I agree. This behavior is apparent in the Parmecium which does not have a neural network but it does have cilia. Thus, Paramecia are brainless but sentient or at least proto-sentient. And learns to synthesize Adrenalin, I tend to agree, but I've always wondered, why C elegans, a worm with a well mapped neural network does not respond to pain. According to Hameroff the worm has a neural network but it isn't used for "pain" transmission. The reason is that the worm has no cilia (surface receptors) to detect any introduced surface stimulation. Thus the single celled Paramecium feels "stress" from it's cilia, the worm C. elegans cannot, in spite of its neural network. The worm was stimulated with an electric shock, but just laid there. No pain response. https://www.livescience.com/50087-brain-pain-meter.html https://www.ncbi.nlm.nih.gov/books/NBK216/ It looks like cilia are a common denominator in all organisms with ability to "feel", and a neural network is required to transmit the sensation of "feel" to a central processor. Is the microtubular "sensor/transmitter" (cilia), and the neural "transmission distribution network", terminating with the translation of the transmitted signals by "microtubules in the brain"? Seems logically efficient to me.