Reward-Related Neural Predictors and Mechanisms of Symptom Change in Cognitive Behavioral Therapy for Depressed Adolescent Girls

BACKGROUND

Approximately half of depressed adolescents fail to respond to cognitive behavioral therapy (CBT). Given the variability in response, it is important to identify pretreatment characteristics that predict prognosis. Knowledge of which depressed adolescents are likely to exhibit a positive versus poor outcome to CBT may have important clinical implications (e.g., informing treatment recommendations). Emerging evidence suggests that neural reward responsiveness represents one promising predictor.

METHODS

Adolescents with major depressive disorder (n = 36) received CBT and completed a reward task at 3 time points (pretreatment, midtreatment and posttreatment) while 128-channel electroencephalographic data were acquired. Healthy control participants (n = 29) completed the same task at 3 corresponding time points. Analyses focused on event-related potentials linked to 2 stages of neural processing: initial response to rewards (reward positivity) and later, elaborative processing (late positive potential). Moreover, time-frequency analyses decomposed the reward positivity into 2 constituent components: reward-related delta and loss-related theta activity.

RESULTS

Multilevel modeling revealed that greater pretreatment reward responsiveness, as measured by the late positive potential to rewards, predicted greater depressive symptom change. In addition, a group × condition × time interaction emerged for theta activity to losses, reflecting normalization of theta power in the group with major depressive disorder from baseline to posttreatment.

CONCLUSIONS

An event-related potential measure of sustained (late positive potential)-but not initial (reward positivity)-reward responsiveness predicted symptom improvement, which may help inform which depressed adolescents are most likely to benefit from CBT. In addition to alleviating depression, successful CBT may attenuate underlying neural (theta) hypersensitivity to negative outcomes in depressed youths.

Measuring appetitive conditioned responses in humans

Clinical and preclinical findings suggest that individuals with abnormal responses to reward cues (stimuli associated with reward) may be at risk for maladaptive behaviors including obesity, addiction and depression. Our objective was to develop a new paradigm for producing appetitive conditioning using primary (food) rewards in humans, and investigate the equivalency of several outcomes previously used to measure appetitive responses to conditioned cues. We used an individualized food reward, and multimodal subjective, psychophysiological and behavioral measures of appetitive responses to a conditioned stimulus (CS) that predicted delivery of that food. We tested convergence among these measures of appetitive response, and relationships between these measures and action impulsivity, a putative correlate of appetitive conditioning. 90 healthy young adults participated. Although the paradigm produced robust appetitive conditioning in some measures, particularly psychophysiological ones, there were not strong correlations among measures of appetitive responses to the CS, as would be expected if they indexed a single underlying process. In addition, there was only one measure that related to impulsivity. These results provide important information for translational researchers interested in appetitive conditioning, suggesting that various measures of appetitive conditioning cannot be treated interchangeably.

Working memory and reward association learning impairments in obesity

Obesity has been associated with impaired executive functions including working memory. Less explored is the influence of obesity on learning and memory. In the current study we assessed stimulus reward association learning, explicit learning and memory and working memory in healthy weight, overweight and obese individuals. Explicit learning and memory did not differ as a function of group. In contrast, working memory was significantly and similarly impaired in both overweight and obese individuals compared to the healthy weight group. In the first reward association learning task the obese, but not healthy weight or overweight participants consistently formed paradoxical preferences for a pattern associated with a negative outcome (fewer food rewards). To determine if the deficit was specific to food reward a second experiment was conducted using money. Consistent with Experiment 1, obese individuals selected the pattern associated with a negative outcome (fewer monetary rewards) more frequently than healthy weight individuals and thus failed to develop a significant preference for the most rewarded patterns as was observed in the healthy weight group. Finally, on a probabilistic learning task, obese compared to healthy weight individuals showed deficits in negative, but not positive outcome learning. Taken together, our results demonstrate deficits in working memory and stimulus reward learning in obesity and suggest that obese individuals are impaired in learning to avoid negative outcomes.

Evaluative Conditioning with Facial Stimuli in Dementia Patients

We present results of a study investigating evaluative learning in dementia patients with a classic evaluative conditioning paradigm. Picture pairs of three unfamiliar faces with liked, disliked, or neutral faces, that were rated prior to the presentation, were presented 10 times each to a group of dementia patients (N = 15) and healthy controls (N = 14) in random order. Valence ratings of all faces were assessed before and after presentation. In contrast to controls, dementia patients changed their valence ratings of unfamiliar faces according to their pairing with either a liked or disliked face, although they were not able to explicitly assign the picture pairs after the presentation. Our finding suggests preserved evaluative conditioning in dementia patients. However, the result has to be considered preliminary, as it is unclear which factors prevented the predicted rating changes in the expected direction in the control group.

