The hippocampal-medial prefrontal circuit has been shown to serve a critical role
in decision making and goal directed actions. While the hippocampus (HF) exerts a direct
influence on the medial prefrontal cortex (mPFC), there are no direct return projections
from the mPFC to the HF. The nucleus reuniens (RE) of the midline thalamus is strongly
reciprocally connected with the HF and mPFC and represents the major link between
these structures.
We investigated the role of RE in functions associated with the hippocampus and
the mPFC -- or their interactions. Using two different inactivation techniques
(pharmacological and chemogenetic), we sought to further define the role of RE in spatial
working memory (SWM) and behavioral flexibility using a modified delayed non-match
to sample (DNMS) working memory task. We found that the reversible inactivation of
RE with muscimol critically impaired SWM performance, abolished well-established
spatial strategies and produced a profound inability to correct non-rewarded, incorrect choices on the T-maze (perseverative responding). We observed similar impairments in
SWM following the chemogenetic (DREADDs) inactivation of RE or selective RE
projections to the ventral HF. In addition, we showed that the inhibition of RE terminals
to the dorsal or ventral HF altered task related behaviors by increasing or decreasing the
time to initiate the task or reach the reward, respectively. Finally, we examined discharge
properties of RE cells across sleep-wake states in behaving rats. We found that the
majority of RE cells discharge at high rates of activity in waking and REM and at
significantly reduced rates in SWS, with a subpopulation firing rhythmically in bursts
during SWS. We identified five distinct subtypes of RE cells that discharged differently
across vigilant states; those firing at highest rates in waking (W1, W2), in REM sleep
(R1, R2) and SWS (S1). Given the differential patterns of activity of these cells, we
proposed they may serve distinct functions in waking – and possibly in SWS/REM sleep.
In sum, our findings indicate that RE is critically involved in mnemonic and
executive functions and the heterogeneous activity of these cells support a role for RE in
arousal/attention, spatial working memory and cognition. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection
| Identifer | oai:union.ndltd.org:fau.edu/oai:fau.digital.flvc.org:fau_40892 |
| Contributors | Viena, Tatiana Danela (author), Vertes, Robert P. (Thesis advisor), Florida Atlantic University (Degree grantor), Charles E. Schmidt College of Science, Center for Complex Systems and Brain Sciences |
| Publisher | Florida Atlantic University |
| Source Sets | Florida Atlantic University |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation, Text |
| Format | 189 p., application/pdf |
| Rights | Copyright © is held by the author with permission granted to Florida Atlantic University to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder., http://rightsstatements.org/vocab/InC/1.0/ |
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