A pain memory 'trace': cumulative pain perception and damping during fight-or-flight response
Introduction
The fight-or-flight response is a well-known physiological reaction to perceived threats, but the decision-making process behind it is often overlooked. This study introduces the concept of cumulative pain perception as a critical factor in this decision-making. We propose that the body's pain signaling systems play a crucial role in how cumulative pain is perceived, influenced by nociceptors and neuroplasticity.
The body's pain signaling systems, including nociceptors, transmit signals to the central nervous system when tissues are damaged or under stress. In cases of cumulative pain, these signals may become more pronounced due to repeated or chronic stressors. Neuroplasticity, the brain's ability to adapt and reorganize its neural connections, also contributes to the perception of cumulative pain. The brain may "sensitize" to persistent pain signals, increasing sensitivity to pain and making previously minor discomforts feel more intense.
The perception of cumulative pain reflects the interaction between the body's physiological responses, an individual's emotional and cognitive state, and the broader social environment. This multi-input interaction informs whether the appropriate decision to a pain-generating situation is to fight or to flee.
Methods
To simulate cumulative pain, a sequence of rapid-onset and short-duration bite or swipe events inducing acute pain was modeled. The sensory input of each bite or swipe event was modeled as a rectangular function with a sudden onset of pain. The model equations, derived in detail in Fink and Raffa, were numerically solved using the Runge-Kutta-4 method.
Results
The simulation results demonstrated the model's ability to register, monitor, and discern individual consecutive pain signals. The pain perception rises rapidly as a function of stimulus intensity, then begins to decline and saturates at a lower level. The model can handle varying pain input characteristics, including different magnitudes and superimposed pain signals.
Discussion
The study suggests that the model can be applied to cumulative pain, providing a quantifiable mechanism to monitor cumulative injury. The modulation of pain, influenced by the diffuse noxious inhibitory control (DNIC) pathways, allows for time and intensity discrimination, aiding in the decision to fight or flee.
