Responses In Medial Prefrontal Cortex Research Articles

Hippocampal-prefrontal long-term potentiation-like plasticity with transcranial direct current stimulation in rats

Transcranial direct current stimulation (tDCS) has been explored as a new treatment method for improving cognitive and motor functions. However, the neuronal mechanisms of tDCS in modulating brain functions, especially cognitive and memory functions, are not well understood. In the present study, we assessed whether tDCS could promote neuronal plasticity between the hippocampus and prefrontal cortex in rats. This is important because the hippocampus-prefrontal pathway is a key pathway in cognitive and memory functions and is involved in various psychiatric and neurodegenerative disorders. Specifically, the effect of anodal or cathodal tDCS on the medial prefrontal cortex was investigated in rats by measuring the medial prefrontal cortex response to electrical stimulation applied to the CA1 region of the hippocampus. Following anodal tDCS, the evoked prefrontal response was potentiated compared to that in the pre-tDCS condition. However, the evoked prefrontal response did not show any significant changes following cathodal tDCS. Furthermore, the plastic change of the prefrontal response following anodal tDCS was only induced when hippocampal stimulation was continuously applied during tDCS. Anodal tDCS without hippocampal activation showed little or no changes. These results indicate that combining anodal tDCS of the prefrontal cortex with hippocampal activation induces long-term potentiation (LTP)-like plasticity in the hippocampus-prefrontal pathway. This LTP-like plasticity can facilitate smooth information transmission between the hippocampus and the prefrontal cortex and may lead to improvements in cognitive and memory function.

Replication of neural responses to monetary incentives and exploration of reward-influenced network connectivity in fibromyalgia

Neuroimaging research has begun to implicate alterations of brain reward systems in chronic pain. Previously, using functional magnetic resonance imaging (fMRI) and a monetary incentive delay (MID) task, Martucci et al. (2018) showed that neural responses to reward anticipation and outcome are altered in fibromyalgia. In the present study, we aimed to test the replicability of these altered neural responses to reward in a separate fibromyalgia cohort. In addition, the present study was conducted at a distinct U.S. location but involved a similar study design. For the present study, 20 patients with fibromyalgia and 20 healthy controls participated in MID task fMRI scan procedures and completed clinical/psychological questionnaires. fMRI analyses comparing patient and control groups revealed a consistent trend of main results which were largely similar to the prior reported results. Specifically, in the replication fibromyalgia cohort, medial prefrontal cortex (MPFC) response was reduced during gain anticipation and was increased during no-loss (non-punishment) outcome compared to controls. Also consistent with previous findings, the nucleus accumbens response to gain anticipation did not differ in patients vs. controls. Further, results from similarly-designed behavioral, correlational, and exploratory analyses were complementary to previous findings. Finally, a novel network-based functional connectivity analysis of the MID task fMRI data across patients vs. controls implied enhanced connectivity within the default mode network in participants with fibromyalgia. Together, based on replicating prior univariate results and new network-based functional connectivity analyses of MID task fMRI data, we provide further evidence of altered brain reward responses, particularly in the MPFC response to reward outcomes, in patients with fibromyalgia.

Multi-modal assessment of reward functioning in adolescent anhedonia.

Anhedonia is a core symptom of depression that predicts worse treatment outcomes. Dysfunction in neural reward circuits is thought to contribute to anhedonia. However, whether laboratory-based assessments of anhedonia and reward-related neural function translate to adolescents' subjective affective experiences in real-world contexts remains unclear. We recruited a sample of adolescents (n = 82; ages 12-18; mean = 15.83) who varied in anhedonia and measured the relationships among clinician-rated and self-reported anhedonia, behaviorally assessed reward learning ability, neural response to monetary reward and loss (as assessed with functional magnetic resonance imaging), and repeated ecological momentary assessment (EMA) of positive affect (PA) and negative affect (NA) in daily life. Anhedonia was associated with lower mean PA and higher mean NA across the 5-day EMA period. Anhedonia was not related to impaired behavioral reward learning, but low PA was associated with reduced nucleus accumbens response during reward anticipation and reduced medial prefrontal cortex (mPFC) response during reward outcome. Greater mean NA was associated with increased mPFC response to loss outcome. Traditional laboratory-based measures of anhedonia were associated with lower subjective PA and higher subjective NA in youths' daily lives. Lower subjective PA and higher subjective NA were associated with decreased reward-related striatal functioning. Higher NA was also related to increased mPFC activity to loss. Collectively, these findings demonstrate that laboratory-based measures of anhedonia translate to real-world contexts and that subjective ratings of PA and NA may be associated with neural response to reward and loss.

