Newswise — Roughly 50% of patients who suffer a stroke in the right cerebral hemisphere eventually exhibit an extraordinary symptom: a loss of perception concerning the left side of their surroundings. Consequently, they exhibit peculiar behaviors such as exclusively eating from the right side of their plate, overlooking individuals on their left, and struggling considerably with navigation. This condition is termed "hemispatial neglect" and primarily affects spatial awareness, while their fundamental visual capabilities remain unaffected.
According to Paolo Bartolomeo, a neurologist and researcher at the Paris Brain Institute, these patients possess normal visual acuity. The issue lies in their attentional focus rather than a lack of visual information. They fail to be conscious of a portion of their surroundings because they are not directing their attention towards it. The treatment approach for these patients involves a form of re-education to enhance their attentional abilities.
The intriguing paradox of perceiving elements of reality while simultaneously remaining unaware of them raises questions about the intricate connection between consciousness and attention. Numerous researchers have attempted to elucidate this relationship over the years, leading to various competing theories, yet none have emerged as the definitive explanation. To delve deeper into this mystery, Paolo Bartolomeo and Jianghao Liu, a doctoral student in the PICNIC team, have taken the initiative to experimentally test these theories.
Gabor to starboard
Jianghao Liu explains that their objective was to explore the intricate interactions between attention and conscious perception in meticulous detail. This endeavor aimed not only to gain insights into attention-related disruptions in specific cognitive disorders but also to advance our overall comprehension of human consciousness. While clinical studies have indicated that attention is a necessary but not sufficient factor for conscious perception, the exact translation of this process in the brain remained elusive. Hence, their research focused on unraveling the mechanisms underlying attention processing within the frontoparietal networks.
In their quest to uncover answers, the researchers directed their attention towards exogenous attention, which involves focusing on environmental stimuli. Traditional neuroimaging methods like fMRI and EEG proved inadequate in providing precise data on brain activity during cognitive tasks. To overcome this limitation, the team turned to intracerebral electrophysiological recordings. They analyzed data from 13 epileptic patients who had undergone deep brain electrode implantation as a treatment for drug-resistant epilepsy. This approach allowed them to gain more detailed insights into the neural mechanisms involved in cognitive processes related to attention.
During the study, participants were tasked with a cognitive challenge involving the detection of a Gabor patch, which can become barely noticeable when the contrast of its black and white bars is altered. The Gabor patch target would appear on either the left or right side of the screen and was preceded by a visual cue—a simple black dot. The cue could be either accurate, correctly indicating the side where the target would appear, or misleading, announcing the wrong side. Additionally, in certain instances, the Gabor patch did not appear at all, introducing a condition without the target stimulus.
Supporting neural evidence
Jianghao Liu explains that through this experiment, they were able to establish that manipulating participants' attention using the visual cue had a profound impact on their conscious perception of the Gabor patch and their ability to describe what they had seen. Depending on the stimuli, their attention capacities either decreased significantly or increased dramatically. Moreover, they observed distinct neural networks being engaged in various types of interactions between attention and conscious perception. This insight shed light on the intricate relationship between attention and conscious awareness within the brain.
In a more detailed analysis, the researchers employed electrophysiological recording to pinpoint five clusters of electrical activity linked to attention maintenance and redirection within the frontoparietal networks. To validate these findings further, they utilized white matter tractography—an imaging technique—to confirm that these clusters aligned with the anatomical neural projections that could be observed. To enhance the reliability of their results, a computer model was employed to verify that the observed neural dynamics were not exclusive to epileptic patients and could be generalized across broader populations eventually.
According to the researcher, a significant milestone has been achieved as, for the first time, they successfully mapped the specific brain regions responsible for the interplay between attention and conscious perception. This breakthrough challenges prevailing hypotheses that suggest conscious perception and attention are entirely separate functions, each relying on distinct neural networks. In contrast, the data they obtained demonstrates the opposite, indicating a strong correlation and interaction between these cognitive processes within the brain.
Undoubtedly, the interactions between attention and conscious perception play a crucial role in shaping our perception of the world. Our attention is continually directed toward various events, whether significant or minor, in our surrounding environment. Paolo Bartolomeo adds that their next objective is to explore whether attention to endogenous events, those originating from our thoughts, internal sensations, and inner experiences, could also impact consciousness. This exploration is just as intriguing as our capacity to perceive the external universe, as our ability to attend to ourselves holds equal fascination.
RSS