Reduced structural connectivity of the medial temporal lobe including the perforant path is associated with aging and verbal memory impairment.

The perforant path, the white matter bundle connecting the entorhinal cortex (ERC) with the hippocampal formation deteriorates with age-related cognitive decline. Previous investigations using diffusion-weighted MRI to quantify perforant path integrity in-vivo have been limited due to image resolution or have quantified the perforant path using methods susceptible to partial volume effects such as the tensor model and without consideration of its 3-dimensional morphology. In this investigation, we use quantitative-anisotropy informed tractography derived from ultra-high resolution diffusion imaging (ZOOMit) to investigate structural connectivity of the perforant path and other medial temporal lobe (MTL) pathways in older adults (63 to 98 years old, n = 51). We show that graph density within the MTL declines with age and is associated with lower delayed recall performance. We also show that older age and poorer delayed recall are associated with reduced streamlines connecting the ERC and dentate gyrus of the hippocampus (the putative perforant path). This work suggest that intra-MTL connectivity may new candidate biomarkers for age-related cognitive decline.

Hippocampal dentate gyrus integrity revealed with ultrahigh resolution diffusion imaging predicts memory performance in older adults.

Medial temporal lobe (MTL) atrophy is a core feature of age-related cognitive decline and Alzheimer's disease (AD). While regional volumes and thickness are often used as a proxy for neurodegeneration, they lack the sensitivity to serve as an accurate diagnostic test and indicate advanced neurodegeneration. Here, we used a submillimeter resolution diffusion weighted MRI sequence (ZOOMit) to quantify microstructural properties of hippocampal subfields in older adults (63-98 years old) using tensor derived measures: fractional anisotropy (FA) and mean diffusivity (MD). We demonstrate that the high-resolution sequence, and not a standard resolution sequence, identifies dissociable profiles for CA1, dentate gyrus (DG), and the collateral sulcus. Using ZOOMit, we show that advanced age is associated with increased MD of the CA1 and DG as well as decreased FA of the DG. Increased MD of the DG, reflecting decreased cellular density, mediated the relationship between age and word list recall. Further, increased MD in the DG, but not DG volume, was linked to worse spatial pattern separation. Our results demonstrate that ultrahigh-resolution diffusion imaging enables the detection of microstructural differences in hippocampal subfield integrity and will lead to novel insights into the mechanisms of age-related memory loss.

Fixation, flexibility, and creativity: The dynamics of mind wandering.

The mind-wandering literature is long on results and short on theory. One notable exception is the Dynamic Framework, a theoretical framework that characterizes mind wandering as thoughts that are relatively unconstrained from deliberate and automatic sources, or "freely moving." Critically, this framework makes numerous testable predictions, including (a) a positive association between freely moving thought and ADHD, (b) negative associations between freely moving thought and depression, anxiety, and OCD, and (c) a positive association between freely moving thought and divergent thinking ability. In Study 1, to test these predictions, we measured participants' reports of freely moving thoughts during a cognitive task and assessed divergent thinking and various psychopathological symptoms. Results failed to support any of the Dynamic Framework's predictions. In Study 2, we assessed the predicted relations between freely moving thought and divergent-thinking performance by manipulating thought constraint during a creative-incubation interval that preceded a divergent-thinking task. Here, we found some evidence (albeit very weak) to support the Dynamic Framework's prediction. Finally, in Study 3, we examined the possibility that indexing freely moving thought during a divergent-thinking task would yield the predicted associations but failed to find support for these associations. These results, most of which are at odds with the predictions of the Dynamic Framework, suggest either the need to revise the framework and/or that current methods are inadequate to properly test these predictions. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

First-Day Use of the Newborn Weight Loss Tool to Predict Excess Weight Loss in Breastfeeding Newborns.

Background and Objectives: Exclusive breastfeeding is recommended for most newborns. However, exclusively breastfed newborns sometimes experience excess weight loss (EWL, loss ≥10% of birth weight) while lactation is being established. Our primary objective was to evaluate the sensitivity and specificity of the Newborn Weight Loss Tool (NEWT) in early identification of exclusively breastfed newborns who develop EWL; and secondarily, identify breastfeeding variables associated with an at-risk NEWT trajectory. Materials and Methods: We conducted a secondary analysis of prospective data from mother-infant dyads screened for inclusion in the U.S. site of the WHO Growth Reference Study. We excluded records if: NEWT-specific criteria not met, missing key data, or >60 mL formula consumed. We defined NEWT "test-positive" based on an in-hospital weight at about 24 hours falling within the NEWT trajectory consistent with eventual EWL. We defined cases as true EWL based on weight measured at home on day of life 4 (DoL4). Results: Of 280 original records, 60 were excluded (n = 27, NEWT-specific exclusion; n = 15, missing data; n = 18, >60 mL formula), resulting in 220 paired newborn weights measured in-hospital (17 ± 8 hours), and at DoL4 (84 ± 8 hours). NEWT status correctly identified 6/28 EWL cases (21% sensitivity [95% confidence interval, CI, 8-34%]), and 158/192 noncases (82% specificity [95% CI, 75-89%]). NEWT test-positive status was associated with greater weight loss, lower perceived breastfeeding support, and infant less often showing feeding cues on DoL4 (p < 0.05). Conclusion: Sensitivity in predicting EWL is low when applying NEWT at about 24 hours of life; however, early test-positive status is associated with indicators of breastfeeding difficulties on DoL4.

Dissociating the freely-moving thought dimension of mind-wandering from the intentionality and task-unrelated thought dimensions.

The recently forwarded family-resemblances framework of mind-wandering argues that mind-wandering is a multidimensional construct consisting of a variety of exemplars. On this view, membership in the mind-wandering family is graded along various dimensions that define more or less prototypical instances of mind-wandering. In recent work, three dimensions that have played a prominent role in defining prototypicality within the mind-wandering family include: (a) task-relatedness (i.e., how related the content of a thought is to an ongoing task), (b) intentionality (i.e., whether thought is deliberately or spontaneously engaged), and (c) thought constraint (i.e., how much attention constrains thought dynamics). One concern, however, is that these dimensions may be redundant with each other. The utility of distinguishing among these different dimensions of mind-wandering rests upon a demonstration that they are dissociable. To shed light on this issue, we indexed the task-relatedness, intentionality, and constraint dimensions of thought during the completion of a laboratory task to evaluate how these dimensions relate to each other. We found that 56% of unconstrained thoughts were "on-task" and that 23% of constrained thoughts were "off-task." Moreover, we found that rates of off-task thought, but not "freely-moving" (i.e., unconstrained) thought, varied as a function of expected changes in task demands, confirming that task-relatedness and thought constraint are separable dimensions. Participants also reported 21% of intentional off-task thoughts that were freely moving and 9% of unintentional off-task thoughts that were constrained. Finally, off-task thoughts were more likely to be freely-moving than unintentional. Taken together, the results suggest that these three dimensions of mind-wandering are not redundant with one another.