Frequency tagging and the steady state evoked potentials

we aim to conduct three studies to clarify the influence of frequency tagging
on the brain response. The effects of frequency tagging will be analyzed
considering intrinsic aspects of the stimulation (i.e., topography and
likelihood of the response, questions analysed in all the experiments) as well
as aspects related to the effect of the use of the frequency tagging technique
(i.e. does the technique disturb the execution of a task, or may it provide
some advantage in some case, questions addressed in experiment 1). Experiment 2
and 3, will use frequency tagging as a tool to underpin the neural dynamics of
divided attention addressing differences between within modality (visual and
auditive, experiment 2) and cross modal (experiment 3) divided attention.

Understand the influences of repeated sensorial stimulations on brain*s
activity. Specific questions will be: 1) induction of alpha synchronization and
its relation with individuals* performance; 2) neural correlates of divided
attention in a within and cross modal divided attention context.

individuals will participate to one experiment where EEG will be measured while
performing a task. Experiment 1 will use the attentional blink paradigm (AB,
Raymond et al, 1992) as a cognitive task to test if increases in alpha rhythm
increases performance. In the AB paradigm 2 letter targets are embedded in a
stream of 12 digit distractors. Participants* task is to identify the two
targets. Usually the second of the two targets is missed when it follows 500 ms
after the first. In our version of the paradigm half of the trials will be
displayed with an oscillating object on the background. The oscillating object
will induce synchronization of the alpha rhythm, thus should improve
individuals* performance.
In Experiment 2 individuals will participate to one experimental session where
EEG will be measured while performing a letter detection task. Two streams of
alphanumeric characters (letters A to K and the digit 5) will be displayed on
the left and right side of the screen. Participants*task is to detect the 5 on
the stream while their eyes will be fixed on a *+* in the centre of the screen.
Attentional conditions will require the participants to direct their attention
either to the left, right, or to divide attention between both streams.
Experiment 3 will be performed in two sessions. In one session (i.e. visual
divided attention) the participants will have to detect colour or shape changes
in 4 squares oscillating with 2 different frequencies. The squares will be
arranged at the vertexes of a fixation cross (+). In the other session (cross
modal divided attention) two squares will be displayed on the horizontal mid
line of the computer monitor and simultaneously a sound will be played.
Participants will have to detect the changes in colours or dimensions of the
squares or the frequency change of the sound.

(valid for the three experiments): EEG measurements are not invasive. The
nature of the stimulation (a flickering square) can induce epilepsy in
epileptic individuals. Photosensitivity (or epilepsy history) will be specified
as exclusion criteria on the experiment advertise. The experiment is not
harmful for the participants.