Neural Physiology and Intelligence
Neocortex and Glial Cells
Throughout the cetaceans evolutionary history the neocortex has expanded and now has more gyrification, folding that adds surface area, than any other mammal. The neocortex is the portion of the brain that is associated with decision making, language, and perception. The layers in this part of the brain have been shown to be very dense with neurons and have a high glial cell to neuron ratio. Though their brain is larger, it surprising has less neurons than the human brain. They seem to make up for this with a high amount of glial cells. The neocortex of the Minke whale has been found to have 98.2 billion of these cells, which is the most that’s been found in any mammal. Glial cells like oligodendrocytes help with signal transmission which is important for rapid communication, efficient signaling, and has been shown to be useful in information processing. (Marino, Sherwood, Delman 2004) This leaves us to wonder if the way in which whales process information and thoughts is just fundamentally different from what we currently believe to be standard.
Cetacean Brain Compared to other Animals
Compared to other mammals the size of the corpus callosum, nerve fibers that join the two hemispheres of the brain, is small compared to the overall size of the brain, perhaps the result of energetic trade offs. The cerebellum, which functions to coordinate muscle activity, has a higher ratio of mass in cetaceans than in primates. This may be due to the fact that during deep dives with limited oxygen storage, whales need to be able to regulate oxygen to certain muscles in the body and need to be efficient in their movements. The limbic lobe, which is the system in the brain that is associated with memory, emotions, maintaining homeostasis, and sexual behaviors is also extremely well-developed in whales compared to other animals. The temporal operculum, which contains the auditory reception center known as Heschl’s gyrus, seems to also be quite developed.It is speculated that this portion of the brain may be used for speech related purposes as the opercular cortex is in humans. (Body et al 2012) Moreover, in the frontopolar cortices, which is in the anterior part of the frontal lobe and is an area thought to play a role in complex behavior, there is a large density of Von Economo spindle neurons. These kinds of neurons have been found in humans and apes to be part of the neural network that is responsible for social cognition. More research is still needed to learn the exact functions of each brain region, after millions of years of divergence it’s likely that the regional composition of the cetacean brain serves different purposes than what we see in humans and terrestrial mammals. (Marino, Sherwood, Delman 2004) Although we cannot always make a definitive line between brain anatomy and intelligence, we can observe behaviors that give us better insight into the intellectual capacity of these animals.
Intelligence
Cetaceans in a laboratory setting have shown an understanding of abstract rules, shown they can problem solve by manipulating structures or situations, discern between different individuals, learn and remember new techniques, demonstrated abilities in vocal and behavioral mimicry, are able to understand the behaviors of others, and have been shown to have an understanding of their own image and body leading to the conclusion that they are self aware.
In the wild whales demonstrate their intelligence by working in groups to hunt, communicating with each other, navigating multiple migration routes, forming long term bonds, and creating alliances. Culture is defined as the transmission of learned behavior and we are learning more and more about how this characteristic sets cetaceans apart from other mammals. Examples of learned behaviors in the wild include feeding sites and remembered navigation to them, hunting strategies, and even dialects from other populations they encounter. Along with their complex vocalizations whales also communicate through changes in their body posture and behaviors like touch, breaching, and teeth raking which signals dominance or aggression. (Marino and Connor 2007)
Sleep
Cetaceans never fully sleep the way other mammals do. Since their breathing occurs consciously they need to keep a portion of their brain active in order to know when to resurface and take a breath. They have been found to rest vertically, horizontally, or by slowly swimming forward. When a mother has her calf she is unable to stop swimming in the early stages because the calf is not born with enough blubber to stay buoyant, if it stops swimming it will simply sink. Cetaceans have adapted a form of sleeping where they are still about to remain fairly alert. They have been shown to only shut down half a hemisphere of the brain at a time. The other side of the brain shows decreased activity but remains alert to potential predators, obstacles, and keeps track of when it is time to breathe. After about two hours the alert and resting side of the brain will trade off. Researchers aren’t sure if whales dream during these times of rest, but there has been a pilot whale that has been recorded to have had 6 minutes of REM sleep, which is a characteristic of deep sleep that might include dreams. (Hector 1998)
