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Deconstructing the Direct Reciprocal Hippocampal-Anterior Thalamic Pathways for Spatial Learning
- Source :
- The Journal of Neuroscience
- Publication Year :
- 2020
- Publisher :
- Society for Neuroscience, 2020.
-
Abstract
- The hippocampus is essential for normal memory but does not act in isolation. The anterior thalamic nuclei may represent one vital partner. Using DREADDs, the behavioral consequences of transiently disrupting anterior thalamic function were examined, followed by inactivation of the dorsal subiculum. Next, the anterograde transport of an adeno-associated virus expressing DREADDs was paired with localized intracerebral infusions of a ligand to target specific input pathways. In this way, the direct projections from the anterior thalamic nuclei to the dorsal hippocampal formation were inhibited, followed by separate inhibition of the dorsal subiculum projections to the anterior thalamic nuclei. To assay spatial working memory, all animals performed a reinforced T-maze alternation task, then a more challenging version that nullifies intramaze cues. Across all four experiments, deficits emerged on the spatial alternation task that precluded the use of intramaze cues. Inhibiting dorsal subiculum projections to the anterior thalamic nuclei produced the severest spatial working memory deficit. This deficit revealed the key contribution of dorsal subiculum projections to the anteromedial and anteroventral thalamic nuclei for the processing of allocentric information, projections not associated with head-direction information. The overall pattern of results provides consistent causal evidence of the two-way functional significance of direct hippocampal-anterior thalamic interactions for spatial processing. At the same time, these findings are consistent with hypotheses that these same, reciprocal interactions underlie the common core symptoms of temporal lobe and diencephalic anterograde amnesia. SIGNIFICANCE STATEMENT It has long been conjectured that the anterior thalamic nuclei might be key partners with the hippocampal formation and that, respectively, they are principally responsible for diencephalic and temporal lobe amnesia. However, direct causal evidence for this functional relationship is lacking. Here, we examined the behavioral consequences of transiently silencing the direct reciprocal interconnections between these two brain regions on tests of spatial learning. Disrupting information flow from the hippocampal formation to the anterior thalamic nuclei and vice versa impaired performance on tests of spatial learning. By revealing the conjoint importance of hippocampal-anterior thalamic pathways, these findings help explain why pathology in either the medial diencephalon or the medial temporal lobes can result in profound anterograde amnesic syndromes.
- Subjects :
- Male
hippocampus
Behavioral/Cognitive
Hippocampus
Amnesia
Biology
Hippocampal formation
Spatial memory
Temporal lobe
03 medical and health sciences
Diencephalon
0302 clinical medicine
amnesia
Neural Pathways
medicine
Animals
0501 psychology and cognitive sciences
050102 behavioral science & comparative psychology
Research Articles
spatial learning
General Neuroscience
05 social sciences
Subiculum
anterior thalamic nuclei
Rats
DREADDs
subiculum
Thalamic Nuclei
Axoplasmic transport
medicine.symptom
Neuroscience
030217 neurology & neurosurgery
Subjects
Details
- ISSN :
- 15292401 and 02706474
- Volume :
- 40
- Database :
- OpenAIRE
- Journal :
- The Journal of Neuroscience
- Accession number :
- edsair.doi.dedup.....061ea936b33222cd0aa55f394a7a1ae3