Monday, May 11, 2009

Brain Power

Now call me naive, I don't know but until the FSH board I had never ever heard that a horse exchanged information poorly from one side of the brain to the other, or indeed didn't have any connections between the hemispheres of the brain at all. In fact while researching today for this blog, I found out there are magazines that are actually telling their readers that horses have poorly developed Corpus Callosums. Of what little I do know, I'm more than happy to tell you that this just isn't true.

The corpus callosum is a structure, deep inside the cerebral hemispheres, that joins the two hemispheres together and is the pathway for information between the two sides. Horses have a reasonably well developed corpus callosum, and on this information alone I would be content to say that horses have a reasonable exchange of information between the hemispheres of the brain, because in nature you either use it or you lose it.

Frankly, it is easy to see why the myth of disconnected hemispheres developed, because it is a well known fact that horses need to be taught things from both sides. The current theory is that because horses have monocular vision, the information from the eye is only processed by one side of the brain. This is simply not true, however, because horses do have binocular vision in front of them. Poor exchange of information between the hemispheres would seriously disadvantage a horse. Say a plastic bag blows at him form the left eye and wraps around his leg, panicking him. If he cannot exchange information well, he should not be startled by a blowing plastic bag coming from the right eye, but I would bet good money that when he sees that plastic bag coming, he is going to be out of there. This allows the horse, a prey animal, to quickly escape from danger regardless of which eye he sees the negative stimulus in.

Often, the defense of the no connections theory is that a horse will spook at an object, and then be fine with it but when they go the other way they will spook again. However, I personally wonder how much this has to do with how a horse sees. horses do not focus on objects that well and use different parts of their eyes to see. Through the center gives an overall view, through the bottom for objects in the distance, and through the top for close objects. I suspect the spooking has to do with the object coming into focus suddenly, the rider being focused on and tensing up at the object going the other way or the horse having effectively forgotten the object and then re noticing it. I don't think it's a strong enough defense for saying a horse has no connections between the hemispheres.

When you first start training a horse, he will learn slowly compared to how he will learn further into the process. The unit of the brain, and nervous system, is the neuron. This is the cell that passes information from one part of the brain to the other. Dendrites develop from one neuron to another neuron to create a pathway for information. When you are training a horse, you are using the plasticity (ability to change) of the brain to create new connections and new circuits (both simple and complex) which allow the horse to access information related to the stimulus more quickly. This means the horse will both respond more quickly to known cues, as well as learn related cues more quickly, and learn new behaviours more quickly also. The plasticity of the brain also allows the re-training of the horse, with the connections that pertain to the wrong or bad behaviour becoming reduced, however, because the pathway still exists, it is easier to re trigger the bad or wrong behaviour than it is to trigger a novel behaviour.

A good experiment that demonstrated the plasticity of the brain involved horses being in front of a circle or a square. Touching the circle resulted in a food reward and it took some 100 attempts before the horse would consistently touch the circle first. Then they changed the correct behaviour to touching the square. It then took 150 attempts before the horse would consistently touch the square first. The right behaviour was consistently switch, and rapidly the horses, would touch the circle, which was incorrect, before immediately touching the square to get the reward, changing the amount of mistakes from 100 initially to 1. This demonstrates how as the horse learns, he creates more pathways, and is able to respond correctly more quickly.

One sidedness may also arise from training. Most often horses are approached and handled from the left, giving them an expectation of being handled from the left. Horses are well known to like routine and predictable behaviour. If you lunge your horse only clockwise, he learns that the pressure comes off when he trots around nicely clockwise. When you then turn him around to lunge the other way, he balks because to him to correct behaviour is to move clockwise, and he wants to go that way and take the pressure off. To be fair when you teach a horse something, I personally have found they pick it up on the next side much quicker, and the repetitions of the stimulus is all working to strengthen those neural pathways. It's important to note also that most horses have a side in which they are stronger and more balanced, either naturally or because of previous training, and this is far more likely to be the cause of one sidedness than the horses brain connections.

Finally, in a study done by Dr Evelyn Henggi, horses with one eye blindfolded were given a food reward in response to touching a circle. Once this behaviour was established, the blindfold was swapped to the other eye and the horses instantly responded correctly, touching the circle, indicating the information crossed to the other side of the brain and eye. I'd love to hear your opinions on this.


  1. Awesome post! It took me back to 1st year Psychology which was a bit... *grabs at face in horror* but it's quite interesting when it relates to horses!

    I've heard the 'no connection' myth a few times on the internet, and I definitely disagree with it. I think you're right about the eyesight. And really, when coming from the opposite direction, the sunlight is different, the shadows are different, etc etc, so it's really not surprising the horse is startled again. I've found that Blizzid, if she startles at something on the left, will have a look when going to the right, but not react as much as when she first encountered the object going left... does that make sense? Anyway, excellent post, you should do more of this!

  2. Excellent post - there's a lot of mythology out there, most of which is designed to support the opinions of people who think horses are stupid or slow learners. Most of the one-sided issues horses have, as you point, are either the same issues anyone would have (different approach to the same object), due to the differences in their vision from ours, or due to holes in their training.