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Hippocampal inputs mediate theta-related plasticity in anterior thalamus

Tsanov, M., Wright, Nicholas Fraser, Vann, Seralynne Denise ORCID:, Erichsen, Jonathan Thor ORCID:, Aggleton, John Patrick ORCID: and O'Mara, S. M. 2011. Hippocampal inputs mediate theta-related plasticity in anterior thalamus. Neuroscience 187 , pp. 52-62. 10.1016/j.neuroscience.2011.03.055

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Hippocampally-driven oscillatory activity at theta frequency is found in the diencephalon, but an understanding of the fundamental role of theta in the hippocampo-diencephalic circuit remains elusive. An important strategy in determining how activity modifies oscillatory properties of hippocampo-diencephalic circuitry comprises investigations of anterior thalamic responses to their main inputs: the descending dorsal fornix and the ascending mammillothalamic tract. Here, we show that the amplitude of thalamic theta spectral power selectively increases after plasticity-inducing stimulation of the dorsal fornix, but not of the mammillothalamic tract in urethane-anaesthetized young male rats. Furthermore, we show that low-frequency stimulation (LFS) significantly augments the fornix-driven theta ratio (theta over delta power, T-ratio), in parallel with depressing thalamic synaptic responses. However, the mammillothalamic synaptic response after LFS did not correlate with the slow band of theta oscillation (low T-ratio), but did correlate positively with the fast band of theta oscillation (high T-ratio). Our data demonstrate that the descending direct fornix projection is a pathway that modulates theta rhythm in the hippocampo-diencephalic circuit, resulting in dynamic augmentation of thalamic neuronal responsiveness. These findings suggest that hippocampal theta differentially affects synaptic integration in the different structures with which the hippocampus is reciprocally connected.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Optometry and Vision Sciences
Neuroscience and Mental Health Research Institute (NMHRI)
Subjects: R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
R Medicine > RE Ophthalmology
Uncontrolled Keywords: anterior thalamic nuclei; fornix; mammillothalamic tract; synaptic plasticity; theta oscillation; LTP
Publisher: Elsevier
ISSN: 0306-4522
Last Modified: 07 Nov 2023 11:17

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