Indian Institute of Science, Bengaluru.
Two new studies from the Centre for Neuroscience, Indian Institute of Science, explore how closely attention and eye movements are linked and unveil how the brain coordinates the two processes.
According to IISc, attention is a unique phenomenon that allows us to focus on a specific object in our visual world and ignore distractions.
“When we pay attention to an object, we tend to gaze towards it. Therefore, scientists have long suspected that attention is tightly coupled to rapid eye movements, called saccades. In fact, even before our eyes move towards an object, our attention focuses on it, allowing us to perceive it more clearly – a well-known phenomenon called pre-saccadic attention,” IISc said.
However, in a new study published in PLOS Biology, the researchers at CNS show that this perceptual advantage is lost when the object changes suddenly, a split second before our gaze falls upon it, making it harder for us to process what changed.
“Our study provides an interesting counterpoint to many previous studies which suggested that pre-saccadic attention is always beneficial,” said Devarajan Sridharan, Associate Professor at CNS and corresponding author of the study.
In the PLOS Biology study, Priyanka Gupta, a PhD student in Prof. Sridharan’s lab, trained human volunteers to covertly monitor gratings (line patterns) presented on a screen without directly looking at them and to report when one tilted slightly.
“Importantly, the participants did this task just before their eyes moved in the pre-saccadic window. So, we were able to study the relationship between pre-saccadic attention and the detection of changes in the visual environment,” said Ms. Gupta.
A tracker was used to monitor their eye movements before, during and after their gaze fell on the object. “To our surprise, participants found it harder to detect the changes in the pre-saccadic window,” Ms Gupta said.
In the other study published in Science Advances, carried out with collaborators at Stanford University, the researchers used an unusual experiment – this time, to decouple attention from eye movements – in monkeys. Their goal was to tease out what is happening in the brain while these processes play out.
The monkeys had been trained on a counter-intuitive task called an “anti-saccade” task. Like the human study, the monkeys covertly monitored several gratings on a computer screen without directly looking at them. But when anyone grating tilted slightly, the monkeys had to look away from it instead of focusing more sharply on it. This helped the researchers delink the location of the monkey’s attention from the location where its gaze ultimately fell.
IISc said the researchers believe that uncovering such brain signatures can eventually point to what fails in attention disorders. “Discovering such mechanisms is vital for developing therapies for disorders like ADHD,” Prof. Sridharan said.
