AS DEPICTED IN THE PHOTOGRAPH, YOU SEE
2.4 Neuroscience and Socio-Emotional Aging
Concept Checks
1. What effect does environmental enrichment have on aging rodents?
2. Does environmental enrichment affect neural plasticity in aging humans?
3. What are the benefi ts of aerobic exercise on the developing brain?
2.4 Neuroscience and
underpinnings of socio-emotional processing with increasing age will be the focus.
Emotional Processing and the Brain
Given the diff erences between cognitive and emo- tional aging, a number of questions have served to guide contemporary research in the area of emotional processing. Such questions include:
what declines, what is preserved, and what improves? In addition, it is important to identify the conditions under which we observe decline, preservation, and improvement. Th e neuroscience approach takes this a step further by identifying the specifi c biological mechanism refl ected in the structure and activation patterns of the brain associated with, for example, preserved emotional processing.
As we saw in the cognitive neuroscience sec- tion, neuroimaging allows us to identify brain regions of activation that underlie successful infor- mation processing, for example, activation of the prefrontal cortex (PFC) during encoding relates to better memory. Much behavioral work indicates that if information has emotional signifi cance, we will more likely remember it than informa- tion that is more neutral in nature. A number of researchers have been interested in uncovering the neural circuitry that is most responsible for this enhanced memory for emotional information (e.g., Kensinger & Corkin, 2004).
Kensinger and colleagues (Kensinger, 2006;
Kensinger & Corkin, 2004) propose two distinct cognitive and neural processes that contribute to emotional memory enhancement. Processing of negative high-arousal information for memory is relatively automatic in nature and is linked to activation of the amygdala as it interacts with the hippocampus to support memory performance.
For memory processing of negative low-arousal stimuli, more activation of the prefrontal cortex–
hippocampus network is necessary. Th is area is associated with controlled self-generated encoding processes (Kensinger & Corkin, 2004). Kensinger
(2006) argues that emotional enhancement in memory for detail is a result of more engagement in emotion-specifi c processes that are linked to these distinct neural processes. Th us, when one accurately remembers negative high-arousal items, this corresponds to increased activation of the amygdala and orbitofrontal cortex. Other studies support this in that if the amygdala is damaged, individuals do not attend to arousing stimuli. How do structural and functional changes in the brain aff ect these processes?
Aging and Emotional Processing
Similar to the behavioral research on younger adults above, there is growing research indicating that older adults also detect emotional information (e.g., in visual search tasks; Leclerc & Kensinger, 2008) and remember emotional information (e.g., remembering emotional words; Kensinger, 2008) better than nonemotional information. However, despite this emotional enhancement eff ect on infor- mation processing, evidence suggests that younger and older adults process positive and negative information diff erently. An abundance of research has examined a positivity eff ect in older adults (e.g., Carstensen, Isaacowitz, & Charles, 1999).
Portrait of senior adult African American woman smiling.
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Th is research has shown that older adults are more motivated to derive emotional meaning from life and to maintain positive aff ect. Given these goals, older adults are more likely than younger adults to attend to the emotional meaning of information or to how information makes them feel (Carstensen &
Mikels, 2005). In fact, studies show that younger adults have a tendency to attend to and remem- ber more negative information relative to positive information, while older adults display a tendency to attend to and remember more positive informa- tion relative to negative information (e.g., Mather &
Carstensen, 2005).
Neurological Recruitment Underlying the Positivity Effect in Memory
We begin this section by examining what we know about the emotional memory network and the degree to which corresponding brain struc- tures decline or are preserved with increasing age.
Interestingly, the regions implicated in emotional processing such as the ventromedial prefrontal cortex (VMPFC) undergo relatively modest struc- tural changes with aging, and the amygdala is relatively structurally preserved with aging (Raz, 1996). In contrast, other regions of the prefrontal cortex (PFC) undergo a more rapid and earlier pace of decline, such as the dorsolateral regions of the PFC (Raz, 1996). Even more importantly, it is necessary to examine the function (i.e., activation) of emotion processing regions of the brain across the adult life span.
LaBar and Cabeza (2006) describe a core emotional memory network that consists of the amygdala, hippocampus, and lateral orbitofron- tal cortex. Activation in these areas relate to the successful encoding of emotional information in general. Again, these regions are well preserved in emotional memory as one grows older. Indeed, for both younger and older adults, activation of the amygdala and lateral orbitofrontal cortex corre- sponds to memory performance for both positive and negative items (Kensinger & Schacter, 2008).
