21 February 2009

A cure for addiction?

At present, there is no reliable treatment for addiction. However, inhibitory closed-loop deep brain stimulation of the reward circuit might increase cognitive control in patients suffering from addiction.

Electrical inhibition of deep brain structures has been performed since neurosurgeons began doing stereotactic surgery aimed at the thalamus and basal ganglia (Kiss et al, in press). The procedure involves placing one or several implants with their electrode-covered tips in pathologically hyperactive brain regions. Current at inhibitory frequencies is to disrupt or normalize neural activity in the region. The operation takes 8-12 hours and costs ~£25.000. 1-3% of operations result in serious complications. Since 1997, 40.000 patients have recieved a Medtronic's Activa System - the most widely used deep brain stimulation (DBS) implant (Schwalb & Hamani, 2008). Many disorders, including Parkinson's, essential tremor, dystonia and obsessive compulsive disorder are characterized by hyperactive brain regions. Deep brain stimulation is replacing lesioning as standard treatment for these disorders, is EMA and FDA approved and is 'very benificial' in 80% of cases (Gritsun et al, 2006).

I suspect a DBS electrode placed in the human reward circuit could be trained to detect, extracellularly, the unique pattern of spikes, or even the readiness potential, of an unwanted behavior, such as a cue-induced or spontaneous drug-seeking behavior, or consumption of a drug (indicated by a sharp increase in firing frequency) (see Lee et al, 2008, for the latest in closed-loop DBS).

I also think such an implant could be programmed to disrupt activity in the reward circuit upon detection of an unwanted pattern of activity, through application of current at inhibitory frequencies. This should reduce the probability of the behavior being fully expressed or repeated.

This is not suggested as a method for law enforcement or rehabilitation of criminals, although such use is a possibility that should be discussed and probably prevented. Rather, it is suggested as a voluntary cure for addiction. Many addicts experience a profound desire to abstain from their drug of choice but find themselves compelled to increasingly frequent drug-seeking behavior and use. They should have the choice of simply turning their addiction off available to them. Moreover, deep brain stimulation is already being applied to the human reward system (nucleus accumbens) in successful attempts to use current at stimulating frequencies to treat depression (see image below). Furthermore, such implants should make decent iPlants, and patients suffering from addiction may be particularly well-suited for behavioral programming.
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