scholarly journals Fornical and nonfornical projections from the rat hippocampal formation to the anterior thalamic nuclei

Hippocampus ◽  
2015 ◽  
Vol 25 (9) ◽  
pp. 977-992 ◽  
Author(s):  
Christopher M. Dillingham ◽  
Jonathan T. Erichsen ◽  
Shane M. O'Mara ◽  
John P. Aggleton ◽  
Seralynne D. Vann
Keyword(s):  
Hippocampal Formation ◽  
Thalamic Nuclei ◽  
Anterior Thalamic Nuclei

scholarly journals Hippocampal–diencephalic–cingulate networks for memory and emotion: An anatomical guide

2017 ◽  
Vol 1 ◽  
pp. 239821281772344 ◽  
Author(s):  
Emma J. Bubb ◽  
Lisa Kinnavane ◽  
John P. Aggleton
Keyword(s):  
Prefrontal Cortex ◽  
Medial Temporal Lobe ◽  
Current Knowledge ◽  
Hippocampal Formation ◽  
Retrosplenial Cortex ◽  
Thalamic Nuclei ◽  
Mammillary Bodies ◽  
Individual Site ◽  
Multi Stage ◽  
Anterior Thalamic Nuclei

This review brings together current knowledge from tract tracing studies to update and reconsider those limbic connections initially highlighted by Papez for their presumed role in emotion. These connections link hippocampal and parahippocampal regions with the mammillary bodies, the anterior thalamic nuclei, and the cingulate gyrus, all structures now strongly implicated in memory functions. An additional goal of this review is to describe the routes taken by the various connections within this network. The original descriptions of these limbic connections saw their interconnecting pathways forming a serial circuit that began and finished in the hippocampal formation. It is now clear that with the exception of the mammillary bodies, these various sites are multiply interconnected with each other, including many reciprocal connections. In addition, these same connections are topographically organised, creating further subsystems. This complex pattern of connectivity helps explain the difficulty of interpreting the functional outcome of damage to any individual site within the network. For these same reasons, Papez’s initial concept of a loop beginning and ending in the hippocampal formation needs to be seen as a much more complex system of hippocampal–diencephalic–cingulate connections. The functions of these multiple interactions might be better viewed as principally providing efferent information from the posterior medial temporal lobe. Both a subcortical diencephalic route (via the fornix) and a cortical cingulate route (via retrosplenial cortex) can be distinguished. These routes provide indirect pathways for hippocampal interactions with prefrontal cortex, with the preponderance of both sets of connections arising from the more posterior hippocampal regions. These multi-stage connections complement the direct hippocampal projections to prefrontal cortex, which principally arise from the anterior hippocampus, thereby creating longitudinal functional differences along the anterior–posterior plane of the hippocampus.

scholarly journals BIFURCATING NEURONS IN THE ANTERIOR THALAMIC NUCLEI

2021 ◽  
Author(s):  
Y Pei ◽  
S (Yee T) Tasananukorn ◽  
M Wolff ◽  
JC Dalrymple-Alford
Keyword(s):  
Hippocampal Formation ◽  
Nodal Point ◽  
Primary Source ◽  
Brain Structures ◽  
Retrosplenial Cortex ◽  
Thalamic Nuclei ◽  
Neural Ensembles ◽  
Multiple Structures ◽  
Anterior Thalamic Nuclei ◽  
New Perspective