Shared and distinct brain fMRI response during performance of working memory tasks in adult patients with schizophrenia and major depressive disorder.

Working memory (WM) impairments are common features of psychiatric disorders. A systematic meta‐analysis was performed to determine common and disorder‐specific brain fMRI response during performance of WM tasks in patients with SZ and patients with MDD relative to healthy controls (HC). Thirty‐four published fMRI studies of WM in patients with SZ and 18 published fMRI studies of WM in patients with MDD, including relevant HC, were included in the meta‐analysis. In both SZ and MDD there was common stronger fMRI response in right medial prefrontal cortex (MPFC) and bilateral anterior cingulate cortex (ACC), which are part of the default mode network (DMN). The effects were of greater magnitude in SZ than MDD, especially in prefrontal‐temporal‐cingulate‐striatal‐cerebellar regions. In addition, a disorder‐specific weaker fMRI response was observed in right middle frontal gyrus (MFG) in MDD, relative to HC. For both SZ and MDD a significant correlation was observed between the severity of clinical symptoms and lateralized fMRI response relative to HC. These findings indicate that there may be common and distinct anomalies in brain function underlying deficits in WM in SZ and MDD, which may serve as a potential functional neuroimaging‐based diagnostic biomarker with value in supporting clinical diagnosis, measuring illness severity and assessing the efficacy of treatments for SZ and MDD at the brain level.

Play, but not observing play, engages rat medial prefrontal cortex.

Rats have elaborate cognitive capacities for playing Hide & Seek. Playing Hide & Seek strongly engages medial prefrontal cortex and the activity of prefrontal cortex neurons reflects the structure of the game. We wondered if prefrontal neurons would also show a mirroring of play-related neural activity. Specifically, we asked how does the activity in the rat medial prefrontal cortex differ when the animal plays itself versus when it observes others playing. Consistent with our previous work, when the animal plays itself we observed medial prefrontal cortex activity that was sharply locked to game events. Observing play, however, did not lead to a comparable activation of rat medial prefrontal cortex. Firing rates during observing play were lower than during real play. The modulation of responses in medial prefrontal cortex by game events was strong during playing Hide & Seek, but weak during observing Hide & Seek. We conclude the rat prefrontal cortex does not mirror play events under our experimental conditions.

Effects of Transcranial Direct Current Stimulation on Baseline and Slope of Prefrontal Cortex Hemodynamics During a Spatial Working Memory Task.

Background: Transcranial direct current stimulation (tDCS) has been shown to be an inexpensive, safe, and effective way of augmenting a variety of cognitive abilities. Relatively recent advances in neuroimaging technology have provided the ability to measure brain activity concurrently during active brain stimulation rather than after stimulation. The effects on brain activity elicited by tDCS during active tDCS reported by initial studies have been somewhat conflicted and seemingly dependent on whether a behavioral improvement was observed.Objective: The current study set out to address questions regarding behavioral change, within and between-participant designs as well as differentiating the effects on hemodynamic amplitude and baseline during active tDCS stimulation.Methods: We tested the effects of transcranial direct current stimulation (tDCS) on anterior hemodynamics in prefrontal cortex during performance on a spatial memory task. Prefrontal cortex activity was measured with functional near infrared spectroscopy (fNIRS), a wearable and portable neuroimaging technique that utilizes near infrared light to measure cortical oxygenated and deoxygenated hemoglobin changes non-invasively. There were two groups, one group (n = 10) received only sham stimulation and the other group (n = 11) received sham followed by anodal stimulation to right ventral lateral prefrontal cortex.Results: Analyses revealed an increase in spatial memory performance following tDCS stimulation. This augmented performance was accompanied by changes to oxygenation (HbO–HbR) at the onset of the hemodynamic response in bilateral dorsolateral prefrontal cortex and left ventral medial prefrontal cortex. In these regions we also observed that stimulation improved neural processing efficiency, by reducing oxygenation and increasing performance from block to block. During and following tDCS stimulation, it was also observed that in bilateral dorsolateral prefrontal cortex the relationship between performance and oxygenation inverted, from a negative relationship to a positive relationship.Conclusion: The results suggest that tDCS is predominately a mechanism for changing neurons propensity for activity as opposed to their strength of activity. tDCS not only alters the efficiency of task relevant processing, but also the nature in which hemodynamic resources are used during augmented task performance.

