Humans are highly imaginative animals. Each transient moment leaves a lasting trace in our brains that can be brought back to the surface during recall. So if the brain stores these traces as physical changes in brain cells can we label them, retrieve them, or implant them? That's exactly what Susumu Tonegawa and colleagues set out to do. To determine whether it's possible to create false memories in mice the group exposed them to a negative stimuli while activating an unrelated memory - would the mice now falsely associate these two things? They created a false memory in mice by optogenetically manipulating memory engram-bearing cells in the hippocampus. Dentate gyrus (DG) or CA1 neurons activated by exposure to a particular context were labeled with channelrhodopsin-2. These neurons were later optically reactivated during fear conditioning in a different context. The DG experimental group showed increased freezing in the original context, in which a foot shock was never delivered. The recall of this false memory was context-specific, activated similar downstream regions engaged during natural fear memory recall, and was also capable of driving an active fear response.

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Several epidemiological studies show that sleep loss correlates with obesity. In this fMRI study, the authors seek to characterize the impact of sleep deprivation on the brain mechanisms governing appetitive desires. Results show that sleep loss is associated with altered functioning of cortical (anterior cingulate cortex, orbitofrontal cortex and insular cortex) and subcortical (amygdala) areas implicated in food processing. The findings suggest a link between this pattern of activity and the choice of weight-gain promoting (high-calorie) food.

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People from higher socioeconomic status (SES) tend to show less social engagement and more self-focused patterns in behavior, as shown in previous studies. Since greed and unethical behavior are often associated with the behavior that prioritize self-interest, the authors in this study explored whether rich people (university and nation-wise samples) more often express greed and unethical behavior in naturalistic and laboratory settings (driving, self-reporting, SES-ranking, job-interviewing, and die games). The results show that the positive correlation between unethical behavior and SES can be extended to both samples and all tasks in the study and that the reasons might be attributed to the set of culturally shared norms among upper-class individuals that facilitates unethical behavior.

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The issue of innate versus acquired bias toward same/different race conspecifics still remains debated. Evidence exists that racial preferences can appear very early, at the age of three months, and studies have suggested that the differential preference or perception of race is contingent on environment, including the caregivers and the social diversity. A negative racial bias has been associated with a increased amygdala activation, for instance, a positive correlation has been reported between amygdala reactivity and negative valence. Here the authors investigated the hypothesis that racial biases are not innate, but instead emerge during development and are contingent on environment (learning of cultural norms, level of ethnic heterogeneity of the social environment etc..). They thus used an Emotional Matching Task paradigm and functional magnetic resonance imaging to examine the differential amygdala response to race across childhood and adolescence - a developmental period where the social behavior becomes characterized by the active identification to a group. Moreover, they investigated the impact of the social environment (neighborhood diversity) on amygdala response. The authors discuss their results and claim for an environmental origin of racial biases.

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The difficulties in studying human language are due to its incredible complexity, an obstacle shared with many other cognitive abilities, but also to the lack of good animal models, that instead are available for other fields of cognitive research. In this study, the authors try to shed light on a specific component of any language capacity: the ability of arrange vocal elements in new sequences. And they show the existence of a fundamental analogy between birds and humans in the way the problem is solved. The study tracks the development of vocal combinatorial capacity in three species: zebra finches, Bengalese finches and pre-lingual human infants. The result is a common stepwise pattern of acquisition of new vocal transitions, inconsistent both with the possibility of freely move syllables around in new sequences and with the hypothesis of trial and error learning.

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The subjective confidence we have in our decision-making has far reaching consequences. This confidence fluctuates over time leading to different decisions for identical choice options with which we are presented. However, it is not clear how (decision-making and its relative confidence state) interacts at the level of brain and behavior. Therefore this paper attempts to study the role of confidence in making choices. The authors used fMRI data in humans to propose a dynamic model for the evolution of decision over time.

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Humans have specific cognitive abilities, as the result of a complex reorganization of brain structure and function during primate evolution. But, what is the relationship between anatomical and functional changes? In this study with monkeys and humans Mantini et al tried to answer this question by using fMRI and looking for spatial and temporal correspondences between cortical networks during resting state. They found networks with conserved topology and function, but also human networks with a topological correspondent in monkey but with different functions, as the language and default mode networks. Interestingly, the authors also described two frontoparietal networks in the humans with neither topological nor functional correspondence in the monkey. In conclusion, Mantini's work is a new approach for comparative studies, directly connecting the spatial localization of networks in the cortex with their function.

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The ability to recognize facial expressions and to share the physiological patterns associated with an another person's emotional experience are two of the basic components of empathy. In this study, the authors analyzed facial expression detection and facial mimicry behavior in response to an emotional empathic task. During the experimental task, they applied repeated transcranial magnetic stimulation (rTMS) to the medial prefrontal cortex (MPFC) to verify the role of this area in the brain mechanism of emotional empathy, and they measured the electrical activity of facial muscles (EMG) for assessing the empathic response. The results suggest that a “simulation mechanism” underlies emotion detection in an empathic situation, and this mechanism appears to be supported and regulated by the MPFC.

