Fiber Photometry: An Introductory Guide to This Revolutionary Technique, Part 2

Fiber Photometry: An Introductory Guide to This Revolutionary Technique, Part 2

In part one of this series, we introduced the fundamental concepts of Fiber Photometry and discussed how this revolutionary technique is advancing the field of neuroscience. In part two, we will transition into discussing the inner workings of Fiber Photometry and how the process works on a technical level.

Part 2: How Does Fiber Photometry Work?

Understanding the Components

To better understand how Fiber Photometry allows researchers to record neural activity in real time, it is first important to break the typical Fiber Photometry system down into its individual components. From the hardware of the optical components, the surgical implantation of cannulae, and the software based data analysis, these must all come together in order to produce quality data. There are 4 key components for a working Fiber Photometry system, each of which will be discussed briefly below:

1. Light Source

The choice of light source is pivotal in ensuring accurate and reliable fiber photometry measurements. It must emit a precise wavelength of light that matches the excitation spectrum of the fluorescent indicator being used. Additionally, considerations for light intensity and stability are crucial. A stable and well-calibrated light source guarantees consistent excitation, which directly impacts the quality and reliability of the recorded signals. Advanced light sources may also offer modulation capabilities, enabling researchers to perform more sophisticated experiments by synchronizing light pulses with specific events or behaviors.

2. Optical Fiber

The optical fiber acts as the conduit through which the excitation light travels from the source to the target area within the brain. It must be carefully selected based on factors such as numerical aperture, core diameter, and material composition. A higher numerical aperture allows for better light-gathering efficiency, while a larger core diameter permits more flexibility in positioning the fiber. Additionally, specialized coatings can enhance the fiber’s durability and protect against potential damage during implantation or use. Researchers must also consider factors like numerical aperture matching with the collection optics and the compatibility with chosen light sources.

3. Photodetector

The photodetector is responsible for capturing the emitted fluorescent signals from the neural tissue. It must be highly sensitive to the specific wavelengths emitted by the fluorescent indicator. Additionally, factors like quantum efficiency, noise levels, and dynamic range are critical considerations. A high quantum efficiency ensures that a larger proportion of emitted photons are converted into electrical signals, enhancing the detector’s sensitivity. Low noise levels are crucial for detecting weak signals amidst background noise, while a wide dynamic range allows for accurate recording of both strong and weak signals without saturation or loss of resolution.

4. Fluorescent Indicator

Genetically encoded fluorescent indicators are the cornerstone of fiber photometry. These indicators are typically proteins engineered to fluoresce in response to changes in calcium ion or neurotransmitter concentrations, providing a direct readout of neuronal activity. Choosing the right indicator is a crucial decision, as it determines the sensitivity and specificity of the measurements. Factors to consider include the indicator’s excitation and emission spectra, its target affinity and kinetics, as well as potential interactions with other cellular processes (Shen et.al. 2020). Additionally, researchers must ensure that the chosen indicator is compatible with the chosen excitation wavelength and photodetector.

Expression of Genetic Sensors

Advances in genetic engineering have been hand in hand with advances in imaging techniques. As such, researchers are now able to express complex fluorescent protein structures in a highly efficient cell type specific manner, allowing for unprecedented specificity when collecting neural activity data. Achieving success in fiber photometry relies heavily on obtaining optimal expression of genetically encoded fluorescent indicators (GEFIs) within your selected animal model. This critical step determines the quality and reliability of the fluorescent signals that will be measured, ultimately influencing the accuracy of the neural activity data obtained. Now we will briefly discuss the two primary methods for achieving optimal GEFI expression: viral expression and transgenic mouse models.

Day-Cooney et al., (2023) J.Neurochemistry.

