Anatomical body planes

In the last post we covered the anatomical terms for directions. Now we'll discuss planes - not the flying kind, but planes that divide the body into two. Planes can be important when considering medical imaging, embryology (how an embryo develops) and descriptions of body motion.

Please note that different terminology seems to be used about humans and about non-human animals. Here I focus on the terminology used about animals.

Median plane: Median plane divides the body into the right and left half, exactly from the center. 

Sagittal plane: If one divides the body just off the median plane, that would be called a sagittal plane. It still divides the body into right and left, but not from the center. The halves are not identical anymore.

Dorsal plane: Dorsal plane divides the body to dorsal and ventral areas, cutting lenghtwise through the midsection of the body.

Transverse plane: Transverse plane is a local plane, meaning that it's in the right angle to the axis of the thing we're looking at. If you're looking at a leg, the transverse plane would go from the front of the leg to the back, at the right angle to the leg itself. If you're looking at the body, the transverse plane is from the back to the stomach (at a right angle to the spine).

The planes are used when talking about the entire animal. When talking about a skeleton, two more distinctions can be made. Now we'll have axial skeleton, which comprises of the head, the vertebral column (spine) and the ribcage. Ventrally to the axial skeleton is the appendicular skeleton, comprising of the limbs.

Anatomically correct directions

An old Internet story claims that a 10-year old boy described a cow thus:

"A cow has seven sides: upside, downside, upper side, below side, right side, left side and inside. The head is on the upper side."

He is right, in a way, but the description could be more specific. We could say that the cow has head, body and legs.. but what about the neck? Is that a separate part, or does it belong to the head or the body? 

Also, a cow is easy since we all know how they look like. It's relatively easy to say where the head is (in the front, attached to the neck) or where the hind legs are (under the pelvic area, attached to the body). Alright, but where is the liver in relation to the spleen?  Where's the lump you felt, the one kinda close to the ribs but more to the top, if you look directly at the cow and you're about the same height as the cow? There's a wound in the intestines - where is it? 1".5 meters from the start"?

We need anatomical directions. Words that are unambiguous and describe things in relation to the animal itself. With these words we can describe precisely where something is.

Let's start with the main regions. We can divide the body to regions and cavities (hollow areas). A vertebrate has usually

• A head, with three cavities: 
• nasal cavity or rhinarium (the hollow space in the nose)
• oral cavity (mouth)
• the orbit (which contains the eyeballs)
• The neck, attached to the head
• The trunk, with three cavities: 
• the thorax or thoracic cavity (lung area)
• abdomen (stomach(s) and intestines)
• pelvis (urinary tract and reproductive organs)
• Forelegs
• Hind legs

To get more into detail several specific words are used to describe location. Note that they are not related to the animal's position. Think of the phrase "above the dog's hind legs". If the dog is standing, above the legs is the pelvis. If the dog is sitting, above the legs is his stomach!   

Caudal - Cranial

Caudal means to the direction of the tail (or rump in animals without a tail), and cranial means to the direction of the head. For example, an important blood vessel called caudal vena cava , which goes from the heart to the direction of the tail. They can also be used in the meaning "related to or located in", like cranial nerve are nerves emerging from the brain (cranial region). 

Dorsal - Ventral

Dorsal is to the direction of the back, and ventral to the direction of the stomach. Easy to remember when you think about people who "speak from their stomach" - ventriloquists! 

Distal - Proximal

Distal means moving away from the trunk. This could be to any direction, as long as it's away from the trunk. Proximal is to the direction of the trunk. The hooves of an animal are distal to their body, and the shoulders are proximal to the hooves. 

These words have no meaning on some organisms, such as starfish. For these we could use "peripheral" instead of distal - something away from the center.

Medial - Lateral

Let's again use a hind leg as the example. How do we describe something which is on one side of the leg? Right/left is difficult. Are you facing the animal, is it the animal's right/left, and and what if the animal is on it's side? 

Medial refers to "closer to the midline", i.e. inside of the leg. Lateral is away from the midline, i.e. the outside of the leg. Note that the when you face the animal, the right side of the right foreleg is lateral, but the right side of the left foreleg is medial... Hence, medial and lateral rather than right and left.

