June 29, 2008
Research On Ritalin Mechanism Of Action

Some people are tempted to use Ritalin (Methylphenidate) in order to boost their cognitive performance. But will it burn out your brain the way methamphetamine can? Ritalin does not appear to work as a stimulant.

MADISON - Stimulant medications such as Ritalin have been prescribed for decades to treat attention deficit hyperactivity disorder (ADHD), and their popularity as "cognition enhancers" has recently surged among the healthy, as well.

What's now starting to catch up is knowledge of what these drugs actually do in the brain. In a paper publishing online this week in Biological Psychiatry, University of Wisconsin-Madison psychology researchers David Devilbiss and Craig Berridge report that Ritalin fine-tunes the functioning of neurons in the prefrontal cortex (PFC) - a brain region involved in attention, decision-making and impulse control - while having few effects outside it.

Because of the potential for addiction and abuse, controversy has swirled for years around the use of stimulants to treat ADHD, especially in children. By helping pinpoint Ritalin's action in the brain, the study should give drug developers a better road map to follow as they search for safer alternatives.

At the same time, the results support the idea that today's ADHD drugs may be safer than people think, says Berridge. Mounting behavioral and neurochemical evidence suggests that clinically relevant doses of Ritalin primarily target the PFC, without affecting brain centers linked to over-arousal and addiction. In other words, Ritalin at low doses doesn't appear to act like a stimulant at all.

Emphasis on the "at low doses". At higher doses the picture is different.

Ritalin at lower doses appears to cause the prefrontal cortex (PFC) to be more sensitive to signals coming in from the hippocampus.

When they listened to individual PFC neurons, the scientists found that while cognition-enhancing doses of Ritalin had little effect on spontaneous activity, the neurons' sensitivity to signals coming from the hippocampus increased dramatically. Under higher, stimulatory doses, on the other hand, PFC neurons stopped responding to incoming information. "This suggests that the therapeutic effects of Ritalin likely stem from this fine-tuning of PFC sensitivity," says Berridge. "You're improving the ability of these neurons to respond to behaviorally relevant signals, and that translates into better cognition, attention and working memory." Higher doses associated with drug abuse and cognitive impairment, in contrast, impair functioning of the PFC.

Ritalin may work by reducing the number of things the mind pays attention to. This lets you more productively do mental processing on what actually gets the mind's focus.

More intriguing still were the results that came from tuning into the entire chorus of neurons at once. When groups of neurons were already "singing" together strongly, Ritalin reinforced this coordinated activity. At the same time, the drug weakened activity that wasn't well coordinated to begin with. All of this suggests that Ritalin strengthens dominant and important signals within the PFC, while lessening weaker signals that may act as distractors, says Berridge.

But be careful. Ritalin has side effects.

Share |      Randall Parker, 2008 June 29 11:02 PM  Brain Enhancement


Comments
Guillaume Theoret said at June 30, 2008 7:11 AM:

My brother was diagnosed with ADHD when we were kids. He wasn't on Ritalin long though because my mother eventually refused to give it to him anymore. He couldn't sleep at all and basically walked around like a living zombie. Sure the 'H' was gone, but I don't think it was doing much for the 'AD' part.

Rob said at June 30, 2008 12:51 PM:

Ritalin strengthens dominant and important signals within the PFC, while lessening weaker signals that may act as distractors

Less cross-talk could be why some people report that ritalin makes them less creative. Though as far as I know no one has done tests of divergent thinking with and without ritalin

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