  • Viral Expression: One approach to achieve targeted GEFI expression involves viral expression, a technique that involves injecting a specially engineered virus carrying the genetic code for the desired GEFI directly into the brain. This method offers the advantage of precision, allowing researchers to target specific cell types or regions within the brain for GEFI expression. However, the effectiveness of viral expression hinges on a critical consideration: virus selection. Different types of viruses are commonly used in neuroscience research, each with specific characteristics that make them valuable tools for manipulating and studying neural circuits. Adeno-Associated Viruses (AAVs) are widely employed due to their efficiency in transducing neurons without causing significant damage. While lentiviruses are useful for studies requiring prolonged expression of genetic constructs as they can integrate their genetic material into the host genome. Additionally, Retrograde Rabies Viruses have gained significant attention in recent years (Osakada et al. 2011). These modified viruses are particularly valuable for tracing neuronal pathways. By introducing a genetically engineered rabies virus into a specific target area, researchers can trace its path backward to identify the upstream neurons that project to that region. This technique provides crucial insights into the connectivity and communication between different brain regions, offering a powerful tool for mapping neural circuits. Finally, achieving the desired level of expression requires careful consideration of virus dilution. Dilution significantly influences the balance between optimal GEFI expression and potential drawbacks such as background noise or over-expression, which can result in inaccurate data interpretation. Researchers must carefully fine-tune the concentration of the injected virus to strike the right balance between signal intensity and stability in order to collect reliable neural activity data.
  • Transgenic Mouse Models: Another effective strategy involves utilizing transgenic mouse models. These models are genetically engineered to express GEFIs uniformly across the entire brain or in specific brain regions. This approach offers versatility and convenience, as it eliminates the need for viral injections and allows researchers to explore neural activity across multiple brain areas simultaneously. However, it’s important to note that transgenic models may have variations in GEFI expression levels between different brain regions. Researchers must account for these potential differences when analyzing the data and drawing conclusions about neural circuitry and behavior. Furthermore, the choice of transgenic mouse model is a critical aspect of the experimental design. Different lines may have distinct patterns of GEFI expression, allowing researchers to select models that align with the specific brain regions or cell populations under investigation. Additionally, advancements in genetic engineering techniques have enabled the development of more sophisticated transgenic models, including those that allow for cell-type-specific expression of GEFIs. These models provide an even higher level of specificity, allowing researchers to target specific neuronal populations with precision.

Implanting the Optical Cannula

In fiber photometry, successful expression of GEFIs represents a critical step, laying the foundation for the subsequent implantation of an optical cannula. This step is of paramount importance as it provides access to the fluorescent signal emitting from specific regions of interest within the brain. Optical cannulas are instrumental in this process, capturing the emitted light and conveying it to a photodetector for subsequent analysis. Their compact design serves to minimize tissue disruption and damage during the implantation, preserving the neural tissue’s integrity.

The significance of mitigating tissue damage and inflammation during the implantation process is crucial in neuroscience research, particularly in techniques like fiber photometry. Inflammation and tissue trauma can trigger a cascade of unintended physiological responses, including immune activation and the release of signaling molecules that have the potential to impact neighboring cells and brain regions. This phenomenon introduces unwanted signals and noise into the recorded data, complicating the task of accurately interpreting the neural activity of interest. Therefore, attention to detail and precision in the implantation of optical cannulas are imperative to uphold the integrity of the experimental system. Things to consider are locating precise stereotaxic coordinates, using fine tip micropipettes for injection, slow and controlled placement of the injection needle and injection rate, controlled viral delivery using a pneumatic pump, minimizing total volume injected, and implementing a post-injection wait period. This diligence ensures minimal tissue damage ensuring that subsequent fiber photometry measurements yield precise, reliable insights into neural dynamics. Join us for part 3, where we will discuss novel approaches and recent innovations in the realm of Fiber Photometry.

If you missed Part 1 of this introduction to Fiber Photometry take a look here. Learn more about Amuza’s cutting-edge Wireless Fiber Photometry system, TeleFipho.

Learn more about Amuza’s cutting-edge Wireless Fiber Photometry system, TeleFipho.

