Exploring the effect of new brain stimulation techniques on cognitive functioning.

INTERVENTION: High‐definition transcranial electrical stimulation (TES) treatment targeting the anti‐correlated activity of the triple brain networks [Salience network (SN), Default mode network (DMN), and Central Executive Network (CEN)] will be administered for four individual treatment sessions, each of 30 minutes duration, by the researcher experienced in administering neuromodulation techniques. This study will be a double blinded (participant and assessor) pilot randomized placebo‐controlled cross‐over trial with one‐week of washouts in between the four treatments [High definition transcranial infraslow grey noise stimulation (HD‐tIGNS), High definition transcranial infraslow black noise stimulation (HD‐tIBNS), High definition transcranial infraslow violet noise stimulation (HD‐tIVNS), and Acti‐sham stimulation]. Each of the four interventions will be administered for a single session of 30 minutes (i.e., each participant will attend only 4 treatment sessions in total; with one of the four treatments administered at each session in a randomised order). A battery‐driven wireless 32 channel transcranial current stimulator (Starstim32 TES®, Neuroelectrics, Spain, http://www.neuroelectrics.com) will be used to deliver stimulation while the participants are comfortably and quietly seated. The Starstim32 is a high definition system with small electrode size that can focally target deeper brain regions. Forty circular Ag/AgCl stimulation electrodes will be placed on a neoprene head cap following the International 10‐20 EEG system. For the active stimulation phases (HD‐tIGNS, HD‐tIBNS, and HD‐tIVNS), the stimulation will be delivered at a current strength of maximum of 2mA for 30min, with 60s ramp up and ramp down at the beginning and the end of each stimulation s CONDITION: Cognition; ; Cognition Mental Health ‐ Studies of normal psychology, cognitive function and behaviour Neurological ‐ Studies of the normal brain and nervous system PRIMARY OUTCOME: Cambridge Neuropsychological Test Automated Battery (CANTAB) test battery: Reaction Time (RTI); ; [Baseline and immediately post individual treatment sessions.] CANTAB test battery: Pattern Recognition Memory (PRM)[Baseline and immediately post individual treatment sessions.] CANTAB test battery: Spatial Working Memory (SWM); [Baseline and immediately post individual treatment sessions.] INCLUSION CRITERIA: To be included in the study, participants must meet all of the following INCLUSION CRITERIA: • Capable of understanding and signing an informed consent form • Cognitively healthy, as determined by age norms of Mini Mental Status Examination • Age between 35 to 75 years on the day of the consent and • Right dominant SECONDARY OUTCOME: CANTAB test battery: Motor Screening Task (MOT) ; ; [This will be a primary outcome measure, but has been listed here because of space limitations above].[Baseline and immediately post individual treatment sessions.] Executive function: Emotional stroop task ; ; [This will be a primary outcome measure, but has been listed here because of space limitations above].[Baseline and immediately post individual treatment sessions.] Executive function: Stroop colour and word test ; ; [This will be a primary outcome measure, but has been listed here because of space limitations above].[Baseline and immediately post individual treatment sessions.] Executive function: Trail making tests A and B ; ; [This will be a primary outcome measure, but has been listed here because of space limitations above].[Baseline and immediately post individual treatment sessions.] Resting‐state Electroencephalography (EEG) [Current source density and functional and effective connectivity at the targeted triple network (SN, DMN, CEN) brain regions]. ; ; [This will be a primary outcome measure, but has been listed here because of space limitations above].[Baseline and immediately post individual treatment sessions.] Safety measures: Any adverse events or side effects (e.g. tingling or burning under stimulation electrodes). Participants will be asked to report the side‐effect and rate the intensity on a scale of 0‐10, and the relationship of the side‐effects to the intervention on a likert scale of 1 to 5 [1 being strongly unrelated, 3 being neutral, and 5 being strongly related]. ; ; [This will be a primary outcome measure, but has been listed here because of space limitations above].[During each intervention session, and immediately post individual treatment sessions.] State‐Trait Anxiety Inventory (STAI) questionnaire [Baseline and immediately post individual treatment sessions.]