Bidirectional Optogenetically-Induced Plasticity of Evoked Responses in the Rat Medial Prefrontal Cortex Can Impair or Enhance Cognitive Set-Shifting.

Chronic stress compromises cognition, including executive function mediated in the medial prefrontal cortex (mPFC). To investigate mechanisms underlying these processes, we use chronic unpredictable stress (CUS), which reduces activity in the mPFC and impairs cognitive set-shifting, a measure of cognitive flexibility in laboratory rats. It has been shown that CUS attenuates the local electrical field potential response evoked in the mPFC by stimulation of the ascending excitatory afferent from the mediodorsal thalamus (MDT). Thus, in this study, to investigate the role that such changes in afferent-evoked responsivity of the mPFC might play in the cognitive deficits induced by CUS, we used optogenetics to directly induce plastic changes in the thalamic-mPFC afferent pathway. Glutamatergic neurons in the MDT were virally-induced to express the ChETA variant of channelrhodopsin. Then, to first validate the optogenetic induction of plasticity, long-term depression (LTD) or long-term potentiation (LTP) were induced by laser stimulation of ChETA-expressing terminals in the mPFC of anesthetized rats. In subsequent experiments, induction of opto-LTD in awake animals produced set-shifting deficits similar to those induced by CUS. By contrast, inducing opto-LTP in rats that had received prior CUS treatment corrected the stress-induced deficit in set-shifting. These results suggest that stress-induced plasticity in the thalamic-mPFC pathway is sufficient to produce stress-induced cognitive deficits, and may represent a novel target for effective therapeutic intervention to correct cognitive impairment in stress-related psychiatric disorders.

Anterior cingulate and medial prefrontal cortex response to systematically controlled tonal dissonance during passive music listening

Several studies have attempted to investigate how the brain codes emotional value when processing music of contrasting levels of dissonance; however, the lack of control over specific musical structural characteristics (i.e., dynamics, rhythm, melodic contour or instrumental timbre), which are known to affect perceived dissonance, rendered results difficult to interpret. To account for this, we used functional imaging with an optimized control of the musical structure to obtain a finer characterization of brain activity in response to tonal dissonance. Behavioral findings supported previous evidence for an association between increased dissonance and negative emotion. Results further demonstrated that the manipulation of tonal dissonance through systematically controlled changes in interval content elicited contrasting valence ratings but no significant effects on either arousal or potency. Neuroscientific findings showed an engagement of the left medial prefrontal cortex (mPFC) and the left rostral anterior cingulate cortex (ACC) while participants listened to dissonant compared to consonant music, converging with studies that have proposed a core role of these regions during conflict monitoring (detection and resolution), and in the appraisal of negative emotion and fear‐related information. Both the left and right primary auditory cortices showed stronger functional connectivity with the ACC during the dissonant portion of the task, implying a demand for greater information integration when processing negatively valenced musical stimuli. This study demonstrated that the systematic control of musical dissonance could be applied to isolate valence from the arousal dimension, facilitating a novel access to the neural representation of negative emotion.

Long-Term Potentiation of Prelimbic Cortex Ascribed to Heat-Sensitization Responses of Moxibustion.

