Scientists at the University of Colorado have created a tiny, lightweight microscope, dubbed “MiniVolt,” capable of recording neuronal activity in moving animals at unprecedented speeds. This innovative instrument allows scientists to gain a more complete picture of how brain cells process information during natural behavior. Details of MiniVolt were published in the journal Biomedical Optics Express.
Most existing miniature microscopes typically track slow calcium signals. However, MiniVolt’s key advantage is its speed: it can capture the neurons’ electrical spikes at hundreds of frames per second. This is essential for detecting the exact moment of neuronal activation, as well as the “quiet” signals that accumulate in neurons prior to the final activation.
The microscope is designed to capture images of genetically encoded voltage indicators (fluorescent dyes) through a small window placed in the skull while the animal is awake.
The electrical signals of neurons, called action potentials, are extremely fast, occurring in milliseconds. Due to this speed, seeing these signals has previously been difficult, requiring large, heavy equipment.
The creators of MiniVolt solved this problem by:
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Developing a compact and efficient lens system (with a high numerical aperture) that collects a large amount of light. This helps them see even small changes in signals.
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Pairing this system with a high-speed sensor (camera).
This combination made it possible for the microscope to reliably record both the electrical “spikes” (moments of activation) and the small, initial electrical changes.
Key Features of MiniVolt:
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Weight: 16.4 grams.
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Frame Rate: Approximately 500 frames per second.
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Field of View: 250 microns.
The researchers paired the microscope with the state-of-the-art voltage indicator, Voltron2. Experiments conducted on mice demonstrated that the recordings obtained with MiniVolt are comparable to the signal quality of standard microscopes, ensuring reliable measurement of action potentials in individual neurons.
The team anticipates that the increased understanding of how neural circuits operate will ultimately facilitate the development of new treatments for neurological disorders and neurodegenerative diseases.
Currently, the researchers are working on further reducing the microscope’s weight to enable its use in shrews, which are often utilized to study human diseases.
