Are old adults just like low working memory young adults? Filtering efficiency and age differences in visual working memory.

While it is well known that working memory functions decline with age, the functional reasons for this decline are not well understood. A factor that has proven critical for general individual differences in visual working memory capacity is the efficiency of filtering irrelevant information. Here, we examine to what degree this factor is also responsible for age differences in working memory. Young and old participants performed a change-detection task where some items in the encoding display were marked as irrelevant. The contralateral delay activity of the electroencephalogram was used to assess individual participants' filtering efficiency (see Vogel EK, McCollough AW, Machizawa MG. 2005. Neural measures reveal individual differences in controlling access to working memory. Nature. 438:500-503.). Older adults showed smaller filtering scores than young adults, but only early in the retention interval, suggesting that efficient filtering was delayed. In contrast, age-independent individual differences in filtering were reflected primarily later in the retention interval. Thus, age and individual differences in filtering are reflected in different ways showing that old adults are not simply like less efficiently performing young adults.