The authors trained five pigeons on a directed forgetting test, a variation on the classic match-to-sample test. After viewing sample stimuli consisting of one of two shapes (a circle or dot) or colors (red or white), the birds were cued to remember or forget the sample (signaled by either a high- or low-frequency tone or one of two distinct patterns). A delay period followed these cues. If a forget cue was presented, the trial ended after the delay, and no memory test was given. If the remember cue was presented, the birds were given a memory test in which they saw two stimuli after the delay; if they responded to the sample stimulus (by pecking on a key), they were rewarded with wheat.
Rose and Colombo found that during the remember trials only, neurons in the NCL showed sustained activation throughout the cue and delay periods; during the forget trials, sustained activation disappeared. These results suggest that sustained NCL neuronal activation reflects working memory or at least some type of cognitive activity associated with executive control. And though the avian NCL and mammalian prefrontal cortex clearly differ after 320 million years of divergen
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