Heat-sensitization responses occurred in certain patients while exposed to suspended moxibustion. The response often indicated that the efficacy of moxibustion to those with it tended to triumph over those without. However, its mechanism remains to be explained. Our previous fMRI and EEG studies confirmed the changes of activities in cerebral certain regions accompanied with heat-sensitization responses, especially in prefrontal cortex. Therefore, we hypothesize that neurological system is involved in moxibustion-induced heat-sensitization responses. In the present study, phosphorylation of Cofilin representing long-term potentiation in synapse of prelimbic cortex of medial prefrontal cortex in stroke rats over suspended moxibustion was assessed, and the size of phosphorylated Cofilin positive spine in synapse was also measured. The result showed that heat-sensitization responses were observed to augment cerebral ischemic stroke-induced phosphorylation of Cofilin in prelimbic cortex of rats and increase the numbers of large synapses. This indicated that long-term potentiation of prelimbic cortex was attributed to heat-sensitization responses that were certain neurological responses of medial prefrontal cortex to suspended moxibustion.

Enhanced food-related responses in the ventral medial prefrontal cortex in narcolepsy type 1

Narcolepsy type 1 is a chronic sleep disorder caused by a deficiency of the orexin (hypocretin) neuropeptides. In addition to sleep regulation, orexin is important for motivated control processes. Weight gain and obesity are common in narcolepsy. However, the neurocognitive processes associated with food-related control and overeating in narcolepsy are unknown. We explored the neural correlates of general and food-related attentional control in narcolepsy-type-1 patients (n = 23) and healthy BMI-matched controls (n = 20). We measured attentional bias to food words with a Food Stroop task and general executive control with a Classic Stroop task during fMRI. Moreover, using multiple linear regression, we assessed the relative contribution of neural responses during Food Stroop and Classic Stroop to spontaneous snack intake. Relative to healthy controls, narcolepsy patients showed enhanced ventral medial prefrontal cortex responses and connectivity with motor cortex during the Food Stroop task, but attenuated dorsal medial prefrontal cortex responses during the Classic Stroop task. Moreover, the former activity but not the latter, was a significant predictor of spontaneous snack intake. These findings demonstrate that narcolepsy, characterized by orexin deficiency, is associated with decreased dorsal medial prefrontal cortex responses during general executive control and enhanced ventral medial prefrontal cortex responses during food-driven attention.

Electrophysiological responses of medial prefrontal cortex to feedback at different levels of hierarchy

Recent advances in computational reinforcement learning suggest that humans and animals can learn from different types of reinforcers in a hierarchically organised fashion. According to this theoretical framework, while humans learn to coordinate subroutines based on external reinforcers such as food rewards, simple actions within those subroutines are reinforced by an internal reinforcer called a pseudo-reward. Although the neural mechanisms underlying these processes are unknown, recent empirical evidence suggests that the medial prefrontal cortex (MPFC) is involved. To elucidate this issue, we measured a component of the human event-related brain potential, called the reward positivity, that is said to reflect a reward prediction error signal generated in the MPFC. Using a task paradigm involving reinforcers at two levels of hierarchy, we show that reward positivity amplitude is sensitive to the valence of low-level pseudo-rewards but, contrary to our expectation, is not modulated by high-level rewards. Further, reward positivity amplitude to low-level feedback is modulated by the goals of the higher level. These results, which were further replicated in a control experiment, suggest that the MPFC is involved in the processing of rewards at multiple levels of hierarchy.

Not on my team: Medial prefrontal cortex responses to ingroup fusion and unfair monetary divisions.

ObjectivePeople are highly attuned to fairness, with people willingly suffering personal costs to prevent others benefitting from unfair acts. Are fairness judgments influenced by group alignments? A new theory posits that we favor ingroups and denigrate members of rival outgroups when our personal identity is fused to a group. Although the mPFC has been separately implicated in group membership and fairness processing, it is unclear whether group alignments affect medial prefrontal cortex (mPFC) activity in response to fairness. Here, we examine the contribution of different regions of the mPFC to processing from ingroup and outgroup members and test whether its response differs depending on how fused we are to an ingroup.MethodsSubjects performed rounds of the Ultimatum Game, being offered fair or unfair divisions of money from supporters of the same soccer team (ingroup), the fiercest rival (outgroup) or neutral individuals whilst undergoing functional Magnetic Resonance Imaging (fMRI).ResultsStrikingly, people willingly suffered personal costs to prevent outgroup members benefitting from both unfair and fair offers. Activity across dorsal and ventral (VMPFC) portions of the mPFC reflected an interaction between fairness and group membership. VMPFC activity in particular was consistent with it coding one's fusion to a group, with the fairness by group membership interaction correlating with the extent that the responder's identity was fused to the ingroup.ConclusionsThe influence of fusion on social behavior therefore seems to be linked to processing in the VMPFC.

