If the central nervous system has truly stopped functioning, that would imply insensibility. That’s why loss of all measurable brain activity is taken as a sign of unconsciousness in clinical contexts. In humans, episodes with reduced CNS activity (for example, during deep anaesthesia or certain brain injuries) are generally associated with a lack of subjective experience.
For decapods, the challenge is that most studies measure spontaneous CNS activity rather than testing every possible form of responsiveness, such as testing to see whether we can evoke CNS responses through stimulation. So while prolonged inactivity is a strong sign of insensibility, researchers should still gather more data to increase confidence (especially given that, as you mention, we are putting a lot of resources behind this!)
The studies I linked above started measuring 2-10 minutes after stunning, but there are other studies which have measured CNS activity before, during, and immediately after the stunning process—for example, Fregin & Bickmeyer (2016). Interestingly, they observed that before settling into a quiescent state, intense epileptic-form seizures occur in the CNS that last for up to an hour after stunning. In mammals, epileptic-form seizures are associated with a loss of consciousness and a lack of subjective experience during that period, suggesting insensibility (and this is roughly how the authors interpret their finding). However, more work needs to be done to better understand this phenomenon in decapod crustaceans.
I’m not focussing on the asphyxiation process, so I’ll let someone with more knowledge in that area chime in. If no one does, I’d be happy to look into it!
If the central nervous system has truly stopped functioning, that would imply insensibility. That’s why loss of all measurable brain activity is taken as a sign of unconsciousness in clinical contexts. In humans, episodes with reduced CNS activity (for example, during deep anaesthesia or certain brain injuries) are generally associated with a lack of subjective experience.
For decapods, the challenge is that most studies measure spontaneous CNS activity rather than testing every possible form of responsiveness, such as testing to see whether we can evoke CNS responses through stimulation. So while prolonged inactivity is a strong sign of insensibility, researchers should still gather more data to increase confidence (especially given that, as you mention, we are putting a lot of resources behind this!)
I see, thanks. Is it possible to measure spontaneous CNS activity from beginning to end of the stunning and asphyxiating process?
The studies I linked above started measuring 2-10 minutes after stunning, but there are other studies which have measured CNS activity before, during, and immediately after the stunning process—for example, Fregin & Bickmeyer (2016). Interestingly, they observed that before settling into a quiescent state, intense epileptic-form seizures occur in the CNS that last for up to an hour after stunning. In mammals, epileptic-form seizures are associated with a loss of consciousness and a lack of subjective experience during that period, suggesting insensibility (and this is roughly how the authors interpret their finding). However, more work needs to be done to better understand this phenomenon in decapod crustaceans.
I’m not focussing on the asphyxiation process, so I’ll let someone with more knowledge in that area chime in. If no one does, I’d be happy to look into it!