When we open the eyes, we effortlessly perceive a large amount of information. Despite the efficiency of our perceptual system in capturing and organizing vast amounts of information, it is not perfect, and sometimes, in integrating all this information, we can make errors. For example, imagine you are riding your bike down the street and see a friend of yours in a green shirt walking next to another person in a blue shirt. It may happen that you mistakenly perceive your friend's shirt color as blue, which would be due to an incorrect integration of your friend's form with the shirt color of the person walking nearby.
In our study, we used recordings of brain electrical activity to understand why these errors in perception occur. Our brain activity oscillates cyclically in low and high frequencies, and these oscillations are associated with attentional or memory processes, among others. In our experiment, participants performed a perceptual task in which approximately 30% of integration errors were made. The electroencephalographic data showed that brain activity in low frequencies (alpha) was different when the perception was correct and when an error was made. Moreover, these differences were present even before the stimuli were presented, indicating that the brain's preparatory activity before perceptual processing was related to the occurrence of these errors.
Additionally, without informing the participants, an unexpected stimulus appeared in the last block of trials (a white stimulus that had not been presented throughout the experiment), breaking their expectations (they expected to find a red, blue, or green stimulus). Interestingly, only half of the participants noticed this unexpected stimulus, and these participants exhibited greater power in high-frequency oscillations (gamma) compared to those who did not notice. Gamma frequency has been associated with complex cognitive processes such as memory or consciousness, indicating that these participants seem to perform the task more efficiently.
Our study highlights that visual perception is not limited to a single cognitive process and can fail for various reasons. These perceptual processes can be altered following brain damage, as occurs in Balint's syndrome or spatial hemineglect. Identifying these failures in perceptual processes could improve the quality of life for these patients.
Contact:
cobosm@ugr.es
Full Reference:
Cobos, M. I., Melcón, M., Esteban, P. R.-S., Capilla, A., & Chica, A. B. (2024). The role of brain oscillations in feature integration. Psychophysiology, 61(3):e14467. doi: 10.1111/psyp.14467