Hippocampal neuron activity in humans and animals represents distinct memory elements, such as individuals 9, 10, places 11, 12 and associations between them 12, 13. They become virtually unable to encode such memories 5 and their recollections of past events or spatial sceneries are schematic and lack contextual details 6– 8. Patients with hippocampal lesions generally retain normal intelligence 2, 5 but show severe memory deficits, particularly in the episodic 6 and spatial domain 7.
1a,b), is crucial for declarative memory functions. The hippocampus, located in the brain’s temporal lobes ( FIG. Memories must first be encoded 2 as a permanent trace or ‘engram’, maintained and ‘consolidated’ over time 3, 4 and finally recalled to become accessible to other cognitive processes. Episodic memories associate items and events with the spatial and temporal context in which they were experienced 2. Conscious or ‘declarative’ memories come in two flavors 1: semantic memories comprise factual knowledge about the world (for example, that Brooklyn is a borough of New York), whereas episodic memories depict unique experiences (for example, your first train ride to Brooklyn). Memories about ourselves and our interactions with the environment are fundamental to our life.