Using transcranial direct current stimulation (tDCS) on the dorsolateral prefrontal cortex to promote long-term foreign language vocabulary learning.

Transcranial direct current stimulation (tDCS) on the dorsolateral prefrontal cortex (DLPFC) was used to improve foreign-langue learning while using mental imagery. Participants underwent two sessions of 1 mA, 1.5 mA, or sham stimulation prior to learning Swahili-English word pairs two consecutive days. During learning, participants were encouraged to create a mental image of the associated English word. Twenty-four hours after learning and one week later, participants received a cued recall test. A linear dose-response effect of stimulation was found across both tests that occurred long after the immediate effects of stimulation. Follow-up comparisons revealed that only the 1.5 mA condition differed from the sham group. Exploratory moderating effects revealed interactions with sleep quality and handedness. Those with poorer sleep and who were left-handed showed greater recall after 1.5 mA of stimulation than those with better sleep and right-handers. A follow-up behavioral study probing strategy usage indicated that mental imagery strategy use did not strongly impact learning but point to other possible mechanisms including the importance of attending to multimodal perceptual details and memory consolidation. This preliminary evidence supports the role of the DLPFC or connected regions in foreign language vocabulary learning and verbal memory encoding.

Is there more to metamemory? An argument for two specialized monitoring abilities.

Metamemory is the process of monitoring and controlling one's beliefs, knowledge, and mental processes of memory. One fundamental question is whether the monitoring component of this theory should be considered as only one ability or an umbrella of more specialized abilities. In the current study, we aimed to understand the structure of metamemory monitoring by testing unitary versus specialized measurement models of metamemory. Monitoring accuracy and mean ratings from four common monitoring judgments across different stimulus presentation pairs were calculated to create latent factors for each judgment using structural equation modeling. Our results suggest that although each of the monitoring judgments was correlated with one another, monitoring may be composed of two distinct abilities: one occurring during initial presentation and one occurring at retrieval. These results can help explain prior behavioral and brain dissociations between predictions at encoding and retrieval in terms of experimental and material manipulations. We caution against the conceptualization and use of metamemory monitoring as a unitary construct.

Cognitive Reserve Moderates Older Adults' Memory Errors in Autobiographical Reality Monitoring Task.

False memory rates differ in individuals with high versus low cognitive reserve and between young-old and old-old age groups. Here we tested how two types of false memory (false alarms to new items and source memory) in two age groups differed with cognitive reserve. Subjects were presented with words and either instructed to generate a past event from their memory associated with the word or to imagine a future event associated with the word. At test, participants were instructed to determine whether the event was a past, future, or new event. Results showed overall false memory rates were lower for young-old adults and those with high reserve. Critically, low cognitive reserve was most associated with source memory errors in young-old but not old-old adults. Reflecting the opposite pattern, false alarms to new items were most associated with low cognitive reserve for old-old, but not young-old adults. These results seem to suggest two different classes of false memories in old age. That is, cognitive reserve was most protective for familiar lures in earlier stages of old age, whereas it was most protective for new lures in later stages of old age. These results support the idea that retrieval monitoring deteriorates with age, potentially due to declines in working memory capacity, but that the decline may be attenuated by cognitive reserve. Furthermore, we suggest that different levels of working memory capacity may be required for monitoring source memory versus item memory, leading to differential effects of cognitive reserve depending upon age.