Cerebral Cortex Advance Access published online on June 19, 2009
Cerebral Cortex, doi:10.1093/cercor/bhp116
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Dissociation Between Memory Accuracy and Memory Confidence Following Bilateral Parietal Lesions
1 Department of Experimental Psychology, 2 Behavioural and Clinical Neuroscience Institute, University of Cambridge, CB2 3EB, UK, 3 MRC Cognition and Brain Sciences Unit, Cambridge, CB2 7EF, UK, 4 Center for Cognitive Neuroscience, University of Pennsylvania, PA 19104, USA, 5 Department of Psychology, Temple University, Philadelphia, PA 19122, USA
Address correspondence to Dr Jon Simons, Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, UK. Email: jss30{at}cam.ac.uk.
Numerous functional neuroimaging studies have observed lateral parietal lobe activation during memory tasks: a surprise to clinicians who have traditionally associated the parietal lobe with spatial attention rather than memory. Recent neuropsychological studies examining episodic recollection after parietal lobe lesions have reported differing results. Performance was preserved in unilateral lesion patients on source memory tasks involving recollecting the context in which stimuli were encountered, and impaired in patients with bilateral parietal lesions on tasks assessing free recall of autobiographical memories. Here, we investigated a number of possible accounts for these differing results. In 3 experiments, patients with bilateral parietal lesions performed as well as controls at source recollection, confirming the previous unilateral lesion results and arguing against an explanation for those results in terms of contralesional compensation. Reducing the behavioral relevance of mnemonic information critical to the source recollection task did not affect performance of the bilateral lesion patients, indicating that the previously observed reduced autobiographical free recall might not be due to impaired bottom-up attention. The bilateral patients did, however, exhibit reduced confidence in their source recollection abilities across the 3 experiments, consistent with a suggestion that parietal lobe lesions might lead to impaired subjective experience of rich episodic recollection.
Key Words: metamemory • neuropsychology • recall • recollection • source memory