Cerebral Cortex Advance Access published online on November 21, 2007
Cerebral Cortex, doi:10.1093/cercor/bhm201
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Neural Correlates of Availability and Accessibility in Memory
1 Department of Psychology, Department of Computer Science, and School of Medicine, Southern Illinois University Carbondale, Carbondale, IL 62901, USA, 2 Memorial Hospital of Carbondale, Southern Illinois Health Care, Carbondale, IL 62901, USA, 3 Department of Radiation Sciences (Radiology) and Integrative Medical Biology (Physiology), Umeå University, SE-901 87 Umeå, Sweden
Address correspondence to Reza Habib, PhD, Department of Psychology, Life Sciences II, Room 281, 1125 Lincoln Drive, Carbondale, IL 62901, USA. Email: rhabib{at}siu.edu.
Failure to remember can be due to not having information available in memory or to an inability to access information that is available. We used functional magnetic resonance imaging to examine brain responses during encoding and successive cued recall and associative recognition tests of paired associates. Items were classified into 3 categories based on performance on the 2 retrieval tests: 1) successfully remembered (both recalled and recognized), 2) inaccessible (not recalled but later recognized), and 3) forgotten (neither recalled nor recognized). During cued recall, availability in memory was signaled in a network of regions including bilateral medial temporal lobe, left middle temporal cortex, and the parietal cortex. Memory access resulted in heightened activity in these regions as well as in left inferior frontal cortex. Encoding-related activity in hippocampus and inferior temporal cortex predicted subsequent availability and left inferior frontal activity predicted subsequent access. These results suggest that failure to access information that is available in memory may reflect weaker memory representations.
Key Words: encoding • fMRI • memory • recall • recognition • trace strength