The mammalian brain has two types of synapses: chemical and electrical. The vast majority of research on neuronal communication has focused on chemical synaptic transmission, particularly in mammalian systems. As a result, virtually all neuro- and psychopharmacology is targeted towards modulation of chemical neurotransmission. In contrast, the importance of mammalian electrical synapses, or gap junctions, has been appreciated only recently. Over the last decade, neuronal gap junctions have been identified throughout the mammalian brain, and have been shown to primarily connect inhibitory neurons with similar biochemical profiles. The plasticity of gap junctions remains sparsely studied, however.
Our research goals are two-fold: to elucidate mechanisms that underlie gap junctional plasticity, and to explore how modification of synaptic strength changes the functional role of gap junctions in the thalamo-cortical network.
To accomplish these goals, we use paired whole-cell recordings in rodent brain slices and imaging of neuronal network activity with activity-sensitive dyes. By studying these phenomena in intact local networks, we hope to provide a broader picture of the interplay between chemical and electrical synapses in the central nervous system (CNS).
Our most recent work has focused on a region of the thalamus populated exclusively by inhibitory neurons: the thalamic reticular nucleus, or TRN. This area provides massive inhibition to the thalamus, which regulates most of sensory input destined for the neocortex. The TRN makes reciprocal connections with thalamic nuclei, many of which lack inhibitory neurons, and it receives feedback excitation from cortex. It therefore plays a critical role in the thalamo-cortical circuit. Because it is anatomically segregated, the TRN is an ideal location to study inhibition in general and its role in feedback and feed-forward pathways in particular. Furthermore, the TRN is a central player in thalamocortical rhythms associated with sleep and epilepsy.
We have found that neurons within the TRN communicate not only by chemical synapses, but also by gap junctions (Landisman et al., 2002). In the past few years it has become apparent that gap junctions are pervasive throughout the mammalian brain. Since there is currently very little information on how these synapses operate in the CNS, the major focus of my lab is to better understand the function, mechanisms and plasticity of gap junctions.
About Carole Landisman
Carole Landisman received her BS in Electrical and Bioengineering from Rice University. She then received her PhD in Neurobiology from Rockefeller University. Following her PhD, Landisman trained as a postdoctoral fellow at Brown University in the lab of Dr. Barry Connors, where she went on to be an Investigator (Research Faculty) for several years. During her postdoc, she received a Helen Hay Whitney fellowship. She is currently an assistant professor in the Harvard University Center for Brain Science and in the Department of Neurology at Children's Hospital Boston.
- Landisman C.E., Connors B.W., (2007) VPM and PoM nuclei of the rat somatosensory thalamus: intrinsic neuronal properties and corticothalamic feedback. Cereb. Cortex, 17(2):2853-2865.
- Patrick S., Connors B.W., Landisman C.E. (2006) Developmental changes in somatostatin-positive interneurons in a freeze lesion model of epilepsy. Epilepsy Res.70:161-71.
- Landisman C.E., Connors B.W. (2005) Long-term modulation of electrical synapses in the mammalian thalamus. Science 310:1809-1813.
- Long M.A., Landisman C.E., Connors B.W. (2004) Small electrically coupled clusters generate synchronous rhythms in the thalamic reticular nucleus. J. Neurosci. 24(2):341-349.
- Landisman C.E., Long M.A., Beierlein M., Deans M.R., Paul D.L., Connors B.W. (2002) Electrical synapses in the thalamic reticular nucleus. J. Neurosci., 22(3):1002-1009.
- Landisman C.E., Ts'o D.Y. (2002) Color processing in primate striate cortex: electrophysiological properties. J. Neurophysiol., 87:3138-3151.
- Landisman C.E., Ts'o D.Y. (2002) Color processing in macaque striate cortex: relationships to ocular dominance, cytochrome oxidase, and orientation. J. Neurophysiol., 87:3126-3137.
For a list of Carole Landisman's publications on PubMed, click here.