With these terms we can now say that the lump is 5 cm caudal and 10 cm proximal to the last rib. Or that the horse has soreness on the left medial forelimb, distal to the knee. Much better than "let me show you, if you squeeze here then OOW it kicked me!"

Sources:

Wikipedia https://en.wikipedia.org/wiki/Anatomical_terms_of_location

Coursera, becoming a veterinarian

Tinbergen's four questions

Animals, just like humans, show behaviors. If you just see a picture without a context it's hard to say what is happening - or why. For example you might see an image of a horse running. 

If you can monitor the animal for a while and see it's surroundings, you might be able to deduce what it is doing. A film could show the horse running, and a dog running after it. Looking more closely at the body language of the horse and the dog we can deduce if they're playing or there's a real chase taking place. 

(c) Picography

Now we know what is happening, but we still don't know why.

A Nobel-winning researcher Nikolaas Tinberger has formulated four questions to ask to find out why an animal is showing a specific behavior. These four requirements and their corresponding questions are

1. Cause: What controls the behavior?
2. Development: How and when is the behavior acquired in the animal's lifetime?
3. Evolution: Why the species carry on doing this behavior?
4. Function: How does the behavior contribute to the animal's survival and reproduction? 

A cause is something that motivates the animal to spend time and energy to perform a behavior. It could be an internal or external stimulus. In our example the horse was running. For example,it might have seen a predator (visual stimulus) which caused a fight-or-flight -response.  

Development explains how the behavior is acquired and how it changes. Newborn calves will seek an angle similar to the cow's hind legs and flank to find the udder. When they grow older, this behavior is lost. A behavior could also be learned, like a dog who learns that they get petted when they jump on the owner's lap.

For our example, let's assume that the horse saw a dog. The horse then escaped following it's natural instinct. Had it learned that this particular dog is friendly, this behavior would not have occurred.  Development can alter a behavior, or cause differences in how individuals express that behavior.

Evolution looks at how the behavior impacts the species. Wolves live in packs, because hunting together improves their chances of success and ensuring enough food for adults and pups. The ancestors of horses who ran from predators were more successful in raising their descendants to adulthood. This ensured that the behavior stayed with the species.

Function asks about why the behavior keeps occurring in the species. Suckling, play-fighting and mating are behaviors that survive in the species and directly impact the survival of the individual showing the behavior. Note that trained behaviors don't survive from one animal to another: they're learned. When a horse runs from a predator, the function is to escape from a  threat and to survive.

For example, let's look at the behavior of a cow picking up shredded silage. We can assume that the cow is eating. How can we answer the four questions? 

Cause: Hormonal signals create the feeling of hunger, when the intestines are getting empty. The cow sees others eating, which can promote eating behavior also in animals who are not hungry.  

Development: As a calf, the animal suckles their dam for milk. As their metabolism develops and solid food is offered, the animals learns to eat also silage, hay and similar solid feeds. Their rumen and intestines develop a bacterial flora capable of metabolizing the feed.  

Evolution: Animals who ate high-quality grass were healthier and had better chances of raising their offspring into adulthood. 

Function: To provide the animal's body with nutrients it needs to survive and to grow/produce milk.

For more information, enroll to the free Animal Behavior and Welfare -course on Coursera.  

Sensitization and habituation

Sensitization and habituation are two essential terms when it comes to animal research. They describe the way animals' reactions change to a specific stimuli over time. After every time a stimulus is met, learning occurs. The animal is changed through the experience, and these changes lead to a more profound, noticeable change if the stimulus is repeated. 

Sensitization happens when after repeated occurrences, usually with a lot of time in between them, an animal starts to react more strongly to a stimulus. Their reaction may be more pronounced, and the physiological measurements (blood pressure for one) can be more extreme than before. Examples of sensitization:

• Repeating unpleasant handling. Animal learns that the experience is painful, and can start reacting even stronger every time. (for humans this can be the case with dentist's appointments).
• Loud, sudden sounds like fireworks on New Year's Eve. A dog may not react to the first bangs, but as they keep repeating on uneven intervals, the dog starts reacting more and more strongly during the evening and night. 
• Traumatic event, which leads to fear of smells, sights or other items that coincided with the place of the original event. 

