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Perceptual load and neural competition. Determinant factors in selective attention

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To ignore or not to ignore- How does the brain decide?

When our thinking brain is exhausted, it falters in processing all the information that bombards it. Revealing the mechanisms behind the brain's perceptual load is important for understanding how selective attention works and the theories behind it.


The brain is quite efficient in ignoring input it doesn't want, particularly when it feels overloaded. According to the perceptual load theory, our ability to ignore distracting information depends on how much a task exhausts perceptual capacity. There is no single definition on what high and low perceptual loads are, which is crucial for understanding the concept of attention. The EU-funded project 'Perceptual load and neural competition. Determinant factors in selective attention' (LOADATCMC08) looked at new approaches to define perceptual resources. Project partners explored visual cortex activity and the mechanisms involved in attentional selection. They looked at neural mechanisms underlying perceptual load-based selection, closely examining selective processing and limits of capacity in the human brain through several methods. More specifically, the project team studied how resource allocation depends on the demands required to process the task-relevant information. The neural signature of perceptual load was studied after collecting brain scans of participants as they performed attention-demanding tasks where the load is gradually increased. These studies showed how the fronto-parietal brain regions are affected. Results demonstrated the strong push–pull relationship in neural activity in attended vs. unattended processing to support load theory predictions. On another level, research also focused on behavioural studies to address recent criticisms of load theory. In addition, experiments revealed that when task demands are low there is a competition between stimuli for the spare attentional-processing resources. These conclusions have strengthened load theory's main concept that distractor processing is determined by the amount of resource allocation to task-relevant stimuli. Overall results showed that attention and expectation could well share some level of stimulus representation. The project team found that load reduces distractor representation, possibly also affecting the expectation that can be formed from it. This could improve our understanding of a pivotal pillar of human cognition, that of attention. By bringing researchers closer to defining perceptual load, science stands to learn how the brain processes the enormous amount of data it is exposed to. Such understanding is likely to contribute to promoting well-being and mental health in the long run.

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