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Background: Eating disorders (EDs) are among the least studied mental disorders in individuals at clinical high risk for psychosis (CHR-P). The primary aim (a) of this systematic review and meta-analysis was to identify factors predicting ED diagnoses in CHR-P individuals. The secondary aim (b) was providing a comprehensive clinical description of individuals with both CHR-P and EDs/ED-related symptoms., Methods: Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) 2020-compliant systematic review and meta-analysis, searching PubMed/(EBSCO)PsycINFO/Web of Science for studies published between 01/01/2018 and 30/05/2023, including individuals with CHR-P and EDs/ED symptoms (PROSPERO CRD42023488792). Quality assessment was performed using the Newcastle-Ottawa Scale (NOS). We performed a meta-regression model on the proportion of EDs in CHR-P individuals (primary aim) and conducted a narrative synthesis (secondary aim)., Results: We included 26 articles, reporting on 2,060 and 589 subjects for study aim (a) and (b), respectively (mean NOS score = 6.38). The prevalence of EDs in CHR-P individuals was 0.05 (95% CI 0.3-0.8). No factor had a significant effect on the proportion of EDs in CHR-P individuals. This result is limited by the inability to include ED-related symptoms and antipsychotic prescriptions in the meta-regression model, due to an insufficient number of studies reporting on these variables. The narrative synthesis offers a characterization of individuals with both CHR-P and ED/ED-related symptoms; however, the limited number of included studies is insufficient to support definitive conclusions., Conclusions: No significant predictor of EDs was found in CHR-P individuals. Transdiagnostic, prospective cohort studies are warranted to examine long-term outcomes in individuals with both CHR-P and EDs, beyond diagnostic silos., Level of Evidence: I. Systematic review and meta-analysis., Competing Interests: Declarations. Ethics approval and consent to participate: Ethical approval was not sought for the current study because we retrieved and analyzed data from published studies. Competing interests: MS received honoraria/has been a consultant for Angelini, AbbVie, Lundbeck, Otsuka., (© 2024. The Author(s).)

Background: Defense mechanisms play a crucial role in depression and anxiety. The current study aimed at estimating the network structure of defense mechanisms in individuals with symptoms of depression and anxiety to understand the most central defenses and relevant connections. Moreover, we aimed at examining the associations between defense mechanisms and symptoms., Methods: We employed the Symptom Checklist-90 to recruit 655 individuals with depressive and anxiety symptoms during the first wave of the COVID-2019 Pandemic in Italy. Defense mechanisms were assessed with the DMRS-SR-30., Results: Results showed a main component in the network graph featuring 16 defense mechanisms. Self-assertion was the most central node in the network, displaying positive and negative connections with an array of mature and immature defenses, respectively. Among immature defenses, passive aggression was the most interconnected node. Some mature defenses (i.e., humor, affiliation, and sublimation) were not connected to other nodes. A range of defense mechanisms were associated with anxiety and depressive symptoms., Conclusions: This is the first research effort supporting the conceptualization of defense mechanisms as a complex system. Results suggest that defense mechanisms of the same cluster (e.g., mature defenses) play different roles in the network. Central defenses (i.e., self-assertion and passive aggression) detected in this study may be promising intervention targets., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Di Giuseppe, Lo Buglio, Cerasti, Boldrini, Conversano, Lingiardi and Tanzilli.)

To be relevant to healthcare systems, the clinical high risk for psychosis (CHR-P) concept should denote a specific (i.e., unique) clinical population and provide useful information to guide the choice of intervention. The current study applied network analyses to examine the clinical specificities of CHR-P youths compared to general help-seekers and non-CHR-P youth. 146 CHR-P (mean age = 14.32 years) and 103 non-CHR-P (mean age = 12.58 years) help-seeking youth were recruited from a neuropsychiatric unit and assessed using the Structured Interview for Psychosis-Risk Syndromes, Children's Depression Inventory, Multidimensional Anxiety Scale for Children, Global Functioning: Social, Global Functioning: Role, and Wechsler Intelligence Scale for Children/Wechsler Adult Intelligence Scale. The first network structure comprised the entire help-seeking sample (i.e., help-seekers network), the second only CHR-P patients (i.e., CHR-P network), and the third only non-CHR-P patients (i.e., non-CHR-P network). In the help-seekers network, each variable presented at least one edge. In the CHR-P network, two isolated "archipelagos of symptoms" were identified: (a) a subgraph including functioning, anxiety, depressive, negative, disorganization, and general symptoms; and (b) a subgraph including positive symptoms and the intelligence quotient. In the non-CHR-P network, positive symptoms were negatively connected to functioning, disorganization, and negative symptoms. Positive symptoms were less connected in the CHR-P network, indicating a need for specific interventions alongside those treating comorbid disorders. The findings suggest specific clinical characteristics of CHR-P youth to guide the development of tailored interventions, thereby supporting the clinical utility of the CHR-P concept., (© 2024. The Author(s).)

