Mitochondrial iron deficiency triggers cytosolic iron overload in PKAN hiPS-derived astrocytes.

Disease models of neurodegeneration with brain iron accumulation (NBIA) offer the possibility to explore the relationship between iron dyshomeostasis and neurodegeneration. We analyzed hiPS-derived astrocytes from PANK2-associated neurodegeneration (PKAN), an NBIA disease characterized by progressive neurodegeneration and high iron accumulation in the globus pallidus. Previous data indicated that PKAN astrocytes exhibit alterations in iron metabolism, general impairment of constitutive endosomal trafficking, mitochondrial dysfunction and acquired neurotoxic features. Here, we performed a more in-depth analysis of the interactions between endocytic vesicles and mitochondria via superresolution microscopy experiments. A significantly lower number of transferrin-enriched vesicles were in contact with mitochondria in PKAN cells than in control cells, confirming the impaired intracellular fate of cargo endosomes. The investigation of cytosolic and mitochondrial iron parameters indicated that mitochondrial iron availability was substantially lower in PKAN cells compared to that in the controls. In addition, PKAN astrocytes exhibited defects in tubulin acetylation/phosphorylation, which might be responsible for unregulated vesicular dynamics and inappropriate iron delivery to mitochondria. Thus, the impairment of iron incorporation into these organelles seems to be the cause of cell iron delocalization, resulting in cytosolic iron overload and mitochondrial iron deficiency, triggering mitochondrial dysfunction. Overall, the data elucidate the mechanism of iron accumulation in CoA deficiency, highlighting the importance of mitochondrial iron deficiency in the pathogenesis of disease.

Neural correlates of metacognition: Disentangling the brain circuits underlying prospective and retrospective second-order judgments through noninvasive brain stimulation.

Metacognition encompasses the capability to monitor and control one's cognitive processes, with metamemory and metadecision configuring among the most studied higher order functions. Although imaging experiments evaluated the role of disparate brain regions, neural substrates of metacognitive judgments remain undetermined. The aim of this systematic review is to summarize and discuss the available evidence concerning the neural bases of metacognition which has been collected by assessing the effects of noninvasive brain stimulation (NIBS) on human subjects' metacognitive capacities. Based on such literature analysis, our goal is, at first, to verify whether prospective and retrospective second-order judgments are localized within separate brain circuits and, subsequently, to provide compelling clues useful for identifying new targets for future NIBS studies. The search was conducted following the preferred reporting items for systematic reviews and meta-analyses guidelines among PubMed, PsycINFO, PsycARTICLES, PSYNDEX, MEDLINE, and ERIC databases. Overall, 25 studies met the eligibility criteria, yielding a total of 36 experiments employing transcranial magnetic stimulation and 16 ones making use of transcranial electrical stimulation techniques, including transcranial direct current stimulation and transcranial alternating current stimulation. Importantly, we found that both perspective and retrospective judgments about both memory and perceptual decision-making performances depend on the activation of the anterior and lateral portions of the prefrontal cortex, as well as on the activity of more caudal regions such as the premotor cortex and the precuneus. Combining this evidence with results from previous imaging and lesion studies, we advance ventromedial prefrontal cortex as a promising target for future NIBS studies.

Novel Approaches for the Treatment of Post-Traumatic Stress Disorder: A Systematic Review of Non-Invasive Brain Stimulation Interventions and Insights from Clinical Trials.

First-line treatments for post-traumatic stress disorder (PTSD) encompass a wide range of pharmacotherapies and psychotherapies. However, many patients fail to respond to such interventions, highlighting the need for novel approaches. Due to its ability to modulate cortical activity, non-invasive brain stimulation (NIBS) could represent a valuable therapeutic tool. Therefore, the aim of this systematic review is to summarize and discuss the existing evidence on the ameliorative effects of NIBS on PTSD and comorbid anxiety and depressive symptoms. Our goal is also to debate the effectiveness of an integrated approach characterized by the combination of NIBS and psychotherapy. This search was conducted following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines in the PubMed, PsycINFO, PsycARTICLES, PSYINDEX, MEDLINE, and ERIC databases. Overall, 31 studies met the eligibility criteria, yielding a total of 26 clinical trials employing transcranial magnetic stimulation (TMS) and 5 making use of transcranial direct-current stimulation (tDCS). From these studies, it emerged that NIBS consistently reduced overall PTSD symptoms' severity as well as comorbid anxiety and depressive symptoms. Moreover, we speculate that combining NIBS with prolonged exposure or cognitive processing therapy might represent a promising therapeutic approach for consistently ameliorating subjects' clinical conditions.

Iron imbalance in neurodegeneration.

