Optical detection of neuron connectivity by random access two-photon microscopy.

Area of Science:

• Neuroscience
• Systems Neuroscience
• Optical Imaging

Background:

• Understanding neuronal network connectivity is vital for brain function.
• Traditional electrophysiology lacks spatial resolution, while calcium imaging has insufficient temporal resolution for action potential detection.
• Existing methods cannot reliably determine the direction of synaptic connections.

Purpose of the Study:

• To develop a novel optical recording technique for high-fidelity detection of action potentials.
• To resolve the directionality of synaptic connections within neuronal networks.
• To provide a new perspective on the functional architecture of neural circuits.

Main Methods:

• Utilized a voltage-sensitive dye (DiO/DPA) combination with fast kinetics.
• Employed a custom-made random-access two-photon microscope for rapid scanning.
• Performed long-duration recordings (up to 100 minutes) from cultured hippocampal neurons.

Main Results:

• Successfully resolved individual action potential events from multiple neurons.
• Cross-correlation analysis enabled clear identification of synaptically connected neuron pairs.
• Demonstrated reliable detection of neuronal firing events using voltage-sensitive dye, outperforming calcium indicators.

Conclusions:

• Long-duration optical voltage recording with voltage-sensitive dyes offers superior fidelity compared to calcium imaging.
• This advanced method allows for the determination of synaptic connection direction.
• The technique provides unprecedented insights into the functional organization of neuronal networks.