Superadditive memory strength for item and source recognition: the role of hierarchical relational binding in the medial temporal lobe.

Source memory depends on our ability to recollect contextual information--such as the time, place, feelings, and thoughts associated with a past event. It is acknowledged that the medial temporal lobe (MTL) plays a critical role in binding such episodic features. Yet, controversy exists over the nature of MTL binding--whether it contributes specifically to source recollection or whether it contributes equally to both item familiarity and source recollection. To resolve this issue, the authors propose that the MTL acts to bind contextual features through a process of hierarchical relational binding. That is, by way of multiple levels of associative bindings (i.e., bindings of bindings), the MTL links episodic features in a superadditive manner. To account for this binding feature, the authors develop a recognition model that includes positively skewed distributions of memory strength. Such skewed distributions can account for many empirical findings and regularities of both item familiarity and source recollection.