Emad Eskandar, M.D.
Associate Professor of Surgery
WACC 331, 15 Parkman Street
Boston, MA 2114
The primary focus of our lab is on studying the role of the primate basal ganglia in learning and motivation. The basal ganglia are a group of large nuclei located in the center of the brain. For decades, the role of the basal ganglia was defined, or inferred, from disorders caused by disruption of the basal ganglia such as Parkinson and Huntington disease. Fortunately, recent advances now allow for direct study of the basal ganglia in primates and humans, and exciting new data suggest that the basal ganglia play a critical and previously under-appreciated role in learning and motivation.
The nuclei comprising the striatum (putamen, caudate, and nucleus-accumbens) form the input stage of the basal ganglia and are extremely interesting because of their connections and their strong dopaminergic input. Dopamine is posited to play an important role by providing a feedback signal during learning that serves to enhance biologically profitable associations. Our hypothesis is that there are two streams of information processing in the striatum, dorsal and ventral, that perform complementary but different roles. Specifically, we hypothesize that the dorsal stream, which includes the caudate is involved in associative learning, whereas the ventral stream, which includes the nucleus-accumbens is involved in providing motivation for the performance of learned behaviors.
We utilize multiple approaches in order to understand both the physiology and neuropharmacology of these circuits. Microelectrode single-neuron recordings are used to evaluate the activity of neurons in both primates and humans performing associative learning and motivation tasks. The primate data is obtained in the laboratory, while the human data is obtained intra-operatively during recordings that are performed to localize specific nuclei. This is a unique approach in that ideas from the laboratory can quickly be tested in the clinical arena and vice-versa. In addition to standard microelectrode techniques, we also employ the electrochemical technique of fixed-potential amperometry using carbon-fiber electrodes to record dopamine fluctuations during learning. Finally, in order to go beyond correlation and begin to understand causation, we also employ micro-stimulation. For example, in one set of experiments we discovered that intermittent electrical stimulation in the primate caudate enhances learning beyond baseline rates. We are now exploring the use of such intermittent stimulation as a means to promote recovery in patients who have suffered from stroke or traumatic brain injury.
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Last Update: 10/30/2013