Pros and Cons of Fiber Photometry
Fiber photometry is a system where light is projected to optical fibers paired with a cannula implanted in the brain or directly and the light can activate the optogenetic actuators or encode reporters genetically after which light is projected back along the same fiber but is separated from the excitation light by mirrors, and has the following advantages.
To kick off on advantages, fiber photometry is simple because its simple formats like single fiber or photodiode allow for taking note of the neuron population without the need of other complex information, making it an easy method of data generation as the required optic components are easily available and analog signals can easily be digitized using materials that are common in neuroscience labs.
Secondly, the weight on the head is at its minimum, going up to a maximum of 10g, because there are no electronics placed on the head.
Thirdly, the system is cost effective, considering that a simple set up only consist of bandpass filters, LED, bandpass filters, fiber mount, fiber, and a detector which can be a cheap photodiode, as the materials.
The other advantage is on less heat generation and it comes about because there are no electronics, that could generate heat and damage the tissues of the animal, on the head.
The other benefit enjoyed by having this system is that it potentially has a fast acquisition rate, considering that the analogue signals from the photodiodes and RMT are digitized at a high frequency that range in kHz. This frequency is quite high enough to detect the action potentials which may be of high interest considering the recent improvements with the genetically encoded voltage indicators (GEVIs).
The last benefit is that the use of thin fiber implants in fiber photometry decreases invasiveness considering that they are 240 to 480 um thin, a figure less than in both micro-lenses and GRIN lenses method that use implants, making this method a less invasive one, and could even go much less but the signal levels and recording area would be compromised.
The first disadvantage is that there are limited commercial options for fiber photometry as it is only a few companies like Amuza Inc that offer these systems, and a few labs that have the technical capability.
The other restriction is the one that comes with the tethering where the fiber implant is connected to detection hardware directly, making it hard to handle chronic recordings and is not allowed by some ethics based authorities.
The last limitation of these systems is the limitation of spatial information as the photometry systems do not offer this information about the area near the probe’s tip but instead offer the data from population in this volume.