A Multifocal tDCS-EEG Protocol for Improving Symptoms of Mild Cognitive Impairment and Early Dementia

The global prevalence of dementia is expected to continue to rise. Recent estimates forecast that the number of people with dementia worldwide will increase to 152 million cases in 2050. This calls for the development of effective prevention and treatment strategies. Recently, the benefits of non-pharmacological interventions for the intervention in dementia and its preclinical conditions are being explored. Within this contex, transcranial direct current stimulation (tDCS), represents a safe and straightforward approach to modulate brain excitability with the potential to reduce symptomatology in individuals with dementia and Mild Cognitive Impairment (MCI).

The objective of this study is to evaluate a protocol for the treatment of the cognitive and affective symptoms in dementia and MCI with several specific novel features.

First, the protocol adopts multifocal stimulation of relevant brain structures involved in the genesis of the symptoms. While previous studies focused on specific areas in the frontal and temporal cortex in separate treatment conditions, the present study employes multifocal tDCS over such structures to strengthen distribution of direct current over the left fronto-temporal network, and to possibly boost the achievable outcomes.

Second, to address the issue of heterogeneity of stimulation effects, the study combines electrophysiological measures (EEG) with brain stimulation to monitor the effect of brain stimulation following specific polarities, also considering possible individual differences in response to stimulation. Such a protocol would allow identifying responders (and non responders) to stimulation, thus targeting individuals which may benefit (or not) from a given intervention.

Third, the study will further explore the variability in response to brain stimulation raised by previous studies, considering the relationship between some demographic and psychological factors with clinical and electrophysiological outcomes. Previous studies have shown a buffering effect of age and education on global cognitive response following brain stimulation, and a relevant association of cognitive functioning with cognitive reserve. The contribution of these variables will be explored in the study to provide a more complex interpretation of either positive or null effects associated with the intervention.

Inclusion criteria

• age between 55 and 85 years;
• diagnosis of minor neurocognitive disorder, or major neurocognitive disorder with mild severity, according to Diagnostic and Statistical Manual of Mental Disorders (DSM-5; APA 2013) with a Clinical Dementia Rating Scale (CDR) of .05 or 1 (Morris, 1993);
• right handedness.

Exclusion criteria

• brain events with an acute aetiology (stroke, traumatic brain injury, neoplastic ablation);
• psychiatric disorders (schizophrenia, psychosis, bipolar disorder) and assumption of psychotropic drugs;
• diagnosis of moderate or severe major neurocognitive disorders (DSM-5; APA 2013) with CDR scores equal or above 2 (Morris, 1993);
• any condition with may also hypothetically interfere with electrophysiological recording and neurostimulation (metallic implants in the brain, cochlear implant, pacemakers, or suffering from epilepsy) (Antal et al., 2017; Bikson et al., 2016).