Excitatory Prefrontal Weak Current Stimulation in Vegetative Patients:Potential to Induce Modulation in Neurocognitive Features of Awareness

In response to "conscious" EEG findings related to detectable cognitive function that reliably denote awareness in vegetative state patients, in the current study, we will assess the covert conscious EEG activity (as well as standard clinical overt measures) and neuroplasctic propensity (i.e., changes in EEG spectral power synchronization values following tDCS intervention) in vegetative-state patients receiving repetitive transcranial direct current stimulation (tDCS) treatment over frontal motor areas for a period of two weeks. In support of this approach, a recent tDCS study with vegetative and minimally conscious patients implied that a twenty minutes anodal stimulation (i.e., excitatory stimulation) to the left dorsolateral prefrontal cortex (DLPFC) significantly increased CRS-R scores versus sham (placebo: non-active stimulation) stimulation condition. It was noted that this tDCS effect was more pronounced in minimally conscious state patients versus vegetative state patients excluding effects of chronicity or etiology. Thus, the investigators in this study suggested that tDCS could be effective in improving cognitive recovery in severely brain-injured patients. However, their findings would benefit neural activation correlates that could support their conclusion regarding the effectiveness of this type of non-invasive intervention in promoting neurocognitive recovery. Most importantly, tDCS is safe for use in humans, has no adverse effects, is considered the most non-invasive transcranial stimulation method because it uses extremely weak currents (0.5 to 2 mA), and, is known to only temporarily shift the neuron's membrane potential towards excitation/inhibition. In regard to the method's potential to induce functional recovery in vegetative state patients, recent clinical studies indicate that tDCS could counteract the negative effects of brain damage by influencing neurophysiological mechanisms, and is likely to contribute to the "formation of functionally meaningful connections and the maintenance of existing pathways" .