Development of a head-mounted miniscope for simultaneous volumetric microscopy and optogenetic stimulation in freely moving rodents

• Applicants: Professor Dr. Caglar Ataman; Professorin Dr. Marlene Bartos; Professorin Dr. Ilka Diester
• Subject Area: Microsystems ; Cognitive, Systems and Behavioural Neurobiology ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 555645878

Recent advances in deep brain imaging and targeted neural stimulation techniques have provided unprecedented insights into the inner workings of the mammalian brain. A key breakthrough has been two-photon microscopy (2P microscopy), which, with its ability to penetrate up to 700 µm into brain tissue and visualise specific neuronal activities by imaging calcium-dependent markers of neuronal function, is proving indispensable for unravelling local neuronal circuits. Optogenetics, on the other hand, is a neural manipulation technique based on light-responsive membrane proteins that allows the selective triggering or suppression of genetically engineered cells using light of precise wavelengths. The advent of holographic stimulation for the first time allowed the activation of up to 100 selected neurons either simultaneously or in pre-defined temporal sequences. However, both 2P-microscopy and holographic optogenetic stimulation (HOS) currently rely on complex and cumbersome microscopy setups that are tied to head-fixed, making it impossible to simultaneously observe and manage unrestricted animal behaviour. To address this crucial gap, 2PMOS proposes an innovative functional microscope that can be attached to the head of a rodent, opening up previously unattainable avenues for neuroscience. This new instrument will have two ground-breaking capabilities, enabled by new microsystem engineering methods adapted from multi-modal endomicroscopy. The first will be its capability of simultaneous volumetric 2P-microscopy and optogenetic 2P-stimulation of neural activity in cortical layers. This unique combination will allow neuroscientists to probe the intricate neural processes within cortical layers while exerting precise control over neural responses. 2PMOS will also offer an unprecedented penetration depth for 2P-miniscopes, enabling the visualisation of deep neuronal activity within the hippocampus, a feat previously unattainable in freely-moving animals. Complementing the technical advances, the project also includes the establishment of the necessary hardware and software infrastructure for the seamless operation of the instrument in relevant environments. This will be followed by a carefully planned series of animal studies to validate the functionality and potential of the ground-breaking new tool. Specifically, we will target the following neuroscientific questions related to learning and memory processes that remain at the heart of current systems neuroscience: (1) Can learning-related memory traces generated in head-fixed and freely moving animals be compared? (2) Does neural activity differ between the two conditions? (3) Can animals transfer learned information from one condition to the other? (4) Does excessive exposure to virtual environments alter neural activity compared to exposure to real environments? The last question, in particular, has major implications for society due to the increasing use of virtual tools in our daily lives.

• DFG Programme: New Instrumentation for Research