Dr. Masri’s laboratory focuses on understanding the pathogenesis of intractable pain conditions and the approaches to ameliorate these devastating conditions. Specifically, we are interested in studying the pathophysiology of spinal cord injury pain.
Using behavioral, imaging (Fig. 1) and electrophysiological methods (Fig. 2), we have recently demonstrated that central pain following spinal cord injury can be caused by abnormally reduced inhibition from the zona incerta to the posterior thalamus and that electrical stimulation of zona incerta reduces hyperalgesia in an animal model of central pain. These interesting findings steered us toward examining potentially effective treatments for central pain syndrome, namely mechanisms that restore inhibition in zona incerta. One such therapeutic approach is: motor cortex stimulation. This approach was discovered serendipitously, and its utility remains in dispute. This is due to the fact that the mechanisms by which motor cortex stimulation ameliorates central pain are completely unknown, and because of the absence of an animal model in which to study these mechanisms. We take advantage of our central pain model and our exciting findings to elucidate the mechanisms by which MCS ameliorates chronic neuropathic pain. We hypothesize that motor cortex stimulation reduces hyperalgesia by enhancing inhibitory inputs from zona incerta to the posterior thalamus.
Figure 1: fMRI of a rat brain. Activation maps and BOLD signals following electrical stimulation of the hindpaw.
Figure 2: Electrophysiological responses of a single neuron in the posterior thalamus to the application of the muscarinic agonist carbachol.