Biological Computation

The Never-Ending Story    ◾    309

involves the lowered ecacy over time of psychiatric drugs, many of

which achieve their eects by mimicking the structure of naturally

occurring neurotransmitters (e.g., by attaching to the receptors of

neurotransmitters and eectively blocking them). e body reacts in a

variety of ways, including changes in the number and density of neu-

rotransmitters receptors expressed, which cause the brain to readjust

to the changing levels of neurotransmitters and to return over time to

its activity state prior to the administration of the drug.

30. A relevant discussion and references can be found in Bonabeau et al.

(1999). e discussion in this book explains why drawing graphs is a

hard problem and why us