Transfer of judgments of control to a target stimulus and to novel stimuli through derived relations

Three experiments examined the effect of response-outcome contingencies on human ratings of causal efficacy and demonstrated that such ratings transfer to novel situations through derived stimulus relations. Efficacy ratings generally followed the delta probability rule when positive response-outcome contingencies were employed (Experiment 1) and when some outcomes were not contingent on participants' responses (Experiment 2). Experiment 3 employed a negative response-outcome contingency and manipulated performance expectancies in the task. All three groups overestimated their causal efficacy ratings. A learned helplessness effect was observed when the response-outcomes were uncontrollable and in the high-expectancy group when participants' performance in the task was worse than they had expected. In all experiments, ratings transferred to a stimulus presented during the task and often generalized to novel stimuli through derived relations. These results corroborate the view that outcome probability is a determinant of causal efficacy ratings and that schedules can be employed as UCS in procedures that share characteristics of evaluative conditioning procedures.

Extinction learning of stimulus reward contingencies: The acute effects of alcohol

BACKGROUND

Recent theories suggest that extinction is, at least partly, new learning suppressing original associations between a conditioned stimulus and a conditioned response without severing those associations. During extinction alcohol via its effects on inhibitory control may reduce the ability to suppress the original associations between a conditioned stimulus and a conditioned response leading to an impairment of extinction learning. Thus, the present study is set out to examine the effects of alcohol on extinction learning to enhance current knowledge on mechanisms of extinction and conditions that might hamper extinction, which is an important aspect for the treatment of alcohol-dependent patients.

METHODS

Light to moderate social drinkers (N=32) acquired an instrumental reward seeking response. Extinction training of the reward seeking response was performed after administration of a dose of 0.8 g/kg alcohol resulting in a peak blood alcohol concentration ranging from 112 to 184 mg/dL. In addition, we assessed subjective alcohol effects and administered a Stop-Signal task which measures the ability to inhibit a pre-potent motor response.

RESULTS

Alcohol influenced subjective ratings of light-headedness and increased the Stop-Signal reaction time indicating disinhibiting effects. However, our results did not show any impairment of learning of extinction after the administration of alcohol. Behavioural as well as attentional responses indicated extinction of conditioned responses for both experimental groups.

CONCLUSIONS

These findings suggest that alcohol at a dose that impairs performance in a task of inhibitory control does not impair learning of extinction.

Intact Preference Conditioning in Acute Intoxication Despite Deficient Declarative Knowledge and Working Memory

BACKGROUND

The impact of alcohol on implicit, emotional learning is not well understood, partly because family history, drug use, and task demands influence these processes. The conditioned pattern preference (CPP) task provides a more ecologically valid means to investigate implicit cognition in the lab because it has low demand awareness and relies on learning to associate nonverbal cues with reward.

METHODS

This study examined the effects of acute alcohol intoxication on implicit learning using the CPP task in 83 intoxicated and 69 sober young adults. Information on individual drug use, family history, impulsivity, and alcohol expectancies was also collected.

RESULTS

Alcohol intoxication affected explicit, but not implicit learning on the CPP task. In addition, participants who reported a positive family history of addiction (FH+) or individual recreational drug use did not exhibit a preference for cues previously paired with reward.

CONCLUSIONS

Preference formation on the CPP task recruits motivational neurocircuitry, an effect that is unaltered by alcohol. Group differences in implicit emotional learning on this task may represent neurocognitive differences in individuals at risk for addiction.

I don't like it because it eats sprouts: conditioning preferences in children

Although little is known about how preferences develop in childhood, work in adults suggests that evaluative responses to stimuli can be acquired through classical conditioning. In two experiments children were exposed to novel cartoon characters, that were either consistently paired with a picture of a disliked food (Brussels sprouts) or a liked food (ice cream). Relative preferences for these stimuli (and others) were measured before and after these paired presentations (Experiment 1): preferences for the cartoon character paired with Brussels sprouts decreased, whereas preferences for the character paired with ice cream increased. These preferences persisted after 10 un-reinforced trials. Experiment 2 replicated this finding using affective priming as an index of preference for the cartoon characters. These findings demonstrate that preferences to novel stimuli can be conditioned in children and result from associations formed between the stimulus and a stimulus possessing positive or negative valence.

