• 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

1) Coherence-Gated Doppler (CGD):

CGD is a hybrid of two optical technologies, conventional laser Doppler and optical coherence tomography (OCT). One can think of it is a “confocal” version of the laser Doppler. Critical advantage over parent technologies: Minute size of the optical probe (0.15 mm), probe is a single optical fiber with no moving parts, a simpler technology that is less expensive to build.

Data from rat femoral vessels:

The CGD probe (stabilized inside tubing) is moved across the visually identified vessels.

Artery audio signal – [click here]

Vein and Surrounding Area: audio signal – [click here] 

Coherence- gated Doppler during stereotactic procedure in the sheep brain

CGD is used to identify at risk vessels during simulated stereotactic procedure as the probe is advanced in an anesthetized sheep brain. This video shows ultrasound monitoring of the CGD probe as it is advanced towards a vein (blue spot lower right corner of green box) with the CGD audio signal played simultaneously. The tip of the 30G needle in which the CGD probe is located produces a strong ultrasound signal (moving bright white spot). The squeaky sound is the signal from the relative motion of the probe and the brain. At 3 millimeters from the vein the CGD probe begins to pick up the flow signature from the vein as a high amplitude white noise. To help the inexperienced listener recognize the blood flow signal of the vein a chime is provided in the audio to indicate the beginning of the detected signal. The probe is advanced until it constricts the flow and the ultrasound signal is lost; the CGD signal also attenuates. A second chime is provided as the flow signal attenuates. [Click here to view video]

CGD Manuscript for Grant Reviewers

The manuscript was accepted with revisions to Biomedical Optics Express.  

2) 3D display of blood vessels relevant to human DBS procedures:

In this 3D animation of a sagittal section of the human brain near the STN the vessels are displayed relative to the STN which is segmented in a beige color. [video - click here]

3) Anisotropic Scattering Imaging

An optical technology we have invented to enhance tissue contrast and extract fiber orientation in brain tissue. One can use this information for tractography of the fiber tracts. Preliminary results in mapping the structures near the STN are illustrated below [Click here for video]

The STN is green. The red nucleus is maroon. Pigmented nigra neurons are in orange. ChAT positive neurons in the PPN are in blue. The posterior commissure is displayed as the dark circular structure dorsal to the red nucleus. The blue lines represent a previously unrecognized unmyelinated fiber pathway connecting the PPN and the STN. Parts of other fiber pathways are illustrated in different colors.

4) Dendritic function:

Our focus is directed towards the properties and functional roles of the long thin terminal dendrites, a morphologically distinct and understudied region of the dendritic arbor. We have 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. More specifically, they can support short term memory function with a phenomenon called “dendritic hold and read” or DHR (Santos et al., 2012). The properties of DHR are ideally suited for feedforward memory. 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 and can lower seizure threshold.

• 3D digital holographic photolysis
• Patch clamp recording from acute brain slices
• Catheter based optical coherence tomography
• Coherence gated Doppler
• Anisotropic scattering imaging
• Computer vision assist devices for the blind