Transcranial Alternating Current Stimulation (tACS) as a Tool to Modulate P300 Amplitude in Attention Deficit Hyperactivity Disorder (ADHD): Preliminary Findings

Abstract

Studies examining event-related potentials (ERP) in patients affected by attention deficit/hyperactivity disorder (ADHD) have found considerable evidence of reduced target P300 amplitude across different perceptual modalities. P300 amplitude has been related to attention-driven context comparison and resource allocation processes. Altered P300 amplitude in ADHD can be reasonably assumed to be related to ADHD typical cognitive performance deficits. Transcranial alternating current stimulation (tACS) can increase the amplitude of endogenous brain oscillations. Because ERP components can be viewed as event-related oscillations (EROs), with P300 translating into the delta (0-4 Hz) and theta (4-8 Hz) frequency range, an increase of delta and theta ERO amplitudes by tACS should result in an increase of P300 amplitudes in ADHD patients. In this pilot study, 18 adult ADHD patients (7 female) performed three consecutive blocks of a visual oddball task while the electroencephalogram (EEG) was recorded. Patients received either 20 min of tACS or sham stimulation at a stimulation intensity of 1 mA. Individual stimulation frequency was determined using a time-frequency decomposition of the P300. Our preliminary results demonstrate a significant increase in P300 amplitude in the stimulation group which was accompanied by a decrease in omission errors pre-to-post tACS. However, studies including larger sample sizes are advised.

Transcranial alternating current stimulation (tACS): from basic mechanisms towards first applications in psychiatry

“…(3) the novelty of its treatment approach targeting specific alterations of brain functions at specific locations makes it significantly differ from conventional treatment strategies, such as pharmacotherapy. Although psychotropic drugs are widely accepted and approved in psychiatry, they still pose substantial problems with resistance, compliance and safety profile [195][196][197]; (4) tACS could help to target baseline oscillations, as well as event-related potentials [185]; (5) utilization of tACS should not be restricted to therapeutic purposes. The reactivity of the brain circuits to the stimulation protocol could serve as a possible tool to determine the diagnosis, classification or prognosis of psychiatric disorders, for instance, in patients with MCI [194].…”

“…Remission after three months C. OCD: Klimke et al [ 3 ] Cases series 7 OCD treatment-resistant patients 3 session per week. Treatment duration varied across patients Follow-up duration was 58 days and one year for 4 patients and the other three, respectively 20 min 650 µA 40 Hz Fp1-T3 and Fp2-T4 YBOCS, CGI The symptoms improved in all patients, and the improvement lasted throughout the follow-up duration D. ADHD Dallmer-Zerbe et al [ 185 ] Randomized single-blind controlled study 18 ADHD patients One stimulation or Sham 20 min 1 mA Timing and frequency personalized to coincide the stimulation peaks with P300 oscillation peaks Multiple electrodes on the central, parietal and temporal lobes EEG, visual oddball task Increase in P300 amplitude in the stimulation group accompanied by a behavioural improvement defined by a decrease in omission errors E. Dementia: Naro et al [ 194 ] Longitudinal case–control study 35 AD and 25 MCI individuals and 27 age-matched health participants Both sham and one of five verum stimulation sessions on a weekly basis 10 min 1 mA A range between 40 and 120 Hz at steps of 20 Hz Left M1, PMA, SMA, DLPFC, or DMPFC EEG and different neuropsychological tests (see text) - Enhancement of gamma-band oscillations and a clinical improvement in MCI, but not AD patients - tACS predicted the progression from MCI to AD …”

“…Interestingly, this P300 amplification was accompanied by a behavioural improvement in task performance. No serious adverse events were reported [ 185 ].…”

Lacking Effects of Envelope Transcranial Alternating Current Stimulation Indicate the Need to Revise Envelope Transcranial Alternating Current Stimulation Methods

“…The effects tACS has on neural processing has potential to be used in the medical field; although the use of tACS for medical application is still very new, there have been results for tACS as treatment for auditory 2 Neuroscience Insights hallucinations in schizophrenic patients 36,37 and attention deficit hyperactivity disorder (ADHD). 38 A new method dubbed envelope-tACS 28,29 has shown results in improving speech perception by electrically stimulating the envelope of a targeted speech stimulus. By subthreshold enhancing neural excitability in phase with the speech envelope, entrainment to the stimulus could potentially be strengthened.…”

“…The effects tACS has on neural processing has potential to be used in the medical field; although the use of tACS for medical application is still very new, there have been results for tACS as treatment for auditory hallucinations in schizophrenic patients 36 , 37 and attention deficit hyperactivity disorder (ADHD). 38 …”