Inhibitory sensory-motor links in the human brain

Several studies have investigated inhibitory mechanisms by combining the so
called Stop Signal Task (SST) with EEG. In the typical SST, participants are
required to respond to go-stimuli (typically letters) by means of a button
press. In a small percentage of trials, a stop signal is presented after the
go-stimulus. The stop stimulus requires the prepotent response to be withheld.
Two specific variants of the SST have been reported in the literature, the
auditive and the visual SST. In the visual SST, stop stimuli are presented in
the same domain (stop stimuli are often letters) as the go-stimuli. In the
auditive SST, the stop stimuli are presented in the auditive domain (stop
stimulus is a tone). The specific inhibitory mechanism that is activated
differs between variants of the SST. In the auditive variant, a potentiated
inhibition link between sensory (auditory) cortex and motor cortex is active,
which is under control of the right frontal cortex. In the visual variant,
however, the right frontal inhibition mechanism is active only after onset of
the stop-stimulus.

The specific mechanism of inhibition differs between SST variants, it remains
the question why. Our envisaged study focuses on this question. We expect that
the difference is caused by the amount of perceptual overlap between the go
stimulus and the stop stimulus (for a complete overview of the rationale, see
protocol). Hence, we expect that by reducing perceptual overlap between the go
and stop stimulus in the visual SST, a similar inhibition mechanism is in
effect as in the auditory SST. That is, a potentiated link between sensory
cortex (in this case visual cortex) and motor cortex will be evident.

The design is a randomized within-subjects design. More specifically,
participants will perform in three variants of the SST, the auditive, visual
overlap (sizeable perceptual go/stop-stimulus overlap), and visual non-overlap
(low perceptual go/stop-stimulus overlap) variant, while EEG is recorded. The
order of SST variants will be counterbalanced accross participants, and
participants will be randomly attributed a specific order (with optimal
balancing as a prerequisite).

not applicable

Risks are negligible , EEG is a non-invasive measurement. The burden for
participants is estimated to be minimal. There is ample opportunity for short
breaks and between SST variants there is room for a 10 minute break.
Particants are informed that they can withdraw from the study at any time and
that it is not necessary to explain the reason for withhdrawing from the
experiment.