Events

 In recent years, groundbreaking research revealed many surprising roles for astrocytes in addition to their well characterized supportive roles, in modulating neuronal activity and even behavior. I will talk on one hand about manipulating astrocytes to alter neuronal activity and behavior and on the other hand about imaging astrocytes in behaving animals.

We chronically imaged CA1 astrocytes using 2-photon microscopy when head-fixed mice were trained mice to run on a linear treadmill and proceed in a virtual environment to obtain water rewards. We found that astrocytic activity persistently ramps towards the reward location in a familiar environment. When the reward location was changed in the same environment or when mice were introduced to a novel context, the ramping was not apparent. Using linear decoders, we accurately reconstructed mice location trajectories in a familiar environment from astrocyte activity alone. This is the first indication that astrocytes can encode position related information in learnt spatial contexts, thus broadening their known computational abilities, and their role in cognitive functions.

To directly and specifically modulate astrocytic activity we employed a chemogenetic approach: We expressed the Gq-coupled designer receptor hM3Dq in astrocytes, which allowed their time-restricted manipulation, and discovered that astrocytic activation is sufficient to induce de-novo long term potentiation, enhance memory allocation and augment memory recall on the following day. I will talk about these published works and about non-published results on the role of astrocytes in Alzheimer's disease

Understanding how cortical circuits give rise to perception-allowing us, for example, to hear and see the world-remains a central challenge in neuroscience. The application of concepts from cognitive science, such as Representational Similarity Analysis, has proven valuable for interpreting large-scale neuronal recordings, including in rodent models. In this work, I present recent efforts from our laboratory to characterize the structure of auditory representations in the mouse cortex and demonstrate how these representations can be used to predict behavioral phenomena such as stimulus generalization and perceptual choice biases. Moreover, leveraging neuronal activity recordings at single-cell resolution, I describe our findings on the circuit mechanisms that organize sound-evoked activity into structured representational maps and maintain their integrity in the face of perturbations, including synaptic volatility and neuronal loss.

Numerous drugs have the ability to alter our perception, cognition, and mood. Some of these compounds, such as ketamine and serotonergic psychedelics, have also shown promise as treatment for mental illnesses. The behavioral effects are often long-lasting, presumably because the drugs act on synapses and dendrites to induce plasticity in the brain. In this talk, I will describe a series of studies from my lab aimed at understanding the mechanism of action of psilocybin, using subcellular-resolution two-photon imaging, in vivo electrophysiology, rabies viral tracing, and other molecular and behavioral approaches in mice. The results provide insights into the drug action of psychedelics on neural circuits.