Habits: Stress and the brain
Man, it has been said, is a creature of habit. We learn to do things in a certain way, and by repeating our actions, we develop a sense of comfort and satisfaction in their doing. This is certainly true of behaviors, but it is equally true of thoughts and feelings. Since thoughts and feelings begin with brain activity in the prefrontal and
The front of the brain is comprised of the frontal cortex and the pre-frontal cortex. This is the central command area from which we do our thinking, generate ideas, initiate actions, build up (and exercise) our personal will. It is sometimes referred to as our ‘thinking brain.’ The pre-frontal cortex is larger in humans than in any other animal, comprising about 30% of our total brain mass, and this is primarily what distinguishes us as a species. The pre-frontal cortex in Chimpanzees, by comparison, makes up approximately 12% of their total brain mass, and in dogs it makes up approximately 5%.
Behind and deep to the pre-frontal cortex is an area called the cingulate gyrus. Shaped like the Nike ‘swoosh’ turned upside down, the cingulate gyrus is responsible for flexibility of mind, the ability to shift from one thought to the next, to make comparisons, to multi-task; to mentally shift gears, as it were. The cingulate is sometimes referred to as the ‘flexibility brain.’
Finally, deep to the cingulate gyrus lies the limbic system. As described above, this small, very deep area is the center of emotion. It is also the storage center for long term memory. Fear, love, reproductive drives, and the physiological processes that mediate those and many other emotional experiences are generated here. The limbic system is sometimes referred to as the ‘emotional brain.’
FMRI (functional magnetic resonance imaging) is providing new, fascinating data about the brain. FMRI measures blood flow. Since more blood is needed when we are actually using an area of the brain, blood flow is an indicator of brain activity. Because we have known for some time that different areas of the brain have different functions, there was a long held assumption that normal brain activity should show selective areas of activation and quiet at any given time. For example, it would make sense to predict that while your are doing math, the pre-frontal cortex, or ‘thinking brain,’ should be active, while the cingulate gyrus and limbic system should stay, relatively speaking, more quiet. Similarly, we might expect that while experiencing rage or fear, the ‘emotional brain’ would light up with activity while the ‘thinking’ and ‘flexibility brains’ would be dimmed.
In fact, FMRI has shown something very different. Rather than patterns of selective areas of activation and deactivation, what FMRI has shown is that healthy brains demonstrate a pattern of more generalized activation, with virtually the entire brain lighting up or quieting down as one functionally integrated organ. In a healthy brain, we may see slightly more or less activity in a particular area depending on what type of activity the brain is primarily engaged in at any given moment, but there is generalized activation of the pre-frontal, cingulate, and limbic areas whenever the brain is engaged to do anything! In healthy people, all three brains act together.
This is not to say that we never see selective areas of activation and deactivation. We do see it–too often in fact–just not in healthy brains. The brains of drug addicts, alcoholics, patients who have sustained brain injuries, patients with major depression, or other psychiatric conditions, show hot and cold spots, giving a ‘Swiss cheese” like appearance on FMRI. Even more interesting, is that patients with chronic pain but without any identified disease or history of injury show this same pattern, as do people who are under chronic stress.
July 27th, 2015
Stress and the Nervous System
The connection between the CNS and the ANS is extremely important to understand, not only because it explains the manner in which emotions are generated and experienced, but also because the stress response is conducted along the same pathways. For example, the famous “Fight or Flight Response,” starts in the brain as an activation of the limbic system during conditions of stress. Stressful situations activate the limbic system which in turn sends messages to the heart, skin, pupils, blood vessels, breathing muscles, and muscles in the jaws, neck, and upper back. When a stressor is sudden and strong the response is generally widespread and profound.
Imagine that you are alone at night in an empty parking garage when you notice a man lurking behind your car. Immediately, your heart begins to pound, your breathing quickens. You halt. Your body is telling you not to approach. “Can I help you?” you call out from a distance. The man stands taller and you can see that he is big with a menacing look on his face. “Can I help you?” he responds threateningly.
This situation happened to a patient of mine, a woman who is not generally a fearful person. She described how her heart felt like it was coming up through her throat. She turned and ran. Fortunately, she was not chased. She returned to her office where a co-worker called the police. After investigating the scene and finding no one, they walked her to her car. She drove home feeling sick to her stomach. She said that she felt her face flushed as though embarrassed and her heart rate did not calm down for the rest of the night. She had trouble getting to sleep that night and has subsequently developed a fear of parking garages which she experiences as a racy-queasy feeling in her stomach and chest.
