• B.S. (Biology), B.S.(Electrical Engineering) and  M.S., Massachusetts Institute of Technology (M.I.T.)
• M.D. and Ph.D. (Physiology), University of Pennsylvania
• Residency (Neurology), Johns Hopkins Hospital
• Assistant Professor (Neurology), University of Pennsylvania
• Associate Professor (Neurology), University of Maryland

Our lab has two areas of interest: dendritic function and developing better tools to study brain function.

Dendritic function:
The dendrite arbor is not a passive antenna but is a complex structure that actively and simultaneously processes thousands of synaptic inputs as they are received. Our focus is directed on the properties and functional roles of the long thin terminal dendrites, a morphologically distinct and understudied region of the dendritic arbor. We have recently found that individual terminal dendrites can function as quasi-independent electrical compartments with characteristics that are distinct from those of the main apical trunk (Wei et al.). Under appropriate input conditions terminal dendrites have the essential characteristics of binary logic devices. Because large numbers of terminal dendrites are connected in parallel, they greatly expand the computational power of a single neuron.

Changes in the intrinsic excitability of terminal dendrites may contribute to the pathogenesis of neurological disorders such as post-traumatic epilepsy, chronic pain, and dyskinesias. We have found that partial deafferentation (i.e. following traumatic brain injury) can lead to dramatic prolongation of the fundamental suprathreshold terminal dendritic response.

Technical innovations
We find developing the techniques and instruments that enable biologists to overcome critical technical barriers intellectually challenging and rewarding. As an example, we cite the method recently developed for fluorescence-guided focal photolysis in brain slices (Tang, 2001, in press) that has allowed us to resolve the behavior of individual terminal apical dendrites (Wei et al.).

A second example is a novel wide-field microscopy method for imaging 3-D structures that simultaneously optimizes resolution and depth of field, and captures z-axis information without having to take a stack of images at different focal planes. These abilities are illustrated in the image below of the complex 3-D orientation of  the basal dendrites of a CA1 pyramidal neuron. Note the ability to image the fine dendritic spines as well as the dendritic processing far removed from the plane of focus. Structures close to the plane of focus are displayed in white while blue and green provide z-axis information. This image was acquired without changing the focus of the microscope and in a tiny fraction of the time that would have take to acquire the stacks of images required for confocal, two-photon, or deconvolution microscopy methods.

Other ongoing instrumentation projects include: a fiber optic method for guiding stereotactic probes during neurosurgical procedures (i.e. DBS for treating Parkinson's disease, depth electrode placement for epilepsy evaluation, brain biopsy, etc), and biosensors utilizing nanocrystalline diamond technology to measure in real time the concentration of neurotransmitters and second messengers.

• Focal photolysis of caged neurotransmitter using argon ion UV laser.
• Calcium imaging with fast CCDs.
• Patch clamp recording.
• Expression of GFP and other gene products in slice cultures.
• Organotypic slice cultures of the hippocampus, substantia nigra, and striatum.