Mapping the interconnected neural systems underlying motivation and emotion: A key step toward understanding the human affectome

Altered reward sensitivity to sucrose outcomes prior to drug exposure in alcohol preferring rats

Addiction involves key impairments in reward sensitivity (RS). The current study explored impaired RS to natural reward as a predisposing factor to addictive-like behavior. Alcohol preferring (P) rats are selectively bred based on significantly greater ethanol consumption and preference and offer the ability to inspect differences in subjects with a positive family history of addictive-like behavior. P rat's RS was compared to RS in the well-used Sprague-Dawley (SD) strain. To assess RS in a novel manner, instrumental incentive contrast, discrimination and consumption of sucrose solution were examined. Animals performed in a free operant situation for different sucrose concentration solutions using a block of 'mixed' trials with alternating outcome concentrations (e.g., 5 and 10 % sucrose) to change outcome value in a predictable manner. Animals also performed for reward in blocks of single outcome trials (5 or 10 or 20 or 40 % sucrose daily exposure) surrounding the mixed block. RS (e.g., reward discrimination and contrast effects between and within-sessions) was measured by changes in trials completed, instrumental response latency and consumption. P rats expressed an altered profile of RS with a greater tendency toward equivalent responding to different outcomes within the same session and an absence of incentive contrast from diverse reward comparisons. In contrast, SD animals expressed within-session reward discrimination and a subset of incentive contrast effects. These effects were moderated by food deprivation more consistently in SD compared to P rats. P rat alterations in processing natural rewards could predispose them to addictive-like behaviors including greater alcohol consumption and preference.

The Human Affectome

Over the last decades, theoretical perspectives in the interdisciplinary field of the affective sciences have proliferated rather than converged due to differing assumptions about what human affective phenomena are and how they work. These metaphysical and mechanistic assumptions, shaped by academic context and values, have dictated affective constructs and operationalizations. However, an assumption about the purpose of affective phenomena can guide us to a common set of metaphysical and mechanistic assumptions. In this capstone paper, we home in on a nested teleological principle for human affective phenomena in order to synthesize metaphysical and mechanistic assumptions. Under this framework, human affective phenomena can collectively be considered algorithms that either adjust based on the human comfort zone (affective concerns) or monitor those adaptive processes (affective features). This teleologically-grounded framework offers a principled agenda and launchpad for both organizing existing perspectives and generating new ones. Ultimately, we hope the Human Affectome brings us a step closer to not only an integrated understanding of human affective phenomena, but an integrated field for affective research.

Negative emotion reduces the discriminability of reward outcomes in the ventromedial prefrontal cortex

Reward and emotion are tightly intertwined, so there is a growing interest in mapping their interactions. However, our knowledge of these interactions in the human brain, especially during the consummatory phase of reward is limited. To address this critical gap, we conducted a functional magnetic resonance imaging study to investigate the effects of negative emotion on reward outcome processing. We employed a novel design where emotional valence (negative or neutral) indicated the type of outcome (reward or no-reward) in a choice task. We focused our functional magnetic resonance imaging analysis on the ventro-medial prefrontal cortex (vmPFC), ventral striatum and amygdala, which were frequently implicated in reward outcome processing. In these regions of interest, we performed multi-voxel pattern analysis to specifically probe how negative emotion modulates reward outcome processing. In vmPFC, using decoding analysis, we found evidence consistent with the reduced discriminability of multi-variate activity patterns of reward vs no-reward outcomes when signaled by a negative relative to a neutral image, suggesting an emotional modulation of reward processing along the plausible common value/valence dimension. These findings advance our limited understanding of the basic brain mechanisms underlying the influence of negative emotion on consummatory reward processing, with potential implications for mental disorders, particularly anxiety and depression.

The mGlu2/3 agonist LY379268 reduces sucrose taking, seeking, and motivation in male and female rats

OBJECTIVES

The mGlu2/3 receptor agonist LY379268 reduces sucrose-seeking, but not sucrose-taking, in male rats. This study explored the generality of this effect across the sexes. In addition, the effect of the drug on motivation to receive sucrose was assessed.

