The role of reentrant processes in feature binding: Evidence from neuropsychology and TMS on late onset illusory conjunctions

We report data on illusory conjunctions (ICs) in a colour/letter identification task from a patient with simultanagnosia following bilateral parietal lesions and from a study using transcranial magnetic stimulation (TMS) with normal participants. We show that, even though target conjunctions were reported well above chance across a range of exposure durations, ICs were only generated at longer display exposures while feature errors decreased across time. With normal participants we found that TMS to the right posterior parietal cortex but not to occipital cortex increased the number of ICs. Moreover, ICs tended to occur after delayed stimulation, with the critical time window for stimulation being later for ICs than for feature errors. The data provide support for the critical role of posterior parietal cortex in a late process of feature binding.