Anhedonia, the loss of pleasure or interest in previously rewarding stimuli, is a core feature of major depression. While theorists have argued that anhedonia reflects a reduced capacity to experience pleasure, evidence is mixed as to whether anhedonia is caused by a reduction in hedonic capacity. An alternative explanation is that anhedonia is due to the inability to sustain positive affect across time. Using positive images, we used an emotion regulation task to test whether individuals with depression are unable to sustain activation in neural circuits underlying positive affect and reward. While upregulating positive affect, depressed individuals failed to sustain nucleus accumbens activity over time compared with controls. This decreased capacity was related to individual differences in selfreported positive affect. Connectivity analyses further implicated the fronto-striatal network in anhedonia. These findings support the hypothesis that anhedonia in depressed patients reflects the inability to sustain engagement of structures involved in positive affect and reward.anhedonia ͉ emotion regulation ͉ nucleus accumbens

Objective Deficits in positive affect and their neural bases have been associated with major depression. However, whether reductions in positive affect result solely from an overall reduction in nucleus accumbens activity and fronto-striatal connectivity or the additional inability to sustain engagement over time of this network is unknown. Accordingly, we sought to determine whether treatment-induced changes in the ability to sustain nucleus accumbens activity and fronto-striatal connectivity during the regulation of positive affect are associated with gains in positive affect. Method Using fMRI, we assessed the ability to sustain activity in reward-related networks when attempting to increase positive emotion during performance of an emotion regulation paradigm in 21 depressed patients prior to, and after 2 months of antidepressant treatment. 14 healthy control subjects were scanned over the same interval. Results After 2 months of treatment, self-reported positive affect increased. Those patients demonstrating the largest increases in sustained nucleus accumbens activity over the 2 months were those demonstrating the largest increases in positive affect. In addition, those patients demonstrating the largest increases in sustained fronto-striatal connectivity were also those demonstrating the largest increases in positive affect when controlling for negative affect. Healthy controls showed none of these associations. Conclusions Treatment induced changes in the sustained engagement of fronto-striatal circuitry tracks the experience of positive emotion in daily life. Studies examining reduced positive affect in a variety of psychiatric disorders might benefit from examining the temporal dynamics of brain activity when attempting to understand changes in daily positive affect.

Empathy is the combined ability to interpret the emotional states of others and experience resultant, related emotions. The relation between prefrontal electroencephalographic asymmetry and emotion in children is well known. The association between positive emotion (assessed via parent report), empathy (measured via observation), and second-by-second brain electrical activity (recorded during a pleasurable task) was investigated using a sample of one hundred twenty-eight 6-to 10-year-old children. Contentment related to increasing left frontopolar activation (p < .05). Empathic concern and positive empathy related to increasing right frontopolar activation (ps < .05). A second form of positive empathy related to increasing left dorsolateral activation (p < .05). This suggests that positive affect and (negative and positive) empathy both relate to changes in prefrontal activity during a pleasurable task.

Background Anhedonia, a reduced ability to experience pleasure, is a chief symptom of Major Depressive Disorder (MDD) and is related to reduced fronto-striatal connectivity when attempting to up-regulate positive emotion. The present study examined another facet of positive emotion regulation associated with anhedonia—namely, the down-regulation of positive affect—and its relation to prefrontal cortex (PFC) activity. Method Neuroimaging data were collected from 27 individuals meeting criteria for MDD as they attempted to suppress positive emotion during a positive emotion regulation task. Their PFC activation pattern was compared to the PFC activation pattern exhibited by 19 healthy controls during the same task. Anhedonia scores were collected at three time points: at baseline (Time 1), 8 weeks after Time 1 (i.e. Time 2) and 6 months after Time 1 (i.e. Time 3). PFC activity at Time 1 was used to predict change in anhedonia over time. Analyses were conducted utilizing hierarchical linear modeling (HLM) software. Results Depressed individuals who could not inhibit positive emotion—evinced by reduced right ventrolateral prefrontal cortex (RVLPFC) activity during attempts to dampen their experience of positive emotion in response to positive visual stimuli—exhibited a steeper anhedonia reduction slope between baseline and 8 weeks of treatment with antidepressant medication (p<.05). Controls showed a similar trend between baseline and Time 3. Conclusions To reduce anhedonia, it may be necessary to teach individuals how to counteract the functioning of an overactive pleasure-dampening prefrontal inhibitory system.