METHODS

Adult male and female Long-Evans rats ( N  = 91) were challenged with LY379268 in three experiments: (1) a fixed ratio (FR) schedule of reinforcement (taking), (2) extinction of responding previously reinforced on the FR (seeking) or (3) responding reinforced on a progressive ratio (PR) schedule of reinforcement (motivation). For each experiment, rats first responded to 10% liquid sucrose on an FR in 10 daily 2-h sessions. For the PR study, this was followed by training on a PR for 7 daily 3-h sessions. Rats were then challenged in a counterbalanced order with LY379268 (0, 1.5, 3 and 6 mg/kg; IP; 30-min pretreatment) on test days, followed by either three reacquisition days of FR (experiments 1 and 2) or PR (experiment 3) responding.

RESULTS

Female rats responded more to sucrose on the FR and PR. LY379268 reduced responding in all three experiments. LY379268 challenge to sucrose taking on the FR produced an inverted U-shaped function while extinction responding and responding for sucrose on the PR were decreased dose-dependently, with PR responding insensitive to the 1.5 mg/kg dose. There were no sex-dependent effects of the drug on sucrose-directed responding.

CONCLUSIONS

The sucrose anti-taking, -seeking, and -motivation effects of LY379268 across male and female rats support further evaluation of glutamate modulation as an antiaddiction pharmacotherapy.

Gender-affirming hormonal treatment changes neural processing of emotions in trans men: An fMRI study

BACKGROUND

Some transgender people desire a transition through gender-affirming hormone treatment (GAHT). To date, it is unknown how GAHT changes emotion perception in transgender people.

METHODS

Thirty transgender men (TM), 30 cisgender men (CM), and 35 cisgender women (CW) underwent 3 Tesla functional magnetic resonance imaging (fMRI) while passively viewing emotional faces (happy, angry, surprised faces) at two timepoints (T0 and T1). At T0 all participants were hormone-naïve, while TM immediately commenced testosterone supplementation at T0. The second scanning session (T1) occurred after 6-10 months of GAHT in TM. All 3 groups completed both T0 and T1 RESULTS: GAHT in TM shifted the neural profile whilst processing emotions from a sex-assigned at birth pattern at T0 (similar to CW) to a consistent with gender identity pattern at T1 (similar to CM). Overall, the brain patterns stayed the same for the cis people at T0 and T1.

CONCLUSIONS

These findings document the impact of hormone treatment, and testosterone supplementation specifically, on emotion perception in TM.

Dopamine D2/3-receptor availability and its association with autonomous motivation to exercise in older adults: An exploratory [11C]-raclopride study

Background

Autonomous motivation to exercise occurs when the activity is voluntary and with a perceived inherent satisfaction from the activity itself. It has been suggested that autonomous motivation is related to striatal dopamine D2/3-receptor (D2/3R) availability within the brain. In this study, we hypothesized that D2/3R availability in three striatal regions (nucleus accumbens, caudate nucleus, and putamen) would be positively associated with self-reported autonomous motivation to exercise. We also examined this relationship with additional exploratory analyses across a set of a priori extrastriatal regions of interest (ROI).

Methods

Our sample comprised 49 older adults (28 females) between 64 and 78 years of age. The D2/3R availability was quantified from positron emission tomography using the non-displaceable binding potential of [11C]-raclopride ligand. The exercise-related autonomous motivation was assessed with the Swedish version of the Behavioral Regulations in Exercise Questionnaire-2.

Results

No significant associations were observed between self-reported autonomous motivation to exercise and D2/3R availability within the striatum (nucleus accumbens, caudate nucleus, and putamen) using semi-partial correlations controlling for ROI volume on D2/3R availability. For exploratory analyses, positive associations were observed for the superior (r = 0.289, p = 0.023) and middle frontal gyrus (r = 0.330, p = 0.011), but not for the inferior frontal gyrus, orbitofrontal cortex, anterior cingulate cortex, or anterior insular cortex.

Conclusion

This study could not confirm the suggested link between striatal D2/3R availability and subjective autonomous motivation to exercise among older adults. The exploratory findings, however, propose that frontal brain regions may be involved in the intrinsic regulation of exercise-related behaviors, though this has to be confirmed by future studies using a more suitable ligand and objective measures of physical activity levels.

