I cannot give a clinical answer but I will respond based on experience.

I believe that it does increase the CNS efficiency but not to the same extend of the PNS.

The PNS efficiency is drastically improved upwards of 300-400%.

Can I say that the CNS efficiency is doubled? Perhaps.

I am able to overtrain on cycle but it is more difficult than off cycle.

If my nutritional intake is low on cycle or if I drop a strong AAS like Dianabol from my cycle and continue to train with equal volume and intensity, overtraining is easily achieved.

Is this to say Dianabol affects the CNS efficiency? Don't know.

There is a fine line between CNS and PNS relationship and performance. Getting to the limit of PNS without dipping into the CNS has been the key to adding tissue and overall athletic performance.

Not sure if I added thing of value or was mumbling. Hope this helps.