Altered prefrontal correlates of monetary anticipation and outcome in chronic pain.

Chronic pain may alter both affect- and value-related behaviors, which represents a potentially treatable aspect of chronic pain experience. Current understanding of how chronic pain influences the function of brain reward systems, however, is limited. Using a monetary incentive delay task and functional magnetic resonance imaging (fMRI), we measured neural correlates of reward anticipation and outcomes in female participants with the chronic pain condition of fibromyalgia (N = 17) and age-matched, pain-free, female controls (N = 15). We hypothesized that patients would demonstrate lower positive arousal, as well as altered reward anticipation and outcome activity within corticostriatal circuits implicated in reward processing. Patients demonstrated lower arousal ratings as compared with controls, but no group differences were observed for valence, positive arousal, or negative arousal ratings. Group fMRI analyses were conducted to determine predetermined region of interest, nucleus accumbens (NAcc) and medial prefrontal cortex (mPFC), responses to potential gains, potential losses, reward outcomes, and punishment outcomes. Compared with controls, patients demonstrated similar, although slightly reduced, NAcc activity during gain anticipation. Conversely, patients demonstrated dramatically reduced mPFC activity during gain anticipation-possibly related to lower estimated reward probabilities. Further, patients demonstrated normal mPFC activity to reward outcomes, but dramatically heightened mPFC activity to no-loss (nonpunishment) outcomes. In parallel to NAcc and mPFC responses, patients demonstrated slightly reduced activity during reward anticipation in other brain regions, which included the ventral tegmental area, anterior cingulate cortex, and anterior insular cortex. Together, these results implicate altered corticostriatal processing of monetary rewards in chronic pain.

Intimate partner violence perpetration corresponds to a dorsal-ventral gradient in medial PFC reactivity to interpersonal provocation

ABSTRACTIntimate partner violence (IPV) perpetration is often preceded by perceived interpersonal provocations such as slights, insults, and rejections. Yet the neural mechanisms that link provocation to IPV remain unclear. In the context of interactions with strangers, the medial prefrontal cortex (MPFC) has been repeatedly shown to respond to provocation, with more dorsal activation associated with more aggressive reactions and more ventral activation associated with less aggressive reactions. We used functional brain imaging to test whether this dorsal-ventral MPFC reactivity gradient would also correlate with greater aggression towards an unexamined target: intimate partners. To do so, 61 undergraduates (27.87% male, age range: 18–22) reported whether they had ever committed various acts of IPV perpetration (e.g., punching, hitting, shoving) and then were repeatedly provoked by a stranger while undergoing functional MRI (fMRI) scanning. Individuals with a disproportionately dorsal, rather than ventral, MPFC response were more likely to have perpetrated IPV and had perpetrated more kinds of IPV, even when controlling for gender. These findings provide further evidence that the dorsal-ventral MPFC gradient is a critical, biological indicator of whether an individual is more or less likely to react aggressively and suggest new avenues for understanding and potentially preventing IPV perpetration.

Altered monetary loss processing and reinforcement-based learning in individuals with obesity

Individuals with obesity are often characterized by alterations in reward processing. This may affect how new information is used to update stimulus values during reinforcement-based learning. Here, we investigated obesity-related changes in non-food reinforcement processing, their impact on learning performance as well as the neural underpinnings of reinforcement-based learning in obesity. Nineteen individuals with obesity (BMI > = 30 kg/m2, 10 female) and 23 lean control participants (BMI 18.5–24.9 kg/m2, 11 female) performed a probabilistic learning task during functional magnetic resonance imaging (fMRI), in which they learned to choose between advantageous and disadvantageous choice options in separate monetary gain, loss, and neutral conditions. During learning individuals with obesity made a significantly lower number of correct choices and accumulated a significantly lower overall monetary outcome than lean control participants. FMRI analyses revealed aberrant medial prefrontal cortex responses to monetary losses in individuals with obesity. There were no significant group differences in the regional representation of prediction errors. However, we found evidence for increased functional connectivity between the ventral striatum and insula in individuals with obesity. The present results suggest that obesity is associated with aberrant value representations for monetary losses, alterations in functional connectivity during the processing of learning outcomes, as well as a decresased reinforcement-based learning performance. This may affect how new information is incorporated to adjust dysfunctional behavior and could be a factor contributing to the maintenance of dysfunctional eating behavior in obesity.

