and support theories of dyslexia that involve differences in the early visual system.
View details for DOI 10.1016/j.nicl.2015.03.011
View details for Web of Science ID 000373172600091
View details for PubMedID 26082892
- Alexithymia and Impairment of Decoding Positive Affect: An fMRI Study JOURNAL OF COMMUNICATION 2013; 63 (4): 786-806