How did changing speech sounds affect short-term memory and brain activity?

Details

The irrelevant sound effect describes a reduction in verbal short-term memory during irrelevant changing-state sounds made up of different, distinct auditory tokens. Steady-state sounds lack these changing-state features and do not impair performance.

In an EEG experiment with 16 participants, researchers explored the neurophysiological differences between detrimental changing-state speech, presented as a 3-token sequence, and ineffective steady-state speech, presented as a 1-token sequence, during serial recall. They analyzed evoked and induced activity related to the memory items, as well as spectral activity during the retention phase.

The main finding was that the behavioral sound effect was reflected exclusively in attenuated token-induced gamma activation, most pronounced between 50–60 Hz and 50–100 ms after stimulus onset. Changing-state speech seems to disrupt a behaviorally relevant process ongoing during target presentation, such as the serial binding of items.