Imagine that you strained your neck and upper back after being rear-ended at a stop light. Your car was damaged and, even though it was returned to you “fixed,” it continued to make a rubbing noise every time you turned the wheel fully to the left while moving–a sound that was not there before the accident. Your primary care doctor gave you some anti-inflammatory medicines and you were told the pain would go away as your muscles healed over the next 2-4 weeks. But the medicines bothered your stomach and the pain did not go away, in fact it got worse and you started to have difficulty sleeping as well since you could not seem to find a comfortable position for your neck. Returning to your doctor, you were given a prescription for muscle relaxants to help you sleep, and a you were referred to physical therapist. The medicine helped you sleep but made you feel extremely tired and groggy in the mornings so you stopped taking it. At physical therapy you were given ice and electrical stimulation therapies and taught stretches for your neck and shoulders. You thought that you were feeling a little better after the first week but on the second week you noticed an escalation of pain. Your P.T. increased your frequency of care from twice per week to three times per week. Unfortunately your busy work schedule made impossible for you to get away from the office that often, and your boss made a comment about your work product of the the previous few weeks since the accident. The P.T. explained that without more frequent treatment she would not be able to help you with the pain.
One month post-accident, you receive a call from the insurance claims adjuster who questions the need for ongoing care. He tells you that the accident was a minor fender-bender, that statistically you should not have even been injured, that even those who do get injured only require on average three sessions of P.T. to get well. He informs you that a lot of people try to run up big bills in the hope of getting a better final settlement, but that the insurance company’s policy was to pay for only a maximum of three sessions. He offers you $500 to settle your claim and informs you that you have forty eight hours to accept the offer or it will be withdrawn. You hang up the phone and your neck and shoulders are so tight that it feels the muscles might tear. You have a terrible headache.
This event, taken as a totality, gives us the experience of stress, and it takes place automatically, irrespective of logic or reason.
When a friend sneaks up behind us and yells, “Boo!,” the sudden surprise rings a loud alarm in the emotional brain, causing a massive discharge of neurons which then mediate the following event: the muscles in our shoulders and neck tense suddenly, our heart beats fast in our chest, and our breathing quickens. This generalized state of arousal is called the ‘startle response,’ and is the first stage of the famous ‘fight or flight’ response which is hardwired into our nervous systems at birth. The combination of the loud sound, the suddenness of its intrusion into our otherwise calm environment, and the unexpectedness of it, lead to our emotional brain’s automatic interpretation of the event as a perceived threat. Once we find out that no authentic threat exists, that we’ve merely been teased by a friend, the startle response, rather than blossoming into a full-on state of fight or flight, recedes, while other emotions begin to rise. We may feel our cheeks flush (vasodilation of the blood vessels in the face, consistent with the feeling of embarrassment), our stomachs, shoulders, and upper back tighten (tensing of the muscles consistent with feeling hurt or angry). These feelings come and go without our request or consent, serving the will of the emotional brain (limbic system), not the thinking brain (prefrontal cortex). Acting through the ANS, the emotional brain is half-responsible for one of the great dichotomies of human existence: how we think and how we feel do not necessarily agree and in complex societies may often run directly counter to one another.
The Five Primary Emotions
There are five primary emotions: fear, anger, joy, sadness, and lust. There are many other emotions which are not considered to be primary emotions, and a primary emotion is not more intense or more important than any other emotion. The emotions are primary in the sense that all other emotions are either a variation of them (think of the numerous shades of a primary color) or consist of a mix of two or more primary emotions experienced simultaneously. For example, as mentioned above, anxiety and panic are lighter and darker shades, respectively, of the primary emotion fear. Similarly, frustration and rage are lighter and darker shades, respectively, of the primary emotion anger. Familial love, by contrast, is a mix of sympathy (which is a shade of sadness) and joy. And romantic love, the king of all emotions, is a cocktail of exuberance (a shade of joy), lust, longing (a shade of sadness), with just a dash of anxiety (a shade of fear) to keep things interesting. Part of what makes romantic love such a powerful experience is that involves the activation of so many (four out of the five) primary emotions all at the same time.
Some emotions are the product of physiological changes which take place in the chest cavity, some are primarily in the upper back, shoulders, neck, and jaws, some are primarily felt in the abdomen, and some emotions, like the startle response involve powerful physiological responses throughout the body. Variations of emotion are practically endless and, ultimately, are subjective. For the purposes of this blog, the point I am trying to make is that emotions are physiological changes which are attended by body sensations, and that these changes take place not as acts of reason or will, but automatically, unconsciously, from the parts of the brain collectively called the limbic system, and are carried out by the ANS which is not under conscious control. Emotions are much more about physiology than they are about psychology.