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Neurological patients show a remarkable range of anomalies in bodily experience. A particular aberration in the experience of one’s body is xenomelia, that is the continuous experience of being ‘overcomplete’ in possessing four limbs and the resulting request for surgical removal of the unwanted ‘foreign’ extremity. In 13 individuals and 13 pair-matched control participants MRI was performed and surface-based morphometry revealed significant group differences in cortical architecture. Structural changes between participants with and without xenomelia were mainly found in the right hemisphere, in particular: superior and inferior parietal lobule, the subcentral cortex comprising SII, the paracentral lobule housing the primary somatosensory leg representation and the anterior insular cortex. These findings suggest that the desire for healthy limb amputation is the consequence of a breakdown in a network underlying the establishment and maintenance of body ownership. Moreover because half of subjects with xenomelia considers an early childhood experience as causally related to their desire of amputation, the authors suggest the possibility that a hyperempathic response may constitute at least a correlate of the disorder.

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Numerous neuroimaging studies have shown that the default mode network (DMN) is involved in both internally driven processes and memory. Nevertheless, it is unclear whether memory operations reflect a particular case of internally driven processing or alternatively involve the DMN in a distinct manner, possibly depending on memory type. In this study, the authors used functional MRI to examine DMN activity and connectivity patterns while participants overtly generated words according to nonmnemonic (phonemic) or mnemonic (semantic or episodic) cues. The results showed that distinct part of the DMN contribute to specific memory processes, demonstrating a different recruitment depending on the type of memory retrieval. These findings, therefore suggest that DMN does not show a unified involvement in memory processes, but a balance within it may forge a memory by optimizing the internal search and retrieval of specific mnemonic aspects.

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This study examines how the learning of new visuo-spatial working memory tasks is reflected in changes of prefrontal cortex (PFC) activity. Authors recorded from neurons in dorsal lateral PFC (dlPFC) and ventral lateral PFC (vlPFC) of two macaque monkeys before and after they had learnt two working memory tasks. Results revealed that dlPFC and vlPFC encoded the new information differently. Before learning the task, only basic stimulus information was reflected in dlPFC, while after learning the task both dlPFC and vlPFC reflected the new task related information. Authors suggest that these results support domain-specific theories and adaptive coding models of the PFC.

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Serotonin has been involved in reward-based decision making. Although its interaction with the dopaminergic system is clearly established and modelled, its precise computational roles and the way it affects behavioral outcomes remain unclear. In particular, it is unknown whether it acts on the value system (ventral striatum) or on the reward based action selection system, by simply switching up or down the threshold of action selection (dorsal striatum). That paper reports a study whereby the effect of serotonin depletion on socio-economical choices (Ultimatum Game) and on striatal activity were investigated. The authors observed significant effects of serotonin depletion on the reward based decisions but also brain activity within both striatal systems, giving rise to a rather specific pattern of (suboptimal) economical decisions in a social context. The interest of the paper consists in shedding some light on the nature and the way rewarding decision systems are selectively influenced by serotonergic input. Moreover, it provides interesting insights on the cognitive mechanisms affected in depression (serotonin depleted condition).

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The authors propose that decisions to cease and resume work are triggered by a cost evidence accumulation signal reaching upper and lower bounds, respectively. Using Functional MRI and magnetoencephalography recordings, they revealed that this signal was expressed in proprioceptive regions (bilateral posterior insula). This study provides a dynamical mechanistic account of how the human brain maximizes benefits while preventing exhaustion.

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Previous studies have shown that individuals can voluntarily block memories from awareness. Although several neuroimaging studies have examined the brain systems involved in intentional forgetting, they have not revealed the cognitive tactics that people use or the precise neural underpinnings. Two possible ways to forget unwanted memories are to suppress them or to substitute them with more desirable memories, and these tactics could engage distinct neural pathways. To test this possibility, the researchers used functional magnetic resonance imaging to examine the brain activity of volunteers who had learned associations between pairs of words and subsequently attempted to forget these memories by either blocking them out or recalling substitute memories. Although the strategies were equally effective, they activated distinct neural circuits. Besides being the first study demonstrating the neurocognitive mechanisms of voluntary forgetting, this study stands out for the implication that a better understanding of these mechanisms and how they break down may ultimately help understanding disorders that are characterized by a deficient regulation of memories, such as posttraumatic stress disorder.

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The anterior cingulate cortex (ACC) has been implicated in cost-benefit decision-making, in humans and other mammals. Despite this, its role in competitive effort has not been examined. The authors devised a competitive foraging choice task, to record ACC neurons from freely moving rats. The authors found that neither the reward magnitude or the competitive effort were sufficient to account for the difference in the firing rates between the task conditions. Moreover, the authors were able to modulate the competitive effort for the rat, finding the expected ACC firing rates for the best integration effort/outcome. The results show that the ACC is critical for encoding competitive effort as a decision cost.

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