The relation between empathy subtypes and prosocial behavior was investigated in a sample of healthy adults. "Empathic concern" and "empathic happiness," defined as negative and positive vicarious emotion (respectively) combined with an other-oriented feeling of “goodwill” (i.e. a thought to do good to others/see others happy), were elicited in 68 adult participants who watched video clips extracted from the television show Extreme Makeover: Home Edition. Prosocial behavior was quantified via performance on a non-monetary altruistic decision-making task involving book selection and donation. Empathic concern and empathic happiness were measured via self-report (immediately following each video clip) and via facial electromyography recorded from corrugator (active during frowning) and zygomatic (active during smiling) facial regions. Facial electromyographic signs of (a) empathic concern (i.e. frowning) during sad video clips, and (b) empathic happiness (i.e. smiling) during happy video clips, predicted increased prosocial behavior in the form of increased goodwill-themed book selection/donation.

Individual variation in the experience and expression of pleasure may relate to differential patterns of lateral frontal activity. Brain electrical measures have been used to study the asymmetric involvement of lateral frontal cortex in positive emotion, but the excellent time resolution of these measures has not been used to capture second-by-second changes in ongoing emotion until now. The relationship between pleasure and second-by-second lateral frontal activity was examined with the use of hierarchical linear modeling in a sample of 128 children aged 6-10 years. Electroencephalographic activity (EEG) was recorded during "pop-out toy," a standardized task that elicits pleasure. The task consisted of three epochs: an anticipation period sandwiched between two play periods. The amount of pleasure expressed during the task predicted the pattern of non-linear change in lateral frontal activity. Children who expressed increasing amounts of pleasure during the task exhibited increasing left lateral frontal activity during the task, whereas children who expressed contentment exhibited increasing right/decreasing left activity. These findings indicate that taskdependent changes in pleasure relate to dynamic, non-linear changes in lateral frontal activity as the task unfolds. Keywords pleasure; EEG; lateral frontal cortex Pleasure, the euphoric feeling that can occur as a result of the internal representation of hedonic information, is an important ingredient of positive affect (Meehl, 1975;Klein, 1987). Activity in subcortical brain structures and multiple regions of the prefrontal cortex relate to the occurrence of pleasure (Berridge, 2003;Leon & Shadlen, 1999;Gable and Harmon-Jones, 2008). Specifically, the ability to consciously experience pleasure relates to (1) an ability to internally represent hedonic information and (2) translate represented hedonic information into conscious positive emotional experience; and these processes are likely subserved by prefrontal Dubois, 2002). In particular, it is likely that the representational (e.g. the ability to represent the hedonic value of 4 drops of a sweet liquid versus 8 drops), executive (e.g. enacting a plan to obtain a reward), and working memory functions subserved by activity in the frontal cortex-particularly the lateral prefrontal cortex -contribute to pleasure capacity (Watanabe, 1996;Hikosaka & Watanabe, 2000;Pochon et al., 2002;Kobayashi, Lauwereyns, Koizumi, Sakagami & Hikosaka, 2002;Schultz, 2006).In addition to neuroimaging techniques, brain electrical (i.e. electroencephalographic-EEG) measures of frontal function have been extensively used to examine relations between baseline levels of frontal activity and the propensity to experience certain emotional states. Specifically, the left and right frontal regions of the cerebral hemisphere are differentially involved in the expression of approach-related emotions and withdrawal related emotions, respectively (Davidson, 1992;Wheeler, Davidson & Tomarken, 1993;Davidson, 2004a;Urry, Nitschke, Dolski...

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Cognitive dysfunction and anhedonia, the reduced ability to experience pleasure, are commonly comorbid symptoms that are persistent following successful resolution of negative affect in major depressive disorder (MDD). Little is known about whether they share common etiology. In the present study, the relationship between ventrolateral prefrontal cortex (VLPFC) activity, cognitive dysfunction (i.e., executive dysfunction), and positive emotionality was investigated in conjunction with mu-opioid neurotransmission in a sample of 39 MDD patients. Results suggest that increased endogenous mu-opioid tone in the VLPFC mediates the relationship between increased trait positive emotionality and more efficient executive functioning.