Th ere are also areas in the brain beyond this
emotional core that are more valence-dependent.
For example, for both younger and older adults, the occipito-temporal regions (more specifi cally the fusiform gyrus) are more likely to be recruited during successful encoding of negative infor- mation, whereas anterior prefrontal regions are activated during successful encoding of positive information (Mickley & Kensinger, 2008).
Neuroimaging studies reveal diff erential age- related activation of neural substrates that might help us understand the neurological mechanisms underlying the positivity eff ect. For example, older adults show activation of the medial prefrontal cortex and regions of the cingulate gyrus when responding to positive stimuli whereas younger adults do not (Kensinger & Schacter, 2008).
Similarly, compared to the young, older adults show greater amygdala activation for positive pic- tures than for negative ones (Mather et al., 2004).
Such fi ndings indicate that it may not be overall decline in functioning of the amygdala that causes age-related responding to emotional stimuli, but rather a shift in the type of emotional stimuli to which the amygdala is most responsive (Leclerc &
Kensinger, 2008).
Finally, another intriguing possibility raised in the literature is that the positivity eff ect may arise from changes in controlled emotional process- ing or emotion regulation (Leclerc & Kensinger, 2008; Mather & Knight, 2005). It is proposed that the positivity eff ect should be seen only when an individual has a high degree of cognitive con- trol resources. If these resources are limited, this reduces the ability to regulate responses to emo- tional information. Accordingly, older adults who are low in resources show no positivity eff ect (Mather & Knight, 2005).
Research conducted in diff erent domains of emotional processing also has demonstrated age- related diff erences in brain activation. For exam- ple, fMRI studies have found age diff erences in brain activation when viewing faces with negative emotional expressions (e.g., Anderson, Christoff , Panitz, De Rosa, & Gabrieli, 2003). Younger adults show increased activity in the amygdala when
viewing negative emotional expressions, whereas activity in the amygdala is reduced in older adults when viewing these faces. Interestingly over- recruitment of areas such as the anterior cingulate gyrus is increased in older adults when viewing these faces (Gunning-Dixon et al., 2003). Th is is quite reminiscent of the compensation models discussed in the context of cognitive aging and neuroscience perspectives.
Overall, fi ndings in this line of research have revealed that the core emotional memory network is preserved with aging. Age-related diff erences are most evident in the successful encoding of positive information as opposed to processes contributing
to the memory for negative information. Th us, the structural preservation with increasing age of various regions in the cortex may subserve the preservation of emotional processing.
Concept Checks
1. How does emotional processing differ from cognitive processing in older adulthood?
2. How does the neural circuitry operate when younger and older adults process emotional information?
3. How do age-related changes in brain structure account for the positivity effect found in older adults?
S O C I A L P O L I C Y I M P L I C A T I O N S
On the one hand, the dismal thought that the human brain gradually loses tissue from age 30 onward and the projected rapid growth of an aging population present society with numerous public policy issues regarding the staggering costs of geri- atric care. On the other hand, the good news is that advanced research in neuroscience tells us that this is an oversimplifi cation of what happens to the aging brain. Of importance to policymakers is to realize that researchers are identifying ways in which such cerebral deterioration can be re- duced or even reversed. In addition, researchers have identifi ed areas of the brain that are relatively preserved and may even show growth. Th us, it is important for policymakers to obtain a more com- plete picture of aging.
Research in neuroscience and aging is extremely important, not only for health care policies, but also for the psychological and physiological well-being
of the aging adult. Th e mission of the National Institute on Aging has focused much of its eff orts onto biomarkers of healthy aging, demanding more interdisciplinary work in this area. Whereas be- havioral research alone has been suffi cient to move our understanding of aging forward, it is critical to incorporate all levels of understanding, including the neurological/biological aspects, in future work.
A good example is the compelling fi ndings regard- ing aerobic exercise and aging. Th e use-it-or-lose-it model of aging has reached new heights. We are not only talking about weight loss with respect to aerobics, but now we are talking about extending the vitality of older adulthood. Finally, evidence showing that emotional brain functions may im- prove with age provides a platform from which new interventions might be developed to draw on strategies of emotional control to better cope with any declines in functioning.
Summary
2.1 The Neuroscience Approach