Background
The inhibition of an ongoing response is a key component of executive control implying the voluntary
suppression of inappropriate behaviours 1 . Physiological mechanisms underlying this response are based on
an integrated cortical network, including the inferior frontal gyrus (IFG) and the dorsal premotor cortex (PMd) 2 .
Inhibition of unwilling actions can be experimentally probed through a standardised paradigm, the Stop Signal
Task (SST) 3-4 , that requires subjects to start a movement as quickly as possible when a Go Signal is presented
and to refrain from it if suddenly a Stop Signal appears during the reaction time (RT). This protocol allows for
the assessment of the inhibitory ongoing response, reflected by the Stop Signal Reaction Times (SSRT).
Recently, it has been demonstrated in healthy subjects (HS) that the activation of these cortical areas during
specific behaviours is reflected by modulations of beta-/gamma- oscillations 5 . These oscillations can be
experimentally and noninvasively modulated by transcranial alternating current stimulation (tACS) protocols.
The aim of this study is to explore the role of cortical beta-/gamma- oscillations in the physiology of inhibitory
human behaviours through SST protocol performed during specific tACS paradigms, in HS.
Methods
Six HS performed the SST during three different tACS protocols (β-, γ- and sham-tACS) randomly delivered
over the IFG and PMd, bilaterally, over two different days. The coordinates of right and left IFG and PMd were
first assessed through neuronavigation. During the SST paradigm we quantified RT and SSRT.
Results
Preliminary results suggest that beta- and gamma- tACS differently modulate action inhibition in HS. A two-
way repeated measures Anova revealed a significant interaction among the factors Area (IFG; PMd) and
tACS(β; γ). Post-hoc comparisons pointed out a significant difference in γ-tACS modulation among the two
areas (p=.03); gamma-tACS applied over the IFG decreased RTs, while the stimulation of the PMd increased
RTs. Furthermore, gamma-tACS increased SSRTs when applied over both IFG and PMd.
Conclusion
We demonstrated that beta- and gamma- tACS can modulate cortical oscillations underlying physiological
mechanisms of inhibitory control behaviours, in frontal cortical areas, in HS. These preliminary results provide
the background for future applications in neurological disorders characterised by deficit of inhibitory control,
such as Parkinson's Disease