References

Shen et al., (2020) ‘Engineering genetically encoded fluorescent indicators for imaging of neuronal activity: progress and prospects’, Neurosci. Res., 152, pp. 3-14. doi: 10.1016/j.neures.2020.01.01

Osakada et al., (2011) ‘New rabies virus variants for monitoring and manipulating activity and gene expression in defined neural circuits’, Neuron, Aug 25;71(4):617-31. doi: 10.1016/j.neuron.2011.07.005.

Day-Cooney et al., (2023) Genetically encoded fluorescent sensors for imaging neuronal dynamics in vivo. J. Neurochemistry, 164, 284–308. Available from: https://doi.org/10.1111/jnc.15608

Using the ELG-2 Wireless EEG system to examine the role of the claustrum in cortical slow-wave activity

Using the ELG-2 Wireless EEG system to examine the role of the claustrum in cortical slow-wave activity

During sleep and quiet wakeful states, the neocortex exhibits large-scale slow-wave (SW) activity. The synchronous generation of the neocortical SWs implies the existence of an as-yet unknown spatiotemporal coordinating mechanism with long-range afferents driving inhibitory interneurons.

The Yoshihiro Yoshihara lab at the RIKEN Center for Brain Science sought to examine the role of the claustrum in this brain-wide cortical activity. In their recent report, The claustrum coordinates cortical slow-wave activity; the authors report that the claustrum is the neural network mechanism that facilitates the synchronous neocortical SWs.

To assess the role of the claustrum in this phenomenon, the authors generated a claustrum-specific Cre-expressing transgenic mouse line. The use of in vitro and in vivo techniques enabled the genetic visualization and manipulation of a subpopulation of claustral glutamatergic neurons.

Here, we address the author’s use of the ELG-2 Datalogger Wireless EEG system- a telemetry system designed to reduce the behavioral restrictions and data noise associated with the traditional telemetry systems.

Tethered EEG:
Traditional in vivo electroencephalography (EEG) experiments use a tethered system, where implanted electrodes are connected to the recording platform through a long cable. These systems, however, are plagued with issues due to the very nature of the tether. The long cables often tangle and restrict the animal, disrupting natural behavior. If the tether gets caught or the animal’s movement pulls too hard, damage to the cable or complete disconnections are possible. Damaged or frayed cables will cause data artifacts while complete disconnections will result in an abrupt end to data collection and injury to the animal.

Furthermore, tethered EEG equipment also suffers from poor signal-to-noise ratios. The tether acts as an antenna which can pick up electrical noise from AC power lines, motors, and other outside sources. These artifacts within the data complicate processing and interpretation. While Faraday cages may limit the noise from outside sources, they do not shield against the motion artifacts that are caused by movement of the tether itself.

Another issue evident in the traditional tethered EEG experiments is the limitation of animal scale-up. Additional tethers pose the threat of tangling and interfere with natural animal behavior as well as social interaction. Excessive environmental and motion artifacts are particularly evident when simultaneously recording EEGs from multiple rodents in close proximity. The use of Faraday cages inhibits the study of social interactions and ultimately takes up more physical space per animal in the laboratory. Limitations in the software and hardware systems of tethered EEG also reduce the possibilities of animal scale-up.

Wireless EEG:
The Amuza ELG-2 Datalogger Wireless EEG system enables researchers to wirelessly record EEG, electromyography (EMG), and local field potential (LFP) activity in freely moving animals. Designed to remove motion artifacts, the wireless lightweight headstage is small enough to sit on the head of an animal without disrupting natural behavior. The simple and flexible electrode design connects directly to a well-shielded headstage. Not only does this system reduce electrical noise from outside sources, but it also reduces implantation surgery time and complexity compared to the traditional PCB-based electrodes. The headstage is also easily removed and attached to the electrode implants, allowing researchers to interchange the device between animals. Since data is directly stored onto a microSD card, there is no signal interference across devices and animal scaleup is unlimited.