Sensitization usually does not last for very long. The stronger the stimulus, the longer the sensitization lasts. Makes sense, doesn't it - after a quiet "pop!" we're jumpy for a while, but after the bang of explosion the jitters are considerably worse!

Sensitization is not very specific to a stimulus. An unpleasant experience at the veterinarian can cause sensitization towards the vet, but also towards people with similar clothes, the physical location or the smells that were present.  

(c) https://www.dreamstime.com/

Habituation is the opposite of sensitization. According to Lumen Learning, "Habituation occurs when we learn not to respond to a stimulus that is presented repeatedly without change, punishment, or reward". Something happens, but nothing follows from it - therefore it's not needed to react to this stimulus. Broom uses an example where a flock of sheep is moved from a quiet pasture to a field next to a road. At first, they will react to every passing car. As the cars keep on driving by, they get used to it and react less and less. You could say they got bored of the cars, which is in a sense correct. The more scientific terms is that they've habituated.

Other examples of habituation are

• Habituation to humans and human touch
• Habituation to light-dark rhythm.

Habituation is very stimulus-specific. An animal might habituate to a specific type of noise, but if it changes in volume, pitch or sound, the animal will react to it again. In our example the sheep might ignore a car, but react strongly to a Harley-Davidson.

Habituation rely heavily on repetition. Factors influencing the result are regularity (how often does the event repeat), pattern (does it repeat in an predictable interval) and time between repetitions. For example, animals habituate quickly to stimulus repeating often in a short time. However, the recovery (when the habituation wears off) is also quick.

 

More on habituation and sensitization

Biological Basis of Learning | Boundless Psychology (lumenlearning.com)

Microsoft PowerPoint - Learning.ppt (ucsd.edu)

 

Behavioural modeling

There you are, looking for a job, and one of the requirements is "experience in behavioural modeling".  What does that actually mean? 

The first thing to determine is what are behaviours.  Behaviours, or behaviors for the Americans among us, are easily understood but harder to define. Purely based on the linguistic definition, Oxford Languages says they are "the way in which one acts or conducts oneself, especially towards others" but also "the way in which an animal or person behaves in response to a particular situation or stimulus." Lee Alan Dugatkin agrees with the latter, formulating that "behavior is the coordinated responses of whole living organisms to internal and/or external stimuli." A behavior happens where there is a need "If an animal has a need, its motivational state is affected so that behavioral and physiological responses that should result in remedying that need can be made." (D. M. Broom).

It seems to me that behaviors are coordinated movements and acts, directed to addressing a need. Some behaviors are learned (styles of playing, replies to human commands), and some are inherited (searching for a teat after birth). 

Now that we know about behaviors, let's see what are models? Modeling means to build models, abstract representations of complex truths. A model can be a simplification, and can fit to all instances of a repeating concept. A model can be used to compare representations across species or in time.  Schank, Joshi and May write that "Models can be physical, symbolic, mathematical, or computational, but they are always simpler than the animal systems they represent." Clearly then there are several methods of modelling, and the best fit can be chosen based on the goal of the research. If we intend to use behavioral data in a computer system, a mathematical or computational description would seem the most suitable. If we intend to demonstrate the behavior to others or even mimic it, physical modelling is the way to go.  

Schank et. al. also give models nine dimensions:

1. Realism
2. Detail
3. Generality
4. Match
5. Precision: how quantitatively precise a model is in it's predictions  
6. Tractability: how analyzable or manipulable a model is
7. Integration: Can it be used together with other models?
8. Level: Cellular, population, strain...
9. Medium

Let's take a look at some models to better understand how they really could look like.  The first example is a hidden Markov model (HMM) from the publication of Leos-Barajas, Gangloff, Adam et. al (2017).  This is a mathematical model. It looks complicated, and will require understanding about the mathematical notation and statistics to understand and to apply. 

Another beautiful example is from Ellen Evers from the University of Utrecht. In her presentation she explains the differences of Agent-based models (ABM) and Ordinary differential equations (ODE). 

An ABM looks at individuals: how each individual moves and acts during the behavior. It is less effective in modeling the group. An ODE looks at a group and determines the behavior of the group as a whole, losing sight of each individual. Her example uses the balance of wolves and sheep. Sheep are increased by births, and decreased by predation by wolves. Wolves are increased by predation, and decreased by natural death. 

