Yes, but the amount of neurons is limited in beeings with less than 5mm, to envolve they must turning also somewhat bigger.

The reason why Asimov wrote a second novel after Fantastic Voyage, which was an work based on the movie, but Asimov are not satisfied about it as scientific, because reducing the size of the people to molecular level, there are impossible that they are capable even to think more than a molecule, so he wrote a second part and in this the bodies are not reduced, but partially traslated to an parrallel dimension, so that the remaining part were small enough to be inyected in the body of the pacient.