Objective: Youths at clinical high risk for psychosis (CHR-P) are characterized by a high prevalence of anxiety and depressive disorders. The present study aimed at developing and analyzing a network structure of CHR-P symptom domains (i.e., positive, negative, disorganization, and general subclinical psychotic symptoms), depressive and anxiety symptoms, and general functioning., Methods: Network analysis was applied to data on 111 CHR-P children and adolescents ( M age = 14.1), who were assessed using the Structured Interview for Prodromal Syndromes, the Children's Depression Inventory, the Children's Global Assessment Scale, and the Multidimensional Anxiety Scale for Children., Results: In the network, negative and disorganization symptoms showed the strongest association ( r = 0.71), and depressive and anxiety symptoms showed dense within-domain connections, with a main bridging role played by physical symptoms of anxiety. The positive symptom cluster was not associated with any other node. The network stability coefficient (CS) was slightly below 0.25, and observed correlations observed ranged from 0.35 to 0.71., Conclusion: The lack of association between subclinical positive symptoms and other network variables confirmed the independent nature of subclinical positive symptoms from comorbid symptoms, which were found to play a central role in the analyzed network. Complex interventions should be developed to target positive and comorbid symptoms, prioritizing those with the most significant impact on functioning and the most relevance for the young individual, through a shared decision-making process. Importantly, the results suggest that negative and disorganization symptoms, as well as depressive and anxiety symptoms, may be targeted simultaneously., Competing Interests: Author MS received honoraria and has been a consultant for Angelini, Lundbeck, Otsuka, outside the submitted work. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Lo Buglio, Pontillo, Cerasti, Polari, Schiano Lomoriello, Vicari, Lingiardi, Boldrini and Solmi.)

Hippocampal place responses can be prospectively or retrospectively modulated by the animal's future or prior trajectory. Two main hypotheses explain this. The "multiple-map hypothesis" switches between different maps for different trajectories (rate remapping). In contrast, in the "buffer hypothesis," the hippocampus encodes an ongoing representation that includes the recent past and/or the impending future choice. This study examines the distribution of prospective and retrospective responses distributed along a common path in a continuous T-maze (providing all four combinations of provenance and destination) during a visual discrimination task. The multiple-map hypothesis predicts either uniform distributions or concerted shifts about a task-decision relevant point, whereas the buffer hypothesis predicts a time-limited overexpression around choice points (with retrospective responses after the central arm entry point and prospective responses nearer its exit). Here bilateral recordings in the dorsal CA1 region of the rat hippocampus show that retrospective responses were twice as prevalent as prospective responses. Furthermore, retrospective and prospective modulations have distinct spatial distributions, with retrospective primarily in the first two-thirds of the central arm and prospective restricted to the last third. To test for possible trial-by-trial remapping in relation to the two-thirds transition point, data from the first and second halves of the sessions were compared. Backward drift of path-modulated activity was significant only for retrospective, but not prospective, fields. Thus, these data are more consistent with the buffer hypothesis. Retrospective and prospective modulation would then participate in a single hippocampal representation of spatial and behavioral context., (Copyright © 2014 the authors 0270-6474/14/3413163-07$15.00/0.)

To solve novel problems, it is advantageous to abstract relevant information from past experience to transfer on related problems. To study whether macaque monkeys were able to transfer an abstract rule across cognitive domains, we trained two monkeys on a nonmatch-to-goal (NMTG) task. In the object version of the task (O-NMTG), the monkeys were required to choose between two object-like stimuli, which differed either only in shape or in shape and color. For each choice, they were required to switch from their previously chosen object-goal to a different one. After they reached a performance level of over 90% correct on the O-NMTG task, the monkeys were tested for rule transfer on a spatial version of the task (S-NMTG). To receive a reward, the monkeys had to switch from their previously chosen location to a different one. In both the O-NMTG and S-NMTG tasks, there were four potential choices, presented in pairs from trial-to-trial. We found that both monkeys transferred successfully the NMTG rule within the first testing session, showing effective transfer of the learned rule between two cognitive domains.

Neural computation models have hypothesized that the dentate gyrus (DG) drives the storage in the CA3 network of new memories including, e.g., in rodents, spatial memories. Can recurrent CA3 connections self-organize, during storage, and form what have been called continuous attractors, or charts-so that they express spatial information later, when aside from a partial cue the information may not be available in the inputs? We use a simplified mathematical network model to contrast the properties of spatial representations self-organized through simulated Hebbian plasticity with those of charts pre-wired in the synaptic matrix, a control case closer to the ideal notion of continuous attractors. Both models form granular quasi-attractors, characterized by drift, which approach continuous ones only in the limit of an infinitely large network. The two models are comparable in terms of precision, but not of accuracy: with self-organized connections, the metric of space remains distorted, ill-adequate for accurate path integration, even when scaled up to the real hippocampus. While prolonged self-organization makes charts somewhat more informative about position in the environment, some positional information is surprisingly present also about environments never learned, borrowed, as it were, from unrelated charts. In contrast, context discrimination decreases with more learning, as different charts tend to collapse onto each other. These observations challenge the feasibility of the idealized CA3 continuous chart concept, and are consistent with a CA3 specialization for episodic memory rather than path integration.

