Abstract
Our sensory system is able to build a unified perception of the world,
which although rich, is limited and inaccurate. Sometimes, features from
different objects are erroneously combined. At the neural level, the
role of the parietal cortex in feature integration is well-known
(Humphreys, 2016; Shafritz et al., 2002). However, the brain dynamics
underlying correct and incorrect feature integration are less clear. To
explore the temporal dynamics of feature integration, we studied the
modulation of different frequency bands in trials in which feature
integration was correct or incorrect. Participants responded to the
color of a shape target, surrounded by distractors. A calibration
procedure ensured that accuracy was around 70% in each participant. To
explore the role of expectancy in feature integration, we introduced an
unexpected feature to the target in the last blocks of trials. Results
demonstrated the contribution of several frequency bands to feature
integration both pre- and post-stimulus. During the pre-stimulus period,
alpha power was higher for illusions compared to hits. After stimulus
onset, alpha, beta, and gamma-band power was reduced for hits compared
to illusions. Moreover, gamma power was overall larger during the
experiment for participants who were aware of the unexpected target
presented during the last blocks of trials (as compared to unaware
participants). These results demonstrate that feature integration is a
complex process that can go wrong at different stages of information
processing and is influenced by top-down expectancies.