Subjective sense of memory strength and the objective amount of information accurately remembered are related to distinct neural correlates at encoding
SourceThe Journal of Neuroscience, 31, 24, (2011), pp. 8920-7
Article / Letter to editor
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Donders Centre for Cognitive Neuroimaging
PI Group Memory & Emotion
F.C. Donders Centre for Cognitive Neuroimaging
The Journal of Neuroscience
Subject130 000 Cognitive Neurology & Memory; 130 001 Bridging the gap: hippocampus and memory; 130 026 VENI Hermans, ‘In a fit of fear’; DCN 2: Functional Neurogenomics
Although commonly used, the term memory strength is not well defined in humans. Besides durability, it has been conceptualized by retrieval characteristics, such as subjective confidence associated with retrieval, or objectively, by the amount of information accurately retrieved. Behaviorally, these measures are not necessarily correlated, indicating that distinct neural processes may underlie them. Thus, we aimed at disentangling neural activity at encoding associated with either a subsequent subjective sense of memory strength or with a subsequent objective amount of information remembered. Using functional magnetic resonance imaging (fMRI), participants were scanned while incidentally encoding a series of photographs of complex scenes. The next day, they underwent two memory tests, quantifying memory strength either subjectively (confidence on remembering the gist of a scene) or objectively (the number of details accurately remembered within a scene). Correlations between these measurements were mutually partialed out in subsequent memory analyses of fMRI data. Results revealed that activation in left ventral lateral prefrontal cortex and temporoparietal junction predicted subsequent confidence ratings. In contrast, parahippocampal and hippocampal activity predicted the number of details remembered. Our findings suggest that memory strength may reflect a functionally heterogeneous set of (at least two) phenomena. One phenomenon appears related to prefrontal and temporoparietal top-down modulations, resulting in the subjective sense of memory strength that is potentially based on gist memory. The other phenomenon is likely related to medial-temporal binding processes, determining the amount of information accurately encoded into memory. Thus, our study dissociated two distinct phenomena that are usually described as memory strength.
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