Early stressful experiences are associated with reduced neural responses to naturalistic emotional and social content in children

How do children's experiences relate to their naturalistic emotional and social processing? Because children can struggle with tasks in the scanner, we collected fMRI data while 4-to-11-year-olds watched a short film with positive and negative emotional events, and rich parent-child interactions (n = 70). We captured broad, normative stressful experiences by examining socioeconomic status (SES) and stressful life events, as well as children's more proximal experiences with their parents. For a sub-sample (n = 30), parenting behaviors were measured during a parent-child interaction, consisting of a picture book, a challenging puzzle, and free play with novel toys. We characterized positive parenting behaviors (e.g., warmth, praise) and negative parenting behaviors (e.g., harsh tone, physical control). We found that higher SES was related to greater activity in medial orbitofrontal cortex during parent-child interaction movie events. Negative parenting behaviors were associated with less activation of the ventral tegmental area and cerebellum during positive emotional events. In a region-of-interest analysis, we found that stressful life events and negative parenting behaviors were associated with less activation of the amygdala during positive emotional events. These exploratory results demonstrate the promise of using movie fMRI to study how early experiences may shape emotional, social, and motivational processes.

Dynamic interaction between hippocampus, orbitofrontal cortex, and subthalamic nucleus during goal conflict in the stop signal task in rats

Action stopping depends on at least two (fast, slow) frontal circuits depending on the urgency of execution of the 'go' response. Human EEG suggests a third (even slower, limbic) circuit that activates frontal areas at frequencies typical of 'hippocampal theta'. Here we test in male rats whether stop-go conflict engages the hippocampus and so may send theta-modulated information via the frontal cortex to the subthalamic nucleus. We recorded from multi-electrode arrays in the hippocampus, orbitofrontal cortex, and subthalamus in 5 male Long Evans rats performing a stop signal task and, as in previous human experiments, assessed stop-signal specific power for effects of goal conflict. Conflict increased 11-12 Hz theta power modestly in all three structures but with the largest increase in power being at 5 Hz in the frontal cortex but not the hippocampus. There was increased conflict-related coherence in all circuits in the range 5-8 Hz and particularly at 5-6 Hz. Increased coherence coupled with an increase in conflict-induced low frequency power in the frontal cortex may reflect communication with the hippocampus. The data are consistent with a third limbic circuit that can generate stopping when go responses are particularly slow (as, e.g., in a go/no go task). [199 words; 200 max].

Mapping the brain basis of feelings, emotions and much more: A special issue focused on 'The Human Affectome'

The Human Affectome Project was launched by the non-profit organization Neuroqualia (www.neuroqualia.org) in 2015 with the seemingly impossible goal: To map a psychological process and form possible definitions and working models for affective states and related emotions. Twelve reviews based on emotions, feelings and motivation were written dedicated to mapping the brain basis of affect. A capstone piece 'The Human Affectome' provides a foundation for the special issue by giving detailed up-to-date definitions for key terms including feeling, affect, emotion and mood. Critically, the piece offers an overall model synthesizing three main features of affect: valence, motivation, and arousal. Affect itself is explored as the main umbrella function capturing all feeling states and related processes. Overall, the project and the special issue has been a highly successful interdisciplinary effort producing a novel approach that can be used to understand, guide and revise contemporary research on the brain basis of feeling and how diverse feeling states interact with each other in typical and atypical fashions.

Neural Connectivity Underlying Reward and Emotion-Related Processing: Evidence From a Large-Scale Network Analysis

Neuroimaging techniques have advanced our knowledge about neurobiological mechanisms of reward and emotion processing. It remains unclear whether reward and emotion-related processing share the same neural connection topology and how intrinsic brain functional connectivity organization changes to support emotion- and reward-related prioritized effects in decision-making. The present study addressed these challenges using a large-scale neural network analysis approach. We applied this approach to two independent functional magnetic resonance imaging datasets, where participants performed a reward value or emotion associative matching task with tight control over experimental conditions. The results revealed that interaction between the Default Mode Network, Frontoparietal, Dorsal Attention, and Salience networks engaged distinct topological structures to support the effects of reward, positive and negative emotion processing. Detailed insights into the properties of these connections are important for understanding in detail how the brain responds in the presence of emotion and reward related stimuli. We discuss the linking of reward- and emotion-related processing to emotional regulation, an important aspect of regulation of human behavior in relation to mental health.

