Connections explored between brains and sleep

As a veterinary pathologist, I hold the brains of animals in my hands almost every week. A cat brain fits comfortably in the palm of my hand, while the brain of a 1,000 pound feedlot steer needs a two-handed grip.

Removing a brain involves opening the skull and then carefully severing the 12 pairs of cranial nerves. These delicate strings of white tissue transmit vital information to and from the brain. Among them are special nerves that lead to the eyes, the inner ears and the nasal cavity.

The thick spinal cord exits the back of the brain to communicate with the trunk and limbs. Altogether, these keep the body functioning and responsive to external factors.

The brain is a bi-lobed mound of pink and off-white tissue that is remarkably fragile and squishy. It’s the fat in brains that make them soft, but it has a critical job, insulating the connections between neurons.

Compared to other organs, like the four-chambered heart and the tree-like branches that create the airways in the lungs, the outward structure of a brain is a bit dull. It is, however, capable of amazing feats that far exceed expectations based on the physical structure alone.

One of the astounding things brains do is sleep. Indeed, all animals need a certain dose of daily slumber.

According to Matthew Walker’s recent book, Why We Sleep, there is little association between size and complexity of an animal and the amount of sleep that is required.

He provides elephants as an example of large animals that sleep very little, only four hours per day. Comparatively, brown bats are apparently the animal that sleeps the longest at 19 hours. While this is a big number, I wonder if he’s observed the hours slept by the average house cat.

Another fascinating point he raises is the way the brain functions in deep sleep. Both people and animals in this state experience synchronized waves that pulse through the brain, a process that is necessary for integrating recent events into long-term memory storage.

Walker further describes in detail the deleterious effects of lack of sleep on human health. This led me to consider the linkages between animal health and sleep in certain agricultural settings. What are the sleep effects of light alteration to bring mares into heat earlier in the spring? Do chickens held in artificially low light conditions sleep OK without the dramatic shifts between light and dark found outside? Do bright lights in a feedlot disturb the sleep of steers? And if these light management practices affect an animal’s ability to sleep, are there subtle impacts of disturbed or abnormal sleep on health and disease?

As neuroscience continues its march forward to understand the brain, perhaps these types of questions will reach our animal production systems.

You would never guess by looking at a brain or its microscopic structures that it needs sleep. Many brains I examine as a pathologist come from bodies that were either previously frozen or had time to decompose. The mass of nervous tissue that makes up a brain is incredibly dependent on oxygen, thus they quickly deteriorate after death.

In these cases, the best I can hope for is to find or rule out really severe and overt disease, such as large areas of bleeding, infection or tumours. The subtler details of the brain are usually lost in a sea of pink that has been shattered by ice crystals or degraded by decomposition.

But even in a fresh brain, the appearance of this tissue is undeniably boring compared to the wild and remarkable things a brain is able to do.

Dr. Jamie Rothenburger, DVM, MVetSc,PhD, DACVP, is a veterinarian who practices pathology and is an assistant professor at the University of Calgary’s Faculty of Veterinary Medicine. Twitter: @JRothenburger

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