When I think of lithium, batteries and rechargeable batteries come to my mind. If I think back to the periodic table, there are some typical alkali metal properties, i.e. it's flammable and coated by a layer of oxid when exposed to air. It also burns read when lit.

But a few days ago I heard for the first time in my life that lithium is used as a drug against bipolar disorder, hyperactivity, mania, etc., so basically to calm people down. I haven't understood the exact mechanism yet, but what people know, is, that it works.

I learned this during a talk given by Matthew Fisher who is a physics professor here at my university. He used to be interested in condensed matter systems and now changed his field of study to interdsiciplinary neuroscience. There's an article in the "New Scientist" about him and his theory (Is quantum physics behind your brain’s ability to think?).

So, what's the point? Lithium occurs in two isotopes, Lithium-6 and Lithium-7. Their chemical properties are really close to being exactly the same because they have the same outer electron shell. Thus, one would expect the same therapeutic effect for Lithiums as a drug. Nowadays, a mixture seems to be most common for medication.

But, about 20 years ago,  there was a study with female rats which showed that one of the isotopes (as far as I remember Lithium-6) made rats even more active and Lithium-7 made them calm down. So the resulting behavior had the opposite effect! How can that be possible if the chemical properties should be the same?!

The answer might lie in the time for the nuclear spin of a solve lithium-ion to entangle to the surrounding water molecules. This time is highly different for both isotopes (10s and about 5 min!). If this time difference would account for the rats' opposing behavior, there would be quantum effects involved in the brain. There are not many other molecules in the human brain which indicate the relevance of possible quantum processing; nevertheless, there is one large phosphor complex which has an "entanglement time" of about 10 min as well and it's properties are studied.

Since physics is still an experimental science, we have to wait for the rat experiment to be conducted (which should happen in the next year at Stanford).