Study of the Neural Basis for Subjective Feature Binding

While it is known that the brain perceives color and motion asynchronously, the specific locations in which the brain binds signals remain unknown. This study distinguishes subjective perception of the capability to bind features and the objective accuracy in feature binding. The stimuli were the same for individual subjects, consisting of random dots (red and green, or yellow and blue) moving either vertically or horizontally. Subjects responded to questions regarding the color or the direction of motion of the dots (objective judgment) and rated their capability in performing the task (subjective judgment). The imaging results of contrasting subjective judgment showed that the activation of the anterior rostral cingulate cortex (rACC) and inferior frontal gyrus (Brodmann area [BA] 45/47) during incapable-of-binding responses, compared with the capable-of-binding responses. It is suggested that the rACC is for uncertainty of subjective judgment and BA 45/47 is for the increased burden on working memory. In contrast, there was no imaging results of contrasting the correct and incorrect responses (i.e., objective judgment), and neither was there for the interaction between subjective and objective judgment. The results of conservative conjunction analysis indicated common and shared brain areas for the 2 distinctive binding situations (the correct and capable-of-binding vs the incorrect and incapable-of-binding), including increased activity in the intraparietal lobe (IPL) and the junction areas of the posterior rostral ACC (dACC) and the prefrontal areas, but decreased activity in the medial portion of the IPL, suggesting that feature binding requires maintaining attention. These results clearly isolated subjective judgment from objective judgment and support the view that maintaining attention is involved in feature binding of color and motion.

Neuronal Response to Reward and Luminance in Macaque LIP During Saccadic Choice

Recent work in decision neuroscience suggests that visual saliency can interact with reward-based choice,and the lateral intraparietal cortex(LIP)is implicated in this process.In this study,we recorded from LIP neurons while monkeys performed a two alternative choice task in which the reward and luminance associated with each offer were varied independently.We discovered that the animal’s choice was dictated by the reward amount while the luminance had a marginal effect.In the LIP,neuronal activity corresponded well with the animal’s choice pattern,in that a majority of reward-modulated neurons encoded the reward amount in the neuron’s preferred hemifield with a positive slope.In contrast,compared to their responses to low luminance,an approximately equal proportion of luminance-sensitive neurons responded to high luminance with increased or decreased activity,leading to a much weaker population-level response.Meanwhile,in the non-preferred hemifield,the strength of encoding for reward amount and luminance was positively correlated,suggesting the integration of these two factors in the LIP.Moreover,neurons encoding reward and luminance were homogeneously distributed along the anterior-posterior axis of the LIP.Overall,our study provides further evidence supporting the neural instantiation of a priority map in the LIP in reward-based decisions.