Scientists find key brain circuits for attention

By Michael Kahn
17 july 2008--Scientists have identified the brain circuits that play a key role in helping us pay attention, a finding that may help explain why things go wrong in diseases such as Alzheimer's and attention deficit disorders.
The finding published in the journal Nature could provide a new target for potential drugs to treat some neurodegenerative conditions and attention deficit hyperactivity disorder or ADHD, the researchers said.
"What we have identified is the way this works in one particular area of the brain," said Alex Thiele, a neuroscientist at Newcastle University, who led the study.
"If we ever want to have a smart drug for diseases like Alzheimer's, we need to understand this level of detail."
Alzheimer's is a degenerative condition for which there is no cure. An estimated 24 million people worldwide suffer from the memory loss and problems with orientation that signal Alzheimer's and other, less common forms of dementia.
Existing drugs such as Aricept from Pfizer and Eisai, Exelon by Novartis and Razadyne or Reminyl from Johnson & Johnson and Shire can ease symptoms but do not stop the disease.
One new drug that could make a real difference is an experimental antibody-based treatment called bapineuzumab from Wyeth and Elan, which is now in final Phase III clinical tests. The companies are also working on a vaccine.
ADHD is a common condition that often becomes apparent in preschool and early school years. Treatments include drugs such as Ritalin, or methylpenidate, a stimulant intended to curb impulsiveness and hyperactivity, and boost attention.
"Our finding could potentially give researchers a more specific drug target," Thiele said in a telephone interview.
The researchers trained macaque monkeys to detect an object flashing on, while ignoring another one flashing nearby, and then injected tiny amounts of a compound called acetylcholine that helps carry nerve signals in the brain.
They then monitored both the brain cells and how well the monkeys performed a task that required attention. Acetylcholine appeared to make the neurons in the brain work better and help the monkeys pay attention more closely.
When the researchers blocked these receptors located in the visual cortex using a different naturally occurring chemical, attention worsened. This helped pinpoint these key receptors when it comes to paying attention, Thiele said.
Current Alzheimer's drugs do not target the receptors, but Thiele said a drug that activated them might be one approach to increasing attention and slowing Alzheimer's.
"This is the first time we can understand at least part of this mechanism," Thiele said. "It plays a main role."