Dietary restraint and US devaluation predict evaluative learning

Previous research has indicated that flavor-flavor learning is impaired in restrained eaters. In Experiment 1 we sought to extend this finding using a larger sample and a more comprehensive assessment of dietary behavior. Participants (N=90, including 30 current dieters) sampled three novel flavors (CSs), each on 10 separate occasions, in a randomized order. Each flavor was paired with chocolate (US) either 10%, 50%, or 90% of the time. We then assessed liking for the three CSs and asked participants to complete the DEBQ-restraint and TFEQ-disinhibition sub-scales. After these CS-US parings, restrained eaters tended to prefer the 10% paired flavor whereas unrestrained eaters tended to prefer the 90% paired flavor. Differential CS liking was not evident in dieters and it was not predicted by disinhibition. Using a similar methodology, in Experiment 2 (N=76) we assessed evaluative change following picture-sweet pairings. Relative to the other CSs, the restrained eaters reported a greater increase in their liking for the 10% paired CS and the unrestrained eaters reported a greater increase in their liking for the 90% paired CS. We also discovered that evaluative change is related to the level of US devaluation that takes place during conditioning. Evidence that a sweet US can bring about a decrease in liking has not been reported previously. One interpretation is that negative beliefs and attitudes can contaminate the representation of the US during training.

Evaluative conditioning is intact after unilateral resection of the anterior temporal lobe in humans

Several lesion and functional imaging studies conducted in animals and humans suggest that structures within the amygdaloid nuclear complex (ANC) are important for the occurrence of fear conditioning. Whether this brain structure is also critical for evaluative conditioning, has been investigated less frequently. In the current experiment, a group of participants with unilateral resection of the anterior temporal lobe and a control group received a differential evaluative flavor-taste conditioning task. In the pre-acquisition phase, two fruit flavors (the conditioned stimuli (CSs)) were presented and participants were instructed to evaluate both. In the subsequent acquisition phase, one of these fruit flavors (CS+) was presented together with a bad tasting substance Tween20 (polysorbate 20, the US), while the other flavor (CS-) was never paired with Tween20. Finally, in the post-acquisition phase, the two flavors were presented again without Tween20 and participants were asked to evaluate both of them for a last time. The control group as well as the lesion group rated the CS+ in the post-acquisition phase less favorable than in the pre-acquisition phase, while the ratings of the CS- remained the same in both phases. We clearly demonstrated evaluative conditioning in both test groups. Because the lesion group had still one intact ANC it would be premature, however, to conclude that the ANC is not involved in evaluative conditioning. We conclude that despite evidence for impaired fear conditioning, unilateral damage to the ANC does not impair evaluative conditioning.

The development of affect regulation: bringing together basic and clinical perspectives

Some discussion of the development of affect regulation in relation to two papers by Drs. Kalin and Leibenluft is provided. The goals are to frame the broader issues, including the conceptualization and definitions of affect regulation, to address questions about the development of affect regulation, and to consider ways to bridge between basic and clinical approaches to understanding disorders of affect regulation emerging in childhood and adolescence. The conceptual framework for affect regulation presented here focuses on interactions between cognitive systems and affective systems. It also appears that this area of research is at a very early point in its development-one rich with opportunities to bridge between basic research in affective neuroscience, developmental psychology, and developmental psychopathology, and holds great promise to advance understanding regarding the earliest roots of these disorders.

Amygdala subsystems and control of feeding behavior by learned cues

A combination of behavioral studies and a neural systems analysis approach has proven fruitful in defining the role of the amygdala complex and associated circuits in fear conditioning. The evidence presented in this chapter suggests that this approach is also informative in the study of other adaptive functions that involve the amygdala. In this chapter we present a novel model to study learning in an appetitive context. Furthermore, we demonstrate that long-recognized connections between the amygdala and the hypothalamus play a crucial role in allowing learning to modulate feeding behavior. In the first part we describe a behavioral model for motivational learning. In this model a cue that acquires motivational properties through pairings with food delivery when an animal is hungry can override satiety and promote eating in sated rats. Next, we present evidence that a specific amygdala subsystem (basolateral area) is responsible for allowing such learned cues to control eating (override satiety and promote eating in sated rats). We also show that basolateral amygdala mediates these actions via connectivity with the lateral hypothalamus. Lastly, we present evidence that the amygdalohypothalamic system is specific for the control of eating by learned motivational cues, as it does not mediate another function that depends on intact basolateral amygdala, namely, the ability of a conditioned cue to support new learning based on its acquired value. Knowledge about neural systems through which food-associated cues specifically control feeding behavior provides a defined model for the study of learning. In addition, this model may be informative for understanding mechanisms of maladaptive aspects of learned control of eating that contribute to eating disorders and more moderate forms of overeating.

