Simon Wiegert: All-optical investigation of the brain: from single synapses to neuromodulatory circuits

Abstract 

The brain is organized at multiple levels of complexity spanning several orders of magnitude in space and time. For example, synapses operate at the sub-micrometer scale, while neuromodulatory brain areas coordinate the dynamics of the entire brain. In the temporal domain, information transfer between neurons occurs on the ms scale, while physiological responses of the animal can take seconds to minutes.

In our lab we develop and apply optical methods to study brain circuits at different scales in rodents in vivo and in slices. In my talk, I will present two projects that focus on different circuit levels.

First, I will present a study investigating spine dynamics in the mouse hippocampus. We used optogenetic presynaptic stimulation of CA3 neurons to functionally identify synaptically connected spines on CA1 pyramidal neurons in awake mice using two-photon microscopy. We relate their physiological properties to their lifespan and ask whether the relationship between synaptic strength and synaptic stability, well established in vitro, also holds in the hippocampus of living mice.

In the second part, I will focus on neuromodulatory brain circuits and their control of pupil-related arousal. Changes in arousal shape the brain dynamics that support cognition and are often accompanied by fluctuations in pupil size. The neuromodulatory control of pupil-linked arousal has traditionally been attributed to noradrenergic cells of the locus coeruleus, while the role of other neuromodulatory systems is less clear. Using multiplexed optogenetic and photometric approaches, we unravel the contribution of the dorsal raphe serotonergic system to pupil dynamics.

About the speaker and his research

Simon Wiegert

Host

Johannes Letzkus

Whole program

NeuroForum