Electrical and chemical signaling in the thalamus and cortex

           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. 

           Our 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. Most recently, our work has focused primarily on mechanisms of gap junctional plasticity and its effects on local networks.

To study these problems, my lab currently uses single and dual intracellular recordings in vitro, calcium imaging, and antibody staining.

The Thalamic Reticular Nucleus (TRN): Gap Junction Central   

           Our work focuses 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 sensory input 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 fundamental aspects of brain function and dysfunction: sleep, schizophrenia and epilepsy.

Recently, we have found that neurons within the TRN communicate amongst each other primarily by electrical (gap junctional) synapses (Landisman et al., 2002). In the past few years electrical synapses have been discovered to be pervasive throughout the mammalian brain, particularly to provide communication amongst like-type inhibitory neurons. Since there is currently very little information on how these synapses operate in the mammalian central nervous system, the major focus in our lab is to understand the function, mechanisms, and plasticity of gap junctional synapses.