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.

Perceptual Priming and Reading Speed among Fourth Grade Children

This study evaluated the perceptual priming in fourth grade primary school children using a word-fragment completion task. The children were classified into two categories according to their reading speed: high and low. Using several sub-scales of the WISC-IV, their working memory was measured, and their total IQ was estimated, in order to control for their effects on priming. The statistical analyses showed that children with high reading speed were significantly better at word-fragment completion and showed greater priming (p < .01); in other words, the prior processing of the words from which the fragments came produced a greater benefit in the performance of the word-fragment completion task. A regression model was developed to explain reading speed based on the following variables: perceptual priming, working memory and percentage of completed fragments belonging to words not previously processed (adjusted R2 = 0.64).