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Wirelessly recording EEG in freely moving animals has unlocked numerous possibilities for discoveries in sleep, seizure, and other neurological disorder research studies. This has previously been limited to tethered recording systems, which can alter animal behavior and add noise to data.

Wireless EEG eBook

The ELG-2 Datalogger Wireless EEG system is also customizable to meet the demands of the researchers and their individual experimental needs. The standard ELG-2 Datalogger Wireless EEG set is designed to record from four channels but can be altered to record from as few as two, to as many as seven. The standard set has two screws for EEG, two silver wires for EMG, and one screw for reference and ground. If you want to record LFP activity, electrode configurations can be custom made to fit your experimental needs. Furthermore, the electrode set uses a universal 1.27 mm pitch pin and socket connector, making it easy for you to create your own electrode sets. The standard sampling frequency is 100 Hz but can be increased to 200 Hz.

In the Narikiyo, K. et al study, the authors opted to use two customized ELG-2 Datalogger Wireless EEG systems to simultaneously record from two mice. The headstage was designed to record from 5-channels with a 200 Hz sampling frequency. They created their own electrode configuration to record LFPs in the neocortex and monitor sleep/wake states with EEG and EMG recordings. Their setup included three perfluoroalkoxy-coated stainless steel wires for LFP recordings, one screw for EEG, one silver wire for EMG, and one screw for ground and reference.

Experimental Design:
To assess the role of the claustrum in the synchronous generation of widespread neocortical SW activity during sleeping and awake rest states, the authors generated a claustrum-specific Cre-expressing transgenic mouse line.

Male and female mice, one to eight months of age, were used for anatomical experiments and slice physiology to determine the neural network connectivity between the claustrum and the neocortex. Male mice, two to six months of age, were used for in vivo EEG and optogenetic experiments to assess the underlying temporal relationship between the claustrum and the neocortex with respect to SW activity.

The authors performed an in vivo loss-of-function experiment with the ELG-2 Datalogger Wireless EEG system in freely moving mice to examine the necessity of the claustrum for synchronized cortical SW generation. The Cre-positive claustral neurons were selectively ablated via AAV-mediated injection of the Cre-dependent diphtheria toxin A subunit (DTA). Control mice were injected with GFP.

The ELG-2 Datalogger Wireless EEG electrodes were surgically implanted into anesthetized mice, 2 weeks after injection. The LFP wire electrodes were implanted into the deep layers of the right prefrontal cortex (coordinates: AP: 2.5–2.8, ML: 0.5–1.5, DV: 1.0–1.5), anterior cingulate cortex (coordinates: AP: 1.0, ML: 0.5, DV: 1.3), and parietal cortex (AP: −2.0, ML: 1.5, DV: 0.4). The EEG electrode and EMG wire electrode were implanted into the left parietal cortex (AP: -2.0; ML: 2.0) and neck muscle, respectively. The electrical ground and reference electrode was implanted above the cerebellum.

Recordings were performed in the home cage under a 12-hour light/12-hour dark cycle, 6 to 12 weeks after AAV injection. Mice were acclimated to the weight and presence of the headstage with a dummy device overnight before experimentation. LFPs were recorded to detect SW activity in the deep layers of the cortex. The EEG and EMG electrodes were used to monitor the behavioral states of the mice.

Results
The generation of a genetic neural circuit map of the claustrum’s input and output connectivity revealed widespread reciprocal connections between the Cre-expressing claustral glutamatergic neurons and cortical areas.

In vitro whole-cell patch clamp recordings during optogenetic stimulation demonstrated that photostimulation of claustral neurons evoked excitatory postsynaptic potentials in all types of neurons but predominantly drove spike responses in inhibitory interneurons.

