Competition and representation during memory retrieval: roles of the prefrontal cortex and the posterior parietal cortex

Abstract

In this functional-MRI study we examined the hypothesis that the prefrontal cortex responds differently to the extent of competition during retrieval, whereas the parietal cortex is responsible for problem representation that should not be directly related to the competition. Participants mastered arbitrary person-location pairs, and their recognition memory was tested in a functional-MRI session. The pairs were constructed such that a person was associated with one, two, or three different locations and vice versa. The recognition time increased with the number of associations, reflecting increased competition. A confirmatory analysis of imaging data with prespecified prefrontal and parietal regions showed that, although both regions were highly involved during memory retrieval, only the prefrontal region responded to the levels of competition. This result was consistent with predictions of an information-processing model as well as with an exploratory identification of regions of interest.

Fig. 1.

Schematic view of three prespecified regions. (a) Regions in the left hemisphere. (b) Axial view of these three regions and their right-hemisphere homologues.

Fig. 2.

Percent activation changes in the prespecified motor region (a and b), the prespecified parietal region (c and d), and the prespecified prefrontal regions (e and f). The baseline was the average of the first three scans. The solid lines indicate the predictions based on the model shown in Fig. 3.

Fig. 3.

Schematic model performance in the low-fan (a) and high-fan (b) conditions.