Integrated Calendar

Spatial learning is a complex behavior which includes, among others, encoding of space, sensory and motivational processes, arousal and locomotor performance. Today, our view on spatial navigation is largely hippocampus-centrist. Less is known about the involvement of brain structures up- and downstream, or out of this circuit. Here, we provide the fist in vivo assessment of the neural matrix underlying spatial learning, using functional manganese-enhanced MRI (MEMRI) and voxel-wise whole brain analysis. Mice underwent place-learning (PL) vs. response-learning (RL) in the water cross maze (WCM) and its readout was correlated to the Mn2+ contrasts. Thus, we identified structures involved in spatial learning largely overlooked in the past, due to methods focused on region of interest (ROI) analyses. Add-on experiments pointed to bias in Mn2+ accumulati! on towards projection terminals, suggesting that our mapping was mostly formed by projection sites of the originally activated structures. This is corroborated by in-depth analysis of MEMRI data after WCM learning showing mostly downstream targets of the hippocampus. These differ between fornical afferences from vCA1 and direct innervation from dCA1/iCA1 (for PL), and structures along the longitudinal association bundle originating in vCA1 (for RL). To elucidate the pattern of Mn2+ accumulation seen on the scans we performed c-fos expression analyses following learning in the WCM. This helped us identify the structures initially activated during spatial learning and its underlying connectivity to establish the matrix. Finally, to test the causal involvement of these structures we inhibited them (through DREADDs) while mice performed in the WCM task. We also focused on the causal involvement of the mPFC-HPC circuit on strategy switch during WCM learning. We believe that this study might shed light into new brain structures involved in spatial learning and strategy switch and complement the current knowledge on these circuits’ connectivity. Moreover, we elucidated some functional mechanisms of MEMRI, clarifying the interpretation of data obtained with this method and its possible future applications.

Micro-algae greatly influence our oceans and have shaped the history of our planet. Recently we have come to realize that bacteria interact with micro-algae in various ways, ranging from pathogenicity to mutualism. My research investigates physical and chemical interactions between micro-algae and bacteria across multiple scales; from the chemical crosstalk to the influence these interactions have on the marine environment.

In my talk I will introduce Emiliania huxleyi, the most prevalent micro-alga in modern oceans. I will discuss the role of bacteria as hidden farmers that control the life cycle of algae, determining how fast algae will grow and how fast they will die. I will link laboratory findings to work conducted at sea and demonstrate the importance of these findings in climate reconstructions.