Alcoholism Treatment by Cognitive Neuromodulation Produced by Repeated Transcranial Direct Current Stimulation Over the Left Dorsolateral Prefrontal Cortex

A hallmark of alcoholism is the deficiency of the frontal lobe, characterized by deficits in attention and working memory and executive dysfunction. This condition is especially marked by an inability to abstain from alcohol, having direct implications for the treatment of alcoholism (Goldstein and Volkow 2002).

In a previous study, we examined the frontal function by the Frontal Assessment Battery (FAB) and mental state through the Mini-Mental State Examination (MMSE) in 170 patients with alcoholism classified according to Lesch's typology (Zago-Gomes and Nakamura- Palacios 2009). In a global analysis, the alcoholics showed total scores on MMSE and FAB significantly smaller compared to non-alcoholics subjects. Type IV alcoholics showed lower scores on MMSE and FAB in comparison with non-alcoholics and all other types (Lesch's types I, II and III) of alcoholics. In a more specific analysis, even in alcoholics Type IV who had mental function (MMSE) preserved, the executive function (FAB) was significantly reduced (Zago-Gomes and Nakamura-Palacios 2009).

Moselhy et al. (2001) suggest that the frontal cognitive deficits observed in alcoholic patients are important predictors of therapeutic results. According to Lesch et al (1989, 1990, and in personal communication), Type IV alcoholics, who showed more severe frontal deficits are the ones who have the worst prognosis, with great difficulty in abstaining from alcohol, but still being treatable under intensive and multiple approaches. Therefore, investigations of new perspectives for the treatment of these alcoholics are especially needed.

A technique of neuromodulation that has been increasingly used and tested is the transcranial Direct Current Stimulation (tDCS). In this method, a weak direct current is induced in the cerebral cortex through two electrodes usually placed on the scalp (Nitsche et al 2008). Several studies have shown that this noninvasive method of brain stimulation is associated with significant changes in cortical excitability - increasing or decreasing it according to the polarity of stimulation (Nitsche and Paulus 2000, Nitsche and Paulus 2001; Zaghi et al 2009). Animal studies from the 50s and 60s showed that the effects of tDCS are associated with changes in the threshold of neuronal membrane at rest (Bindman et al 1964b; Purpura and McMurtry 1965). There is evidence that anodal transcranial stimulation improves cognitive function in man, and this effect seems to be due to a strengthening of glutamatergic synapses (Fregni et al 2005, Iyer et al 2005, Nitsche et al 2003).

In a recent study we examined the clinical and electrophysiological (indicated by the P3 component) effects of tDCS application over the left dorsolateral prefrontal cortex (DLPFC) in different types of alcoholics according to Lesch's typology (data submitted for publication). We enrolled 49 alcoholics aging between 18 and 75 years old during the subacute period of abstinence. These individuals were submitted to event-related potentials (ERP) under the presentation of sounds related or non-related to the use of alcohol before, during and after active tDCS (1mA, 35 cm2, for 10 minutes) or sham procedure at a randomized and counterbalanced order. We observed a significant improvement in the FAB performance after the active tDCS compared to sham in Type IV alcoholics. There was an increase in the amplitude of P3 mainly in frontal site (Fz). This change was also more pronounced in Type IV alcoholics. Thus, we found clinical and electrophysiological evidence of increased frontal activity induced by tDCS specific to the type IV alcoholics. Considering that the frontal dysfunction, may contribute to the loss of control over drinking behavior, these results suggest that a local increase in frontal activity induced by tDCS may have a beneficial clinical impact.