Frontal lobe mechanisms that resolve proactive interference.

Memory of a past experience can interfere with processing during a subsequent experience, a phenomenon termed proactive interference (PI). Neuroimaging and neuropsychological evidence implicate the left mid-ventrolateral prefrontal cortex (mid-VLPFC) in PI resolution during short-term item recognition, though the precise mechanisms await specification. The present functional magnetic resonance imaging (fMRI) experiment sought to further constrain theorizing regarding PI resolution. On each trial, subjects maintained a target set of words, and then decided if a subsequent probe was contained in the target set (positive) or not (negative). Importantly, for half of the negative and half of the positive trials, the probe had been contained in the previous target set (recent). Relative to non-recent trials, negative-recent trials produced an increase in response times and error rates, behavioral markers of PI. In fMRI measures, negative recency was associated with increased activation in the left mid-VLPFC, as well as in the bilateral fronto-polar cortex, providing evidence for multiple components in PI resolution. Furthermore, recency effects were evident during both negative and positive trials, with the magnitude of the recency effect in the mid-VLPFC being greater on negative trials. Collectively, these results serve to specify and constrain proposed models of PI resolution.