Preference formation and working memory in Parkinson's disease and normal ageing

Recent studies in rats have suggested that the amygdala and the dorsal striatum may be differentially involved in the formation of stimulus-reward associations and stimulus-response associations, respectively. In a recent study in humans, conditioned preference learning deficits were observed in a group of patients with damage to the amygdala formation. In this study, patients with Parkinson's disease, which is known to involve pathology of the dorsal striatum, were tested on the same conditioned preference task, together with a group of patients with circumscribed lesions of the frontal lobe. Unlike patients with frontal lobe damage, patients with Parkinson's disease did not exhibit conditioned preferences. However, in this respect their behaviour was indistinguishable from that of age-matched (older) control subjects. In keeping with previous literature, working memory deficits were observed in both patients with Parkinson's disease and patients with frontal-lobe lesions. Compared to young control subjects, a strong increase in preference for familiar, versus novel, items was observed in both patients with Parkinson's disease and in older control subjects. Such a familiarity effect appears to overshadow the conditioning manipulation employed in this task and, therefore, preclude the expression of conditioned preferences in older subjects. These results suggest that there is a developmental progression in the degree to which different mechanisms of 'learning to like' are important over the life span.

Effects of dietary restraint on flavour-flavour learning

Flavour preference learning in 21 restrained and 21 unrestrained females was explored using an evaluative conditioning paradigm. Each participant was exposed to an adapted version of the procedure used by Johnsrude et al., (1999, Learning & Motivation30, 250-264). During conditioning, participants sampled 10 instances each of three novel flavours presented in a semi-randomized order. After sampling a flavour they were instructed to eat a sweet according to three different flavour-reinforcement contingencies. One flavour was accompanied by a sweet on 90% of trials and was presented alone on 10% of the trials, while the remaining flavours were rewarded at ratios 50% : 50% and 10% : 90%, respectively. The conditioning phase occurred in conjunction with a counting task requiring continuous use of working memory, and was immediately followed by the participants making hedonic ratings of each flavour. Very few participants showed awareness of the purpose of the experiment or the specific reward contingencies. Despite this, the ratings given by the unrestrained eaters were highly correlated with the reward ratio experienced during conditioning. In contrast, restrained eaters exhibited no evidence for evaluative learning. These findings may explain the equivocal nature of results from previous studies of positive flavour-flavour learning (FFL) and may offer a novel theoretical context within which to study dietary restraint.

Associative learning of likes and dislikes: a review of 25 years of research on human evaluative conditioning

Evaluative conditioning refers to changes in the liking of a stimulus that are due to the fact that the stimulus has been paired with other, positive or negative stimuli. Although evaluative conditioning appears to be subjected to certain boundary conditions, significant evaluative conditioning effects have been obtained using a large variety of stimuli and procedures. Some data suggest that evaluative conditioning can occur under conditions that do not support other forms of Pavlovian conditioning, and several models have been proposed to account for these differences. In the present article, the authors summarize the available literature, draw conclusions where possible, and provide suggestions for future research.

Affect regulation, brain development, and behavioral/emotional health in adolescence

This paper addresses the importance of affect regulation (AR) in relation to a broad range of behavioral and emotional health problems that emerge during adolescence. AR is defined as the adaptive modulation of emotional experience to serve a goal or purpose. This conceptualization of AR emphasizes the use of cognitive skills to guide, inhibit, or modify emotion and behavior, including the expression of emotional responses, in learned, strategic ways-skills that ultimately underpin adult levels of social maturity and the ability to show "responsible" behavior across a range of emotional situations. Neurobehavioral systems that subserve these AR skills include areas of the inferior and orbital prefrontal cortex (PFC), with rich interconnections to several limbic structures and other cortical areas, including the dorsolateral PFC. Adolescence represents an important developmental period in the functional maturation of adult AR skills; it is also a critical time in the development of clinical disorders of AR (eg, rates of depression increase dramatically and gender differences in depression emerge). Maturational changes in AR that occur during adolescence-particularly with respect to the role of emotions influencing responsible decision making-are also relevant to understanding key aspects of the developmental pathways of some behavioral health problems, such as alcohol use and nicotine dependence. A strong case is made for developmental research in affective neuroscience aimed at this important maturational period, particularly the kind of transdisciplinary research leading toward mechanistic understanding of the development of adolescent-onset disorders. Improving understanding in these areas could ultimately lead to the development of early interventions in targeted high-risk populations, and has enormous clinical and social policy relevance.