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Joel Hahn

Assistant Professor (Research) of Biological Sciences

Contact Information
E-mail: joelhahn@usc.edu
Phone: (213) 821-1837
Office: HNB 416B

 

Description of Research

Summary Statement of Research Interests

The neuron doctrine, which holds that the nervous system is composed of individual cells, owes its existence in large part to the work of Santiago Ramón y Cajal (1852 – 1934). This fundamental understanding gave rise to fundamental questions: How do individual neurons connect and communicate? What diversity of neurons exists within and across different species, and what are the functional consequences of the structural differences? How do distinct patterns of neuronal projections and connections develop? And, ultimately, how does the neuronal architecture produce a functional nervous system with the ability to control the behaviors and regulatory processes that are integral and essential to life? The research that I am engaged in addresses some of these questions. My field of study is the basic structure of the central nervous system with respect to the diversity and connections of its neurons, and my current focus is the lateral hypothalamic area (LHA) – a major multi-region part of the hypothalamus located within the cerebrospinal trunk. The hypothalamus is a heterogeneous and evolutionarily ancient part of the mammalian brain that plays essential roles in the control of fundamental motivated activities such as eating and drinking, defensive, social and reproductive behaviors, and sleep/wake states. At a basic level these activities are instinctual – they can occur in the absence of cognitive (cerebral cortical) control. However, understanding how the cognitive system relates to hypothalamic motor, sensory and behavioral state systems is a major goal, because such an understanding could pave the way to more effective treatment for a host of major neuropsychiatric diseases including eating disorders, post-traumatic stress disorder, depression, schizophrenia and dementia. On the basis of work done so far, it appears the LHA may play a key role in relating cognitive to sub-cognitive (hypothalamic) systems, by effectively integrating cerebral cortex and cerebral nuclei with medial hypothalamic nuclei that constitute a behavioral control column. In fact the LHA (in particular its medial tier) shows an astonishing level of integrative connectivity, unsurpassed by any other brain region studied to date. Exactly how the connectivity of LHA regions enables integration of cognitive and sub-cognitive control in functional terms remains to be understood, but understanding the basic connectivity is an essential starting point: At one time we had no basic plan for the musculoskeletal system, or for the cardiovascular system, yet such knowledge has greatly enhanced our ability to prevent and treat disease of those systems – a sound knowledge of the basic plan of the central nervous system is likely to have similarly utility.
 

Research Keywords

Neuronal Basis of Behavior, Motivation and Emotion; Hypothalamus; Lateral Hypothalamic Area; Neuroendocrine Control Systems; Neuronal Pathway Tracing.
 

Research Specialties

Brain Architecture of Hypothalamic Control Systems; Neuroanatomy; High-Resolution Neuronal Pathway Tracing; Reproductive Neuroendocrinolgy and Neuroanatomy.
 

Affiliations with Research Centers, Labs, and Other Institutions

Laboratory of Larry W. Swanson, University of Southern California
 

Publications

Journal Article

Biag, J., Huang, Y., Gou, L., Hintiryan, H., Askarinam, A., Hahn, J. D., Toga, A. W., Dong, H. (2011). Cyto- and chemoarchitecture of the hypothalamic paraventricular nucleus in the C57BL/6J male mouse: a study of immunostaining and multiple fluorescent tract tracing. Journal of Comparative Neurology. Vol. 520 (1), pp. 6-33. PubMed Web Address Faculty of 1000 evaluated article
Hahn, J. D., Swanson, L. W. (2010). Distinct patterns of neuronal inputs and outputs of the juxtaparaventricular and suprafornical regions of the lateral hypothalamic area in the male rat. Brain Research Reviews. Vol. 64 (1), pp. 14-103. PubMed Web Address Full Text (PDF)
Hahn, J. D. (2010). Comparison of melanin-concentrating hormone and hypocretin/orexin peptide expression patterns in a current parceling scheme of the lateral hypothalamic zone. Neuroscience Letters. Vol. 468 (1), pp. 12-17. PubMed Web Address Full Text (PDF)
 
 
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