Functional Level of the Brain and Psychosomatic Medicine

In order to understand the mechanism of the mind-body relationship (psychosomatic correlation), which is an important aspect of psychosomatic medicine, it is important to understand the “functional level” of the brain.

Three Functional Levels

There are three major functional levels of the brain.


(1) Neocortical System

Human-like function: The neocortical system is the level of mental functions that are conscious, such as adaptation, creativity, and judgment.

(2) Limbic System

Animal-like function: the level of emotional functions such as instinctive behavior, emotion, and homeostatic regulation.

(3) Brainstem-Spinal Cord System

Vegetative functions: level of bodily functions essential for life, such as reflexes, respiration, and circulation.

  • (3) In terms of the body, the third level, the brainstem and spinal cord system, is directly connected to the body. This level is responsible for vegetative, life-supporting, life-supporting functions and is usually not conscious. Without this area functioning, life cannot be sustained. In a tree, it is an important part of the root or trunk.
  • (2) The second level, limbic system is located outside of the neocortex, between the neocortex and the outermost part of the limbic system. It is embryologically older than the neocortical system and is involved in “emotions” and animal instincts. It is not a clear consciousness, but a vague level of awareness. It integrates the autonomic, endocrine, and immune systems and regulates homeostasis, etc. For example, when we are nervous, our heart beats faster and we feel nervous, but we are not doing this consciously. The limbic system is also deeply involved in the physiological system for understanding the internal state of the body: interoception.
  • (1) The outermost part of the limbic system is the first level, neocortical system, which is responsible for advanced human-like functions. It is involved in higher mental functions and is at the level of consciousness. This function is particularly well developed in humans and is responsible for sensory awareness, verbal communication, and volitional decisions that rise to consciousness.

Psychosomatic Correlation and Functional Levels

The “mind” or higher mental functions are carried by the first level, the neocortical system,
The third, the brainstem-spinal cord system, is directly connected to the “body”.
The second limbic system, which is like the filling in a sandwich, is the important level in the psychosomatic correlation.

For example, the sensation of feeling “somewhat well” or “somewhat unwell” is mainly a function of the limbic system, and is at a level that cannot be clearly expressed in words. Even if we are not consciously aware of it, the body senses these sensations and makes appropriate physiological adjustments.

The limbic system, which is responsible for these functions, is at the “interface” between the neocortical system = “mind” and the brainstem-spinal cord system = “body”.
It is the physiological keystone of the psychosomatic correlation (the relationship between mind and body).

(LABs Psychosomatic Medicine,, Jun 2021)