Indestructible plastic: the neuroscience of the new aging brain

Long-term olfactory enrichment promotes non-olfactory cognition, noradrenergic plasticity and remodeling of brain functional connectivity in older mice

Brain functional and structural changes lead to cognitive decline during aging, but a high level of cognitive stimulation during life can improve cognitive performances in the older adults, forming the cognitive reserve. Noradrenaline has been proposed as a molecular link between environmental stimulation and constitution of the cognitive reserve. Taking advantage of the ability of olfactory stimulation to activate noradrenergic neurons of the locus coeruleus, we used repeated olfactory enrichment sessions over the mouse lifespan to enable the cognitive reserve buildup. Mice submitted to olfactory enrichment, whether started in early or late adulthood, displayed improved olfactory discrimination at late ages and interestingly, improved spatial memory and cognitive flexibility. Moreover, olfactory and non-olfactory cognitive performances correlated with increased noradrenergic innervation in the olfactory bulb and dorsal hippocampus. Finally, c-Fos mapping and connectivity analysis revealed task-specific remodeling of functional neural networks in enriched older mice. Long-term olfactory enrichment thus triggers structural noradrenergic plasticity and network remodeling associated with better cognitive aging and thereby forms a promising mouse model of the cognitive reserve buildup.

“Integrative learning” promotes learning but not memory in older rats

Background

We had previously advanced the concept of “Integrative Learning”, that is, “under the role of ‘meta-learning self’, learners actively integrate learning materials to achieve rapid and in-depth understanding of knowledge”, and designed an animal behavioral model to compare the effects of “Integrative Learning” (IL) vs. “Progressive Learning” (PL) in young rats. It was found that IL is more advantageous than PL. Here, we aim to examine whether the same phenomenon persist in older rats.

Methods

Fifteen 12-month-old male Sprague-Dawley (SD) rats were selected as subjects and randomly divided into the IL group and the PL group, and a 14-unit integrative T-maze was constructed for the study. Training and testing procedures contained three stages: the learning stage, the memory retention test stage and the Gestalt transfer learning stage. Data on young rats (1-month-old) from the previous study were also drawn here for comparisons on learning performance.

Results

(1) The 12-session learning stage can be divided into three sub-stages as each sub-stage represented the new opening of one third of the whole path in the PL group. There were significant interactions in total errors made between groups and sessions: the PL group had significantly fewer errors during Sub-stage One due to a much shorter path to be learned, however, the IL group’s errors made sharply dropped as learning progressed into Sub-stage Two and Three, and were maintained at a significantly lower level than the PL group during Sub-stage Three. (2) When compared with young rats, age had a main effect on the number of errors made—the 1-month-old groups learned overall better and faster than the older groups, whereas the pattern of group differences between the IL and PL learning modes remained consistent across young and older groups. (3) Unlike young rats, during the memory retention test stage and the Gestalt transfer learning stage, the IL group did not perform better than the PL group in older rats.

Conclusions

(1) “Integrative Learning” promotes learning but not memory in older rats. (2) Higher-order cognitive abilities that support meta-cognition, long-term retention and knowledge transfer might be deteriorating in older rats.

Construction and evaluation of multidomain attention training to improve alertness attention, sustained attention, and visual-spatial attention in older adults with mild cognitive impairment: A randomized controlled trial

OBJECTIVES

We aimed to analyze the effects of multidomain attention training on alertness, sustained attention, and visual-spatial attention in older adults with mild cognitive impairment (MCI).

DESIGN

The design used in this study was a two-arm, parallel group, double-blind randomized controlled trial.

SETTING AND PARTICIPANTS

The participants of the study were seventy-eight older adults with MCI (mean age: 79.5 ± 7.9 years) from retirement centers and community housing for the elderly.

INTERVENTION

The participants were randomly assigned to an experimental group (multidomain attention training, n = 39) or an active control group (n = 39). Both groups underwent training sessions for 45 minutes three times per week for 6 weeks (18 sessions in total).

MEASURES

The main efficacy indicator was alertness (Trail Making Test Part B), sustained attention (Digit Vigilance Test), and visual-spatial attention (Trail Making Test Part A). The secondary outcome indicators were other cognitive functions (Mini-Mental State Examination [MMSE] and Montreal Cognitive Assessment [MoCA] subscales). Measurements were obtained at pretest, posttest, and 3 and 6 months after training.

RESULTS

The results were analyzed by a generalized estimating equation (GEE), which indicated that attention outcomes (alertness, sustained attention, and visual-spatial attention) of the experimental group did not improve after training. However, the experimental group displayed a significant improvement in the attention, memory, and orientation of MMSE and MoCA subscales over a period of 6 months and also showed superior results compared with the control group.

CONCLUSIONS

Multidomain attention training demonstrated improved alertness and visual-spatial attention for posttest after 6 months. We also outline potential future advances in attention training for improving attention in older adults with MCI.