In ODE terms the  models are

Sheep = + birth*Sheep – pred.*Sheep*Wolves  

Wolves = + pred.*Sheep*Wolves – death*Wolves

But for ABM the rules are for each individual:

SHEEP: If I meet wolve: die!

With chance = birthrate: Reproduce!

WOLVES: If I meet sheep: energy +1

If energy (from sheep) = 0: die!

With chance = birthrate: Reproduce

The big difference is that ODE model is deterministic. It can be used to predict situations when some variables are known. It could change what happens when there are 100 wolves and 50 sheep in comparison to a situation with 100 sheep and 50 wolves (in both cases, it's not looking good for the sheep.) ODE is not spatial (measuring things in terms of movements in space) and requires homogenity. ABM, on the other hand, just models the situation. It is applicable to heterogenous populations. 

I hope that this short introduction has given you some insight into modeling animal behavior. It is a complex field, and the lesson from Ellen Evers is heartily recommended as a good starting point for understand the differences of ABM and ODE.

More information

Lee Alan Dugatkin: What is "behavior", anyway?

D. M. Broom Animal welfare: concepts and measurement

Schank, Joshi, May et. al. Multi-modeling approach

Leos-Barajas, Gangloff, Adam et. al: Multi-scale modeling of animal movement and general behavior data using Hidden Markov models with hierarchical structures

Ellen Evers: ABM and ODE

Types of animal welfare studies

 When talking about animal experiments, it's easy to start thinking along the lines of mice, needles and electric shocks. But there are naturally a lot of other kinds of experiments as well. Consider a simple case where an animal is offered two kinds of food to see which one they choose first. That is also research on animals!

The study of animal welfare is a very complex field. Just to start with: what IS welfare and how to measure it when the animal itself cannot talk or describe it's emotional states? Obviously a complicated set of research methodologies is needed to achieve robust results. The measurements taken to achieve the results can be roughly divided into two: physiological and behavioral.

Physiological	Behavioral
Temperature Heart rate Blood glucose Fat percentage Weight Bacterial count	Time spent sleeping Frequency of a specific behavior Posture changes Social contacts Time taken to approach objects Distance traveled to forage

As you can see, welfare can actually be quite specific!

Next, let's have a look at some types of studies which are conducted to find out more about animal welfare. All of the measurements listed above are just data, but it's of course important to know how to gather the data to make sure - you guessed it - that the data is correct. So what kind of experiments are used?

Preference studies

Preference and motivation studies are both examples of empirical study, where the researcher gathers data on the target of their study. In preference studies the animals choose what they prefer and what factors influence the preference.

An example of preference study is to offer chickens feed with and without NSAIDs (painkillers). Chickens with healthy feet eat more of the feed without medication, while chickens with leg sores and ulcerations prefer the feed with the medication (self-medication). Factors affecting the preferences can be available time, diet, health and pregnancy.  

(c) Louse Buckley, UFAW

Motivation studies

Motivation study measures the motivation or willingness of an animal to reach a specific goal. The aim is to find out the value of things  and what impacts the motivation. For example, an animal might be very motivated to get a treat when alone, but less motivated when they're in a group and know they might need to share their treat. Measurements can be speed and distance traveled to the goal,  latency before the animal tries to reach the goal and energy spent to reach the goal.

In classic examples animal can be trained to press a lever to get a specific treat. Then the treat is disabled, and the amount of times the animal presses the lever trying to get the treat is the "price" they're willing to pay for it. Things like temperature, eating, health and group size can all affect the value of the reward. 

Metastudy

Metastudy is different from the other types, because this is the study of studies. In metastudies the researchers gather a vast amount of previous researches, carefully select the most relevant ones and summarize their findings. The process of selection and omission must naturally be well documented and argumented. The aim is to see wider trends and generalizations. Commonly seen phrases like "many studies prove" or "there is little scientific base on the claim that" arise from metastudies. Metastudy goes further than just being a literature review. It uses for example statistical methods to compare the results of the studies once comparativeness is established.   

More information:

Animal welfare science - Wikipedia

Consumer demand tests (animals) - Wikipedia