The cognitive thalamus: more than a relay

WT Scheme: Investigator Award in Science.

How do brain circuits support different but complementary aspects of event memory? The answer lies in distributed networks across the medial temporal lobe, prefrontal cortex and parietal cortex. Via their widespread connectivity, nuclei within the rostral thalamus support these memory networks. Indeed, one group (the anterior thalamic nuclei) forms the backbone of the extended hippocampal system, thought to be vital for episodic memory. We knowremarkably little, however, about the nature of rostral thalamic information and how it impacts upon memory.

We have recently discovered neurons in the rostral thalamus of freely-moving rats with hitherto unsuspected spatial properties. These cells are unlike any previously described in the region as they closely resemble place cells, boundary vector cells, and grid-cells (Fig.1A-F) found in hippocampal and parahippocampal regions. This discovery is set to transform our understanding of the region. [Rostral thalamus refers to the anterior thalamic nuclei (ATN), the rostral midline nuclei (paraventricular, parataenial, rhomboid, reuniens), and the rostral reticular nucleus. Hippocampus refers to the dentate gyrus and CA fields, but not the subiculum, while hippocampal includes the subiculum.]

Priority questions are:

1. WHAT IS THE NATURE OF THIS SPATIAL INFORMATION? We will determine the various classes and combinations of spatial information in rostral thalamus and compare them to analogous information types in the hippocampus/subiculum/parahippocampus.
2. HOW DOES THIS SPATIAL INFORMATION REACH THE ROSTRAL THALAMUS? We will determine whether different types of spatial information are located in separate thalamic nuclei and whether the patterns of spatial signalling relate to afferents from particular sites such as the hippocampus, subiculum, retrosplenial cortex, or mammillary bodies.
3. WHAT ARE THE FUNCTIONS OF THIS ANCILLARY SPATIAL PROCESSING? We will compare the properties of different rostral thalamic nuclei and determine the functional significance of their hippocampal and nonhippocampal connections.

Award Date
01 July 2014
Award Value
€1,198,797
Principal Investigator
Professor Shane O'Mara
Host Institution
Trinity College Dublin
Scheme
SFI-HRB-Wellcome Research Partnership