Biology subjects

Monasterio, A.

Publications and source records attributed to Monasterio, A..

5 recordsLinked to original sources

bioRxiv2025

Contrasting needle physiological strategies to soil nutrient scarcity in radiata pine plantations

Intensive European forestry practices contribute to soil degradation and nutrient depletion, compromising tree health and ecosystem stability. However, the influence of soil nutrient scarcity on tree physiological responses during drought remains unclear, particularly in Pinus radiata D. Don plantations, where it may impair needle function and overall tree health. We investigated how soil nutrient availability influences leaf-level physiological strategies during drought by comparing same-aged needles from two P. radiata stands with contrasting management stages and ages: (i) trees ({approx}20 years), likely to be clear-cut at 30-35 years (herein managed), and (ii) trees (>45 years) not clear-cut at the typical rotation age (herein abandoned). During the severe summer drought of 2022, both stands exhibited downregulation of the photosynthetic apparatus, indicating impaired photosynthetic performance under drought. However, their leaf-physiological responses to nutrient scarcity diverged. Managed trees exhibited dependence on soil nutrients, with reduced photosynthetic performance under nutrient-poor conditions. In contrast, abandoned trees showed relative independence from soil nutrients, maintaining photosynthetic function even under nutrient-poor conditions. This highlights a trade-off: younger, managed trees may enhance photosynthesis under optimal nutrient conditions but are more susceptible to nutrient imbalances and environmental stress. In turn, older, abandoned trees appeared to buffer the effects of drought and nutrient scarcity through age-related physiological traits. Our findings underscore the physiological value of mature stands. Furthermore, higher soil organic carbon and vegetation diversity in abandoned stands suggest that management cessation may enhance long-term ecosystem resilience. These results emphasise the importance of integrating soil-leaf interactions into sustainable forest management.

plant biology↗

bioRxiv2025

Three-photon population imaging of subcortical brain regions

Recording activity from large cell populations in deep neural circuits is essential for understanding brain function. Three-photon (3P) imaging is an emerging technology that allows for imaging of structure and function in subcortical brain structures. However, increased tissue heating, as well as the low repetition rate sources inherent to 3P imaging, have limited the fields of view (FOV) to areas of [≤] 0.3 mm2. Here we present a Large Imaging Field of view Three-photon (LIFT) microscope with a FOV of >3 mm2. LIFT combines high numerical aperture (NA) optimized sampling, using a custom scanning module, with deep learning-based denoising, to enable population imaging in deep brain regions. We demonstrate non-invasive calcium imaging in the mouse brain from >1500 cells across CA1, the surrounding white matter, and adjacent deep layers of the cortex, and show population imaging with high signal-to-noise in the rat cortex at a depth of 1.2 mm. The LIFT microscope was built with all off-the-shelf components and allows for a flexible choice of imaging scale and rate.

neuroscience↗

bioRxiv2024

A hippocampal astrocytic sequence emerges during learning and memory

Abstract.The dorsal hippocampus is a heterogeneous structure with numerous cell types involved in generating and maintaining detailed representations of space and time. Prior work has established that pyramidal cells contribute to these crucial aspects of associative memory. For example, hippocampal "time cells" encode temporal information through sequential activity. However, the roles of non-neuronal cell types are less often explored. In this study, we investigated dorsal hippocampal CA1 astrocytes using one-photon calcium imaging in freely moving animals during a contextual fear conditioning paradigm, enabling tracking of a population of glial cells across days. In response to foot shock, astrocytes generated robust calcium-event sequences with a time-compressed structure akin to canonical hippocampal time cells. Upon re-exposure to the conditioned context, we again detected astrocytic sequences -- in the absence of shock -- displaying similar time-compressed structure. Importantly, this phenomenon was not observed in a context different from the initial fear conditioning chamber. Lastly, spontaneous astrocytic activity in the initial conditioning context was associated with behavioral state transitions (e.g. freezing), but this was not observed in a novel context. Taken together, these results suggest a direct role for astrocytes in generating hippocampal representations of associative memory, and future work may continue to study how diverse cell types process temporal features of associative memory.

neuroscience↗

bioRxiv2024

CA1 Engram Cell Dynamics Before and After Learning

A fundamental question in neuroscience is how memory formation shapes brain activity at the level of neuronal populations. Recent studies of hippocampal engram cells--neurons identified by learning-induced immediate early gene (IEG) expression--propose that these populations form the cellular substrate for memory. Previous experimental work suggests that cells are recruited into engrams via elevated intrinsic excitability and that learning drives coactivity among these cells to support retrieval. Despite this, an understanding of how engram dynamics evolve across learning and recall remains incomplete. Here, we combined activity-dependent genetic tagging with longitudinal two-photon calcium imaging to track CA1 engram population dynamics before and after fear conditioning. Our results reveal that engram activity is modulated by intrinsic dynamics, behavioral state, and stimulus-cued reactivation. Consistent with the idea that intrinsic dynamics bias engram allocation, spontaneous activity during rest predicted future engram membership--up to two days prior to Fos expression. In parallel, we found sequential activity during locomotion recruited both engram and non-engram cells, but that engram cells were less modulated by velocity. Furthermore, after fear conditioning, within the engram population, we identified a subset of cells that increased their correlations after fear learning, specifically during quiet rest. We also used a trace fear conditioning paradigm to show that conditioned stimulus presentation drove elevated activity and stable correlations amongst engram cells, demonstrating learning-dependent reactivation. Finally, computational modeling of CA3-CA1 circuit dynamics demonstrated that a network with strong excitatory-inhibitory balance, capable of CA3-driven reactivation, is consistent with our experimental results. Together, these results show that engram population dynamics are shaped by spontaneous states, behavior, and memory.

neuroscience↗

bioRxiv2020

Chronic optogenetic stimulation of hippocampal engrams variably modulates social behaviors in mice

The hippocampus processes both spatial-temporal information and emotionally salient experiences. To test the functional properties of discrete sets of cells in the dorsal dentate gyrus (dDG), we examined whether chronic optogenetic reactivation of these ensembles was sufficient to modulate social behaviors in mice. We found that chronic reactivation of dDG cells in male mice was sufficient to enhance social behaviors in a female exposure task when compared to pre-stimulation levels. However, chronic reactivation of these cells was not sufficient to modulate group differences in a separate subset of social behaviors, and multi-region analysis of neural activity did not yield detectable differences in immediate-early gene expression or neurogenesis, suggesting a dissociation between our chronic stimulation-induced behavioral effects and underlying neural responses. Together, our results demonstrate that chronic optogenetic stimulation of cells processing valent experiences enduringly and unidirectionally modulates social interactions between male and female mice.

neuroscience↗