Neural Prosthetics Laboratory
New Jersey Institute of Technology
Department of Biomedical Engineering
Spinal Cord Computer Interface (SCCI)
In search of a solution to the long standing problems encountered in traditional brain computer interfaces (BCI), the descending tracts of the spinal cord present an alternative site for taping into the volitional motor signals. Due to the convergence of the cortical outputs into a final common pathway in the descending tracts of the spinal cord, neural interfaces with the spinal cord can potentially acquire signals richer with volitional information in a smaller anatomical region. The main objective of this study is to evaluate the feasibility of extracting motor control signals from the corticospinal tract (CST) of the rat spinal cord. Polyimide substrate, multi-electrode arrays (MEA) were implanted in the CST of rats trained for a lever pressing task. This novel use of flexible substrate MEAs allowed recording of CST activity in behaving animals for up to three weeks with the current implantation technique. Time-frequency and principal component analyses (PCA) were applied to the neural signals to reconstruct isometric forelimb forces. Computed regression coefficients were then used to predict isometric forces in additional trials.  

Over years this project has been funded by NIH (RO1), The Whitaker Foundation, and The Christopher Reeve Paralysis Foundation.
Keywords: brain-computer interfaces, descending tracts, multi-electrode arrays (MEA)
Floating Light Activated Micro-Electrical Stimulators - FLAMES
Microelectrode implants often fail either due to the chronic tissue response caused by the tethering forces of the wires or their breakage. Our laboratory is developing a floating light activated micro electric stimulator (FLAMES) that is a wireless implantable device for neural stimulation where near-infrared (NIR) light is used for energy transfer to the microstimulator through neural tissue. The FLAMES was acutely tested in the rat spinal cord for feasibility of the main concept. Temperature elevation profile was also measured experimentally using a micro termoprobe inside the rat brain induced by an NIR laser beam to determine the maximum allowable optical power. Our latest chronic implants have shown minimal tissue response to untethered devices implanted into the brain and the spinal cord in rats. These studies so far produced supportive evidence for a wireless microstimulator that can be activated optically by NIR light through neural tissue. Devices at submillimeter scale were designed for wireless activation of neurons in the central nervous system. Prototypes were fabricated in collaboration with Dr. Unlu's group at Boston University. 
 
Keywords: optical neural stimulation, near infrared light (NIR), intraspinal micro stimulation

Electrophysiological Monitoring of Injury Progression in the Rat Cerebellar Cortex
The changes of excitability in affected neural networks can be used as a marker to study the temporal course of traumatic brain injury (TBI). The cerebellum is an ideal platform to study brain injury mechanisms at the network level using the electrophysiological methods.Within its crystalline morphology, the cerebellar cortex contains highly organized topographical subunits that are defined by two main inputs, the climbing (CFs) and mossy fibers (MFs). Here we demonstrate the use of cerebellar evoked potentials (EPs) mediated through these afferent systems for monitoring the injury progression in a rat model of fluid percussion injury (FPI). A mechanical tap on the dorsal hand was used as a stimulus, and EPs were recorded from the paramedian lobule (PML) of the posterior cerebellum via multi-electrode arrays (MEAs). 
 
Keywords: traumatic brain injury, evoked potentials, somatotopic organization

High Frequency Synchrony in the Cerebellar Cortex During Goal Directed Movements
The cerebellum is one of the most densely populated and highly organized neural structures in the CNS. While the specific function of the cerebellum is still a matter of debate, research has demonstrated that it plays a key role in both motor learning and coordination, as well as displaying cognitive function. Because of its crystaline organization and relatively few types of neural connections, the cerebellar cortex represents an amenable site for neural recording. Previous reports of surface recordings from the cerebellar cortex have been limited to local field potentials recorded with single ball electrodes, eliminating the ability to study spatio-temporal features hence giving a very limited picture of cerebellar activity. We are currently studying high frequency (150-350Hz) synchrony in the cerebellar cortex using subdurally placed flexible multi-electrode arrays in rats during lever press. 
 
Keywords: high frequency oscillations, Purkinje cell simple spike activity, coherence, local field potentials

Sleep Apnea
Obstructive sleep apnea (OSA) is occlusion of upper airways (UAWs) during sleep. In general, it is believed that the problem emerges primarily due to anatomical factors that pre-dispose the UAWs for obstruction. The elevated neural outflow to the UAW muscles dilates the airways and compensate for the disadvantaged anatomical factors in wakefulness. However, these neural compensatory mechanisms are lost at the alpha-to-theta transition in NREM sleep, thereby leading to occlusions of the anatomically compromised UAWs. Consequently, the treatment attempts for OSA have focused on both restoring the lost UAW dilating muscle activity via electrical stimulation, and also mechanical devices that can help the UAWs become less collapsible under negative pressure. Hypoglossal nerve (HG) stimulation and that of its medial branch was proposed almost two decades ago as a method to remove UAW obstructions. Closed-loop stimulation of the HG nerve using its own activity as a feedback signal was demonstrated in a dog model of OSA by our group (publication). We have also shown selective activation of the HG nerve with a multi-contact cuff electrode for generation of multiple modes of UAW dilation and thereby increasing the success rate by accounting for anatomical differences between subjects (publication).