Amy A. Overman

Chewing gum does not induce context-dependent memory when flavor is held constant

This study examined the effect of chewing gum on memory when flavor is held constant. Four separate groups of participants (total n=101) completed a word recall task. At learning and recall, participants either chewed a piece of gum or sucked a sweet. Each participant completed the memory task twice, once with abstract words and once with concrete words. A significant effect of word type (concrete vs. abstract) was found, however recall performance was not improved by matched oral activity at learning and recall. The results cast further doubt on the ability of chewing gum to induce context-dependent memory effects.

The effects of item familiarity on the neural correlates of successful associative memory encoding

Associative memory is considered to be resource-demanding, requiring individuals to learn individual items and the specific relationships between those items. Previous research has shown that prior studying of items aids in associative memory for pairs composed of those same items, as compared to pairs of items that have not been prelearned (e.g., Kilb & Naveh-Benjamin, 2011). In the present study, we sought to elucidate the neural correlates mediating this memory facilitation. After being trained on individual items, participants were scanned while encoding item pairs composed of items from the pretrained phase (familiarized-item pairs) and pairs whose items had not been previously learned (unfamiliarized-item pairs). Consistent with previous findings, the overall subsequent recollection showed the engagement of bilateral parahippocampal gyrus (PHG) and hippocampus, when compared to subsequent forgetting. However, a direct comparison between familiarized- and unfamiliarized-item pairs showed that subsequently recollected familiarized-item pairs were associated with decreased activity across much of the encoding network, including bilateral PHG, hippocampus, prefrontal cortex, and regions associated with item-specific processing within occipital cortex. Increased activity for familiarized-item pairs was found in a more limited set of regions, including bilateral parietal cortex, which has been associated with the formation of novel associations. Additionally, activity in the right parietal cortex correlated with associative memory success in the familiarized condition. Taken together, these results suggest that prior exposure to items can reduce the demands incurred on neural processing throughout the associative encoding network and can enhance associative memory performance by focusing resources within regions supporting the formation of associative links.

Computer-based training and cognitive improvement after adult-onset malaria: a case report.

Malaria infection is known to cause cognitive impairments in children and adults. To date, very little research has investigated the efficacy of computer-based cognitive rehabilitation after cerebral malaria, particularly in adults. The aim of this study was to examine whether computer-based cognitive training can be employed to rehabilitate memory and attentional deficits after cerebral malaria, particularly in adults. The current study examines the case of a 20-year-old female who acquired malaria on trip to Ghana. One year after her infection she still exhibited below-average performance on a number of neuropsychological assessments. A computer-based cognitive training program was undertaken for 14 weeks. At the end of training, performance improved on the majority of assessments and was within the normal range for all assessments. The participant also displayed greater improvements from pre-test to post-test than a normal control participant who did not complete cognitive training. The findings extend prior research on cerebral malaria and suggest possible rehabilitation methods for adults who experience cognitive impairments following malaria infection.

Older adults’ associative memory is modified by manner of presentation at encoding and retrieval.

Relative to young adults, older adults typically exhibit a reduced ability to accurately remember associations between stimuli. Prior research has assumed that this age-related memory impairment affects different types of associations similarly. However, research in young adults has suggested that item–item and item–context associations are supported by different underlying neural mechanisms that could be unequally affected by aging. This experiment compared memory across association types in younger and older adults by presenting the same types of stimuli as either item–item or item–context pairs. Manner of presentation during retrieval was also manipulated so that pairs were presented in a manner that was either congruent or incongruent with their presentation during encoding. Older adults showed a particular benefit of encoding–retrieval congruency for item–context associations, supporting the idea that the associative deficit may be reduced by unitization at encoding and reinstatement of this prior stimulus configuration at retrieval.

Modeling age differences in effects of pair repetition and proactive interference using a single parameter.

In this article, we apply the REM model (Shiffrin & Steyvers, 1997) to age differences in associative memory. Using Criss and Shiffrin’s (2005) associative version of REM, we show that in a task with pairs repeated across 2 study lists, older adults’ reduced benefit of pair repetition can be produced by a general reduction in the diagnosticity of information stored in memory. This reduction can be modeled similarly well by reducing the overall distinctiveness of memory features, or by reducing the accuracy of memory encoding. We report a new experiment in which pairs are repeated across 3 study lists and extend the model accordingly. Finally, we extend the model to previously reported data using the same task paradigm, in which the use of a high-association strategy introduced proactive interference effects in young adults but not older adults. Reducing the diagnosticity of information in memory also reduces the proactive interference effect. Taken together, the modeling and empirical results reported here are consistent with the claim that some age differences that appear to be specific to associative information can be produced via general degradation of information stored in memory. The REM model provides a useful framework for examining age differences in memory as well as harmonizing seemingly conflicting prior modeling approaches for the associative deficit.

A Positive Generation Effect on Memory for Auditory Context

Self-generation of information during memory encoding has large positive effects on subsequent memory for items, but mixed effects on memory for contextual information associated with items. A processing account of generation effects on context memory (Mulligan in Journal of Experimental Psychology: Learning, Memory, and Cognition, 30(4), 838–855, 2004; Mulligan, Lozito, & Rosner in Journal of Experimental Psychology: Learning, Memory, and Cognition, 32(4), 836–846, 2006) proposes that these effects depend on whether the generation task causes any shift in processing of the type of context features for which memory is being tested. Mulligan and colleagues have used this account to predict various negative effects of generation on context memory, but the account also predicts positive generation effects under certain circumstances. The present experiment provided a critical test of the processing account by examining how generation affected memory for auditory rather than visual context. Based on the processing account, we predicted that generation of rhyme words should enhance processing of auditory information associated with the words (i.e., voice gender), whereas generation of antonym words should have no effect. These predictions were confirmed, providing support to the processing account.

Same face, same place, different memory: manner of presentation modulates the associative deficit in older adults

ABSTRACT One of the more severe and consequential memory impairments experienced by older adults is the loss of the ability to form and remember associations. Although the associative deficit is often assumed to be unitary, memory episodes may contain different types of associations (e.g., item–item, item–context). Research in younger adults suggests that these different association types may involve different neural mechanisms. This raises the possibility that different association types are not equally affected by aging. In order to investigate this, the current study directly compared memory across item–item and item–context associations in younger and older adults by manipulating the manner of presentation of the associations. Results indicate that the associative deficit in aging is not uniform and that aging has a greater impact on item–context compared to item–item associations. The results have implications for theories of associative memory, age-related cognitive decline, and the functional organization of the medial temporal lobe in aging.