In vivo EEG in head-fixed mice revealed that the claustral glutamatergic neurons were more active during SW periods as compared to non-SW, suggesting that the claustrum activity is more closely related to SW activity than it is to the sleep state. When combined with optogenetic stimulation, in vivo EEG revealed that claustrum-induced SW activity via photostimulation mirrors spontaneous SW activity and suggests that the claustrum can regulate SW generation in neocortical areas through the coordinated activation of inhibitory interneurons.

The recorded LFPs during the loss of function experiment with the ELG-2 Datalogger Wireless EEG system revealed that the claustral-neuron-ablated mice showed a dramatic attenuation of the SW activity during SW sleep and awake rest as compared to the control. The authors indicate that the results demonstrate the importance of the claustrum in the synchronous coordination of cortical SW activity.

Discussion
Through the genetic visualization and manipulation of the Cre-expressing claustral glutamatergic neurons, the authors were able to identify the claustrum as a brain structure that can serve as the spatiotemporal mechanism that generates the synchronous neocortical SW activity during sleep and awake rest.

The use of the ELG-2 Datalogger Wireless EEG system allowed the authors to wirelessly record SW activity in the neocortex while monitoring the behavioral states of mice. This system promotes the natural behavior of animals while removing the artifacts commonly associated with traditional tethered EEG experiments. The ability to accurately and efficiently record in vivo telemetry data from freely moving animals without behavioral restrictions enables reproducible data acquisition across experiments and allows future research to build upon the established findings.

Narikiyo, K., Mizuguchi, R., Ajima, A., Shiozaki, M., Hamanaka, H., Johansen, J.P., Mori, K., Yoshihara, Y. The claustrum coordinates cortical slow-wave activity. Nature Neuroscience, 2020;23(6): 741-753. doi:10.1038/s41593-020-0625-7

Amuza Wireless Neuroscience
The traditional tethered systems do not only impose barriers in EEG experiments, they also hinder natural animal behavior and produce data artifacts during in-vivo optogenetic and fiber photometry experiments. The Amuza TeleOpto and TeleFipho systems are easy to use wireless systems, designed for reproducibility and animal comfort.

5 Tips for Successful EEG and EMG Recording in Freely Moving Mice and Rats

5 Tips for Successful EEG and EMG Recording in Freely Moving Mice and Rats

Sleep research frequently relies on EEG (Electroencephalography) and EMG (electromyography) to discern between different sleep and wake states of the mice and rats used as models. The combination of EEG and EMG is powerful enough to discern not just between the different sleep and wake states, but also between the different stages within sleep and wake states.

In this article, we’ll show you how to reliably record EEG and EMG, with neural stimulation in untethered mice and rats.

EEG is also frequently used to record seizures in mouse and rat models of epilepsy, as well as for studying Huntington’s, Alzheimer’s, schizophrenia, migraine, and other disorders. Typically epidural EEG, aka Electrocorticography (ECoG), where the electrodes are placed directly on the cortex, is used.

1. Consider alternatives to tethers in EEG experiments

Equipment choice affects the success or failure of many EEG experiments. Typically, a tethered system is used, with implanted electrodes connected via a long cable to the recording system. Tethers are often the weak link in EEG experiments. Tethered mice become tangled, especially during seizures, severely limiting normal mice behavior. Slip rings, swivels, and balance arms can help prevent tangling, but mice do not create enough torque when they move to rotate many slip rings. Rats also chew on the cables, frequently damaging or destroying them. Complete disconnections also occur when animals pull on the cables, ending the recording and injuring the animals.

As an alternative to tethered animals, wireless EEG equipment helps reduce altering the normal actions of freely moving and behaving animals. Wireless EEG equipment also reduces the limitations of environments available for studying behavior.

