| dc.description.abstract | Visual selective attention is an important cognitive function that assists us to prioritize the processing of surrounding stimuli with a limited capacity. The flanker task is one of the conventional paradigms for investigating visual selective attention. Previous studies have found that the electroencephalography (EEG) alpha activity in the parieto-occipital lobe plays a crucial role in both visual processing and selective attention. However, due to the lack of essential baseline conditions, the entrainment effect on behavioral indexes was only inferred from the comparison of different stimulus manipulations rather than changes from the typical flanker task performance. Therefore, to decipher the role of alpha oscillation in the selective attention task, we investigated the behavioral performance as well as the corresponding EEG indexes while the participants performed a modified Eriksen flanker task, in which the stimuli were composed of target and flankers flickering at different frequencies (i.e., 10Hz, 6Hz or 15Hz), that is 10T|15F, 15T|10F, 10T|6F and 6T|10F (the flicker frequency of target and flanker position is denoted as T and F, respectively). The typical no-flicker flanker task and 10T|10F trials were also added as one of the baselines to facilitate the interpretation of the 10 Hz entrainment effect.
The results show that:
(1) The overall RT, which is calculated as the average of congruent and incongruent RT, is significantly faster in the 15T|10F condition compared to 10T|15F, as well as 10T|10F and typical flanker conditions. Similar patterns are not found in any 6 Hz combinations.
(2) The congruency effect of the 10T|15F condition is significantly faster than both 15T|10F and typical flanker conditions, but no difference is observed for 6 Hz combinations.
(3) The attentional modulation of the 3 ~ 4 Hz AM modulating 10 Hz SSVEP response decomposed by HHSA is only observed in 15 Hz but not 6 Hz combination.
(4) The stronger the 10Hz power is, the larger the incongruent RTs of the 10T|10F, 6T|10F, and 10T|6F are.
(5) The increment of the congruency effect in 10T|15F trials from the typical flanker condition of each participant can be predicted by their enhanced 10 Hz power elicited by the flicker.
Collectively, in the current study, by depicting the direct relationship between the 10 Hz power change modulated by the external flicker and behavioral performance difference between each condition and the typical no-flicker condition, we aim to elucidate the alpha role in visual selective attention. Moreover, the distinct behavioral performance and the EEG responses in different conditions, which is probably due to the frequency-specific cortical network eliciting SSVEP responses, imply that the alpha inhibitory effect may depend on tagging frequency combinations. Specifically, 3 ~ 4 Hz AM modulating 10 Hz is significantly modulated by attention for 15 Hz combinations, suggesting spatial-specific 10 Hz entrainment, and then leads to the modulation on the congruency effect. On the contrary, for 6 Hz combinations, the incongruent RTs are modulated. The present findings thus contribute to the understanding of the interaction between flicker-induced response and intrinsic oscillation and further shed new lights on the interpretation of the entrainment effect. | en_US |