The fundamental tenant of modern materialism is that the only thing which exists are properties.
It is mathematically impossible to show otherwise, since anything you observe about an entity amounts to some kind of property.
So a neuron is a set of properties. You can't really dispute this.
Furthermore, all properties can be emulated / simulated.
You don't quite understand how this could be done, because you still haven't wrapped your brain around the fact that what you call "physical" properties are relative.
The interactions between particles are relative. The interactions between you and your car are relative. The interactions between the neurons in a brain are relative. Location, velocity, momentum, time, even energy -- all relative properties.
When a relative property is simulated, all relevant sides are included. If not, then the property is not being simulated. Plain and simple.
Obviously, when a car is simulated and you are not, you are not included in the simulation. Obviously, the simulated car and the real you can't interact -- the physical properties of the simulated car are not relative to you anymore.
Obviously, if you were simulated as well, then you could interact with the simulated car.
If you disagree with any of this, then feel free to mathematically prove that we do not live in a simulation right now. Or, simply tell me how it might even be possible to figure out whether we are living in a simulation or not.