Memory for Emotion-Laden Words in Normal Aging:Valence-Arousal Interactions and Neuroanatomical Correlates

G5 Doctoral dissertation (article)


Internal Authors/Editors


Publication Details

List of Authors: Saarela Carina
Publisher: Åbo Akademi University
Publication year: 2018
ISBN: 978-952-12-3753-9


Abstract

Healthy aging can be characterized as a multidimensional process that
involves both age-related physical/cognitive deterioration and
preserved functioning in socioaffective domains and specific cognitive
abilities. This is also true for episodic memory, as healthy aging
simultaneously entails general episodic memory decline and preserved
emotional enhancement effect in memory (EEM). EEM is defined as the
augmentation of the formation and strength of memory traces for
emotion-laden information. In this field of research, emotion is
commonly conceptualized as two bidirectional dimensions, valence
(negative-positive) and arousal (calming-exciting). Even though EEM
is maintained with age, age differences tend to emerge in the valencespecific
preferences for emotion-laden information. This so-called
positivity effect can manifest as a reduced preference for negative over
positive material commonly seen in young adults, or even as a
preference for positive over negative material (positivity bias) in
middle–aged and older adults. Neuroimaging evidence indicates that
also the activation and functional connectivity patterns of EEM-related
brain regions differ between young and older adults. However, due to
the dearth of research in this particular field, the psychological and
neural mechanisms of these age differences remain poorly known.

The overarching aim of the present thesis was to examine the
psychological and neural mechanisms underlying memory for
emotion-laden words in aging. First, age- and gender-specific norms
for valence and arousal ratings for 420 frequency-controlled Finnish
nouns were established (Study I). These norms were used to select
stimuli for the three subsequent studies (Studies II-IV), which aimed at
a) investigating the role of arousal in age differences concerning
valence-specific preferences in memory; and b) examining the
neuroanatomical substrates of memory for emotion-laden words in
cognitively intact middle-aged and older adults. Memory was assessed
using tasks probing immediate free recall and recognition memory of
intentionally encoded words. The neuroanatomical correlates of
interest were regional gray matter (GM) volume and white matter
(WM) microstructure as measured by fractional anisotropy (FA) using
structural magnetic resonance imaging (MRI) methods.

Study I mainly confirmed the expected curvilinear relationship
between valence and arousal ratings, but with distinct relationships for
negative and positive words. Effects of age and gender on the ratings
were weak, but statistically significant, and mostly in line with
expectations. The ratings correlated for the most part adequately with
ratings in other databases. Because the valence factor explained
decidedly more of the variance in the ratings, the findings indicate that
language- and culture-related aspects take precedence over
demographic characteristics when affective properties of words are
rated.

Study II examined the role of arousal in producing the age-related
valence-specific preferences in memory in a group of young adults and
a group of middle-aged and older adults. Contrary to predictions, no
statistically significant age differences emerged concerning valence
and/or arousal effects on immediate free recall and recognition memory
accuracy or response bias. Thus, no age-related positivity effect was
found, only lower overall memory accuracy in the older adults. Valence
and arousal exhibited distinct, but mostly interacting effects on these
measures across the age groups.

Studies III and IV investigated the regional GM volumetric and WM
microstructural correlates of memory in middle-aged and older adults.
The behavioral results showed an unexpected positivity bias and EEM
in recognition memory (Studies III-IV), but no effect of emotion on
immediate free recall (Study III). In Study III, the region-of-interest
(ROI) analyses using amygdalar and hippocampal volumes yielded no
associations with either immediate free recall or recognition memory.
The whole brain analyses unexpectedly showed that better immediate
free recall of negative words was associated with less regional GM
volume in dorsomedial and left dorsolateral prefrontal cortex (PFC).
Surprisingly, the significant positive correlation between local GM
volume and immediate free recall of positive words was located to the
cerebellum, and the negative correlation for recognition memory of
positive words to primary visual cortex. The findings suggest that the
neural areas subserving memory for emotion-laden information
involve posterior brain areas, including the cerebellum, and that
cognitive control functions may constitute the driving mechanism for memory for emotion-laden information. In Study IV, no statistically
significant associations between FA and recognition memory of
negative or neutral words were found. Negative associations between
recognition memory of positive words and FA were unexpectedly
found in several left-hemisphere projection, association, and
commissural tracts. This likely reflects the complex interrelationships
between the positivity bias in memory, structural WM integrity, and
compensatory brain mechanisms in older age.

Study II together with the behavioral results in Studies III-IV revealed
that it is important to consider the contributions of both arousal and
valence to emotional memory. In Studies I-II, the interrelatedness
between these affective dimensions took different forms in different
conditions, indicating that their relationship is variable by nature. The
neuroanatomical Studies III-IV produced several novel findings. The
unexpected localizations and directions of the correlations in these
studies indicate that the structure-function relationships for memory
for emotion-laden stimuli hold unique qualities in healthy aging,
suggesting that these neuroanatomical correlates may be distinct for
healthy aging vs. neuropathological conditions in older age. On a
general level, the counterintuitive directionality of some of the results
highlighted the complexity of the relationships between size/integrity
of brain structure, functional efficiency, and behavioral outcomes. The
results of these data-driven studies were more in line with the
Cognitive Control Model/Socioemotional Selectivity Theory
(CCM/SST) account of the positivity effect than the deficit-based
Dynamic Integration Theory (DIT) or Aging Brain Model (ABM)
accounts. However, no young adult group was included here.
Furthermore, the behavioral study II, which did include young adults,
offered scant evidence to support either theoretical framework, and
showed no evidence for the age-related positivity effect in memory. To
pinpoint the mechanisms driving these results, further studies using
integrative frameworks are warranted. These should collect multilevel
and multidimensional data to analyze and create models that permit
assessing distinct contributions of various processes as well as their
interrelationships. Also, using more ecologically valid stimuli, such as
virtual reality systems, would advance knowledge on emotional
memory.


Last updated on 2019-22-11 at 04:38