In daily life, we can attend to multiple moving objects. For example, the drivers always pay attention to pedestrians, cars and so on while driving a car. Extracting information to which the driver pays attention may allow us to prevent the accidents caused by lack of attention. To investigate attentional state to multiple moving objects, steady state visual evoked potentials (SSVEPs) elicited by flickering stimuli were recorded. SSVEPs reflect the attentional state and if you pay attention to the flickering stimulus, SSVEPs amplitude of the frequency is enhanced. However, is it possible to capture attentional state to multiple targets from the SSVEPs elicited by multiple moving objects. In this study, we investigated attentional state to multiple moving objects, and attempt to determine attended objects using SSVEPs.
In the experiment, three objects moving clockwise were displayed with different flickering frequencies (Square is 12Hz, Rhombus is 13.33Hz, Circle is 15Hz). Participants were instructed to track two moving targets among three (three attentional states).
We analyzed peak amplitude of elicited SSVEPs in each attentional state. In addition, we decoded the attentional state from single-trial SSVEPs by canonical correlation analysis (CCA).
The result showed that SSVEP amplitude was significantly modulated depending on attentional state. Discrimination rate of each condition from SSVEPs by CCA is 60% (gaze 12Hz and 13.33Hz), 52% (gaze 12Hz and 15Hz), and 50% (gaze 13.33Hz and 15Hz). These discrimination rates was significantly higher than chance level (33.3%) (right tailed t-test). These results showed that SSVEP amplitudes differed depending on attentional state suggesting that it is possible to extract attentional state to multiple moving targets using SSVEPs.
Our findings provide the first neural evidence of estimating the attentional state of multiple moving targets by SSVEPs.