Elaboration Benefits Source Memory Encoding Through Centrality Change

Drawing improves memory in patients with hippocampal damage

The hippocampus plays a critical role in the formation of declarative memories, and hippocampal damage leads to significant impairments in new memory formation. Drawing can serve as a form of multi-modal encoding that improves declarative memory performance relative to other multimodal encoding strategies such as writing. We examined whether, and to what extent, patients with hippocampal damage could benefit from the mnemonic strategy of drawing. Three patients with focal hippocampal damage, and one patient with both hippocampal and cortical lesions, in addition to 22 age-, sex-, and education-matched controls, were shown a list of words one at a time during encoding and instructed to either draw a picture or repeatedly write each word for 40 s. Following a brief filled delay, free recall and recognition memory for words from both encoding trial types were assessed. Controls showed enhanced recall and recognition memory for words drawn versus those that were written, an effect that was even more pronounced in patients with focal hippocampal damage. By contrast, the patient with both hippocampal and cortical lesions showed no drawing-mediated boost in either recall or recognition memory. These findings demonstrate that drawing is an effective encoding strategy, likely accruing from the engagement of extra-hippocampal processes including the integration of cortical-based motor, visual, and semantic processing, enabling more elaborative encoding.

Cortical thickness in the right inferior frontal gyrus mediates age-related performance differences on an item-method directed forgetting task

Evidence suggests that older adults have difficulty relative to younger adults in forgetting irrelevant information. Here we sought to understand the physical basis of this deficit by investigating the relationship between cortical thickness and intentional forgetting, using an item-method directed forgetting task. We tested younger (n = 44) and older (n = 54) adults' memories for words that they were instructed to either remember or to forget, and then extracted cortical thickness values from brain regions previously shown, using functional neuroimaging, to be associated with memory suppression, including the right inferior frontal gyrus, the right postcentral gyrus and the left superior/middle frontal gyrus. Results from a parallel mediation model indicated that variations in cortical thickness in the right inferior frontal gyrus, but not the right postcentral gyrus or left superior/middle frontal gyrus, partially explained age-related differences in directed forgetting: older adults with thinner cortices in this area showed worse forgetting ability. This is the first study to explore how neuromorphological differences affect the ability to intentionally suppress items in memory. The results suggest that age-related differences in directed forgetting may be partly driven by cortical thickness in a brain structure known to be functionally involved in directed forgetting, and inhibitory control more broadly, supporting a contribution of deficient inhibition to this phenomenon.

Visualization of Brain Statistics With R Packages ggseg and ggseg3d

There is an increased emphasis on visualizing neuroimaging results in more intuitive ways. Common statistical tools for dissemination of these results, such as bar charts, lack the spatial dimension that is inherent in neuroimaging data. Here we present two packages for the statistical software R that integrate this spatial component. The ggseg and ggseg3d packages visualize predefined brain segmentations as 2D polygons and 3D meshes, respectively. Both packages are integrated with other well-established R packages, which allows great flexibility. In this Tutorial, we describe the main data and functions in the ggseg and ggseg3d packages for visualization of brain atlases. The highlighted functions are able to display brain-segmentation plots in R. Further, the accompanying ggsegExtra package includes a wider collection of atlases and is intended for community-based efforts to develop additional compatible atlases for ggseg and ggseg3d. Overall, the ggseg packages facilitate parcellation-based visualizations in R, improve and facilitate the dissemination of results, and increase the efficiency of workflows.