The electrophysiology of incidental and intentional retrieval: ERP old/new effects in lexical decision and recognition memory.

Event-related brain potentials (ERPs), recorded from a 128-sensor array were used to differentiate brain processes associated with intentional vs incidental memory retrieval. Two experiments examined ERP differences between old (studied) and new (non-studied) words and pseudowords while subjects performed either a recognition memory task or lexical decision task. Previous research has related a P600 old/new effect to the recollection of details, and the present experiments show that this effect was not amplified by intentional retrieval. The P600 effect was larger for words than pseudowords. An earlier (300 to 500 ms), frontally maximal, N400-like old/new effect ('FN400') was similar for words and pseudowords. A third, previously unidentified, mid-frontal, old/new effect was associated with only pseudoword recognition from 300 to 500 ms. Results are discussed with respect to dual-process theories of recognition memory.