AbstractThe anterior thalamic nuclei (ATN) form a nodal point within a hippocampal-cingulate-diencephalic memory system. ATN projections to different brain structures are conventionally viewed as distinct, but ATN neurons may send collaterals to multiple structures. The anteromedial subregion (AM) is the primary source of efferents to the medial prefrontal cortex (mPFC). Using a dual-retrograde neurotracer strategy, we discovered bifurcating AM neurons for tracers placed in the mPFC when paired with other regions. A semi-quantitative analysis found a high proportion of AM neurons (~36%) showed collateral projections when the mPFC was paired with dorsal subiculum (dSub); 20% were evident for mPFC paired with caudal retrosplenial cortex (cRSC); and 6% was found for mPFC and ventral hippocampal formation (vHF). About 10% of bifurcating AM neurons was also identified when the mPFC was not included, that is, for cRSC with dSub, and cRSC with vHF. Similar percentages of bifurcating neurons were also found within the anterior region of the adjacent nucleus reuniens (Re). The high frequency of bifurcating neurons suggests a new perspective for ATN function. These neurons would facilitate direct coordination among distal neural ensembles to support episodic memory and may explain why the ATN is a critical region for diencephalic amnesia.

scholarly journals Trajectory of hippocampal fibres to the contralateral anterior thalamus and mammillary bodies in rats, mice, and macaque monkeys

2019 ◽  
Vol 3 ◽  
pp. 239821281987120 ◽  
Author(s):  
Mathias L. Mathiasen ◽  
Rebecca C. Louch ◽  
Andrew D. Nelson ◽  
Christopher M. Dillingham ◽  
John P. Aggleton
Keyword(s):  
Thalamic Nucleus ◽  
Hippocampal Formation ◽  
Internal Capsule ◽  
Macaque Monkey ◽  
Head Direction ◽  
Thalamic Nuclei ◽  
Tracer Injection ◽  
Mammillary Bodies ◽  
Anterior Thalamus ◽  
Anterior Thalamic Nuclei

The routes by which the hippocampal formation projects bilaterally to the anterior thalamic nuclei and mammillary bodies were examined in the mouse, rat, and macaque monkey. Despite using different methods and different species, the principal pattern remained the same. For both target areas, the contralateral hippocampal (subiculum) projections arose via efferents in the postcommissural fornix ipsilateral to the tracer injection, which then crossed hemispheres both in or just prior to reaching the target site within the thalamus or hypothalamus. Precommissural fornix fibres could not be followed to the target areas. There was scant evidence that the ventral hippocampal commissure or decussating fornix fibres contribute to these crossed subiculum projections. Meanwhile, a small minority of postsubiculum projections in the mouse were seen to cross in the descending fornix at the level of the caudal septum to join the contralateral postcommissural fornix before reaching the anterior thalamus and lateral mammillary nucleus on that side. Although the rodent anterior thalamic nuclei also receive nonfornical inputs from the subiculum and postsubiculum via the ipsilateral internal capsule, few, if any, of these projections cross the midline. It was also apparent that nuclei within the head direction system (anterodorsal thalamic nucleus, laterodorsal thalamic nucleus, and lateral mammillary nucleus) receive far fewer crossed hippocampal inputs than the other anterior thalamic or mammillary nuclei. The present findings increase our understanding of the fornix and its component pathways while also informing disconnection analyses involving the hippocampal formation and diencephalon.

scholarly journals Asymmetric cross-hemispheric connections link the rat anterior thalamic nuclei with the cortex and hippocampal formation

Neuroscience ◽  
2017 ◽  
Vol 349 ◽  
pp. 128-143 ◽  
Author(s):  
Mathias L. Mathiasen ◽  
Christopher M. Dillingham ◽  
Lisa Kinnavane ◽  
Anna L. Powell ◽  
John P. Aggleton
Keyword(s):  
Hippocampal Formation ◽  
Thalamic Nuclei ◽  
Anterior Thalamic Nuclei

Individual Subnuclei of the Rat Anterior Thalamic Nuclei Differently affect Spatial Memory and Passive Avoidance Tasks

Neuroscience ◽  
2020 ◽  
Vol 444 ◽  
pp. 19-32
Author(s):  
Vajihe Safari ◽  
Mohsen Nategh ◽  
Leila Dargahi ◽  
Mohammad Esmail Zibaii ◽  
Fariba Khodagholi ◽  
...  
Keyword(s):  
Spatial Memory ◽  
Passive Avoidance ◽  
Thalamic Nuclei ◽  
Anterior Thalamic Nuclei
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