General slowing of mental processing speed is hallmark of brain and cognitive aging. Thus far it has been limited under-standing in neural mechanisms underlying mental states during fluctuations between efficient versus inefficient cognitiveperformance within individual older adults. Here we examined electrophysiological responses during visual working mem-ory retrieval trials that are fast versus slow reactions. Wireless EEG along with accuracy and reaction times were recordedduring a modified delayed match-to-sample task in 17 cognitively normal older adults (age 65-95) from North America.Compared to trials that are faster than averaged (mean 584 ms), the late positive potentials during trials that are slowerthan average (mean 747 ms) showed increased responses to memory nonmatch distractors than those to object matchingmemory targets in frontal sites, as previously reported in older brains. Interestingly, the brainwaves during efficient andaccurate memory retrievals resemble those typically seen in younger adults.