Memory Deficits for Implicit Contextual Information in Human Amnesics

Marvin M. Chun and Elizabeth Phelps

A classic debate in the study of memory systems concerns the role of the hippocampus and adjacent medial temporal lobe structures. We provide the first new evidence in humans that these structures are important for encoding contextual information from the environment. We employed a contextual cueing task in which repeated visual context facilitates visual search for embedded target objects. An important feature of our tasks is that the memory traces for contextual information were not accessible to conscious awareness, and hence can be classified as implicit or nondeclarative. Although amnesic patients with hippocampal damage typically show intact implicit memory performance, we demonstrate that they are impaired at learning implicit spatial context information.