Snapshot: What is the Pole Test?

The pole test is a common and straightforward test to assess motor coordination in mice. While ataxia might be easy to see in patients, it is not always as apparent in ataxia mouse models. Therefore, this fast and simple test is important for researchers to measure disease severity. It is also important to test the effect of different treatment strategies.

Small experimental mouse is on the laboratory researcher's hand with blue gloves
 Photo used under license by unoL/Shutterstock.com.

How is the pole test performed?

At the beginning of the test, the mouse is placed facing upward on the top of a long pole. The researchers then measure the time the mouse takes to turn around and climb down to the bottom of the pole. A healthy mouse typically takes 10-20 seconds to perform the task. If the mouse struggles and takes a long time to get to the bottom, it suggests that the mouse has motor coordination deficits.

Researchers commonly use the pole test because it’s a quick way to assess coordination in mice, even before the mice show obvious ataxia symptoms. The pole test takes about 5 minutes per mouse. It is thereby much faster than other motor coordination tests, such as the rotarod test, typically performed over multiple days. Another advantage is that the pole test can be repeated on the same mice multiple times. This allows for tracking how a mouse’s motor coordination changes over time.

0 seconds - mouse is at top of a pole facing upward. 5 seconds - mouse climbs to the top of the pole to turn around, so it can face down towards the ground. 10 seconds - mouse has climbed down the pole
Cartoon of mouse performing the pole test. Time is shown in seconds. Image courtesy of Eder Xhako.

How is the pole test used in literature?

One example of the pole test being used in the literature is a study by Nitschke and colleagues. In this study, the researchers identified a small regulatory RNA, miR760, that regulates the levels of ATXN1. ATXN1 is the gene that causes Spinocerebellar Ataxia Type 1 (SCA1). The group showed that injections of miR760 in the brain decreases ATXN1 protein levels in a SCA1 mouse model. The researchers then used the pole test to measure how the treatment with miR760 would affect the ataxia phenotype in the SCA1 model. They found that one month after the treatment the mice displayed improved motor coordination compared to control mice.  

If you would like to learn more about the Pole Test, take a look at this resource by Melior Discovery. You can learn more about other motor coordination tests in our past Snapshots on the Rotarod Test.

Snapshot written by Eder Xhako and edited by Dr. Larissa Nitschke.

Snapshot: What is the International Cooperative Ataxia Rating Scale?

The International Cooperative Ataxia Rating Scale (ICARS) is an assessment of the degree of impairment in patients with cerebellar ataxia. It was developed in 1997 by the Committee of the World Federation of Neurology. The goal of ICARS is to provide a standardized clinical rating score to measure the efficacy of potential treatments. The scale was intended for patients with cerebellar ataxia. But ICARS has also been validated for patients with focal cerebellar lesions, spinocerebellar, and Friedrich’s ataxia.

How Does it Work?

The ICARS is a semi-quantitative examination that translates the symptomatology of cerebellar ataxia into a scoring system out of 100. The assessment is designed to be completed within 30 minutes, and higher scores indicate a higher level of disease impairment. The assessment consists of 19 items and four subscales of postural and gait disturbances, limb movement disturbances, speech disorders, and oculomotor disorders. Detailed descriptions of the scoring metrics are also provided to reduce scoring variability between the examiners.

Advantages and Drawbacks

Since its development, multiple studies have validated the ICARS. It has also been widely used in clinical assessment for ataxia rating of different diseases. One such study accessed 14 instruments of ataxia assessment and identified the ICARS to be highly reproducible and internally consistent.

However, the scale also does not account for some ataxia symptoms, such as hypotonia (muscle weakness), that are difficult to access clinically. Some subscales also have a considerable ceiling effect, where many patients reach the maximum score for a category. This means symptoms are not being accessed past a certain severity.

Doctor writing down patient notes on a clipboard using a checklist while sitting at a desk.
The ICARS is a semi-quantitative examination that translates the symptomatology of cerebellar ataxia into a scoring system out of 100. Photo used under license by eggeegg/Shutterstock.com.

Other Ataxia Rating Scales

The Scale for the Assessment and Rating of Ataxia (SARA) is another semi-quantitative assessment of impairment levels. It consists of only eight items, making it easier to perform for frequent assessments. However, the simplification of the scale excludes some important symptomatology, including oculomotor impairment.

A pilot study has also been conducted for the development of SARAhome, a video-based variation of SARA that can be conducted independently at home, showing promise for the digitization of ataxia assessment.

Another assessment scale that is even more toned-down is the Brief Ataxia Rating Scale (BARS). The scale consists of five items that assess gait, speech, eye movement, and limb mobility, and the estimated assessment time is only five minutes.