A hypothetic model for examining the relationship between happiness, forgiveness, emotional reactivity and emotional security

The ultimate goal of life is happiness, according to Plato. Perhaps the most critical questions in the life of human beings have been on happiness and processes that affect happiness. The present study was planned during the COVID-19 pandemic; perhaps human beings are most needed for happiness. The original hypothetical model and the findings constitute the powerful and different aspects of the present study. This study determined a hypothetical model to examine the relationships among happiness, forgiveness, emotional reactivity, and emotional security. The participant group of the study consists of a total of 916 individuals from Turkey, 617 women, and 299 men. The age scale of the participants is between 18-25. Participants completed the Heartland Forgiveness Scale, the Emotional Security Scale, the Emotional Reactivity Scale, and the Oxford Happiness Scale. Mediation analysis was conducted using Hayes' (2017) process macro. According to the proposed model in the study, emotional reactivity mediates the relationship between forgiveness and happiness. As the individual's forgiveness increases, their emotional reactivity decreases, and as the emotional reactivity decreases, the individual's level of happiness increases.

Neural Representations of the Committed Romantic Partner in the Nucleus Accumbens

Having an intimate romantic relationship is an important aspect of life. Dopamine-rich reward regions, including the nucleus accumbens (NAcc), have been identified as neural correlates for both emotional bonding with the partner and interest in unfamiliar attractive nonpartners. Here, we aimed to disentangle the overlapping functions of the NAcc using multivoxel pattern analysis, which can decode the cognitive processes encoded in particular neural activity. During functional MRI scanning, 46 romantically involved men performed the social-incentive-delay task, in which a successful response resulted in the presentation of a dynamic and positive facial expression from their partner and unfamiliar women. Multivoxel pattern analysis revealed that the spatial patterns of NAcc activity could successfully discriminate between romantic partners and unfamiliar women during the period in which participants anticipated the target presentation. We speculate that neural activity patterns within the NAcc represent the relationship partner, which might be a key neural mechanism for committed romantic relationships.

Effect of non-instructed instrumental contingency of monetary reward and positive affect in a cognitive control task

In recent years, we observed a strong interest in the influence of motivation and emotion on cognitive control. Prior studies suggest that the instrumental contingency between a response and a rewarding or affective stimulus is particularly important in that context-which is resonating with observations in the associative learning literature. However, despite this overlap, and the relevance of non-instructed learning in real life, the vast majority of studies investigating motivation-cognition interactions use direct instructions to inform participants about the contingencies between responses and stimuli. Thus, there is little experimental insight regarding how humans detect non-instructed contingencies between their actions and motivational or affective outcomes, and how these learned contingencies come to influence cognitive control processes. In an attempt to close this gap, the goal of the present study was to test the effect of non-instructed contingent and non-contingent outcomes (i.e. monetary reward and positive affective stimuli) on cognitive control using the AX-continuous performance task (AX-CPT) paradigm. We found that entirely non-instructed contingencies between responses and positive outcomes (both monetary and affective ones) led to significant performance improvement. The present results open new perspectives for studying the influence of motivation and emotion on cognitive control at the insertion with associative learning.

Postnatal exposure to fluoxetine led to cognitive-emotional alterations and decreased parvalbumin positive neurons in the hippocampus of juvenile Wistar rats

The exposure to selective serotonin reuptake inhibitors (SSRIs) during development results in behavioural impairment in adulthood in humans and animal models. Indeed, serotonergic overexpression in early life leads to structural and functional changes in brain circuits that control cognition and emotion. However, the effects of developmental exposure to these substances on the behaviour of adolescent rats are conflicting and remain poorly characterised. We performed a behavioural screening to investigate the effects of postnatal exposure to fluoxetine on memory and behaviours related to anxiety, anhedonia, and depression, as well we evaluate the parvalbumin expression in hippocampus of juvenile (~PND45) female and male rats. Fluoxetine (daily 20 mg/kg s.c. injections from PND7-PND21)- or vehicle-treated adolescent rats went through several behavioural tasks (from PND 38 to PND52) and were subject to transcardial perfusion and brain removal for immunohistochemical analysis (PND53). We found that postnatal exposure to fluoxetine increased anxiety- and depression-like behaviours in the open field and sucrose preference and forced swimming tests, respectively. In addition, this treatment induced working memory and short-term (but not long-term) recognition memory impairments, and reduced parvalbumin-positive interneurons in the hippocampus. In addition, the results revealed developmental sex-dependent effects of fluoxetine postnatal treatment on adolescent rats' behaviour. These outcomes indicate that affective disorders and mnemonic alterations caused by SSRIs perinatal exposure can be present at adolescence.

