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Behavioral and Electrophysiological Properties of Nucleus Reuniens: Role in Arousal, Spatial Navigation and Cognitive Processes
Title
Behavioral and Electrophysiological Properties of Nucleus Reuniens: Role in Arousal, Spatial Navigation and Cognitive Processes.
Creator
Viena, Tatiana Danela, Vertes, Robert P., Florida Atlantic University, Charles E. Schmidt College of Science, Center for Complex Systems and Brain Sciences
Abstract/Description
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...
Show moreThe 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.
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Date Issued
2018
PURL
http://purl.flvc.org/fau/fd/FA00013139
Subject Headings
Midline Thalamic Nuclei, Hippocampus, Prefrontal cortex, Neural pathways, Arousal (Physiology), Space Perception, Cognition
Format
Document (PDF)
The Limbic Thalamus
Title
The Limbic Thalamus.
Creator
Hoover, Walter Boyd III, Florida Atlantic University, Vertes, Robert P., Charles E. Schmidt College of Science, Center for Complex Systems and Brain Sciences
Abstract/Description
The thalamus has been traditionally viewed as a structural relay to specific cortical areas behaviorally associated with sensory or motor functions, and thalamic nuclei that function in this manner are referred to as 'relay nuclei·. However. the parts of the thalamus interconnecting limbic association cortices (functionally involved in memory. reward, emotion. and decision making) comprise the midline and intralaminar nuclei. The midline thalamus has not been examined fully at the anatomical,...
Show moreThe thalamus has been traditionally viewed as a structural relay to specific cortical areas behaviorally associated with sensory or motor functions, and thalamic nuclei that function in this manner are referred to as 'relay nuclei·. However. the parts of the thalamus interconnecting limbic association cortices (functionally involved in memory. reward, emotion. and decision making) comprise the midline and intralaminar nuclei. The midline thalamus has not been examined fully at the anatomical, physiological. or behavioral level, and may serve as an important relay between cortical and subcortical structures and the limbic system. The work incorporated into this dissertation included five axonal tract tracing projects that were conducted in the rat. to explore and test the hypothesis that the midline thalamus serves as an important interface between limbic structures including the amygdala. nucleus accumbens. medial prefrontal cortex and hippocampal formation. An important finding was the demonstration of a closed anatomical loop between the hippocampal formation, the ventral medial prefrontal cortex and the ventral midline thalamus: CA 1/subiculum > PLIIL > RE > CA 1/subiculum. Another finding was that 1) the hippocampal formation innervates the entire medial prefrontal cortex; and 2) the hippocampal formation projects more heavily to ventral as compared to dorsal cortices in the mPFC. The paraventricular, parataenial, rhomboid and reuniens nuclei of the midline thalamus were shown to distribute to limbic structures important for cognitive processing: the amygdala, nucleus accumbens, hippocampal formation, parahippocampal cortex, and the prefrontal cortex. Present results demonstrate that the ventral midline nuclei (reuniens and rhomboid) extensively innervate limbic cortical structures (the medial prefrontal cortex and hippocampal formation) whereas dorsal midline nuclei (paraventricular and parataenial) distribute more heavily to subcortical limbic structures (the amygdala and the nucleus accumbens). These midline nuclei may, therefore, relay information between these limbic areas. This connectivity suggests that the midline nuclei could further be subdivided from the intralaminar and relay groups. The midline thalamic nuclei would, therefore, comprise the limbic thalamus.
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Date Issued
2007
PURL
http://purl.flvc.org/fau/fd/FA00000861
Subject Headings
Neuroanatomy, Limbic system--Physiology, Prefrontal cortex--Physiology, Thalamus--Physiology, Neurotransmitter receptors
Format
Document (PDF)