Neural Oscillations in the Aging Brain Associated With Interference Control in Word Production.

Speaking is not only about retrieving words and structuring them into sentences; it also requires top-down control to plan and execute speech. In previous electrophysiological research with young adult speakers, mid-frontal theta oscillations have been observed using a picture-word interference paradigm. With this paradigm, participants name pictures while ignoring superimposed distractor words. In particular, mid-frontal theta power increases for categorically related distractors relative to other types of distractors, reflecting top-down interference control in resolving the competition between processing streams during word production. In the present study, we conceptually replicated the magnetoencephalography study by Piai, Roelofs, Jensen, et al. (2014) with an older group of healthy adults (mean age: 60 yr). Behaviorally, we replicated distractor semantic interference and Stroop-like interference effects typically observed in young adults. However, we did not find the corresponding theta modulation associated with these interference effects at the neural level. Instead, we found beta power decreases associated with interference control, mostly pronounced in the left posterior temporal and inferior parietal cortex. We further confirmed that these beta modulations were not present in the young adults' data. The distinct spectro-spatial-temporal profile of the oscillatory effects in the older population may reflect different underlying dynamics relative to the midline frontal effect previously found in young adult speakers. Our results indicate that the neural underpinnings of top-down interference control may be modified by aging and that the mid-frontal theta cannot be the exclusive oscillatory pattern enabling interference control during spoken word production.