Measuring neuronal population activity using 3D laser scanning.

Area of Science:

• Neuroscience
• Biophysics
• Optical Imaging

Background:

• Understanding neural network function requires 3D activity measurements from large cell populations in vivo.
• Standard laser-scanning microscopy is too slow for capturing dynamic neural activity.
• High temporal resolution is crucial for observing fast neural processes.

Purpose of the Study:

• To develop a protocol for fast 3D calcium imaging in the living brain.
• To enable the measurement of neural network activity from large cell populations with high temporal resolution.
• To overcome the speed limitations of conventional laser-scanning microscopes.

Main Methods:

• Utilized mechanical laser scanning with galvanometric mirrors and a piezoelectric focusing element.
• Generated 3D scan trajectories using a constrained, sinusoidally swinging microscope objective.
• Achieved 3D line scans to sample homogeneously within a defined observation volume.

Main Results:

• Enabled 10-Hz temporal resolution for population calcium signals from hundreds of neurons and glial cells.
• Successfully imaged within cuboidal volumes with side lengths of approximately 250 µm.
• Demonstrated the technique's ability to capture local network activity by targeting cell bodies.

Conclusions:

• This 3D laser-scanning technique provides a novel method for observing in vivo neural network dynamics.
• The approach allows for direct observation of population activity in substantial cell populations within intact neural tissue.
• It facilitates the inference of local network activity from somatic calcium signals, aiding in understanding neural circuit function.