Brain mechanisms of the Tip-of-the-Tongue state:An electroencephalography-based source localization study.
Background. The Tip-Of-the-Tongue (TOT) state occurs when a person fails to retrieve a familiar word, e.g., a name, from long-term memory, while knowing perfectly well that the forgotten word exists in memory and being able to report some information about it (semantic associations, the first letter, the number of syllables, etc.).
Objective and method. In the present work, we studied the activation of brain structures during the TOT state. The participants (N = 20; age 21.5 ± 4.1) viewed portraits of movie stars whose names they were asked to remember. Event related potentials (ERP) were registered in three conditions: 1) the participant remembered the name; 2) the participant did not know the name; 3) the participant knew the name but could not remember it (TOT-state). The sources of cortical activation were computed (DSPM algorithm).
Results. Time intervals demonstrating significant differences (t-test) in activation among the three conditions were calculated for each activated area, so that up to four different stages of processing could be delineated. According to our analysis, face perception involves activation of the visual cortex (left cuneus and right precuneus cortices), banks of the superior temporal sulci, poles of frontal and temporal lobes, and fusiform gyrus. The early activation does not depend on the successful retrieval of the name. A second increase in activation of the visual cortex is present at a later stage of processing, when name retrieval fails or if it is impeded.
Conclusion. We have shown that successful face recognition involves activation of the posterior cingulate cortex and the isthmus of the cingulate cortex in both hemi- spheres. Additionally, the parahippocampal gyrus is less active at the early stages and more active at the later stages of processing in the TOT-state, when name retrieval from the long-term memory fails.
Themes: Cognitive psychology
Keywords: tip-of-the-tongue (TOT), memory retrieval, verbatim recollection, electro- encephalography (EEG), source localization, event related potentials (ERP), posterior cingulate cortex, parahippocampal gyrus, isthmus of cingulate gyrus