All the assessments described above have been validated and each has its own benefits and drawbacks. However, none of them provides the minimal important difference, which is an important clinical measurement used to determine the effectiveness of potential treatment. Therefore, we are still in need of developing better tools for measuring disease impairment in ataxia patients.

If you would like to learn more about ICARS, take a look at this resource by Physiopedia.

Snapshot written by Christina (Yi) Peng and edited by Dr. Hayley McLoughlin.

Snapshot: What is Cerebrospinal Fluid (CSF)?

Public transit may not be the first thing that comes to mind when we think about the brain, but it’s a great way to understand how all the parts of the central nervous system work together. Nutrients, hormones, and other important molecules (the passengers) need to get on and off at different stations to do their work. They might first stop at the large internal chambers within the brain, called ventricles. From the ventricles, they can get to the central canal in the spinal cord, as well as the subarachnoid space. The subarachnoid space is a space between two membranes that surround the brain and spinal cord. It provides a stable structure for a network of veins and arteries.

The passengers are shuttled from station to station by the cerebrospinal fluid (CSF), a clear, colourless fluid that provides the central nervous system with necessary nutrients and hormones while carrying away waste products. CSF also cushions the brain and spinal cord by circulating between layers of tissues surrounding them. The whole public transit system is enclosed: the subarachnoid space and the ventricles are connected to the central canal in the spinal cord, forming a single reservoir for CSF.

Cerebrospinal fluid written in colorful letters under a Stethoscope on wooden background
Photo used under license by Sohel Parvez Haque/Shutterstock.com.

CSF is made by the choroid plexus, a collection of tiny blood vessels called capillaries. Capillaries filter the blood and secrete it into the ventricles. When the pressure of CSF is less than the pressure in the capillaries, CSF flows out and into the ventricles. When the pressure of CSF is greater than that of the bloodstream, the extra fluid is absorbed from the subarachnoid space and into sinuses (large areas filled with blood), where it can flow into the surrounding veins. The blood supply in the central nervous system tightly regulates the movement of molecules or cells between the blood and brain. This blood-brain barrier is crucial for protecting the brain from toxins and pathogens. Dysfunction of this specific system contributes to the development of neurological diseases.

Anatomical labeled scheme with human head and inside of skull, including superior sigittal sinus, ventricles, arachnoid Villi and spinal cord central canal.
Structure of the ventricles and central canal components that contribute to the public transit system. Photo used under license by VectorMine/Shutterstock.com.

Why is CSF Important for Neurodegenerative Diseases?

In neurodegenerative diseases like Spinocerebellar Ataxias, CSF contains molecules that can be used as biomarkers. Biomarkers are disease-specific proteins that change in concentration depending on disease stages. Biomarkers provide information on disease progression, with or without the impact of therapeutics. They are also crucial for understanding how disease processes work and assist in developing treatments.

The development of intrathecal injections, injecting into the central canal for distribution to the central nervous system (for example, spinal anesthesia), has been monumental for administering drugs in neurodegenerative diseases. In other words, not only can the public transit system of the central nervous system be investigated to see what passengers are associated with the disease, but it can be used to deliver “medicine passengers” to the place where the disease occurs.

If you would like to learn more about Cerebrospinal Fluid, take a look at these resources by MedlinePlus and WebMD.

Snapshot written by Kaitlyn Neuman and edited by Dr. Tamara Maiuri.

Snapshot: What is Gait Analysis in Ataxia Mouse Models?

A key role of the cerebellum is to control and fine-tune coordinated movement such as walking. Although walking is an unconscious behaviour, it is actually very complex and requires many systems to work together. The specific mannerisms and patterns of coordinated movement that make up how an individual walks are called gait.

Since ataxia affects cells in the cerebellum, many ataxia patients exhibit a change in their gait. This change can reduce their mobility and be disruptive to daily life. Analyzing gait using behavioural experiments in ataxia mouse models helps researchers to better understand the disease. But how exactly does one study gait patterns in a mouse?

Black rat walking in front of white background
Photo used under license by Eric Isselee/Shutterstock.com.

Traditionally, a researcher measures gait by performing a footprint analysis that uses non-toxic water-coloured paint and a long strip of white paper. The front and back feet of the mouse are dipped into two different colours of paint. Then the mouse then runs across the paper leaving a trail of coloured footprints to be analyzed. This allows for several gait measurements to be taken. From this, the researcher can then determine how ataxia changed the mouse’s gait. For example, a researcher can look at if the mouse takes shorter strides than a healthy control or whether the mouse tends to walk in a more crooked manner.

