The search for drugs to alter learning and memory processes in animals
and man has its roots in mythology as well as the history of medicine.
The use of plant alkaloids to improve memory was a recommendation of
Benjamin Rush in his "Diseases of the Mind" (1812, P. 284), and the
mysterious contents of lethe, a liquid capable of causing the erasure of
earthly memories is found in Egyptian and Greek mythology, as well as
described by Dante, remains a still-sought amnesic molecule. The
facilitation of learning or improvement of memory has been claimed for
several plant-derived substances including coca, chat, caffeine, and
nicotine. Hypotheses concerning substances found in the brain and their
presumed significance for learning or memory led to the development and
use of agents that contained such substances. For example, as observed
by William James (1892, P. 132), the emphasis, in Germany during the
1860's, upon phosphorus in the brain for cognitive functions gave rise
to the suggestion that foods vii viii CLINICAL PHARMACOLOGY OF LEARNING
AND MEMORY high in phosphorus content, such as fish, were good for brain
function. Phosphorus-containing preparations were advocated for use in
cases of poor memory, exhaustion, etc., and though sometimes useful,
probably were effective due to a non-specific stimulant effect. Whether
the positive cognitive efficacy of non-specific CNS stimulants such as
phosphorus, rosemary, lavender, cubeb berries, etc. were really very
different from those investigated in animal experiments (Lashley, 1917)
or those documented within recent decades remains to be explored.