The good, the bad, and the suffering. Transient emotional episodes modulate the neural circuits of pain and empathy

People's sensitivity to first-hand pain is affected by their ongoing emotions, with positive states (joy, amusement) exerting analgesic-like effects, and negative states (sadness, fear) often enhancing the subjective experience. It is however less clear how empathetic responses to others’ pain are affected by one's own emotional state. Following embodied accounts that posit a shared representational code between self and others’ states, it is plausible that pain empathy might be influenced by emotions in the same way as first-hand pain. Alternatively, other theories in psychology suggest that social resources (including empathetic reactions) might be enhanced by positive states, but inhibited by negative states, as only in the former case, one's mindset is sufficiently broad to take into consideration others’ needs. To disambiguate between these opposing predictions, we conducted two experiments in which volunteers observed positive, neutral, or negative video clips, and subsequently either received painful thermal stimuli on their own body (first-hand pain), or observed images of wounded hands (others’ pain). We measured subjective pain ratings as well as physiological responses and brain activity using fMRI. We found that, contrary to the case of first-hand pain, others’ pain produced weaker galvanic responses and lower neural activity in anterior insula and middle cingulate cortex following negative (relative to neutral and positive) videos. Such inhibition was partially counteracted by personal empathy traits, as individuals with higher scores retained greater sensitivity to others’ pain after negative emotion induction, in both behavioral and neural responses in medial prefrontal cortex. Furthermore, multivoxel pattern analysis confirmed similar neural representation for first-hand and others’ pain in anterior insula, with representation similarity increasing the more the video preceding the observation of others’ suffering was positive. These findings speak against the idea that emotion induction affects first-hand and others’ pain in an isomorphic way, but rather supports the idea that contrary to negative emotions, positive emotions favors a broader access to social resources.

Reward-Based Learning Drives Rapid Sensory Signals in Medial Prefrontal Cortex and Dorsal Hippocampus Necessary for Goal-Directed Behavior

SummaryThe neural circuits underlying learning and execution of goal-directed behaviors remain to be determined. Here, through electrophysiological recordings, we investigated fast sensory processing across multiple cortical areas as mice learned to lick a reward spout in response to a brief deflection of a single whisker. Sensory-evoked signals were absent from medial prefrontal cortex and dorsal hippocampus in naive mice, but developed with task learning and correlated with behavioral performance in mice trained in the detection task. The sensory responses in medial prefrontal cortex and dorsal hippocampus occurred with short latencies of less than 50 ms after whisker deflection. Pharmacological and optogenetic inactivation of medial prefrontal cortex or dorsal hippocampus impaired behavioral performance. Neuronal activity in medial prefrontal cortex and dorsal hippocampus thus appears to contribute directly to task performance, perhaps providing top-down control of learned, context-dependent transformation of sensory input into goal-directed motor output.

Oxytocin Increases the Perceived Value of Both Self- and Other-Owned Items and Alters Medial Prefrontal Cortex Activity in an Endowment Task.

