Aging and olfactory recognition memory: effect of encoding strategies and cognitive abilities

The role of stimulus complexity and salience in memory for face-name associations in healthy adults: Friend or foe?

The associative deficit hypothesis (ADH) posits that age-related differences in recognition of associations are disproportionately larger than age differences in item recognition because of age-related difficulty in binding and retrieval of two or more pieces of information in a memory episode. This proposition rests on the observation of disproportionately greater age differences in memory for associations than in recognition of individual items. Although ADH has been supported in experiments with verbal and nonverbal stimuli, the effects of task or stimulus characteristics on its generalizability remain unclear. In a series of experiments, we examined how salience and variability of face stimuli presented in face-name pairs affect age differences in recognition of items and associations. We found that a disproportionate age-related deficit in the recognition of face-name associations emerges when face stimuli are more complex, salient, variable, and distinctive, but not when standardized faces appear within minimal visual context. These findings indicate that age-related associative memory deficits may stem at least in part from age differences in use of stimulus characteristics for contextual support. (PsycINFO Database Record

Comparative study of aging in the mouse olfactory bulb

Gene knockout technologies have been used to elevate the mouse as a model species. However, little work has examined age and strain differences in the mouse olfactory system. The present study compared the olfactory bulbs of mature (6 month) and aged (24 month) males of BALB/cBy, C57BL/6J, and DBA/2 strains. Volumes of the glomerular (GLM), external plexiform (EPL), and mitral/granule cell (MIG) layers varied little from strain to strain. Volume measurements increased with age even when corrected for body weight differences. Two nonoverlapping interneuron populations were examined with immunohistochemistry. Staining for the calcium binding protein calretinin varied little between strains, but age-related increases in staining were seen in EPL of C57BL/6J mice. Typical patterns of tyrosine hydroxylase immunoreactivity were observed in all subjects except for old DBA/2 mice, which evidenced considerable staining in submitral areas. Age-related increases were observed in BALB/cBy and DBA/2 mice but not in the C57BL/6J strain. Glial fibrillary acidic protein staining was similar in old BALB/cBy and DBA/2 mice, with astrocytes in all layers of the bulb, but more concentrated in the MIG. However, C57BL/6J tissue revealed very large astrocytes relatively evenly distributed in all layers. Cell proliferation dropped dramatically with age. Labeled cells could still be observed along the lateral ventricles, but very few were observed within the rostral migratory stream or subventricular zone. Although TUNEL labeling revealed many apoptotic figures in the granule cell layer of young subjects, almost no staining was seen in aged mice.

Facilitative effects of EGb 761 on olfactory recognition in young and aged rats

The aim of the present study was to evaluate the effects of chronic and acute treatment by the Gingko biloba extract, EGb 761 (IPSEN, France) on olfactory short-term memory in rats, using a spontaneous recognition procedure. The effects of a daily EGb 761 treatment (30 or 60 mg/kg) over a period of 30 days (Experiment 1) were evaluated in young male rats. Those of a single injection of EGb 761 were assessed either in young male rats at 60 or 120 mg/kg (Experiment 2) or in aged female rats at 60 mg/kg (Experiment 3). Results showed that, at the highest dose (60 mg/kg), chronic EGb 761 treatment enhanced the recognition performances, allowing recognition at delays at which control animals did not show any recognition. Acute treatment enhanced recognition at both doses tested. The results of the third experiment showed that EGb 761 had an overall enhancement effect on the performances of aged rats. In summary, our results provide evidence for a short-term memory enhancement effect of EGb 761 in both young and aged rats.