Large-scale functional brain networks for consciousness

The generation and maintenance of consciousness are fundamental but difficult subjects in the fields of psychology, philosophy, neuroscience, and medicine. However, recent developments in neuro-imaging techniques coupled with network analysis have greatly advanced our understanding of consciousness. The present review focuses on large-scale functional brain networks based on neuro-imaging data to explain the awareness (contents) and wakefulness of consciousness. Despite limitations, neuroimaging data suggests brain maps for important psychological and cognitive processes such as attention, language, self-referential, emotion, motivation, social behavior, and wakefulness. We considered a review of these advancements would provide new insights into research on the neural correlates of consciousness.

The self-serving benefits of being a good host: A role for our micro-inhabitants in shaping opioids' function

Opioids are highly efficacious in their ability to relieve pain, but they are liable for abuse, dependence, and addiction. Risk factors to develop opioid use disorders (OUD) include chronic stress, socio-environment, and preexisting major depressive disorders (MDD) and posttraumatic stress disorders (PTSD). Additionally, opioids reduce gut motility, induce loss of gut barrier function, and alter the composition of the trillions of microbes hosted in the gastrointestinal tract, known as the gut microbiota. The microbiota are significant contributors to the reciprocal communication between the central nervous system (CNS) and the gut, termed the gut-brain axis. They have strong influences on their host behaviors, including the ability to cope with stress, sociability, affect, mood, and anxiety. Thus, they are implicated in the etiology of MDD and PTSD. Here we review the latest studies demonstrating that intestinal flora can, directly and indirectly, by affecting sociability levels, responses to stress, and mental state, alter the responses to opioids. It suggests that microbiota can potentially be used to increase the resilience to develop analgesic tolerance and OUD.

Intrinsic motivation in patients with Parkinson's disease: a neuropsychological investigation of curiosity using dopamine transporter imaging

Both intrinsic and extrinsic motivation are believed to involve brain regions that are innervated by the dopaminergic pathway. Although dopaminergic neurons in the midbrain deteriorate in Parkinson's disease (PD), it remains unclear whether intrinsic motivation is impaired in PD patients. To address this issue, we investigated intrinsic motivation in PD patients using a task designed to assess the "Pandora effect," which constitutes a curiosity for resolving uncertainty, even if this curiosity is likely to result in negative consequences. Twenty-seven PD patients and 27 age-matched healthy controls (HCs) completed a curiosity task in which they were required to decide either to view or skip negative pictures (e.g., snakes, spiders) and an examination battery that included the Mini-Mental State Examination, a verbal fluency test, the Trail Making Test, 10-word recall tests, and questionnaires for behavioral inhibition/activation and depression. DaTSCAN images to assess the distribution of dopamine transporters in the striatum were acquired only from PD patients. The results revealed that PD patients, relative to the HCs, viewed the pictures less frequently under both the certain and uncertain conditions. However, both the PD patients and HCs viewed the pictures at a higher frequency under the uncertain condition than under the certain condition. In the PD patients, the proportion of pictures viewed under the certain condition was positively correlated with the distribution of dopamine transporters in the striatum. These results suggest that despite the overall decreasing level of interest in viewing negative pictures, the motivation to resolve uncertainty is relatively intact in PD patients.

Effort-reward balance and work motivation in rats: Effects of context and order of experience

Being motivated means exerting effort toward a goal. The 'law of least work' emphasizes a preference for exerting relatively less effort. The law crosses boundaries among species and between physical and mental work. Organisms should be highly sensitive to shifts in effort-reward balance (ERB) in order to make optimal choices. We used a free operant-foraging task to investigate changes in ERB on choice between options requiring more or less effort. Results showed a consistent preference for the option with less effort and insensitivity to shifts in ERB. A second aim explored the influence of order of experience on effort choice. Choice for the more effortful option significantly increased after experiencing an equal effort-reward relationship during the initial free operant-foraging session. This relative increase in choice for the effortful option persisted even after effort-reward imbalance. The findings highlight the importance of contextual factors such as order of experience when examining the impact of shifting effort-reward associations. Instead of ignoring or reducing order effects, the sequence of experience (e.g. for shifts in ERB) could be manipulated to enhance or reduce value of outcomes or effort itself.