Abstract
A number of studies from neuroimaging and neuropsychology have implicated various regions of parietal cortex as playing a critical role in the binding of conjunctions of color and form. In order to further investigate the network involved in color-form integration, the current study used rTMS to disrupt parietal activity while normal perceivers performed a task that produces frequent binding errors known as ‘illusory conjunctions’. We tested several specific parietal regions that have been associated with feature binding and defined them anatomically for each participant. The voxel location was marked on each high resolution MRI image, and scalp location was determined using a stereotaxic localization system. Participants made fewer contralateral binding errors after suprathreshold 1 Hz rTMS of the right intraparietal sulcus (IPS), while perception of the features themselves (colors and shape) was unaffected. Improved binding after right IPS stimulation was also indicated by a significant increase in the probability of binding as estimated by a multinomial probability model. No perceptual effects were found following left IPS stimulation, or stimulation of the right angular gyrus at the junction of the transverse occipital sulcus (IPS/TOS). Several possible mechanisms as to how right IPS stimulation decreased illusory conjunctions are proposed.