Recruitment and inhibitory action of hippocampal axo-axonic cells during behavior.

The axon initial segment of hippocampal pyramidal cells is a key subcellular compartment for action potential generation, under GABAergic control by the "chandelier" or axo-axonic cells (AACs). Although AACs are the only cellular source of GABA targeting the initial segment, their in vivo activity patterns and influence over pyramidal cell dynamics are not well understood. We achieved cell-type-specific genetic access to AACs in mice and show that AACs in the hippocampal area CA1 are synchronously activated by episodes of locomotion or whisking during rest. Bidirectional intervention experiments in head-restrained mice performing a random foraging task revealed that AACs inhibit CA1 pyramidal cells, indicating that the effect of GABA on the initial segments in the hippocampus is inhibitory in vivo. Finally, optogenetic inhibition of AACs at specific track locations induced remapping of pyramidal cell place fields. These results demonstrate brain-state-specific dynamics of a critical inhibitory controller of cortical circuits

Effects of environmental factors and management on dynamics of mixed calcareous forests under climate change in Central European lowlands

Mixed lowland forests reserved for natural succession are sparse in the Czech Republic. However, their development provides essential insights into the natural processes of these forests and recommendations for forest management in a changing climate. The research describes the dynamics, productivity, structure, diversity, dead wood, and radial growth of hornbeam-oak groves and calcareous beech-dominated forests in the Karlštejn National Nature Reserve (Czechia) based on inventory in 2002, 2008, 2014 and 2020. The objective was to evaluate changes in differently managed stands (high forest, coppice with standards, and coppice) after leaving the stands to spontaneous development in 2004. The tree density increased by 2–10% from 2002 to 2014 and decreased by 6–18% in 2020. In the high forest, an increase in the stand volume was observed during the whole period, while in the coppice with standards and coppice, only until 2014. The stand volume ranged from 190 (coppice) to 630 (high forest) m³ ha−1 in 2020 and increased by an average of 28% over 18 years. Overall diversity of tree layer showed an uneven structure in the high forest and a substantially diverse structure in the other variants. The deadwood volume has been steadily increasing (18–35 m³ ha−1 in 2020), accumulating an average of 1 m³ ha−1 yr−1. A lack of precipitation and high temperatures from June to August were the main limiting factors of the radial growth of tree species, while the number of negative pointer years has increased in the last decade. European beech (Fagus sylvatica L.) was the most sensitive tree species to climate compared to the resilient European ash (Fraxinus excelsior L.). The lowest fluctuations in the diameter increment were recorded in Norway maple (Acer platanoides L.) and the highest in beech in the temperature cycles of 7–15 years. Over the last 20 years, sessile oak [Quercus petraea (Matt.) Liebl.] showed an increase in radial growth by 7%, while other tree species reported a decrease with a maximum in beech (by −38%). The forest stands managed as high forest, characterized by a higher production potential and lower diversity, had slower dynamics when compared to coppice with standards and coppice