Transcranial alternating current stimulation at 10 Hz modulates response bias in the Somatic Signal Detection Task

• Published in: International journal of psychophysiology Vol. 135; pp. 106 - 112
• Main Authors: Craddock, Matt, Klepousniotou, Ekaterini, El-Deredy, Wael, Poliakoff, Ellen, Lloyd, Donna
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.01.2019; Elsevier
• Subjects: Alpha oscillations; Alpha Rhythm - physiology; Female; Humans; Male; Psychomotor Performance - physiology; Signal detection theory; Somatosensation; Touch Perception - physiology; Transcranial alternating current stimulation; Transcranial Direct Current Stimulation - methods; Young Adult; Signal detection theory; Transcranial alternating current stimulation; Alpha oscillations; Somatosensation
• ISSN: 0167-8760; 1872-7697
• DOI: 10.1016/j.ijpsycho.2018.12.001

Ongoing, pre-stimulus oscillatory activity in the 8–13 Hz alpha range has been shown to correlate with both true and false reports of peri-threshold somatosensory stimuli. However, to directly test the role of such oscillatory activity in behaviour, it is necessary to manipulate it. Transcranial alternating current stimulation (tACS) offers a method of directly manipulating oscillatory brain activity using a sinusoidal current passed to the scalp. We tested whether alpha tACS would change somatosensory sensitivity or response bias in a signal detection task in order to test whether alpha oscillations have a causal role in behaviour. Active 10 Hz tACS or sham stimulation was applied using electrodes placed bilaterally at positions CP3 and CP4 of the 10–20 electrode placement system. Participants performed the Somatic Signal Detection Task (SSDT), in which they must detect brief somatosensory targets delivered at their detection threshold. These targets are sometimes accompanied by a light flash, which could also occur alone. Active tACS did not modulate sensitivity to targets but did modulate response criterion. Specifically, we found that active stimulation generally increased touch reporting rates, but particularly increased responding on light trials. Stimulation did not interact with the presence of touch, and thus increased both hits and false alarms. TACS stimulation increased reports of touch in a manner consistent with our observational reports, changing response bias, and consistent with a role for alpha activity in somatosensory detection. •Active tACS stimulation alters response bias, not perceptual sensitivity.•Both true and false reports of touch increase during active versus sham stimulation.•Reports of touch increase more during stimulation when a light-flash occurs.