Brain matters

On average a horse’s brain is the size of a large orange but weighs significantly more at roughly 623g and it is around half the size and weight of a human brain. Given that horses are much larger than humans the brain size is proportionally much smaller in relation to body size.

What is the brain made of?

Located below the ears and above the eyes within the horse’s head, the brain has two layers made up of highly specialised predominantly neural tissue. The inner white matter is a layer of connecting myelinated nerve fibres (encased in a fatty myelin sheath to enhance the transmission of electrical impulses). The outer grey matter contains nerve cells and unmyelinated fibres.

In the centre the brain’s core is ‘hollow’, containing a system of cavities, called ventricles, and ducts filled with cerebro-spinal fluid (CSF).

Brain structure

The horse’s brain is broadly divided into three regions, each with a left and right side or hemisphere.

The cerebral cortex (forebrain) is the largest part of the brain and is responsible for perception, information processing and voluntary control of movement. 

The cerebellum lies behind the cerebral cortex and manages coordination of movement and fine control.

The brainstem is a bridge between various parts of the nervous system and contains tracts carrying information from the cortex and cerebellum towards the spinal column. 

It also contains the roots of nerves to the head and neck (cranial nerve ganglia). These include the trigeminal and facial nerves that coordinate movement and sensation in the face and the vestibular nerve that controls the position of the head, eyes and main body in relation to gravity.

Brain problems

The most common causes of brain disease in horses in the UK are head trauma and metabolic encephalopathy – which is a group of problems caused by chemical changes that affect brain function but which are caused by disease elsewhere in the body. Occasionally horses can suffer from epilepsy too.

Brain trauma

Consequences of damage to the head and brain can be very serious, resulting in anything from mild disorientation to seizures or coma. It’s vital to call your vet immediately if you think your horse may have suffered head trauma.

Metabolic encephalopathy