Every aspect of the state of a neuron which is important for how it will function in future as a part of the brain can be measured.
Every aspect of the neuron mentioned in A1 can in principle be affected in such way that a neuron can be in principle returned to some state which was measured at time t1.
We can measure the input and output signals of the neurons, and reproduce signals of same nature, in same timely manner.
So, we take a brain of John, and do this:
- We record internal signals between the neurons in John’s brain, and the signals that come from his senses to each of the brain neurons starting from time t0 for some time-span dt. John is conscious over the time dt. dt can be for example 30 seconds.
- As we now know the outputs of each neuron we construct replay neurons, which when started fire the exact same outputs as the original neurons did starting from time t0 till the end of the dt period, in same timely manner as the original neurons did. Inputs can be connected to those neurons, but they ignore those.
- We reset (A2), all of the neurons to their states at t0, and replay the inputs which come from the senses to any of the neurons for the dt time period. Also at the start we replay the starting inputs to each of the neurons that don’t come from the senses, and which were measured at t0. Will John be conscious for this replay-dt time period?
- We change one of the original neurons with it’s corresponding replay neuron, and repeat everything as in 3. Let me point that if we take the neurons as black-boxes, i.e. abstract from what is happening inside them, everything about the brain looks same. The inputs and outputs are the same, and John behaves same.
- We replace more and more of the original neurons with the corresponding replay neurons, and repeat everything as in 3.
Q1: Would you agree that after changing all the neurons with their corresponding replay neurons, it can’t be true that John has conscious experience through the replaying?
Q2: If you agree with Q1, would you agree that it can’t be a matter of sudden turning off of conscious experience, but that it will be a gradual process?
Q3: If you agree with Q1, what is that which is lost in the John’s brain and which corresponds to having conscious experience?