“In functional optical imaging of neurons, a fluorescing indicator (typically a protein) sensitive to a biomarker of neural activity is introduced to a cell. Examples of biomarkers include voltage, calcium, potassium, glutamate, sodium, etc…When the level of given biomarker changes, i.e., during or right after a neural firing event, a fluorescent property such as the brightness or emission color of the indicator changes as well. At each image frame, the tissue is illuminated with light at a specific wavelength, and any fluorescing indicators have a probability of raising their energy level. When the energy level falls back to the lower-energy state, light at a longer wavelength is emitted and collected by the microscope. The measured value of the collected light thus reflects the value of the biomarker at a given location…in single photon widefield microscopy, an entire plane is illuminated at once, using a camera to collect full frames simultaneously. Widefield microscopy can thus acquire high-resolution videos at kilohertz framerates; however, it is limited in its ability to image deeper regions in highly scattering tissues. Specifically, scattering of light in brain tissue greatly blurs images, requiring optical methods that better localize fluorescence at depth.” ^e71b1a
“Several groups have shown that cortical regions enter a desynchronized state in response to task involvement and low-frequency brain oscillations are suppressed during these times (Figure 4B,C) [66,95]. The desynchronization appears to be related to the probability of movement. These global signal increases are not due to specific task-related events, but rather to task-performance in general.” ^b80b55