Scientists from Harvard, report the development of a new microscope that greatly improves researchers’ ability to study how neurological disorders such as epilepsy and Alzheimer's disease affect neuronal communication.
The microscope is optimised to perform studies using optogenetic techniques that use light to control and image neurons genetically modified with light-sensitive proteins.
This new microscope can be utilised to investigate the effects of diverse genetic mutations on neuronal function.
This Microscope referred as Firefly can image a 6-millimeter-diameter area, more than one hundred times larger than the field of view of most microscopes used for optogenetics.
Instead of studying the electrical activity of one particular neuron at a time, through this sophisticated microscope, a large imaging area makes it possible to trigger the electrical pulses neurons use to communicate and then watch those pulses travel from cell to cell throughout a large neural circuit containing hundreds of cells.
In the brain, each neuron typically connects to one thousand other neurons, so viewing the larger network is important to understanding how neurological diseases affect neuronal communication.
The microscope also collects light extremely efficiently which provides a high image quality and fast speed necessary to watch neuronal electrical pulses that each last only one-thousandth of a second.
The Firefly optical system is optimised for simultaneous photo stimulation and fluorescence imaging in cultured cells.
The microscope achieves 10-fold higher light collection efficiency at its design magnification than the comparable commercially available microscope using the same objective.
The Firefly microscope enables all-optical electrophysiology (‘Optopatch’) in cultured neurons with a throughput and information content unmatched by other neuronal phenotyping systems. This capability opens possibilities in disease modeling and phenotypic drug screening.
This Firefly microscope is designed to stimulate neurons with a complex pattern containing a million points of light and then record the brief flashes of light fluorescence that correspond to electrical pulses fired by the neurons.
Each pixel of the light pattern can independently stimulate a light-sensitive protein. Because the pixels can be many distinct colors, different types of light-sensitive proteins can be triggered at once.
The light pattern can be programmed to cover an entire neuron, stimulate certain areas of a neuron, or be used to illuminate multiple cells at once.
This optical system provides a million inputs and a million outputs, allowing us to see everything that's going on in these neural cultures.
After the stimulation of the neurons, the microscope uses a camera imaging at a thousand frames a second to capture the fluorescence induced by the extremely short electrical pulses. This optical system is highly efficient to detect good signals within a millisecond.
The Firefly microscope uses an objective lens about the size of a soda can rather than the thumb-sized objective lens used by most microscopes to efficiently collect light over a large area.
The researchers demonstrated their new microscope by using it to optically stimulate and record the fluorescence from cultured human neurons. It resolved 85 individual neurons at the same time in a measurement that took about 30 seconds.
After the initial stimulation and imaging, the team was able to find 79 of those 85 cells a second time. This capability is important for studies that require each cell to be imaged before and after exposure to a drug.
In a second demonstration, the researchers used the microscope to map the electrical waves propagating through cultured heart cells. This showed that the microscope could be used to study abnormal heart rhythms, which occur when the electrical signals that coordinate heartbeats do not work properly.
