Imagine you are standing before a fruit stand and trying to buy some apples. You usually would pick up one apple at a time, evaluate it, decide whether you will have it or leave it, and then move on to the next. Although there are many apples in the sight, they are evaluated sequentially.

The decision to pick up a particular apple is often based on its simple visual features, such as color, shape, or texture. Apples with desired salient features are more likely to capture your attention and be picked up for further scrutiny. However, the transition from parallel processing of sensory information to the sequential decision process and the role that attention plays in this transition is not well understood.

In a recent study published in eLife, Dr. YANG Tianming’s lab at the Institute of Neuroscience of Chinese Academy of Sciences showed that the neuronal activity in the orbitofrontal cortex (OFC) represents the value of the attended item, which indicates that the processing of value information in the brain may be a sequential process and attention plays a key role in guiding this process.

The researchers focused on the processing of value information in the OFC, which is a sub-region in the prefrontal cortex, to see whether value information is processed in the OFC in parallel or sequentially and how attention modulates the processing.

They first carried out an experiment on monkeys to study the interactions between attention, value, and decisions.

The monkeys were asked to stare at pictures on a computer screen with each picture associated with a different amount of juice reward that the monkeys would get. The computer randomly picked one of the displayed picture and delivered its associated reward. In some trials, one of the pictures would have a quick rotation that would capture the monkeys’ attention toward the rotated picture involuntarily. Thereby, attention, value and decision making can be dissociated.

When the monkeys were looking at two simultaneously presented pictures, although they could get the reward associated with either picture, the researchers found that the monkeys’ attention was always focused on the picture with a larger reward. At the same time, the neurons in the OFC only encoded the value of this picture and ignored the other less rewarding picture.

Moreover, when one of the picture was rotated and captured the monkeys’ attention, the OFC neurons followed the attention and encoded the rotated picture’s value.

Using a computational model, they showed that the probability of the rotating picture capturing the monkeys’ attention was influenced by the value difference between the two. If the monkey was attending a highly rewarding picture, it would be less likely to shift its attention toward a less rewarding alternative.

The results showed that the attention guided the value encoding in the OFC, which encoded the value of only one object at a time, suggesting a sequential information mechanism was in play. This will help people understand the parallel-serial transition of information processing in the brain.