Factors controlling neural activity during delayed-response task performance: testing a memory organization hypothesis of prefrontal function.

Understanding the role of prefrontal cortex in delayed-response task performance has been a central focus of neuroimaging research. The first part of this review will emphasize consistent observations of memory-load-related effects on prefrontal cortex activity that have led me and my colleagues to propose a "memory-organization hypothesis" of prefrontal cortex function. The second part examines how predictions of this hypothesis have borne up to empirical testing. The final part of this review suggests that there is important information contained in between-study variance in the anatomical locus and temporal sequence of neural activity. I will examine how subtle variations in task-structure affect subjects' strategies, producing meaningful variability in neuroimaging data. Systematic manipulation of these variables in future research can assist in elucidating the role of prefrontal cortex in delayed response task performance.