How the Brain Evaluates Internal Signals

Week 5 of the Withdrawal Symptoms Series

How brain networks evaluate signals from the body and determine which enter awareness as symptoms.

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Recognizing the Experience

Many withdrawal symptoms begin as body sensations that quickly draw attention. These sensations may seem to appear suddenly, even though signals from the body may already have been present in the background.

A person may notice their heartbeat, breathing, chest tightness, or sensations such as tingling or vibration. These experiences can feel immediate and difficult to ignore, even when they are recognized as part of the withdrawal process.

Earlier in this series, we described how the body constantly sends signals to the brain, most of which remain outside awareness. The next step is how the brain evaluates these signals and determines whether they become noticeable.

This step is critical because only signals that enter awareness are experienced as symptoms. This article focuses on how the brain determines which signals are selected into awareness.

Evaluating the Body’s Internal State

The brain is constantly receiving signals from the body. These signals travel from organs and tissues to the brainstem, and then to higher brain regions that help interpret what is happening inside the body.

Two important regions involved in this process are the insula and the anterior cingulate cortex:

• The insula integrates signals from across the body to build a real-time picture of the internal state.

• The anterior cingulate cortex helps determine which signals are important and directs attention and response.

Together, these regions help determine which signals are important enough to become noticeable.

The brain does not evaluate signals passively. It uses past experience and the body's current state to predict the meaning of incoming signals. During withdrawal, changes in the nervous system can shift this process, making signals more likely to be treated as important.

From Signals to Salience

Most signals from the body remain outside awareness. The nervous system uses these signals to regulate body functions without our having to notice them. However, during benzodiazepine withdrawal, signaling often increases, making these signals more likely to stand out. The brain must then determine which signals are important enough to notice.

Salience refers to how strongly a signal is prioritized by the brain. It determines which signals stay in the background and which become noticeable. As salience increases, signals that were previously unnoticed may enter awareness.

Salience is influenced by several factors, including the signal's strength, the nervous system's overall state, and whether the signal is unexpected.

This reflects a change in how the signal is processed, not a change in the signal itself. The signal may be the same, but it is now more likely to be noticed. This shift—from background signals to conscious awareness—is a key step in symptom formation.

From Salience to Symptom Experience

Symptoms arise when signals from the body enter awareness. A signal becomes a symptom when it enters awareness. Most signals do not become symptoms. They remain in the background and are used by the body to regulate function without being noticed.

When a signal enters awareness, it is first experienced as a sensation and may then be recognized as a symptom. At this point, the signal is no longer just being processed—it is being felt.

For example:

• signals from the heart may be experienced as palpitations

• signals from breathing may be experienced as breathlessness

• signals from the digestive system may be experienced as discomfort

  
  

These sensations are experienced as symptoms once they enter awareness. In this way, symptoms reflect how the brain represents signals from the body, not just the signals themselves.

Connection to the Five-Axis Stress Biology Framework™

Within the Five-Axis Stress Biology Framework™, this step—when signals from the body enter awareness and are experienced as symptoms—reflects how multiple systems work together.

Axis 3 (autonomic signaling) provides the signals from the body. Axis 2 (excitatory–inhibitory balance) influences how strongly those signals are processed. Axis 1 (stress systems) influences how signals are evaluated for relevance.

Together, these systems influence which signals enter awareness and are experienced as symptoms.

Why Symptoms Can Vary

Because this process depends on the overall state of the nervous system, the same signal may be experienced differently at different times. At one moment, a signal may remain outside awareness. At another, it may enter awareness and be felt as a sensation.

Changes in the overall state of the nervous system and signal strength influence which signals are more likely to enter awareness.

What Influences How Signals Are Noticed

These differences are influenced by the overall state of the nervous system.

When the system is more stable, many signals stay in the background or feel manageable. When the system is more activated or sensitized, the same signals are more likely to enter awareness and feel more noticeable.

These differences reflect changes in how the nervous system regulates and prioritizes signals, not changes in the signals themselves.

This ability to regulate signals and maintain stability is what we describe as Regulatory Range and Reserve™.

Diagram

Figure 5. Salience assignment and symptom experience. Signals from the body are evaluated by networks including the insula and anterior cingulate cortex. When salience is assigned to these signals, they enter conscious awareness and are experienced as symptoms.

Looking Ahead

If signals from the body become symptoms when they enter awareness, an important question follows.

Why do symptoms sometimes feel stronger or harder to ignore, even when the underlying signals are similar?

Next, we will examine how attention and the overall brain–body state influence symptom intensity.

Selected Scientific References

1. Critchley, H.D. and Harrison, N.A., 2013. Visceral influences on brain and behavior. Neuron, 77(4), pp.624-638.

2. Craig, Arthur D. Interoception: the sense of the physiological condition of the body." Current opinion in neurobiology 13, no. 4 (2003): 500-505.

3. Bush, G., Luu, P. and Posner, M.I., 2000. Cognitive and emotional influences in anterior cingulate cortex. Trends in cognitive sciences, 4(6), pp.215-222.

4. Barrett, L. F., & Simmons, W. K. (2015). Interoceptive predictions in the brain. Nature Reviews Neuroscience, 16(7), 419-429.