Recent quotes:

ADHD drug Ritalin has no effect on primate prefrontal cortex -- ScienceDaily

Julio Martinez-Trujillo and colleagues refute their hypothesis the caudal prefrontal cortex -- a brain region critical for attention -- is Ritalin's main site of action in the brain. To arrive at this conclusion, the researchers recorded large populations of neurons in this brain region as two male macaque monkeys performed a demanding visual attention task. The team did not observe any differences in neuronal activity after administration of the drug compared to a placebo, even at doses that improved the monkeys' performance on the task.