To our knowledge our study is the first to document

such effects in adolescents in a Stroop task. When children aged 9–10 performed a continuous Sirolimus price performance task, where they must respond to the letter X only when preceded by the letter A, the frontal P3 during No-Go trials was absent and this was associated with higher false alarm and impulsivity scores (Dien et al., 2004 and Jonkman et al., 2003). We interpret developmental P3a changes considering both the adolescent and middle age adult data discussed below. Middle age adults differed from young adults in stimulus level processing. Although several previous studies have tracked adult lifespan changes in the P3a during oddball tasks [(Fjell & Walhovd, 2004), 20–92-year olds; (Stige, Fjell, & Smith, 2007), 6–90-year olds; (Walhovd & Fjell, 2001), 22–95-year olds] to our knowledge ours is the first study to have examined and documented the P3a in a Stroop task with middle age participants. In our data the enlarged P3a in middle age adults was of much lesser amplitude and shorter duration in young adults

and could not be detected at all in adolescents. In young adults the P3a is commonly related to operations at the stimulus selection stage or more specifically attention shifting as part of an attention orienting reflex (Dien et al., 2004 and Gaeta et al., 2001). One common conclusion in the ageing literature is that middle age adults must rely on additional frontal mechanisms to maintain task performance (Cabeza, 2002, Davis et al., 2008 and Eppinger et al., 2007). Fabiani and Friedman (1995) found that when older adults were presented XL184 nmr with a repeated stimulus they maintained P3a frontal activity throughout the task whereas in young adults this response waned after the first few tones. They concluded that older adults have greater susceptibility to distraction and interference and may have difficulty holding information in their working memory. Older adults may therefore engage frontal orienting attention

mechanisms to a greater degree (Fabiani, 2012). Hence, we conclude that the increased P3a in middle age adults reflects increased use of frontal resources to focus on task-relevant stimulus properties. Even though middle age adults also showed a significant delay in P3b STK38 onset latency compared to young adults their RT was not significantly different. Additionally the amplitudes of the stimulus locked LRPs were significantly larger in the middle age group when compared with adolescents and young adults. As noted above this increase in LRP amplitude could represent increased certainty in responding. This has been found in previous studies listed below; although they did not test the significance of the deviation directly an increased amplitude is visible (Falkenstein et al., 2006, Fig. 2; Wild-Wall et al., 2008, Fig. 2). Additionally correct and incorrect hand EMG amplitude did not significantly differ between the young and middle age adult groups.