Survival brain in dementia, explained

We’ve talked about the fact that as humans, we all share five universal needs, which don’t diminish with age or with dementia. (Some behavioral scientists believe there are more than five that we share, but all seem to agree on the five identified by Abraham Maslow, mid-twentieth century: physiological, safety, belonging, value/esteem, and self-actualization, or purpose.) These needs are essential to not only our surviving but also our thriving as well. Let’s examine the ways in which the drive to survive may cause dementia’s symptom-related behavior to escalate.

Our survival instincts come from an area of the brain called the limbic system, located in the center of the cerebrum. The limbic system has four components to it. We will focus on two of those here, the hippocampus and the amygdalae. Both of these parts of us perform essential functions to survival, yet they seem to be polar opposites.

The hippocampus provides our ability to survive by adaptation. Its functions are based in rational thought. Specific skills needed for adaptation include acquiring new knowledge and forming new memories. But this is also the area of the brain responsible for our ability to navigate – to find our way. And, the hippocampus affords us our senses of time (past, present, and future) and place.

The amygdalae provides our ability to survive by defense. Its functions are based in emotional thought. This is where our “fight or flight” responses come from when we sense a threat to our physical (and also our emotional) well-being. The amygdalae drives our emotions and also our pleasure-seeking sensibilities.

Cave man brain

When I think of “survival instincts” I immediately conjure cave man images in my brain. Modern civilization has made it so much easier for us to survive that it hardly seems like a conscious effort. Yet cave men had to work constantly to survive. So I will use a cave man tale to illustrate how these two parts of the limbic system contribute to survival.

Let’s suppose that a cave man is out in the wild, doing something he is most famous for: hunting. Let’s also suppose he climbs to a high point so that he can survey a great swath of land below for potential prey to kill and bring home to feed his family. While standing on the edge of a cliff, he notices a pack of wildebeests clustered on the shoals of a river meandering beneath him. He thinks to himself, “They’ve gathered there before, with their shadows long beside them, to cool themselves and drink from the river. If I return here tomorrow, with my fellow cavemen, to this very spot, at this very time – when the sun is just so in the sky – we can kill a few wildebeests and feed our family for at least a week!”

In order to follow through on his plan, he will need to report his observation (new learning) to his neighbors. He will need to bring them back to that very spot (wayfinding) when the sun is just so in the sky (sense of time) to find the wildebeests gathered at the river’s edge (sense of place) for the hunt. If he succeeds he will be surviving by adaptation.

And as he is hatching out his plan, he revels in the thought of the celebration he and his family and neighbor will share as they fill their bellies (emotions), because it’s been a while since wildebeest has been on the spit. His mouth begins to water. He can taste the flavorful meat and he can smell it cooking in his imagination (pleasure-seeking). A wave of positive emotions surround him.

But…does he notice the sound of leaves crackling behind him? Does he smell the gamey scent of the saber tooth tiger stalking from behind? Can he pivot, raise his spear, and bring it down into the tiger’s shoulder before the tiger sinks its saber teeth into his flesh? Will he be able to respond ably (fight) to this threat in order to survive another day?

For the cave man, he must avoid predators so that he may continue as a predator himself. Thus, these two, very different, survival mechanisms work in tandem to make it possible for humans to defend us against possible threats to our existence, both imminent and long-term.

The dichotomy of the survival brain

Survival by adaptationFunctionSurvival by defense
Rational thoughtBasisEmotional thought
New learning, new memoriesSkillsFight or flight response
Layers of time Pleasure-seeking
Sense of place Emotions
Early lossCognitive declineLate loss
The hippocampus and the amygdalae are both tasked with survival, but function in seemingly opposite ways.

When dementia is present, the hippocampus is usually one of the first areas of the brain to be affected by dementia. Damage to the hippocampus caused by dementia occurs so routinely early that it is considered an early hallmark of dementia. In fact, the dictionary definition of dementia is that at least two parts of the brain are affected – memory and one other. Many people believe that dementia, including Alzheimer’s, is a disease of memory loss and use the terms interchangeably. (However dementia is much more than just memory loss.)

The amygdalae are typically one of the last parts of the brain to be damaged by dementia. Before the amygdalae lose their skill, a person with dementia has experienced a loss of skill in visual, auditory, and tactile processing. And they have lost motor skill necessary for “fight or flight”. As other cognitive skills decline, the amygdalae seem to take over.

Survival brain affects dementia-related behavior

As dementia gradually prevents a person from the ability to detect and respond to threats around him, and to fulfill his needs to not only survive but to thrive through adaptation, his defense mechanisms begin to dominate. Simultaneously, he is losing his ability to effectively express his unmet needs to others. So it is common for a person to develop a heightened sense of anxiety as he loses the ability to fulfill his human needs autonomously, and with certainty.

This heightened sense of anxiety becomes a “default” mode. When anxiety levels are high, it’s easy for dementia’s symptoms to become more pronounced and escalate. Agitation, aggression, hallucinations, delusions, verbal outbursts and other dementia-related behaviors are triggered by various stimuli but all share this heightened anxiety – over unmet needs – as a root cause.

In dementia caregiving, understanding the relationship of the need to survive and thrive to the gradual yet inevitable inability to do so for one’s self is essential to promote well-being through person-centered care.