A new research article from the Knierim lab on the neural mechanisms of pattern separation and pattern completion was published in the journal Neuron, accompanied by a Preview article highlighting the results. This research tested longstanding computational theories of the dentate gyrus and CA3 regions of the hippocampus, a brain structure critical for learning and memory. The dentate gyrus was proposed to perform a process called “pattern separation,” which reduces the overlap in neural representations of distinct events in order to decrease memory retrieval errors. The CA3 region was proposed to perform “pattern completion,” which allows the system to retrieve coherent memories when provided with partial or degraded retrieval cues. This study provided direct evidence to support these models by recording the neural activity in these regions while rats performed a simple spatial task.