Kaoru Nashiro

Age Differences in Brain Activity during Emotion Processing: Reflections of Age-Related Decline or Increased Emotion Regulation?

Despite the fact that physical health and cognitive abilities decline with aging, the ability to regulate emotion remains stable and in some aspects improves across the adult life span. Older adults also show a positivity effect in their attention and memory, with diminished processing of negative stimuli relative to positive stimuli compared with younger adults. The current paper reviews functional magnetic resonance imaging studies investigating age-related differences in emotional processing and discusses how this evidence relates to two opposing theoretical accounts of older adults’ positivity effect. The aging-brain model [Cacioppo et al. in: Social Neuroscience: Toward Understanding the Underpinnings of the Social Mind. New York, Oxford University Press, 2011] proposes that older adults’ positivity effect is a consequence of age-related decline in the amygdala, whereas the cognitive control hypothesis [Kryla-Lighthall and Mather in: Handbook of Theories of Aging, ed 2. New York, Springer, 2009; Mather and Carstensen: Trends Cogn Sci 2005;9:496–502; Mather and Knight: Psychol Aging 2005;20:554–570] argues that the positivity effect is a result of older adults’ greater focus on regulating emotion. Based on evidence for structural and functional preservation of the amygdala in older adults and findings that older adults show greater prefrontal cortex activity than younger adults while engaging in emotion-processing tasks, we argue that the cognitive control hypothesis is a more likely explanation for older adults’ positivity effect than the aging-brain model.

Differential brain activity during emotional versus nonemotional reversal learning

The ability to change an established stimulus–behavior association based on feedback is critical for adaptive social behaviors. This ability has been examined in reversal learning tasks, where participants first learn a stimulus–response association (e.g., select a particular object to get a reward) and then need to alter their response when reinforcement contingencies change. Although substantial evidence demonstrates that the OFC is a critical region for reversal learning, previous studies have not distinguished reversal learning for emotional associations from neutral associations. The current study examined whether OFC plays similar roles in emotional versus neutral reversal learning. The OFC showed greater activity during reversals of stimulus–outcome associations for negative outcomes than for neutral outcomes. Similar OFC activity was also observed during reversals involving positive outcomes. Furthermore, OFC activity is more inversely correlated with amygdala activity during negative reversals than during neutral reversals. Overall, our results indicate that the OFC is more activated by emotional than neutral reversal learning and that OFCs interactions with the amygdala are greater for negative than neutral reversal learning.

Both Younger and Older Adults Have Difficulty Updating Emotional Memories

OBJECTIVE The main purpose of the study was to examine whether emotion impairs associative memory for previously seen items in older adults, as previously observed in younger adults. METHOD Thirty-two younger adults and 32 older adults participated. The experiment consisted of 2 parts. In Part 1, participants learned picture-object associations for negative and neutral pictures. In Part 2, they learned picture-location associations for negative and neutral pictures; half of these pictures were seen in Part 1 whereas the other half were new. The dependent measure was how many locations of negative versus neutral items in the new versus old categories participants remembered in Part 2. RESULTS Both groups had more difficulty learning the locations of old negative pictures than of new negative pictures. However, this pattern was not observed for neutral items. DISCUSSION Despite the fact that older adults showed overall decline in associative memory, the impairing effect of emotion on updating associative memory was similar between younger and older adults.

Age-related similarities and differences in brain activity underlying reversal learning

The ability to update associative memory is an important aspect of episodic memory and a critical skill for social adaptation. Previous research with younger adults suggests that emotional arousal alters brain mechanisms underlying memory updating; however, it is unclear whether this applies to older adults. Given that the ability to update associative information declines with age, it is important to understand how emotion modulates the brain processes underlying memory updating in older adults. The current study investigated this question using reversal learning tasks, where younger and older participants (age ranges 19–35 and 61–78, respectively) learn a stimulus–outcome association and then update their response when contingencies change. We found that younger and older adults showed similar patterns of activation in the frontopolar OFC and the amygdala during emotional reversal learning. In contrast, when reversal learning did not involve emotion, older adults showed greater parietal cortex activity than did younger adults. Thus, younger and older adults show more similarities in brain activity during memory updating involving emotional stimuli than during memory updating not involving emotional stimuli.

Negative emotional outcomes impair older adults' reversal learning.

In a typical reversal-learning experiment, one learns stimulus–outcome contingencies that then switch without warning. For instance, participants might have to repeatedly choose between two faces, one of which yields points whereas the other does not, with a reversal at some point in which face yields points. The current study examined age differences in the effects of outcome type on reversal learning. In the first experiment, the participants’ task was either to select the person who would be in a better mood or to select the person who would yield more points. Reversals in which face was the correct option occurred several times. Older adults did worse in blocks in which the correct response was to select the person who would not be angry than in blocks in which the correct response was to select the person who would smile. Younger adults did not show a difference by emotional valence. In the second study, the negative condition was switched to have the same format as the positive condition (to select who will be angry). Again, older adults did worse with negative than positive outcomes, whereas younger adults did not show a difference by emotional valence. A third experiment replicated the lack of valence effects in younger adults with a harder probabilistic reversal-learning task. In the first two experiments, older adults performed about as well as younger adults in the positive conditions but performed worse in the negative conditions. These findings suggest that negative emotional outcomes selectively impair older adults’ reversal learning.

