P300 Modulation via Transcranial Alternating Current Stimulation in Adult Attention-Deficit/Hyperactivity Disorder: A Crossover Study

Abstract

ObjectiveA repeated finding regarding event-related potentials (ERPs) is that patients with ADHD show a reduced P300 amplitude. This raises the question of whether the attention of ADHD patients can be increased by stabilizing the P300. Assuming that the P300 is generated by event-related oscillations (EROs) in the low frequency range (0–8 Hz), one approach to increase the P300 could be to stimulate the patient’s P300 underlying ERO by means of transcranial alternating current stimulation (tACS). The aim of this follow-up study was to investigate this hypothesized mechanism of action in adult ADHD patients.Materials and MethodsUndergoing a crossover design, 20 adult ADHD patients (10 female) received an actual stimulation via tACS on one day and a sham stimulation on another day. Before and after each intervention, EEG characteristics (P300 amplitudes, low frequency power) and attention performances (d2 attention test, visual oddball task (VOT)) were recorded.ResultsElectrophysiological analyses revealed no evidence for an enhanced P300 amplitude or low frequency power increase after actual stimulation compared to sham stimulation. Instead, a significant effect was found for a stronger N700 amplitude increase after actual stimulation compared to sham stimulation. Consistent with the P300 null results, none of the examined neuropsychological performance measures indicated a tACS-induced improvement in attentional ability.ConclusionContrary to a previous study using tACS to modulate the P300 in adult ADHD patients, the current study yields no evidence that tACS can increase the P300 amplitude in adult ADHD patients and that such P300 enhancement can directly improve neuropsychological parameters of attention.

Transcranial alternating current stimulation in affecting cognitive impairment in psychiatric disorders: a review

“…One study [ 46 ] applied a single session of 1 to 8 Hz over C1/C2 and C5/C6, without any cognitive improvement. This study also evaluated the P300 over centro-parietal regions, based on the hypothesis of reduced P300 generated by low frequency event-related oscillations (EROs), without any significant change.…”

“…Randomized control trials (RCT) were assessed according to the Cochrane database RoB 2 tool [ 52 ], with the assessed domains being randomization process, deviations from intended interventions, missing outcome data, measurement of the outcome, selection of the reported result and overall bias. Out of 15 RCT, three were evaluated as “Some concerns” due to single-blind design [ 23 , 46 , 47 ], two due to insufficiently described statistical analysis [ 21 , 35 ], one due to unsuccessful blinding integrity [ 41 ], and one due to insufficiently described blinding procedure [ 48 ]. Eight studies were considered “Low risk” [ 22 , 28 , 29 , 34 , 40 , 42 , 49 , 50 ].…”

“…In ADHD patients, although the listed studies may be related to certain documented pathological findings, the number of studies is too small, and the protocols with positive results may serve only as a guide for further experiments. It seems that individual phase-locking of tACS results in cognitive improvement [ 47 ], unlike a non-individualized protocol [ 46 ]. This phase-locking is feasible with a visual stimulus without the need for a closed-loop system.…”

“…Individually adjusted tACS involves individually determined electrode montage [ 37 ], frequency [ 46 , 47 ], and phase-locking through closed-loop [ 144 ] or stimulus-locked tACS [ 47 ]. During individually determined electrode montage, the stimulation electrodes are chosen according to the precise location of a given EEG parameter (e.g., highest frequency amplitude) or according to the model of electrical field distribution [ 145 ], which compensates for the inter-individual anatomical differences.…”

Non-pharmacological Interventions for Mental Disorders

“…In fact, to our knowledge, only three studies have so far explored tACS as treatment for adult ADHD (Dallmer-Zerbe et al, 2020;Farokhzadi et al, 2020;Kannen et al, 2022). While one of the studies compared tACS to methylphenidate (Farokhzadi et al, 2020) and reported tACS as an effective treatment, the other two studies investigated tACS as an alternative treatment for ADHD by trying to increase the P300 amplitude (Dallmer-Zerbe et al, 2020;Kannen et al, 2022), which is considered to be diminished in ADHD patients (Hasler et al, 2016;Marquardt et al, 2018;Kaiser et al, 2020). Dallmer-Zerbe et al (2020) observed an increase in the P300 amplitude accompanied by a decrease in omission errors among adult ADHD patients, whereas Kannen et al (2022) did not confirm these results.…”