Asking what life is or what thought is is interesting, but we are only beginning to figure it out; and involves lots of calculus and physics, chemistry and biology, so lets move on to slightly easier to study stuff….like the supplemental motor area and its relevance to motor acts and the unconscious preparation of motor acts.. It seems that the supplemental motor areas are activated when ventilation becomes difficult. Thus accessory muscles can be activated to pitch in to help when the autonomic pathways of the brain stem are insufficient, perhaps due to injury.
Remember that Paula needs to activate more skeletal muscles than the diaghragm in order to manage adequate minute ventilation in the face of a resting breathing rate that is very low. It seems that the SMA [supplemental motor area] is crucial to her altered pattern of breathing, when awake. Paula does experience the extra effort it takes her to breathe, she always thought this to be normal; it is not!
It seems that both involuntary (bulbospinal) and voluntary (corticospinal) pathways interact in respiratory muscle control and this is not well understood.
The SMA and other cortical areas that contribute to premotor potentials are also activated in response to inspiratory mechanical constraints (generally referred to as “inspiratory loads,” a generic term that designate any experimental device imposing an increased effort on the respiratory system, e.g., resistances, elastances, and threshold valves) in normal humans (Raux et al., 2007a,b, 2013). This cortical activation is hypothetized to constitute an adaptative reaction, although its exact pathway is not known. It occurs in conjunction with altered breathing pattern, usually hyperventilation (“overcompensation”; Freedman and Weinstein, 1965; Yanos et al., 1990). It is also accompagnied by breathing discomfort (Raux et al., 2007a, 2013).
In Paula’s case, it seems that the Supplemental Motor Area is active during awake breathing at rest and this is a sign that breathing at rest takes extra effort. Paula has depressed ventilation not hyperventilation. She needs to use more voluntary muscles automatically than just the diaphragm [also a voluntary muscle that is engaged involuntarily]. We have measured her tidal volume, respiratory rate and minute ventilation recently, in a pulmonary function lab. Her tidal volume is just enough to give her a normal minute ventilation, despite her respiratory rate of 3 breaths per minute at rest. And with normal minute ventilation and pulse oximetry [this was also tested] and presumably normal respiratory acid base balance, Paula has no trouble with thinking, speaking, singing and goal oriented voluntary motor actions based on her thoughts.
When Paula became ill, 20 years ago, she not only felt unbearable breathing discomfort that she could not describe, but she also had great difficulty enacting voluntary actions. As a result she could not easily talk, and she could not remember there thoughts long enough to enact them. Her cortical neural processes were disturbed, we think. We think that this was because she had respiratory pump failure and an energy deficit. Interestingly, she could more easily respond to externally triggered actions, it seems that following instructions involved a different neural pathway than voluntary action. This needs more study, we think….It does seem that impaired voluntary action reflects impaired self consciousness and function.
- Nature Communications volume 11, Article number: 289 (2020) Breathing is coupled with voluntary action and the cortical readiness potential Hyeong-Dong Park, Coline Barnoud, Henri Trang,
- Oliver A. Kannape, Karl Schaller & Olaf Blanke
Voluntary action is a fundamental element of self-consciousness. The readiness potential (RP), a slow drift of neural activity preceding self-initiated movement, has been suggested to reflect neural processes underlying the preparation of voluntary action; yet more than fifty years after its introduction, interpretation of the RP remains controversial. Based on previous research showing that internal bodily signals affect sensory processing and ongoing neural activity, we here investigated the potential role of interoceptive signals in voluntary action and the RP. We report that (1) participants initiate voluntary actions more frequently during expiration, (2) this respiration-action coupling is absent during externally triggered actions, and (3) the RP amplitude is modulated depending on the respiratory phase. Our findings demonstrate that voluntary action is coupled with the respiratory system and further suggest that the RP is associated with fluctuations of ongoing neural activity that are driven by the involuntary and cyclic motor act of breathing.
Paula and I think that her cortical readiness potential and her voluntary actions were disturbed because her just good enough minute ventilation became “not good enough” to support much else besides using her remaining energy to continue breathing with the extra effort she barely had strength for; we think that her nervous system was suppressing her thinking and voluntary activity because she had a decline in her cortical readiness potential due to the internal bodily signals affecting the respiratory – action coupling. And these internal bodily signals were screaming fear and danger due to the heightened risk of respiratory pump failure.
We sometimes forget about the stimulus response reflexes due to internal processes and internal signals.