Paying attention helps your brain process what you can’t see


In a nutshell: Paying attention to a location helps the brain to process not just what you can see there, but also what you can’t – suggesting that attention and awareness are controlled by different pathways in the brain.

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Paying attention helps your brain process what you can’t see

When we view a crowded scene – such as a street full of people, traffic and buildings – the various visual stimuli compete for our attention. Because our brain’s processing capacity is limited, we can’t focus on everything at once. Instead, we pay attention to one location at a time, and our brain prioritises the processing of visible stimuli within that area.

Previous studies have suggested that, in these circumstances, our brain also processes ‘invisible’ visual stimuli – very faint or fleeting objects that we don’t perceive consciously. However, it’s not clear which brain pathways are involved in processing visible and invisible stimuli, and how this type of attention is linked to conscious awareness.

To answer these questions, Brain Function CoE researchers Cooper Smout and Jason Mattingley from The University of Queensland developed a novel experiment that combined an awareness task and an attention task. In both tasks, participants focused on the middle of a screen while a series of images were displayed on either side. The images contained a mix of recognisable patterns (the ‘signal’) and random, scrambled patterns. In the awareness task, participants were asked to indicate when the signal appeared on one side of the screen, while ignoring the other side. In the attention task, participants were asked to report how often the quality of the signal briefly decreased. Electroencephalography (EEG) was used to measure participants’ brain activity throughout the tasks.

The experiment allowed the researchers to examine the links between brain activity, attention (whether the participants paid attention to the relevant part of the screen or ignored it) and awareness (whether the signal was visible or invisible, which was determined by the quality of the signal images).

The researchers found that brain activity in response to visible stimuli was greater when participants paid attention to their location rather than ignoring it. Remarkably, the same was true for invisible stimuli. These results suggest that when we pay attention to a particular area, our brain prioritises the processing of all the stimuli there – whether they’re visible or not –  regardless of their relevance or importance to the task at hand.

The researchers also showed that the increase in brain activity did not correspond to an increase in awareness, which provides the first clear evidence that attention and awareness are separate processes that rely on different pathways in the brain.

Next steps:
The research team plans to investigate whether the complex relationship between attention and conscious awareness is affected by other factors, such as knowledge of past events.

Smout, C. A., & Mattingley, J. B. (2018). Spatial attention enhances the neural representation of invisible signals embedded in noise. Journal of Cognitive Neuroscience, 30(8), 1119-1129. doi: 10.1162/jocn_a_01283

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