 

2. Eliminate electrical noise and artifacts

Tethered EEG equipment often suffers from poor signal-to-noise ratios. Cables act as antennae, picking up electrical noise from AC power lines, motors, and other sources. This leads to artifacts in the data, complicating interpretation. Faraday cages can limit noise from external sources but become awkward and inconvenient when working with multiple animals. Faraday cages also do not protect against motion artifacts caused by the movement of the tether itself. Even connecting a preamplifier directly to the electrodes, so that amplified signals are sent through the tether, does not always eliminate AC and other noise from the system. A preamplifier can also make the system too heavy for use with mice. Additionally, multiple tethered systems in the same room can also lead to interference and noise.

3. Eliminate system limitations that affect your EEG experiment

The issues surrounding tethers have led to a shift to wireless EEG equipment. Wireless inductive telemeters addressed many of the problems of tethered systems, but bring with them other challenges.
Limits to Size and Type of Environment – Inductive systems require the animals to remain directly on top of a special charging pad or platform, limiting the size and type of environments which can be used during behavioral research.
Limits to Channel Bandwidth – Some telemetry systems also limit the bandwidth or number of channels available for EEG signals.
Limits to Sensitivity and Scale Up – Surprisingly, some wireless systems are still vulnerable to AC noise, possibly because of inadequate shielding. The number of frequencies available also limits wireless systems using radio to send data, capping the number of animals that can be monitored in one room.

As an alternative, researchers can use a lightweight data logger small enough to sit on the head of a mouse. The electrodes connect directly to the well-shielded data logger, preventing electrical noise from power lines.
Since data is stored onboard using a microSD card, there is less chance of signal interference and scaleup to more animals is unlimited.

The rechargeable data loggers are as small as 2g, allowing mice to behave normally during chronic recording sessions in any size cage or chamber.

 

4. Reduce electrode implant surgery time and complexity

PCB-based electrodes can make implantation surgery more complicated and time-consuming, leading to higher failure rates. A simple, flexible electrode design, such as the one shown below, makes for easy implantation.

The Amuza standard electrode set uses a universal 1.27 mm pitch pin and socket connector, making it easy to create your own electrode sets. Our standard electrode has two screws for EEG, two silver wires for EMG, and one screw for GND.

5. Look for universally compatible EEG data processing and analysis

As part of a research team, or in a collaborative setting, it is important to consider using EEG equipment that makes for seamless sharing of data. Proprietary data formats and readers can complicate sharing and processing your data. Incompatible systems can become an unexpected expense when you need one software license to run your EEG system and another for the PC in your office where you process the data.

Amuza’s EEG data analysis software combats these unplanned expenses in four ways:

  1. Amuza’s EEG data analysis software is included with the system free of charge
  2. Amuza’s EEG data analysis software can be installed on multiple computers without extra licensing fees.
  3. Through an intuitive platform, Amuza’s EEG data analysis software enables a quick overview of your data, as well as

    filtering and simple (FFT-based) alpha, theta, delta power calculation. It can also create hypnogram plots for sleep analysis. 

    4. Data from Amuza’s EEG data analysis software is also compatible with MatLab and Octave and can be exported to EDF or TXT. No dedicated reader or software is required.

Amuza’s EEG data analysis software combats these unplanned expenses in four ways:

  1. Amuza’s EEG data analysis software is included with the system free of charge
  2. Amuza’s EEG data analysis software can be installed on multiple computers without extra licensing fees.
  3. Through an intuitive platform, Amuza’s EEG data analysis software enables a quick overview of your data, as well as

filtering and simple (FFT-based) alpha, theta, delta power calculation. It can also create hypnogram plots for sleep analysis. 

4. Data from Amuza’s EEG data analysis software is also compatible with MatLab and Octave and can be exported to EDF or TXT. No dedicated reader or software is required.

There is no other system which meets my requirements for wireless operation, channel count, and usability with mice.

Yet-to-be-published ELG-2 User

Share your work! Tell us how you have struggled with tethered research animals in the comments below.

