Thalamocortical and intracortical brain circuits operate via a dynamic interplay between feed-forward, recurrent and feedback pathways. Feed-forward excitation is by far the best-studied aspect of thalamocortical processing, but it represents only a small fraction of the neuronal connections in both the thalamus and neocortex. My research focuses on three aspects of thalamocortical circuitry: feedback from cortex to thalamus, inhibitory neuronal circuitry, and gap junctional synapses. All three are critical to the cortical processing of sensory information in thalamus and cortex.
To study these problems, my lab currently uses single and dual intracellular recordings in vitro to study synaptic mechanisms. My goal is to study the relationships between synaptic mechanisms and sensory system function in vitro and in vivo.
My most recent work had focused on a region of thalamus populated exclusively by inhibitory neurons: the thalamic reticular nucleus, or TRN. This area provides massive inhibition to the thalamus, which regulates most of the sensory imput destined for the neocortex. The TRN makes reciprocal connections with other thalamic nuclei, many of which lack inhibitory neurons, and it receives feedback excitation from cortex. It therefore plays a key role in the thalamocortical circuit. Because it is anatomically segregated, it 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 two fundamental aspects of brain function and dysfunction: sleep and epilepsy.
Recently, we have found that neurons within the TRN communicate not only by chemical synapses, but also by electrical synapses (gap junctions). In the past few years it has become apparent that electrical synapses are pervasive throughout the mammalian brain. Since there is currently very little information on how these synapses operate in the central nervous system, a major focus in my lab is to understand better the function, mechanisms, and plasticity of gap junctions.
|
References:
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.
Patrick S, Connors BW, Landisman CE (2006) Developmental changes in somatostatin-positive interneurons in a freeze lesion model of epilepsy. Epilepsy Res 70:161-71.
Landisman CE, Connors BW (2005) Long-term modulation of electrical synapses in the mammalian thalamus. Science 310:1809-1813.
Landisman CE, Ts’o DY, (2002) Color processing in macaque striate cortex: relationships to ocular dominance, cytochrome oxidase, and orientation. J Neurophysiol 87:3126-3137.
|
Harvard University Home / GSAS Home / HMS Home