Age does not increase rate of forgetting over weeks—Neuroanatomical volumes and visual memory across the adult life-span

Abstract

The aim of the study was to investigate whether age affects visual memory retention across extended time intervals. In addition, we wanted to study how memory capabilities across different time intervals are related to the volume of different neuroanatomical structures (right hippocampus, right cortex, right white matter). One test of recognition (CVMT) and one test of recall (Rey-Osterrieth Complex Figure Test) were administered, giving measures of immediate recognition/recall, 20-30 min recognition/recall, and recognition/recall at a mean of 75 days. Volumetric measures of right hemisphere hippocampus, cortex, and white matter were obtained through an automated labelling procedure of MRI recordings. Results did not demonstrate a steeper rate of forgetting for older participants when the retention intervals were increased, indicating that older people have spared ability to retain information in the long-term store. Differences in neuroanatomical volumes could explain up to 36% of the variance in memory performance, but were not significantly related to rates of forgetting. Cortical volume and hippocampal volume were in some cases independent as predictors of memory function. Generally, cortical volume was a better predictor of recognition memory than hippocampal volume, while the 2 structures did not differ in their predictive power of recall abilities. While neuroanatomical volumetric differences can explain some of the differences in memory functioning between younger and older persons, the hippocampus does not seem to be unique in this respect.

Regional Hippocampal Volumes and Development Predict Learning and Memory

“…Developmental changes in the functional organization of the medial temporal lobe have been indicated by studies showing, for example, that adolescents and young adults, in contrast to children, engage regions of the hippocampus and parahippocampal gyrus selectively for subsequent recollection [24]. Further, consistent with the present findings, positive relationships between memory performance over extended time periods and hippocampal volume have been shown for visuospatial material in children and adolescents [55] and for both visuospatial and verbal information in adults [56,57]. …”

Structural and Metabolic Correlates of Episodic Memory in Relation to the Depth of Encoding in Normal Aging

“…However, using longer delays, Tombaugh and Hubley (2001) showed that increasing age was associated with faster rates of forgetting of verbal material after one day of retention, but not beyond. Fjell et al (2005), using visual material, disconfirmed the hypothesis that older subjects had a steeper rate of forgetting than younger. In neuroimaging studies, the retention interval is usually short, from seconds to an hour.…”

“…For instance, Walhovd et al (2004) assessed the correlations between hippocampal volume and recall scores obtained at three different retention intervals (5 min, 30 min, 11 weeks) in subjects aged 20 to 88 years. The results showed that both hippocampal volume and age predicted recall after weeks (see also Fjell et al, 2005;Golomb et al, 1994). Using the same procedure in healthy subjects spanning all the adulthood, Sullivan, Marsh, Mathalon, Lim, and Pfefferbaum (1995) found a relationship between hippocampal volume and delayed recall performance with nonverbal material, but not with the immediate scores, whereas the correlation between hippocampal volume and immediate verbal recall performance was significant (but not with the delayed scores).…”

Higher intraindividual variability is associated with more forgetting and dedifferentiated memory functions in old age

“…In aging research, forgetting rates have been studied across different age groups and retention intervals and the findings are mixed. Whereas some studies reported differences in initial performance, but invariant forgetting rates in older and younger adults (Fjell et al, 2005;Rybarczyk, Hart, & Harkins, 1987;Spikman, Berg, & Deelman, 1995), others have shown greater forgetting in older adults, especially after long delays (e.g., 1 week; see Huppert & Kopelman, 1989;Park, Royal, Dudley, & Morrell, 1988), or when testing individuals on episodic recall, rather than recognition tasks (MacDonald, Stigsdotter-Neely, et al, 2006). With respect to experimental manipulations, encoding factors such as meaningfulness of the material (Underwood & Richardson, 1956), degree of learning (Slamecka & McElree, 1983), and pictorial elaboration (Forbes & Reese, 1974) have been found to affect initial rate of learning, but not rate of forgetting.…”