Suppression of Non-Selected Meanings Via Hippocampal Inhibition as a Possible Brain Mechanism For Ambiguity Resolution: An fMRI Study Using The Word Fragment Completion Task

Dealing with ambiguity, one usually selects one meaning unconsciously and remains unaware of the alternative meanings. The brain systems dealing with multiple meanings of ambiguous stimuli are relatively well studied, while the brain processing of their non-selected meanings is relatively less investigated. The current functional MRI event-related study used a modified version of the word fragment completion task to reveal possible brain mechanisms involved in processing the non-selected meaning of ambiguous stimuli. Some noun stimuli were ambiguous, and the others were not. Adjectives created contexts strongly biasing the choice of the noun meaning in one or the other way. All ambiguous and unambiguous noun stimuli were presented twice during the experiment. It was revealed that ambiguity resolution was associated with a decrement in the BOLD signal within the right and left hippocampi. This finding supported one of the tested hypotheses assumed that non-selected meanings are actively suppressed. The similarity between this result and BOLD signal changes observed for suppression-induced forgetting for purging unwanted memories from awareness allows suggesting the general neurophysiological basis for voluntary and automatic inhibitory awareness control.