Although easy to perform, footprint analysis is time-consuming and highly prone to error as the experimenter does all measurements with a ruler by hand after the mouse has run. Since gait is a complex action with many variables, some subtle differences may be difficult to detect this way. Luckily, researchers have developed several digital gait analysis systems, such as the DigiGait, CatWalk, and TreadScan systems. These digital gait devices make use of transparent corridors with cameras underneath that allow the researcher to record the running behaviour of the animal. Researchers then use software to automatically detect and analyze the footprints.

One lab has taken gait analysis even further. They developed a method to detect extremely subtle differences in gait that the human eye cannot detect. This technique, called LocoMouse, was developed by the Carey lab to analyze patterns of limb movements, rather than simply footprints. LocoMouse utilizes artificial intelligence to recognize and analyze the movement of limb, tail, and head position in a walking mouse.

Using this, the Carey lab has shown a significant difference between a healthy mouse and one with ataxia. Most importantly, the method also detects differences between different ataxia mouse models. By uncovering subtle differences in gait, researchers may better understand the different underlying physiological changes in the cerebellum in different ataxias.

It should be noted that a key pitfall of studying gait in mice is that they are four-legged while humans walk on two legs. This is important, and means that the variables that affect gait in a mouse will be different than those of a human. There may not be a direct correlation between gait changes in ataxia patients and gait changes in mice. That being said, gait analysis remains an important tool in the ataxia researchers’ toolbox. It will continue to provide critical insight into how ataxic physiology affects behaviour.

If you would like to learn more about gait analysis in mice, take a look at these resources by the Noldus Information Technology and Mouse Specifics Inc.

Snapshot written by Eviatar Fields and edited by Dr. Chandana Kondapalli.

Snapshot: What is the Morris Water Maze Test?

Spinocerebellar ataxias (SCAs) are well known for worsening motor coordination symptoms caused by the degeneration of the cerebellum. Yet, increasing reports indicate that broader changes are occurring in the brains of some SCA patients. This includes changes in the hippocampus, a brain region critical for learning and memory. One way to test learning and memory in mice is the Morris Water Maze Test. Researchers use this test on SCA mouse models to investigate how and when learning and memory symptoms arise. More importantly, we can also use this test to evaluate the effect of potential treatments on learning and memory.

white mouse swimming with its head poking up above the water
Although mice can swim quite well, they don’t like swimming. The Morris Water Maze takes advantage of this to test the learning and memory of mice. Photo used under license by Aleksandar Risteski/Shutterstock.com.

The Morris Water Maze consists of a large circular pool of opaque water. A platform is placed in the pool just under the surface of the water so that the mouse won’t be able to see it. Though mice are good swimmers, they don’t particularly enjoy swimming. Mice will always attempt to find the platform as quickly as possible. Shapes on the walls around the pool help the mice orient themselves within the pool (first panel in the figure below).

The first time a mouse swims in the pool (second panel in the figure), the mouse tends to swim aimlessly around until they eventually find the hidden platform. Each subsequent time the mouse swims in the pool, the mouse will get better and better. Using the shapes on the wall to help identify where they are in the pool, the mouse will eventually learn and memorize the platform’s location.

First day, mouse does not know wehere the plaform is an swims a lot. Second day, the mouse still swims a while but remembers where the platform is. On the last day, the mouse knows where the platform is and goes right there.
The three steps in the Morris Water Maze. Image made by Larissa Nitschke use BioRender.

As that happens, they will be better and better at the task. Eventually, the mice will swim immediately to the platform when placed in the pool (third panel in the figure). Researchers can measure this improvement by measuring how much time it takes the mouse to reach the platform and the length of its path to the platform. Additionally, to assess the strength of the memory, researchers can take out the platform from the pool in what is called a “probe trial”. Mice that spend more time in the area where the platform used to be are considered to have built the strongest memories of that location.

As is the case for some SCA mouse models, mice with impaired learning and memory have more difficulty learning and remembering the correct location of the platform. As a result, they spend a longer time searching for and swim longer distances to the platform. Overall, they display a poorer improvement over time. By using the Morris Water Maze Test on SCA models that receive different treatments, scientists can then further test which therapy could improve their learning and memory symptoms. Therefore, the Morris Water Maze Test may help identify new therapeutic strategies to treat learning and memory problems in patients.

If you would like to learn more about the Morris Water Maze, take a look at these resources by the Scholarpedia and JOVE.

Snapshot written by Carrie Sheeler and edited by Dr. Larissa Nitschke.