Neurocognitive inertia

Abstract

Effective functioning within a constantly changing world requires that cognitive functions such as memory and attention can be used not only to react to the moment but, at the same time, to maintain an overarching frame of mind. Understanding this ability, and mapping the mechanisms and processes involved is the motivation behind a recent study of memory by Duzel et al.1 Duzel E. et al. Task-related and item-related brain processes of memory retrieval. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: 1794-1799 Crossref PubMed Scopus (217) Google Scholar that compared the neural activity associated with episodic and semantic memory retrieval. Performance on such tasks can be characterized in terms of both ‘item’ and ‘set’ effects, that is, processes that are specific to the individual items within the task and which change on a moment to moment basis, and processes that are general to performance of each task as a whole. As the authors note, neuroimaging studies have generally confounded item and set effects, but it is possible to investigate these two types of effect (and interactions between them) by employing techniques that allow for ‘event-related’ experimental designs. Although the Duzel et al. study used both PET scanning and ERPs (event-related potentials), it is most noteworthy for its demonstration of a novel procedure for investigating cognitive ERPs, using the direct-coupled (DC) technique, to measure slow cortical potentials. Significantly, the authors argue that the ERP data reveals both set effects (differences in neural activity across the episodic and semantic memory tasks, irrespective of whether test items were old or new) and item effects (differences in neural activity distinguishing old and new items, solely on the episodic memory task). Thus, the study demonstrates that the neural correlates of set and item effects can be dissociated, and highlights the fact that theories of memory must account both for processes that are general to the performance of a task, and those that are specific to individual items within a task. More significant perhaps, is the demonstration of how useful event-related neuroimaging techniques can be in informing and constraining cognitive accounts of behavior.