Biology subjects

Viena, T. D.

Publications and source records attributed to Viena, T. D..

4 recordsLinked to original sources

bioRxiv2022

Reuniens transiently synchronizes memory networks at beta frequencies

Using episodic memories to help guide decisions requires top-down medial prefrontal cortex interactions with the hippocampus. Mechanistically, this integrated prefrontal-hippocampal memory state is thought to be organized by synchronized network oscillations and mediated by connectivity with the nucleus reuniens of the thalamus. Here, we recorded local field potentials from the prefrontal-reuniens-hippocampal network while rats were engaged in a nonspatial sequence memory task which helps isolate memory-related activity from running-related oscillations. We found that synchronous prefrontal-hippocampal beta bursts (15-30 Hz) were dominant during memory trials, whereas synchronous theta (6-12 Hz) was highest during running. Beta rose during a trial and peaked just before a decision, whereas theta was highest during running. Beta bursts first appeared in reuniens and then in prefrontal and hippocampal sites simultaneously, suggesting beta could be directly driven by reuniens. To test this, we used an optogenetic approach (retroAAV-ChR2) to see if reuniens was capable of driving prefrontal-hippocampal beta synchrony. Reuniens activation induced prefrontal-hippocampal beta coherence, and reduced theta coherence, resembling the observed memory-driven network state. These findings demonstrate for the first time that reuniens contributes to memory by driving transient synchronous beta in the prefrontal-hippocampal system facilitating coherent interactions that sub-serve memory-based decision making.

neuroscience↗

bioRxiv2021

Dual medial prefrontal cortex and hippocampus projecting neurons in the paraventricular nucleus of the thalamus

The paraventricular nucleus (PVT) of the midline thalamus is a critical higher-order cortico-thalamo-cortical integration site that plays a critical role in various behaviors including reward seeking, cue saliency, and emotional memory. Anatomical studies have shown that PVT projects to both medial prefrontal cortex (mPFC) and hippocampus (HC). However, dual mPFC-HC projecting neurons which could serve a role in synchronizing mPFC and HC activity during PVT-dependent behaviors, have not been explored. Here we used a dual retrograde adenoassociated virus (AAV) tracing approach to characterize the location and proportion of different projection populations that send collaterals to mPFC and/or ventral hippocampus (vHC). Additionally, we examined the distribution of calcium binding proteins calretinin (CR) and calbindin (CB) with respect to these projection populations PVT. We found that PVT contains separate populations of cells that project to mPFC, vHC, and those that innervate both regions. Interestingly, dual mPFC-HC projecting cells expressed neither CR or CB. Topographically, mPFC- and vHC-projecting CB+ and CR+ cells clustered around dual projecting neurons in PVT. These results are consistent with the features of dual mPFC-vHC projecting cells in the nucleus reuniens (RE) and suggestive of a functional mPFC-PVT-vHC system that may support mPFC-vHC interactions in PVT-dependent behaviors.

neuroscience↗

bioRxiv2020

Calretinin and calbindin architecture of the midline thalamus associated with prefrontal-hippocampal circuitry

The midline thalamus bi-directionally connects the medial prefrontal cortex (mPFC) and hippocampus (HC) creating a unique cortico-thalamo-cortico circuit fundamental to memory and executive function. While the anatomical connectivity of midline thalamus has been thoroughly investigated, little is known about its cellular organization within each nucleus. Here we used immunohistological techniques to examine cellular distributions in the midline thalamus based on the calcium binding proteins parvalbumin (PV), calretinin (CR), and calbindin (CB). We also examined these calcium binding proteins in a population of reuniens cells known to project to both mPFC and HC using a dual fluorescence retrograde adenoassociated virus (AAV) based tracing approach. These dual reuniens mPFC-HC projecting cells, in particular, are thought to be important for synchronizing mPFC and HC activity. First, we confirmed the absence of PV+ neurons in the midline thalamus. Second, we found a common pattern of CR+ and CB+ cells throughout midline thalamus with CR+ cells running along the nearby third ventricle (3V) and penetrating the midline. CB+ cells were consistently more lateral and toward the middle of the dorsal-ventral extent of the midline thalamus. Notably, single-labeled CR+ and CB+ zones were partially overlapping and included dual-labeled CR+/CB+ cells. Within RE, we also observed a CR and CB subzone specific diversity. Interestingly, dual mPFC-HC projecting neurons in RE expressed none of the calcium binding proteins examined, but were contained in nests of CR+ and CB+ cells. Overall, the midline thalamus was well organized into CR+ and CB+ rich zones distributed throughout the region, with dual mPFC-HC projecting cells in reuniens representing a unique cell population. These results provide a cytoarchitectural organization in the midline thalamus based on calcium binding protein expression, and sets the stage for future cell-type specific interrogations of the functional role of these different cell populations in mPFC-HC interactions.

neuroscience↗

bioRxiv2019

RatHat: A self-targeting printable brain implant system

There has not been a major change in how neuroscientists approach stereotaxic methods in decades. Here we present a new stereotaxic method that improves on traditional approaches by reducing costs, training, surgical time, and aiding repeatability. The RatHat brain implantation system is a 3D printable stereotaxic device for rats that is fabricated prior to surgery and fits to the shape of the skull. RatHat builds are directly implanted into the brain without the need for head-leveling or coordinate-mapping during surgery. The RatHat system can be used in conjunction with the traditional u-frame stereotaxic device, but does not require the use of a micromanipulator for successful implantations. Each RatHat system contains several primary components including the implant for mounting intracranial components, the surgical stencil for targeting drill sites, and the protective cap for impacts and debris. Each component serves a unique function and can be used together or separately. We demonstrate the feasibility of the RatHat system in four different proof-of-principle experiments: 1) a 3-pole cannula apparatus, 2) an optrode-electrode assembly, 3) a fixed-electrode array, and 4) a tetrode hyperdrive. Implants were successful, durable, and long-lasting (up to 9 months). RatHat print files are easily created, can be modified in CAD software for a variety of applications, and are easily shared, contributing to open science goals and replications. The RatHat system has been adapted to multiple experimental paradigms in our lab and should be a useful new way to conduct stereotaxic implant surgeries in rodents. Impact StatementWe demonstrate a new approach to rodent stereotaxic surgery. Rodent neurosurgery is a complex skill that requires expensive equipment for head stabilization and micromanipulators for localization. The RatHat is a 3D printable brain implant system that reduces costs and time using pre-mapped and printed surgical files. A surgical stencil allows for quick placement of drill holes, and a RatHat places components in the brain using atlas coordinates. The RatHat system is an easily shared resource facilitating open science goals for simple replications and archiving of specific experimental applications.

neuroscience↗