Recall and Recognition Measures of Paired Associate Learning in Healthy Aging

Neuroimaging and verbal memory assessment in healthy aging adults using a portable low-field MRI scanner and a web-based platform: results from a proof-of-concept population-based cross-section study

Consumer wearables and health monitors, internet-based health and cognitive assessments, and at-home biosample (e.g., saliva and capillary blood) collection kits are increasingly used by public health researchers for large population-based studies without requiring intensive in-person visits. Alongside reduced participant time burden, remote and virtual data collection allows the participation of individuals who live long distances from hospital or university research centers, or who lack access to transportation. Unfortunately, studies that include magnetic resonance neuroimaging are challenging to perform remotely given the infrastructure requirements of MRI scanners, and, as a result, they often omit socially, economically, and educationally disadvantaged individuals. Lower field strength systems (< 100 mT) offer the potential to perform neuroimaging at a participant's home, enabling more accessible and equitable research. Here we report the first use of a low-field MRI "scan van" with an online assessment of paired-associate learning (PAL) to examine associations between brain morphometry and verbal memory performance. In a sample of 67 individuals, 18-93 years of age, imaged at or near their home, we show expected white and gray matter volume trends with age and find significant (p < 0.05 FWE) associations between PAL performance and hippocampus, amygdala, caudate, and thalamic volumes. High-quality data were acquired in 93% of individuals, and at-home scanning was preferred by all individuals with prior MRI at a hospital or research setting. Results demonstrate the feasibility of remote neuroimaging and cognitive data collection, with important implications for engaging traditionally under-represented communities in neuroimaging research.

Dissociable effects of NR2A and NR2B NMDA receptor antagonism on cognitive flexibility but not pattern separation

RATIONALE

N-methyl-D-aspartate (NMDA) receptors play crucial roles in learning and memory, but the role of each NMDA receptor subtype in a specific cognitive process is unclear. Non-selective blockers of NMDA receptor are used to model the cognitive impairment in schizophrenia and Alzheimer's disease. Counter-intuitively selective NR2A and 2B NMDA receptor antagonists are thought to have pro-cognitive properties. These seemingly contrasting findings might in part be the result of different compounds and behavioral measures used across studies.

OBJECTIVE

We compared the effect of NVP-AAM077 (NR2A antagonist), CP 101-606 (NR2B antagonist), and MK-801 (non-selective antagonist) in a series of touch screen tasks that can be used to measure spatial cognition and cognitive flexibility.

METHODS

NVP-AAM077, CP 101-606, and MK-801 were administered prior to testing, in adult male Lister-hooded rats trained in tasks of location discrimination, paired associate learning (PAL), and trial unique non-match to location (TUNL).

RESULTS

Results showed that MK-801 impaired performance on all the tasks. In contrast, CP 101-606 only impaired reversal learning in location discrimination and had minimal effect on working memory in TUNL and caused a modest improvement in accuracy in PAL and acquisition of a spatial discrimination. NVP-AAM077 had little effect on performance across tasks, although these data allude to a potential enhancement of acquisition of a spatial location and impairments in spatial reversal learning in a separation-dependent manner.

CONCLUSIONS

These data demonstrated that non-selective NMDA antagonism will disrupt numerous aspects of cognitive function. However, selective antagonism is capable of impairing or enhancing cognitive function in a task-dependent fashion.

Accelerated long-term forgetting in aging and intra-sleep awakenings

The architecture of sleep and the functional neuroanatomical networks subtending memory consolidation processes are both modified with aging, possibly leading to accelerated forgetting in long-term memory. We investigated associative learning and declarative memory consolidation processes in 16 young (18–30 years) and 16 older (65–75 years) healthy adults. Performance was tested using a cued recall procedure at the end of learning (immediate recall), and 30 min and 7 days later. A delayed recognition test was also administered on day 7. Daily sleep diaries were completed during the entire experiment. Results revealed a similar percentage of correct responses at immediate and 30-min recall in young and older participants. However, recall was significantly decreased 7 days later, with an increased forgetting in older participants. Additionally, intra-sleep awakenings were more frequent in older participants than young adults during the seven nights, and were negatively correlated with delayed recall performance on day 7 in the older group. Altogether, our results suggest a decline in verbal declarative memory consolidation processes with aging, eventually leading to accelerated long-term forgetting indicating that increased sleep fragmentation due to more frequent intra-sleep awakenings in older participants contribute to the reported age-related decline in long-term memory retrieval. Our results highlight the sensitivity of long-term forgetting measures to evidence consolidation deficits in healthy aging.