Is inhibition in working memory domain-general? A study of age-related decline in cross-domain inhibitory abilities

The unitary versus non-unitary nature of inhibitory control in working memory remains an open question: does inhibitory control deficit (i.e. to inhibit irrelevant information) appearing during aging concern all domains (language or visual information, etc.) or are they more important in certain areas (language) than others (visual information)? This study examines the specificity of inhibitory control by investigating the age-related decline in inhibitory abilities across several domains (visual, phonological and semantic) in an immediate target-probe matching task. 129 young adults (20-40 years old) and 130 elderly adults (60-80 years old) where presented two target stimuli and two probe stimuli (visual symbols, words or nonwords); they had to select the probe stimulus that was the most similar to both target stimuli based on visual, semantic or phonological similarity. In the inhibition condition, the wrong probe stimulus was pre-activated via a prime stimulus briefly occurring before the presentation of the target stimuli and thus had to be inhibited for correct response selection; in the facilitation condition, the correct probe stimulus was preactivated. An interference score was calculated by subtracting performance between the two conditions, for each stimulus domain. We observed that interference effects were overall larger in the elderly adults as compared to the young adult group. At the same time, there was decisive Bayesian evidence for an interaction between age group and stimulus domain, with particularly increased interference effects in the elderly group for the semantic and visual conditions. These results suggest domain general inhibition impairment at least for semantic and visual conditions in healthy aging. Differences in task sensitivity may account for the lesser inhibition impairment in the phonological domain.