Behavioral Oscillations in Verification of Relational Role Bindings

Human understanding of relations between objects depends on the ability to code meaningful role bindings. Computational models of relational reasoning have proposed that neural oscillations provide a basic mechanism enabling working memory to code the bindings of objects into relational roles. We adapted a behavioral oscillation paradigm to investigate moment-to-moment changes in representations of semantic roles. On each trial, a picture was presented showing an action (chasing) relating two animals, one animal playing an agent role (chaser) and the other playing a patient role (chased). After the picture disappeared, the inter-stimulus interval (ISI) was varied in densely-sampled increments followed by a verbal probe indicating an animal in a role. Reaction time (RT) to decide the validity of the verbal probe was recorded. We found that RTs varied systematically with ISI in an oscillatory fashion. A task that required memory for a relational role evoked stronger thetaand alpha-band oscillations than did a memory task not involving relational roles. The behavioral oscillation patterns in the role-identification task revealed a phase shift between the two semantic roles in the alpha band.