It also must be having an 'I'. Maybe this 'I' is very simple and small. But an amoeba does not have a brain. When we wake up, we have the same consciousness as before. Where does the consciousness go during this time.
Drug addicts change their thought content and emotions when they are intoxicated.
In psychosis, there is derangement of perception of self and thought content of the person. And this can be treated by drugs with varying degree of success. These drugs interact with the mind and can alter it. Or do these 'tangible' substances also have their own 'I's which interact with your 'I'. There is no way in which one person can communicate with another what one feels except by representations which are, at best, only crude images of the perceptions.