If I don''t see it, I do not believe it, people say when they want to be certain of something. But arewhat we seeandwhat we think we seethe same thing? A new study claims that despite their usual strong correlation, visual information''s perceptual validity and its subjective interpretation useseparate neural mechanisms that can be manipulated independently of each other.
The study, led by researchers from the University of Bologna and the University of Glasgow (UK), has revealed for the first time that the two mechanisms involved are related on the one hand to the frequency of alpha oscillationsand, on the other hand, to their amplitude. This is the first causal evidenceof thedouble dissociation between what we see and what we believe we are. These findings may help to develop new therapies for neurological and psychosocial individuals.
Further, a dissociation between internal representation and external reality observed in the schizophrenia population might be caused by the non-communication, according to Viktor Romei, the professor at the University of Bologna, and the coordinator of the study. We have begun experimenting with new precision therapies to facilitate the integration of these two processes.
Among the most common examples of the divisiveness between perceived sensory events and their subjective interpretation can be found, e.g. at the clinical level in the case of schizophrenia or in everyday life in offalse memories. Researchers asked themselves whether these two aspects may be independently isolated from each other and on which particular component of brain activity they depend.
Researchers carried out a series of experiments based on a sample of 92 individuals. Participants underwent a visual detection task while their neural oscillations were detected using an EEG.
When we see something, it was possible to isolate the two key processes. One is more objective and related to theobservation accuracy, the other is less subjective and related to theinternal representation of the sensory event, e.g. the level of confidence in identifying what is seen.
Researchers say that the process related to the objective sampling of external reality is related to the speed of alpha oscillations. Participants receive more precise responses.
According toFrancesco Di Gregorio, a research psychologist at AUSL Bologna, the research shows that perception is a discrete rather than continuous process. Each alpha oscillations cycle is a sampling cycle of sensory information, thus the faster the oscillations, the more information can be collected, which increases accuracy.
The amplitude of alpha oscillations is crucial in the second process involved in the subjective representation of the sensory event. During the experiment, it was observed that a greater signal corresponded to a decrease in subjective confidence by the participants.
According to a PhD student at the University of Bologna, the amplitude of alpha oscillations has often been linked to inhibition processes. "The analysis also showed that the inhibitory process is particularly related to our subjective experience, not to our objective accuracy."
Through Transcranial Magnetic Stimulation (TMS), researchers analyzed the significance of these two elements in influencing perceptions. This technique enables direct control of neural oscillations by increasing or decreasing the speed and amplitude of alpha oscillations. It was possible to verify that these variations correspond to exact measurements in the perception of a person.
Despite this, it is important to emphasize that objective and subjective aspects of perception are significantly integrated. After the visual stimulus, the amplitude of alpha oscillations is further modulated, and our expectations are enhanced with the new information, according to Roomei. In this study, we demonstrate that the ability to perceive accurately (delivered by the speed of alpha oscillations) intercedes with the confidence of the response (delivered by the amplitude of alpha oscillations). Thus, our subjective representation is
The study was published in the journalCurrent Biology, under the title Tuning alpha rhythms in order to stifle conscious visual perception. The researchers at the Centre for Cognitive Neuroscience (Department of Psychology, Cesena Campus) met with Gregor Thut from the University of Glasgow (UK).
This article has been republished from the University of Bologna materials. Note: material may have been altered for length and content. Contact the cited source for further information.