Complex span measures of working memory do not mediate the effects of age on the P3 and N400 ERPs

• Younger adults had larger working memory complex spans than older adults. • Younger adults had greater amplitudes and shorter latencies for P3 and N400 effects. • Relation between WM span and the P3/N400 was the same for younger and older adults. • Complex span tasks did not affect P3 or N400 ERP amplitudes or latencies because they may rely on different WM processes. • Oddball and word-pair tasks may rely more on attentional control than storage. Working memory (WM), the temporary maintenance of a limited amount of information in an accessible state, is required for the performance of many tasks. Studies have shown that WM demands are related to the neural processing of tasks requiring attention: Age affects the ERP components associated with WM context updating processes in the visual oddball task (P3) and semantic processing in the word-pair judgment task (N400). This study investigated whether WM capacity measured by complex span tasks mediates the effects of age on these ERPs. Younger adults (YA, n = 44, ages 18–23 yr) and older adults (OA, n = 41, ages 69–89 yr) completed operation, reading, and symmetry complex span tasks and two ERP tasks (P3/visual oddball; N400/word-pair judgment). Results showed age-related differences for all complex span tests. Principal components analysis of these tests showed a single factor for both groups, so a combined WM capacity factor score was created. Regressions of age group and WM factor score on P3 and N400 amplitudes and latencies showed that OAs had relatively lower amplitudes and longer latencies. However complex span was not related to P3 or N400 amplitudes or latencies and that result was the same for younger and older adults; that is, complex span did not mediate the age effects. WM processes indexed by the P3 and N400 components appear to be different from those elicited by complex span tasks. Attentional control processes of WM influence oddball and semantic judgement tasks more than storage components.