Inhibition in selective memory retrieval: behavioral and electrophysiological insights

Selectively retrieving information from memory often induces interference from related memories. It is widely assumed that inhibition resolves this competition by suppressing the interfering items' memory representations. However, the exact nature of the inhibitory process is not yet understood. The present work provides insight into the functioning and the effects of inhibition in selective memory from two perspectives. In two electrophysiological experiments, the dynamics of inhibition as it operates in the neural system were investigated by analyzing brain oscillations across repeated cycles of selective retrieval. Theta oscillations reflected the dynamics of inhibition during selective retrieval from episodic memory and predicted later retrieval-induced forgetting (Experiment 1). During retrieval from semantic memory (Experiment 2), however, inhibition was not reflected by theta oscillations. Instead, alpha and beta oscillations were related to retrieval from semantic memory and theta oscillations were related to the formation of new episodic memory traces. Two further behavioral experiments gave insight into the effects of inhibition on the absolute and relative strength of previously interfering items. The absolute item strength was investigated by employing a recognition test procedure (Experiment 3). Retrieval-induced forgetting was found in the selective retrieval but not the reexposure condition, a result in line with the view that inhibition affects the interfering items' memory representation. The relative item strength was assessed by analyzing recall latencies during free recall (Experiment 4). No effect of inhibition on the previously interfering material was found. Together, the results elucidate the nature of inhibitory mechanisms during retrieval from long-term memory, revealing the neural dynamics of inhibition during selective retrieval, and the effects of inhibition on the representation of interfering memory information