Localization contributes to feature binding: A transcranial magnetic stimulation study

Abstract

Feature binding refers to correctly associating one feature of an object (e.g., shape) to another feature of the object (e.g., color). In our previous study, we found that errors in feature binding increased with errors in localization of that feature (Jingling and Zhaoping, 2007, Journal of Vision, 7(9):644, 644a). In this study, we aim to test whether interfering neural activities at a brain region that relates to location process could also affect feature binding. In Experiment 1, we tested whether the chosen area, right intraparietal sulcus (IPS), responsible for localization. Observers performed two tasks before and after they received continuous theta burst stimulation (cTBS), an inhibitory paradigm, on their right IPS. They viewed a target cube (either red or green) presented among yellow cubes during experiment. In one task they were requested to localize the target, and in the other to discriminate its color. Results showed a reduced accuracy in localization after (80.9%) than before (88.0%) cTBS, but not significantly different in color discrimination. In Experiment 2, observers performed feature binding and localization tasks with the same stimuli before and after brain stimulations. They viewed a briefly presented string of different colored letters and either to report identity and color of the target (the feature binding task) or to locate target relative to nontargets (the localization task). Two brain stimulations, the continuous (cTBS) and intermittent theta burst stimulation (iTBS), were applied to the same observer in different day. Preliminary findings revealed that brain stimulations on right IPS modulated the error rates in feature binding and localization in the same direction. Our study thus provides evidence on that spatial localization of features contributes to feature binding.