How it Works

Let’s say your horse was trotting over a jump and clipped a pole with it's right forelimb. The nociceptors would tell the brain “Something touched your right forelimb on the skin”.   To create a pain response, the horse’s spinal cord would send a signal to the thalamus to evaluate, asking, “How dangerous is this stimulus?”

Next, the message moves to the frontal lobe of the brain asking, “Have we been here before?” Then to the back of the brain “Has this happened at this stage of the gait cycle? Is it coming from the same location?”

The horse relies on different regions of the brain including memory and emotion to create a pain sensation that fits the situation at hand. In the case above, if the horse had many safe experiences knocking a pole while jumping, the brain would produce a mild to moderate sensation, a “bonk” on the right forelimb.  

All of this happens so quickly, it feels instantaneous to the horse, just as it would in a human. The central nervous system creates the sensation seemigly at the speed of light.

What if circumstances changed? What if the same horse had an injury while jumping and tore their leg open while going over a jump? The leg needed stiches, the horse had a limp, required time off and pain medication for a time.

What happens if that horse heals, goes back to work and jumps, knocking his right front limb on the pole? Now the nociceptors are stimulated, sending the signal to the spinal cord, which pings the thalamus. When the horses’ brain is bouncing those questions around the answers might be very different…

“How dangerous is this?  Very".

 “Have we been here before?  Yes, we are in the arena the scene of a major accident."         

“Has this signal happened at this stage of the gait cycle? Yes, this exact moment in the gait cycle!  

"Is this coming from the same location? Yes, my right forelimb!” 

It is easy to see how in this second scenario the horses’ brain could produce a strong pain signal, even in an identical set of circumstances.The new, stronger pain signal may set off other bodily responses; The horse could have an increased heart rate and may start sweating. He may even limp after the landing. Which could puzzle the human care givers, and lead to speculation. The horse would eventually calm down but may display sensitivity around the leg for a few minutes.

Neuro Tag, a Signature for a Pain Pathway

In the field of human Pain Science this strong reaction would be labeled a Neuro Tag. Neuro tags are a unique pain signature for a particular injury that can be activated under the right circumstances. Once established a neuro tag is a permanent feature within the brain ready for recall. Since mammals, (horses and humans alike) have similar brain functions, it is possible that horses are developing neurotags as well. 

Horses are different from humans in some important ways. However when it comes to how they develop pain pathways they may not be so different. Horses have been suggested for use in studies as more suitable research animals for human diseases of memory degeneration  like alzheimer's than mice and rats.

When observing pain behavior responses to old healed injuries, many horse owners ask, is the horse really in pain or does he just remember the pain? The pain sensation of a neuro tag is absolutely real pain, there is no question that it hurts.

Remember, pain sensations are a complex creation of the brain and central nervous system they do not occur at the site of the tissues. No wound need exist for pain to occur. This is why amputees have what's called phantom limb pain. They can still feel the limb that is no longer there. An established pain pathway for a serious injury may require less to activate the brain’s neuro tag/ pain signature. This can happen even a decade after tissue is fully healed. Treating this kind of pain is difficult. The nociceptors  in the area of the injury are typically hypersensitized. There are some treatments that may help reduce the pain sensations over time. 

*Note :There is a dysfunctional movement pattern that horses can get accustomed to when an injury is prolonged. This must be corrected with the help of a skilled rehabilitaion therapist. The Central Pattern Generator in horses must be reset in some cases. This is different and pain may or may not play a role in this continued movement dysfunction. This is a topic for another article.

Maladaptive Pain

Short term pain is helpful, but if it is not treated adequately changes can occur in the spinal cord and brain leading to chronic pain. This type of pain is a disease in and of itself and is often not proportionate to tissue damage and can persist long after tissues have healed. Chronic pain is hard to treat. The longer acute pain goes unmanaged the more likely it is to become maladaptive pain.

The most important thing to understand about horses and pain is that they are not capable of faking it.  In this species which is a prey animal they are more inclined to hide pain. If you sense they are hurting, address the need for pain management.

Pain is a protective mechanism and when it is working well it is a sensation necessary for survival and tissue healing and protection. It is not created at the site of the tissue damage but rather is a complex production of the brain and central nervous system. If left unmanaged for too long, it can cause permanent changes to the central nervous system and become chronic pain which is difficult to control and treat. Learn your horses body language and behaviors and be sure to utilize all the treatments for pain relief that are available.