How the reward modulates attention in humans

Have you ever noticed how animals instinctively choose the most ripe fruits in a tree? This behavior, to search for the most enriching option, offers a fascinating overview of the brain. The animals concentrate not only their attention on the most enriching target (the location of the most mature fruit), but they also make a quick decision to act on this information. Interestingly, the behavioral and neural mechanisms underlying this process are relatively under-explored.

Sridharan Devarajan, associate professor at the Center for Neuroscience, Indian Institute of Science (IISC) and his doctorate. Student Ankita Sengpta took the task to study how the expectation of a reward influences attention. Their study in Biology PLOS offers new information on this complex process.

Scientists have long since known that the promise of a guide and dictates behavior. People are faster to detect changes and respond more quickly and more precisely when they expect a reward.

Many previous studies have studied how the expectation of a reward influences attention and decision -making. But when they failed, it is differentiation if these processes are governed by the same regions and processes and processes in the brain.

To fill this gap, Sridharan and Sengupta have designed an experience to examine how the expectation of a reward module The two key components of attention: the sensitivity (the capacity to visually identify the most mature fruit) and the bias (the decision to act to choose the most mature fruits). Researchers have often struggled to disentangle the impact of the reward on sensitivity and bias.

The Sridharan team carried out tests with 24 participants, each carrying out a cognitive task in two parts. The first part tested for the reward effects on sensitivity. The participant looks at a screen displaying two Gabor patches (smooth black and white strips used in the attention of attention), one on each side of the screen.

After a very short break (200 milliseconds), the patches sparkle and one (or both) of the patch orientations may change. Participants should point out whether they have detected a change in one of the two fixes. For each trial they have reported with precision, they received a monetary award.

Here is where the task has become interesting. The researchers strategically rigged the awards – the number of reward points was fixed on one side, while the points varied on the other side; In other words, it could be higher or lower than that on the fixed side.

Participants would realize this during the task, on the basis of the points received, leading them to concentrate and to be more sensitive to tiny changes aside, which would make them greater rewards.

The second part tested for the reward effects on the bias. The only difference in this case was that the points to report an option “yes” (deciding on a change happened), compared to an “no” option (deciding that no modification occurred) varied on one side; As before, this award could be higher or lower than that on the fixed side. Here, the participants would be biased to choose the option yes when it was more rewarding than the no, and vice versa option.

During the tasks, the researchers measured the eye movements of the participants and the brain activity and quantified the two components of attention.

In the first task, where sensitivity was examined, the participants were more careful and their gaze was drawn to the side associated with larger awards.

“However, their decision -making bias has not changed, indicating that only sensitivity has been modulated in this task,” said Sridharan. In addition, well -known brain signatures, including electrical responses and oscillations, reported higher sensitivity.

During the second part of the task, where the biases were examined, the researchers observed that the participants were more likely (biased) to choose the option (yes / no) with the higher reward.

But during this task, the researchers were surprised to note that none of the gaze or brain models of the participants corresponded to those associated with attention. “Unexpectedly, the change of bias has not led to any specific signature to attention centers in the brain,” said Sengpta.

The results of the study show, for the first time, that sensitivity and bias can be governed by distinct neural mechanisms under the hood, each set differently by the anticipation of a reward. In addition, although sensitivity seems to be closely linked to sensory attention centers, the bias can be more closely linked to the decision centers of the brain.

The study also has practical implications to understand how we learn and make decisions in life.

“Studies such as ours will help design tasks to understand propensions to risk taking in individuals, faced with uncertain rewards. The results can help to design treatments for drug addiction behavior, such as game, which involve a complex interaction of reward, attention and impulsive decisions”, adds Sridharan.