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

　　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. 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 the new study, the researchers approached these questions by looking at the processing of value information in the orbitofrontal cortex (OFC). The OFC is a sub-region in the prefrontal cortex, which gets its name because it locates immediately above the eye orbits. Previous studies showed that the OFC plays an important role in representing the association between sensory stimuli and reward during value-based decision making. The current study further looks at whether value information is processed in the OFC in parallel or sequentially and how attention modulates the processing.

　　Attention, value, and decisions making are usually tightly coupled together. To properly study their interactions, the authors designed a clever experiment. They asked the monkeys to stare at pictures on a computer screen. Each picture was associated with a different amount of juice reward that the monkeys would get. The monkeys did not have to make any decision. 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. However, the rotation did not have anything to do with the reward value or decision making. It 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, the authors 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 study 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. The finding helped us to understand the parallel-serial transition of information processing in the brain.

　　This work entitled “Covert shift of attention modulates the value encoding in the orbitofrontal cortex” was published online in eLife on March 13, 2018. The study was performed by XIE Yang in collaboration with NIE Chechang under the supervision of Dr. YANG Tianming, in the Laboratory of Neural Mechanisms of Decision Making and Cognition at the Institute of Neuroscience, CAS. It was supported by Science and Technology Commission of Shanghai Municipality (15JC1400104)

　　Figure 1: (A) OFC neurons reflected the value of more rewarding picture. (B) When one of the pictures was rotated, the OFC neuronal responses shifted to encode the value of the rotated picture. (C) A normalization model explained the interaction between value and attention shift. For details, please see Xie, Nie, and Yang, 2018.