The SPET scans allowed the researchers to check how the system was working by injecting a radiation-emitting chemical which seeks out working NMDAreceptors.
Pharmaceutical companies have made a habit of targeting the wrong cause (acetylcholinesterase inhibitors which are basically useless since as the disease progresses acetylcholinesterase activity declines by 85 percent), one aspect of the disease (Namenda as an antagonist for NMDAreceptors), or insisting on a partially flawed mechanism for the disease (amyloid plaques).