Unveiling the enigma of pain: Visualizing the invisible through brain signals

  Although pain does not occur every day, pain may accompany a person’s life. Trauma, disease, and aging may cause physical pain. Although almost everyone has experienced pain, most people have difficulty describing pain specifically and clearly. So, can pain be “seen” like other diseases of the body? Now, the latest scientific research provides the answer.
  Pain is activated by pain receptors found throughout the body on free nerve endings in the skin, muscles, bones, and other tissues. When the body is subjected to various noxious stimuli or lesions or inflammation occur within the body, the damaged tissues will release some pain-causing substances, such as histamine, bradykinin, 5-hydroxytryptamine and other chemical transmitters. These substances act on free nerve endings to trigger pain impulses, which are quickly transmitted to the spinal cord; then, they ascend to the thalamus through the spinothalamic tract and spinoreticular tract, and are finally projected to the cerebral cortex, causing pain sensations.
  Pain is an unpleasant sensory and emotional experience associated with existing or potential tissue damage. Currently, doctors commonly use the “Pain Level Numerical Assessment Scale” to assess patients’ pain levels. Patients can indicate the degree of pain using a number between 0 and 10, where 0 means no pain and 10 means the most severe pain. During the assessment, patients need to choose a number that best represents their pain level, or the medical staff will ask the patient about the severity of their pain and select the corresponding number based on the patient’s description. According to this scale, mild pain (1-3) can be described as a feeling similar to clapping hard, moderate pain (4-6) can be described as a feeling similar to a knife cutting the hand, soft tissue contusion or sprain, and severe pain (7-7) 10) Can be described as a sensation similar to severe vascular headache or trigeminal neuralgia.
  However, pain is a subjective feeling, and each person’s experience of pain is unique and can only be expressed through the patient’s description. In order to provide more objective diagnosis and treatment methods, researchers have been working hard to visualize pain. Pain visualization means converting pain sensations into an observable form, allowing doctors and researchers to better understand and quantify pain sensations.
  To visualize pain, it is usually necessary to use various detection instruments, such as electroencephalographs and magnetic resonance imaging machines. However, existing instruments cannot fully meet the needs when observing pain, especially when dealing with chronic pain. Chronic pain is often overlooked because it is not as obvious as acute pain, is not easily observed, and may involve complex interactions of multiple body systems.
  Based on the results of magnetic resonance imaging, researchers found that the anterior cingulate area and orbitofrontal cortex area of ​​the brain play an important role in pain. At the same time, a growing number of experimental studies show that the brain processes different types of pain differently. However, researchers found that magnetic resonance imaging cannot make pain “clearly visible”, while brain-computer interfaces can clearly display blood flow and biological signals in the brain through a computer screen. In order to further understand the physiological mechanism of pain, a research team at the University of California, San Francisco, used a brain implant device to continuously monitor the anterior cingulate gyrus and orbitofrontal cortex of four chronic pain patients for several months. Monitoring data were analyzed using machine learning models. The findings indicate that the orbitofrontal cortex is a key brain region associated with chronic pain and identify chronic pain biomarkers in the brain.
  Of the four chronic pain patients who volunteered to participate in the study, three had post-stroke pain and one had phantom limb pain. Researchers implanted a harmless chip into volunteers and monitored and recorded neural signals in the anterior cingulate gyrus and orbitofrontal cortex through a brain implant system (Medtronic Activa PC+S) for a continuous period of time. 3 to 6 months. At the same time, four chronic pain patients will report their conditions to researchers every day, such as describing pain type, pain intensity, and emotional feelings.
  Researchers found that by inputting brain nerve signal data into a machine learning model for analysis, as well as patients’ subjective pain rating data, they could visualize a patient’s pain. Experimental studies have found that power spectrum changes in the orbitofrontal cortex are more important than the anterior cingulate gyrus when predicting and assessing chronic pain states. Among them, the delta wave in the orbitofrontal cortex is a common biomarker when people feel pain. Through the delta wave, pain can be “seen” and the degree of chronic pain felt by the patient can also be inferred. The researchers found that the delta wave power in the orbitofrontal cortex was inversely proportional to the degree of chronic pain. That is, when patients with chronic pain felt higher pain, the delta wave power in the orbitofrontal cortex was lower. Therefore, chronic pain can be visualized through delta wave power changes in the orbitofrontal cortex and reasonable analgesic treatment options can be provided.
  At the same time, the researchers stimulated the volunteers’ body parts at different temperatures to induce varying degrees of acute pain and observed the brain’s response. Experimental results show that the degree of acute pain can be estimated more accurately only through the activity of the anterior cingulate gyrus. Therefore, the anterior cingulate plays a greater role in inferring the intensity of acute pain, allowing researchers to “see” pain from this brain region.
  However, current research on pain visualization is still in its preliminary stages, and further research is needed to verify its accuracy and feasibility. The current pain visualization method requires the implantation of a chip, which is complex and may also cause safety hazards. Therefore, in terms of clinical application, this method is not currently suitable for widespread use.
  Of course, if doctors can “see” a patient’s pain through a computer screen and combine it with other assessment methods, it will help improve the accuracy of diagnosis and the effectiveness of treatment. Especially for infants and young children who cannot accurately express pain feelings, the visualization of pain will be of great significance. If this technology can be applied in the field of pediatrics, it will greatly enhance doctors’ diagnosis and treatment accuracy and improve work efficiency.
  Currently, approximately 1.5 billion people worldwide suffer from conditions that cause chronic pain, so researchers are always looking for simple and effective pain relief methods. A recent study from Norway showed that participating in physical activity can help relieve pain. The research team analyzed partial physiological data from 10,732 Norwegian adults (data from a large population survey study), including participants’ self-reported levels of sports and physical activity and their pain tolerance levels. Statistical analysis showed that participants who were active had higher pain tolerance than those who were more sedentary. However, researchers are currently unable to explain the mechanism by which exercise increases pain tolerance thresholds.
  The research sheds new light on finding ways to relieve chronic pain, while also highlighting the importance of physical activity in promoting physical and mental health. Overall, we should actively participate in physical activities in our daily lives to enhance our physical fitness, relieve chronic pain, and improve our quality of life.

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