How are neuronal representations of space organized in the hippocampus? The self-organization of such representations, thought to be driven in the CA3 network by the strong randomizing input from the Dentate Gyrus, appears to run against preserving the topology and even less the exact metric of physical space. We present a way to assess this issue quantitatively, and find that in a simple neural network model of CA3, the average topology is largely preserved, but the local metric is loose, retaining e.g., 10% of the optimal spatial resolution.

Monkeys can learn the symbolic meaning of tokens, and exchange them to get a reward. Monkeys can also learn the symbolic value of a token by observing conspecifics but it is not clear if they can learn passively by observing other actors, e.g., humans. To answer this question, we tested two monkeys in a token exchange paradigm in three experiments. Monkeys learned token values through observation of human models exchanging them. We used, after a phase of object familiarization, different sets of tokens. One token of each set was rewarded with a bit of apple. Other tokens had zero value (neutral tokens). Each token was presented only in one set. During the observation phase, monkeys watched the human model exchange tokens and watched them consume rewards (vicarious rewards). In the test phase, the monkeys were asked to exchange one of the tokens for food reward. Sets of three tokens were used in the first experiment and sets of two tokens were used in the second and third experiments. The valuable token was presented with different probabilities in the observation phase during the first and second experiments in which the monkeys exchanged the valuable token more frequently than any of the neutral tokens. The third experiments examined the effect of unequal probabilities. Our results support the view that monkeys can learn from non-conspecific actors through vicarious reward, even a symbolic task like the token-exchange task.

Place-selective activity in hippocampal neurons can be modulated by the trajectory that will be taken in the immediate future ("prospective coding"), information that could be useful in neural processes elaborating choices in route planning. To determine if and how hippocampal prospective neurons participate in decision making, we measured the time course of the evolution of prospective activity by recording place responses in rats performing a T-maze alternation task. After five or seven alternation trials, the routine was unpredictably interrupted by a photodetector-triggered visual cue as the rat crossed the middle of central arm, signaling it to suddenly change its intended choice. Comparison of the delays between light cue presentation and the onset of prospective activity for neurons with firing fields at various locations after the trigger point revealed a 420 ms processing delay. This surprisingly long delay indicates that prospective activity in the hippocampus appears much too late to generate planning or decision signals. This provides yet another example of a prominent brain activity that is unlikely to play a functional role in the cognitive function that it appears to represent (planning future trajectories). Nonetheless, the hippocampus may provide other contextual information to areas active at the earliest stages of selecting future paths, which would then return signals that help establish hippocampal prospective activity., (Copyright © 2012 Wiley Periodicals, Inc.)

One obstacle to understanding the exact processes unfolding inside the hippocampus is that it is still difficult to clearly define what the hippocampus actually does, at the system level. Associated for a long time with the formation of episodic and semantic memories, and with their temporary storage, the hippocampus is also regarded as a structure involved in spatial navigation. These two independent perspectives on the hippocampus are not necessarily exclusive: proposals have been put forward to make them fit into the same conceptual frame. We review both approaches and argue that three critical developments need consideration: (a) recordings of neuronal activity in rodents, revealing beautiful spatial codes expressed in entorhinal cortex, upstream of the hippocampus; (b) comparative behavioral results suggesting, in an evolutionary perspective, qualitative similarity of function across homologous structures with a distinct internal organization; (c) quantitative measures of information, shifting the focus from who does what to how much each neuronal population expresses each code. These developments take the hippocampus away from philosophical discussions of all-or-none cause-effect relations, and into the quantitative mainstream of modern neural science., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

In the mammalian hippocampus, the dentate gyrus (DG) is characterized by sparse and powerful unidirectional projections to CA3 pyramidal cells, the so-called mossy fibers. Mossy fiber synapses appear to duplicate, in terms of the information they convey, what CA3 cells already receive from entorhinal cortex layer II cells, which project both to the dentate gyrus and to CA3. Computational models of episodic memory have hypothesized that the function of the mossy fibers is to enforce a new, well-separated pattern of activity onto CA3 cells, to represent a new memory, prevailing over the interference produced by the traces of older memories already stored on CA3 recurrent collateral connections. Can this hypothesis apply also to spatial representations, as described by recent neurophysiological recordings in rats? To address this issue quantitatively, we estimate the amount of information DG can impart on a new CA3 pattern of spatial activity, using both mathematical analysis and computer simulations of a simplified model. We confirm that, also in the spatial case, the observed sparse connectivity and level of activity are most appropriate for driving memory storage-and not to initiate retrieval. Surprisingly, the model also indicates that even when DG codes just for space, much of the information it passes on to CA3 acquires a non-spatial and episodic character, akin to that of a random number generator. It is suggested that further hippocampal processing is required to make full spatial use of DG inputs.