Brain structure and function associated with younger adults in growth hormone receptor deficient humans

Growth hormone receptor deficiency (GHRD) results in short stature, enhanced insulin sensitivity, and low circulating levels of insulin and insulin-like growth factor 1 (IGF-1). Previous studies in mice and humans suggested that GHRD has protective effects against age-related diseases, including cancer and diabetes. Whereas GHRD mice show improved age-dependent cognitive performance, the effect of GHRD on human cognition remains unknown. Using MRI, we compared brain structure, function, and connectivity between 13 people with GHRD and 12 unaffected relatives. We assessed differences in white matter microstructural integrity, hippocampal volume, subregional volumes, and cortical thickness and surface area of selected regions. We also evaluated brain activity at rest and during a hippocampal-dependent pattern separation task. The GHRD group had larger surface areas in several frontal and cingulate regions and showed trends toward larger dentate gyrus and CA1 regions of the hippocampus. They had lower mean diffusivity in the genu of the corpus callosum and the anterior thalamic tracts. The GHRD group showed enhanced cognitive performance and greater task-related activation in frontal, parietal, and hippocampal regions compared with controls. Furthermore, they had greater functional synchronicity of activity between the precuneus and the rest of the default mode network at rest. The results suggest that, compared with controls, GHRD subjects have brain structure and function that are more consistent with those observed in younger adults reported in previous studies. Further investigation may lead to improved understanding of underlying mechanisms and could contribute to the identification of treatments for age-related cognitive deficits. SIGNIFICANCE STATEMENT People and mice with growth hormone receptor deficiency (GHRD or Laron syndrome) are protected against age-related diseases including cancer and diabetes. However, in humans, it is unknown whether cognitive function and brain structure are affected by GHRD. Using MRI, we examined cognition in an Ecuadorian population with GHRD and their unaffected relatives. The GHRD group showed better memory performance than their relatives. The differences in brain structure and function that we saw between the two groups were not consistent with variations typically associated with brain deficits. This study contributes to our understanding of the connection between growth genes and brain aging in humans and provides data indicating that GHR inhibition has the potential to protect against age-dependent cognitive decline.

Evaluating the relationship between white matter integrity, cognition, and varieties of video game learning

BACKGROUND Many studies are currently researching the effects of video games, particularly in the domain of cognitive training. Great variability exists among video games however, and few studies have attempted to compare different types of video games. Little is known, for instance, about the cognitive processes or brain structures that underlie learning of different genres of video games. OBJECTIVE To examine the cognitive and neural underpinnings of two different types of game learning in order to evaluate their common and separate correlates, with the hopes of informing future intervention research. METHODS Participants (31 younger adults and 31 older adults) completed an extensive cognitive battery and played two different genres of video games, one action game and one strategy game, for 1.5 hours each. DTI scans were acquired for each participant, and regional fractional anisotropy (FA) values were extracted using the JHU atlas. RESULTS Behavioral results indicated that better performance on tasks of working memory and perceptual discrimination was related to enhanced learning in both games, even after controlling for age, whereas better performance on a perceptual speed task was uniquely related with enhanced learning of the strategy game. DTI results indicated that white matter FA in the right fornix/stria terminalis was correlated with action game learning, whereas white matter FA in the left cingulum/hippocampus was correlated with strategy game learning, even after controlling for age. CONCLUSION Although cognition, to a large extent, was a common predictor of both types of game learning, regional white matter FA could separately predict action and strategy game learning. Given the neural and cognitive correlates of strategy game learning, strategy games may provide a more beneficial training tool for adults suffering from memory-related disorders or declines in processing speed, particularly older adults.

Illusory conjunctions in visual short-term memory: Individual differences in corpus callosum connectivity and splitting attention between the two hemifields

Overloading the capacity of visual attention can result in mistakenly combining the various features of an object, that is, illusory conjunctions. We hypothesize that if the two hemispheres separately process visual information by splitting attention, connectivity of corpus callosum-a brain structure integrating the two hemispheres-would predict the degree of illusory conjunctions. In the current study, we assessed two types of illusory conjunctions using a memory-scanning paradigm; the features were either presented across the two opposite hemifields or within the same hemifield. Four objects, each with two visual features, were briefly presented together followed by a probe-recognition and a confidence rating for the recognition accuracy. MRI scans were also obtained. Results indicated that successful recollection during probe recognition was better for across hemifields conjunctions compared to within hemifield conjunctions, lending support to the bilateral advantage of the two hemispheres in visual short-term memory. Age-related differences regarding the underlying mechanisms of the bilateral advantage indicated greater reliance on recollection-based processing in young and on familiarity-based processing in old. Moreover, the integrity of the posterior corpus callosum was more predictive of opposite hemifield illusory conjunctions compared to within hemifield illusory conjunctions, even after controlling for age. That is, individuals with lesser posterior corpus callosum connectivity had better recognition for objects when their features were recombined from the opposite hemifields than from the same hemifield. This study is the first to investigate the role of the corpus callosum in splitting attention between versus within hemifields.

Functional magnetic neuroimaging data on age-related differences in task switching accuracy and reverse brain-behavior relationships

The data presented in this article is related to the research article entitled “Age-related Differences in BOLD Modulation to Cognitive Control Costs in a Multitasking Paradigm: Global Switch, Local Switch, and Compatibility-Switch Costs” (Nashiro et al., 2018) [1]. This article describes age-related differences in accuracies for various cognitive costs incurred during task switching across three different age-cohorts: younger (18–35 years), younger-old (50–64 years) and older-old (65–80 years). The cognitive costs evaluated were global switch costs (GSC), local switch costs (LSC) and compatibility switch costs (CSC). Whole brain analyses were conducted to determine the brain regions sensitive to these cognitive costs, irrespective of age. Furthermore, age-related differences in brain-behavior relationships were evaluated by correlating activations from these regions with global switch costs, indexed by both response times and accuracies, for younger and older adults separately. Activations of age-sensitive regions during the task, where younger adults activated more than the combined groups of older adults, were also correlated with response times and accuracies to determine age-related differences in brain-behavior relationships of these under-recruited brain regions by older adults.