Our three brains perform different functions while continuously working simultaneously, exchanging messages between each other, other parts of the brain, and the body. Most of this communication is beyond our awareness on a subconscious level. This is one reason why people are so complex, unpredictable (even to themselves at times), and resilient.
Brain One: The most primitive part of our brain is the reptilian brain, also called the basil ganglia, nearest to and including the brainstem from which the brain receives information from the body. The reptilian brain controls the vital body functions, such as respiration, hormonal control and reproduction drive, heart rate, hunger, body temperature and balance, as well as instinctual behavior that involves fight or flight response,, dominance, territorial behavior and ritual displays. So this “old” part of our brain guides automatic internal functions and interacts with our higher brain which provides the reptilian brain with feedback and interpretation of information coming through the brainstem.
Brain Two: The mammalian brain, also called the limbic system, covers the reptilian brain and generates emotions and is responsible for our survival instinct, including our fight or flight response. The thalamus in the mammalian brain is like a relay station, sending information to other parts of the brain for processing. Beneath the thalamus is the hypothalamus which works together with the pituitary gland to keep the body adapted to the environment. Also in the limbic system is the hippocampus, responsible for long term memory and, lastly, the amygdala, in front of the hippocampus, is where fear and other emotions are registered.
Brain Three: Finally, our third and most complex brain is the neocortex (new brain) which covers the mammalian brain and takes up 76 percent of your gray matter. The neocortex controls awareness, sensory perception, conscious thought, visio-spatial ability, motor commands, language, and the ability to recognize social clues. The neo cortex is responsible for our executive functioning such as critical thinking and assessment, goal setting, creativity, reflection, inhibitory functions, and much memory.
The amygdala, hippocampus, and ventromedial prefrontal cortex work together to attenuate stress. Neuroimaging studies show that traumatic life experiences changes these areas of the brain both physiologically and functionally. During trauma the reptilian brain takes over. It shuts down all non-essential brain and body functions going into survival mode. Stress hormones such as cortisol and adrenaline increase in response to the sympathetic nervous system signals that danger is near, preparing the individual for fight or flight. In non-traumatic situations, the parasympathetic nervous system would typically calm the body down after the danger was gone restoring the neocortex functioning. But in trauma sufferers the brain remains in the reactive state due to an overactive amygdala which responds to a sense of ongoing danger, despite the lack of any real current threats. In addition, the hippocampus actually shrinks as a result of trauma, resulting in the loss of ability to discriminate between the past and the present. Thus, a traumatic event that occurred in the past can be experienced as if it were still occurring. Because the hippocampus becomes less effective in assessing the environment, everyday life stressors result in increased cortisol and norepinephrine responses, leading to adrenal fatigue of the body. The ventromedial prefrontal cortex is also changed by trauma. This part of the neocortex that regulates negative emotional responses triggered by the amygdala decreases in volume as a result of experiencing trauma.
Fortunately, all of these brain changes can be reversed with effective therapy.
