Hosted by Steve Abbott, Nigel Pederson, PhD, is an Assistant Professor of Neurology, Emory University, Atlanta, GA.

In the Pedersen Epilepsy and Systems Neuroscience Laboratory, we study the systems neuroscience of wakefulness and epilepsy in humans and animal models. There are two main streams of research. The first centers on the neurobiological basis of consciousness and the underlying wake-sustaining mechanisms upon which it depends (1-6); another group of projects examines brain networks in epileptic seizures, including the modulatory effects of sleep-wake circuits and networks through which seizures propagate.

We study large-scale brain circuits underlying wakefulness and sleep. Using a variety of genetically encoded technologies in mice, we have recently described a new component of the brain circuit that maintains wakefulness, the supramammillary hypothalamus (3). This region exerts control over both the hippocampal network (important for certain kinds of memory formation) as well as the wake network and cerebral cortex. A unique and interesting feature of this neuronal group is the presence of a subpopulation of neurons that we described to release both inhibitory GABA and excitatory glutamate on to a key population of hippocampal neurons - dentate granule cells (3). These neurons are sparsely firing neurons that control which activity enters the classical hippocampal tri-synaptic circuit. The supramammillary region, comprising three major neuronal populations (3), is thus able to control wakefulness and influence information flow into the hippocampus. Studies continue to understand the role of these circuits on attention, wakefulness and the role of this region in setting hippocampal excitability in epilepsy. A specific ongoing experiment involves disruption of GABA release by supramammillary neurons and examining spontaneous seizures and seizure threshold, using Cre-lox techniques. We are also examining the anatomical connectivity and spontaneous activity of identified supramammillary neuronal subpopulations using unit recording and, later, fiber photometry.