The effect of cognitive load on hemispheric asymmetries in true and false memory.

Studies examining hemispheric asymmetries in false memory have shown that the right hemisphere (RH) is more susceptible to false memories compared to the left hemisphere (LH). Theories suggest that hemispheric asymmetries in true and false memory may be due to differences in representational coding and the use of top-down mechanisms in each hemisphere. In the current study, the Deese-Roediger-McDermott false memory paradigm was used in conjunction with divided visual field presentation to examine the role of top-down mechanisms in hemispheric asymmetries of true and false memory. In Experiment 1, participants studied lists of related words while completing secondary cognitive load tasks. In Experiment 2, the secondary tasks were administered during memory retrieval instead of memory encoding. Results revealed that cognitive loads imposed during the study phase influenced veridical memory in the LH more than the RH, but cognitive loads imposed during retrieval did not influence veridical memory in either hemisphere. Surprisingly, false memory rates were not influenced by cognitive loads and were higher in the LH. These data provide evidence that, at least for veridical memory, top-down control mechanisms are used more readily for the encoding of information into memory in the LH compared to the RH.

The imagination inflation effect in healthy older adults and patients with mild Alzheimer's disease.

OBJECTIVE: The imagination inflation effect is a type of memory distortion defined as an increased tendency to falsely remember that an item has been seen, or an action has been performed, when it has only been imagined. For patients with very mild Alzheimer's disease (AD), susceptibility to the imagination inflation effect could have significant functional consequences in daily life. METHOD: We assessed whether patients with very mild AD were more or less susceptible to the imagination inflation effect when compared with healthy older adults. In the first session, participants were read an action statement such as "fill the pillbox" and engaged in 1 of 3 activities: listened to the statement being read, performed the action, or imagined performing the action. During the second session, participants imagined action statements from the first session, as well as new action statements. During the recognition test, participants were asked to determine whether action statements were or were not performed during the first session. RESULTS: We found that imagining performing actions increased the tendency of patients with very mild AD to falsely recall the action as having been performed to an extent similar to that of healthy older adults. CONCLUSION: We concluded that, similar to healthy older adults, patients with very mild AD were susceptible to the imagination inflation effect, which we attributed to difficulties with source monitoring and reliance on familiarity.

What forgetting tells us about remembering: the influence of top-down control on hemispheric asymmetries in verbal memory.

It has been suggested that left hemisphere (LH) advantages in verbal processing is due to superior top-down control of verbal information. It is not clear how top-down mechanisms affect the encoding and retrieval of verbal information from hemispheric memory and whether they only influence activation or also encompass the inhibition of verbal information. The directed forgetting method, in conjunction with divided visual field presentation, was used to examine the influence of top-down control mechanisms on hemispheric asymmetries in verbal memory. Participants were cued to remember or forget words. Cues were presented either simultaneously with targets or after a short delay. A recognition memory test using divided visual field presentation was then given. Response times (RTs) revealed effects of cue timing in the LH. With simultaneous cues, RTs were faster to "Remember" words compared to "Forget" words. With delayed cues, RTs for "Remember" and "Forget" words were equivalent. In the right hemisphere (RH), "Remember" words were consistently faster than "Forget" words, regardless of cue timing. These data provide evidence that top-down mechanisms influenced LH verbal memory retrieval more than RH verbal memory retrieval. Finally, there was little evidence to suggest the hemispheres differ in inhibitory processing.

Don't shoot the messnger: memory for misspellings in context.

Misspellings in sentences are usually easy to understand by readers due to top-down influences. Although top-down processing allows for fluent reading of misspelled items, the nature of their representations in memory is not known. If representations of misspellings are distinct from representations of correctly spelled words, their influence should be seen in later recognition decisions. In this set of experiments, participants read words and misspellings embedded in sentences and were later given a recognition test. The sentences contained semantically biased or neutral contexts. In Experiment 1, misspellings were created by removing a single letter (e.g., drveway). In Experiment 2, the recognition items probes were presented in uppercase letters (e.g., DRVEWAY) to reduce the visual similarity between study and test items. In Experiment 3, the misspellings were created by substituting visually similar letters (e.g., driweway). In contrast to the previous experiments, in Experiment 4, participants were explicitly told about the memory test to see how response strategies affect performance. Overall, the results indicate that people retain surface feature information about misspellings which seem to inform their memory judgments, and that the processing of this information cannot be strategically controlled.