2021 Optimizations to Wireless Fiber Photometry and Wireless Optogenetics Products, Based on Customer Feedback

2021 Optimizations to Wireless Fiber Photometry and Wireless Optogenetics Products, Based on Customer Feedback

Amuza has spent the last year listening to researchers who use optogenetics and imaging techniques with mice and rats and learning from their experiences. As customers use our products their suggestions for how to optimize our products have been invaluable, which sent our engineers back to work. The results are six new upgrades, options, and improvements for our wireless products, making them easier to use, allowing experiments to run longer, and providing a better customer experience.

Updates to Wireless Neuroscience Products

1. Removable, Rechargeable Batteries to Keep Experiments Running

One of the first questions researchers ask us about our wireless neuroscience products is how long the batteries will last, since this determines how long the experiment can run before the headstage needs to be swapped for recharging. To date, Amuza wireless neuroscience systems have been powered by integrated rechargeable batteries. We have offered versions with larger batteries, but this does increase the weight.

Our wireless systems are now offered with removable rechargeable batteries in several sizes. The batteries connect using a simple plug: To continue your experiment, just swap the battery for a recharged one. Choose a standard battery for mice (total weight for TeleFipho, 3.3 g), or a larger battery (total weight 5 g) with 60% longer battery life for rats.

TeleFipho headstage (left) and removable batteries (center, right).

2. Wired, but better.

Not entirely an update to our wireless products, but still highly relevant for long experiments and experiments where switching the battery would disturb the animal. Amuza now offers a wired version of our fiber photometry system. Unlike fiber photometry using optical patch cords, the headstage still contains the light source and fluorescence detection system. For the tether: instead of an optical signal, power and the amplified data signal are sent through a slim electrical cable. Because of this, compared to other wired systems, the wired version of TeleFipho does not degrade the signal by passing it through multiple optical connections or a rotary joint on the way to the detector. The cable is also very flexible, and bending it will not introduce artifacts into the signal. Just let us know what type of plug we should use on the cable, and we can make certain it will be compatible with the commutator you choose, preventing the cable from twisting or tangling.

Wired TeleFipho

3. Superior protection from interference for cleaner data on fiber photometry

To optimize the data transmission of our wireless fiber photometry system, we improved the shielding and the antenna on the TeleFipho headstage. This cuts down on both electrical noise in the data, and also makes the radio communication more robust in environments where radio interference has been an issue. In addition to the shielding and antenna improvements, a new directional antenna for TeleFipho provides a great solution for radio interference in more complex environments. If you experienced signal dropouts with TeleFipho’s standard antenna, this antenna should completely eliminate them.

4. New fiber optic cannula sizes for fiber photometry and optogenetics

TeleFipho has now been tested with 200 μm (core) diameter fibers as well as 400 μm. Narrower fibers offer the benefit of causing less physical trauma, as well as being able to target smaller structures. But they collect much less light from the target region, so bright, well expressed fluorescent biosensors are required to get high-quality data. Many of our customers in Japan have now used 200-micron fibers with TeleFipho to detect calcium using newer versions of GCaMP and reported excellent results. We now offer fiber optic cannula with either 200 or 400-micron fibers, cut to the length you specify. The cannula can also be used with our optogenetics system. Please see our blog post on fluorescent biosensors for updated information on sensors used for fiber photometry.

5. Scaling up fiber photometry for more animals

At launch, TeleFipho had four separate radio channels, allowing up to four animals to be monitored in the same room. We added 4 more radio channels to TeleFipho, so now up to 8 systems can be used together simultaneously.

6. Headstage protection chamber prevents equipment damage

Group housing gives animals the opportunity to nibble on or dislodge headstages, plus some cages have wire lids and other surfaces which can catch head-mounted equipment. Our new protection chamber isolates the headstage from the environment but is easy to remove between experiments. We recommend using the protection chamber with rats, non-human primates (NHPs), and other larger animals.

For more information on customizing wireless neuroscience products for your experiments to obtain better data from your wireless system, visit our wireless neuroscience products page.

Which upgrade is the most helpful for your research? What other upgrades would be valuable to you? Leave a comment below.