The neuropeptide oxytocin (OXT) can influence self-processing and may help motivate us to value the attributes of others in a more self-like manner by reducing medial prefrontal cortex (mPFC) responses. We do not know however whether this OXT effect extends to possessions. We tend to place a higher monetary value on specific objects that belong to us compared to others, known as the “endowment effect”. In two double-blind, between-subject placebo (PLC) controlled experiments in subjects from a collectivist culture, we investigated the influence of intranasal OXT on the endowment effect, with the second study incorporating functional magnetic resonance imaging (fMRI). In the task, subjects decided whether to buy or sell their own or others’ (mother/father/classmate/stranger) possessions at various prices. Both experiments demonstrated an endowment effect in the self-owned condition which extended to close others (mother/father) and OXT increased this for self and all other-owned items. This OXT effect was associated with reduced activity in the ventral mPFC (vmPFC) in the self-owned condition but increased in the mother-condition. For the classmate- and stranger-owned conditions OXT increased activity in the dorsal mPFC (dmPFC). Changes in vmPFC activation were associated with the size of the endowment effect for self- and mother-owned items. Functional connectivity between the dmPFC and ventral striatum (VStr) was reduced by OXT in self- and mother-owned conditions and between vmPFC and precuneus in the self-condition. Overall our results show that OXT enhances the endowment effect for both self- and other-owned items in Chinese subjects. This effect is associated with reduced mPFC activation in the self-condition but enhanced activation in all other-conditions and involves differential actions on both dorsal and ventral regions as well as functional connectivity with brain reward and other self-processing regions. Overall our findings suggest that OXT increases the perceived value of both self- and other-owned items by acting on neural circuitry involved in self-processing and reward.

Oxytocin blurs the self-other distinction during trait judgments and reduces medial prefrontal cortex responses.

The neuropeptide oxytocin (OXT) may act either to increase or blur the distinction between self and other and thereby promote either more selfish or altruistic behaviors. To attempt to distinguish between these two possibilities we performed a double-blind, between-subject, placebo-controlled design study to investigate the effect of intranasal OXT on self and other (mother, classmate, or stranger) trait judgments in conjunction with functional magnetic resonance imaging. Results showed that OXT reduced response times for making both self and other judgments, but also reduced the accuracy of their subsequent recall, thereby abolishing the normal self-bias observed in this task. OXT also abolished the positive correlation between response and self-esteem scale scores seen in the PLC group, suggesting that its effects were strongest in individuals with higher levels of self-esteem. A whole-brain functional magnetic resonance imaging analysis revealed that OXT also reduced responses during both self and other trait judgments in the dorsal (dmPFC) and ventral (vmPFC) medial prefrontal cortex. A subsequent region of interest analysis revealed that behavioral performance and self-esteem scale scores were associated with dmPFC activation and its functional connectivity with the anterior cingulate and between the vmPFC and posterior cingulate. Thus overall, while OXT may improve speed of decision making in self -vs. other trait judgments it also blunts the normal bias towards remembering self-attributes and reduces mPFC responses and connectivity with other cortical midline regions involved in self-processing. This is consistent with the view that OXT can reduce self-centered behavior. Hum Brain Mapp 37:2512-2527, 2016. © 2016 Wiley Periodicals, Inc.

Neural Reward Processing Mediates the Relationship between Insomnia Symptoms and Depression in Adolescence.

Emerging evidence suggests that insomnia may disrupt reward-related brain function-a potentially important factor in the development of depressive disorder. Adolescence may be a period during which such disruption is especially problematic given the rise in the incidence of insomnia and ongoing development of neural systems that support reward processing. The present study uses longitudinal data to test the hypothesis that disruption of neural reward processing is a mechanism by which insomnia symptoms-including nocturnal insomnia symptoms (NIS) and nonrestorative sleep (NRS)-contribute to depressive symptoms in adolescent girls. Participants were 123 adolescent girls and their caregivers from an ongoing longitudinal study of precursors to depression across adolescent development. NIS and NRS were assessed annually from ages 9 to 13 years. Girls completed a monetary reward task during a functional MRI scan at age 16 years. Depressive symptoms were assessed at ages 16 and 17 years. Multivariable regression tested the prospective associations between NIS and NRS, neural response during reward anticipation, and the mean number of depressive symptoms (omitting sleep problems). NRS, but not NIS, during early adolescence was positively associated with late adolescent dorsal medial prefrontal cortex (dmPFC) response to reward anticipation and depressive symptoms. DMPFC response mediated the relationship between early adolescent NRS and late adolescent depressive symptoms. These results suggest that NRS may contribute to depression by disrupting reward processing via altered activity in a region of prefrontal cortex involved in affective control. The results also support the mechanistic differentiation of NIS and NRS.