Summary of Research Accomplishments
Larry W. Swanson, Ph.D.

Since graduate school Dr. Swanson has been interested in clarifying the organization

of brain systems that mediate the expression of motivated and emotional behaviors. His

experimental research has followed two main paths. First, his group has undertaken a

high resolution structural analysis of central evolution: anterograde and retorgrade axonal

pathway tracing combined with immuno- and hybridization histochemistry. This work

has generated a new global model of hypothamalmic organization, has clarified

the organization and neurotransmitter specificity of brainstem reflex inputs to the

hypothalamus, and is currently focussing on a new model of cerebral hemisphere

inputs to the hypothalamus that mediate the voluntary control of motivated behaviors

common to all animals (ingestive, reproductive, and defensive). On the order of

2000 new axonal connections between different brain structures have been

characterized experimentally since 1974. And second, beginning in the early 1980s Dr.

Swanson's group has characterized functionally relevant changes in gene expression patterns

restricted to neural networks that have identified. Most of this work involves adrenal and

gonadal steroid hormone effects on neuropeptide behavior, and in circuits controlling stress

responses generally. Two interrelated concepts have emerged-- the biochemical switching of

information flow through anatomically fixed networks, and the polytransmitter hypothesis (at

some stage of the life cycle, all neurons use glutamate or GABA, along with a mixture of other

neurotransmitters).

Because motivated behavior utilizes the entire nervous system, Dr. Swanson has also

carried out extensive scholarly research on the fundamental plan of the brain. Are there

simplifyiing principles to help understand the vast amounts of connectional and gene expression

pattern data now available for the mammalian brain? This research has also taken two paths.

First, Dr. Swanson has produced detailed atlases of developing and adult rat brain architecture,

accompanied by systematic, fully documented taxonomy of parts (both cell groups and fiber

tracts). They were the first complee computer graphics atlases of he brain, and have been

used to develop databases of spatial neuroanatomical information as well as prototype

three-dimensional, vector-based computer graphics models of the brain. And second,

Dr. Swanson has translated key historical documents related to brain structural
organization, in particular three Santiago Ramon Cajal's works, including
his two volume masterpiece, This Histology of the Nervous System. Based on
this scholarly and experimental research Dr. Swanson has recently proposed
a four-system network model for the basic plan of the nervous system
(Brain Architecture: Understanding the Basic Plan; Oxford University Press).