Iron is an essential element for the development and functionality of the brain, and anomalies in its distribution and concentration in brain tissue have been found to be associated with the most frequent neurodegenerative diseases. When magnetic resonance techniques allowed iron quantification in vivo, it was confirmed that the alteration of brain iron homeostasis is a common feature of many neurodegenerative diseases. However, whether iron is the main actor in the neurodegenerative process, or its alteration is a consequence of the degenerative process is still an open question. Because the different iron-related pathogenic mechanisms are specific for distinctive diseases, identifying the molecular mechanisms common to the various pathologies could represent a way to clarify this complex topic. Indeed, both iron overload and iron deficiency have profound consequences on cellular functioning, and both contribute to neuronal death processes in different manners, such as promoting oxidative damage, a loss of membrane integrity, a loss of proteostasis, and mitochondrial dysfunction. In this review, with the attempt to elucidate the consequences of iron dyshomeostasis for brain health, we summarize the main pathological molecular mechanisms that couple iron and neuronal death.

Poke And Delayed Drink Intertemporal Choice Task (POKE-ADDICT): An open-source behavioral apparatus for intertemporal choice testing in rodents.

Advancements in neuroscience research present opportunities and challenges, requiring substantial resources and funding. To address this, we describe here "Poke And Delayed Drink Intertemporal Choice Task (POKE-ADDICT)", an open-source, versatile, and cost-effective apparatus for intertemporal choice testing in rodents. This allows quantification of delay discounting (DD), a cross-species phenomenon observed in decision making which provides valuable insights into higher-order cognitive functioning. In DD, the subjective value of a delayed reward is reduced as a function of the delay for its receipt. Using our apparatus, we implemented an effective intertemporal choice paradigm for the quantification of DD based on an adjusting delayed amount (ADA) algorithm using mango juice as a reward. Our paradigm requires limited training, a few 3D-printed parts and inexpensive electrical components, including a Raspberry Pi control unit. Furthermore, it is compatible with several in vivo procedures and the use of nose pokes instead of levers allows for faster task learning. Besides the main application described here, the apparatus can be further extended to implement other behavioral tests and protocols, including standard operant conditioning. In conclusion, we describe a versatile and cost-effective design based on Raspberry Pi that can support research in animal behavior, decision making and, more specifically, delay discounting.

Transcranial direct current stimulation (tDCS) over the orbitofrontal cortex reduces delay discounting.

Delay discounting (DD) is a quantifiable psychological phenomenon that regulates decision-making. Nevertheless, the neural substrates of DD and its relationship with other cognitive domains are not well understood. The orbitofrontal cortex (OFC) is a potential candidate for supporting the expression of DD, but due to its wide involvement in several psychological functions and neural networks, its central role remains elusive. In this study, healthy subjects underwent transcranial direct current stimulation (tDCS) while performing an intertemporal choice task for the quantification of DD and a working memory task. To selectively engage the OFC, two electrode configurations have been tested, namely, anodal Fp1-cathodal Fp2 and cathodal Fp1-anodal Fp2. Our results show that stimulation of the OFC reduces DD, independently from electrode configuration. In addition, no relationship was found between DD measures and either working memory performance or baseline impulsivity assessed through established tests. Our work will direct future investigations aimed at unveiling the specific neural mechanisms underlying the involvement of the OFC in DD, and at testing the efficacy of OFC tDCS in reducing DD in psychological conditions where this phenomenon has been strongly implicated, such as addiction and eating disorders.

Neural Correlates of Delay Discounting in the Light of Brain Imaging and Non-Invasive Brain Stimulation: What We Know and What Is Missed.

In decision making, the subjective value of a reward declines with the delay to its receipt, describing a hyperbolic function. Although this phenomenon, referred to as delay discounting (DD), has been extensively characterized and reported in many animal species, still, little is known about the neuronal processes that support it. Here, after drawing a comprehensive portrait, we consider the latest neuroimaging and lesion studies, the outcomes of which often appear contradictory among comparable experimental settings. In the second part of the manuscript, we focus on a more recent and effective route of investigation: non-invasive brain stimulation (NIBS). We provide a comprehensive review of the available studies that applied transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) to affect subjects' performance in DD tasks. The aim of our survey is not only to highlight the superiority of NIBS in investigating DD, but also to suggest targets for future experimental studies, since the regions considered in these studies represent only a fraction of the possible ones. In particular, we argue that, based on the available neurophysiological evidence from lesion and brain imaging studies, a very promising and underrepresented region for future neuromodulation studies investigating DD is the orbitofrontal cortex.

The Dissociative Subtype of Post-Traumatic Stress Disorder: A Systematic Review of the Literature using the Latent Profile Analysis.

A PTSD subtype with dissociative symptoms (D-PTSD) was included in the DSM-5 recognizing the existence of a more severe form of PTSD, associated to past trauma, high comorbidity, and complex clinical management. As research is rapidly growing and results are inconsistent, a better investigation of this subtype is of primary importance. We conducted a systematic review of studies using Latent Profile Analysis to investigate the existence of a D-PTSD subtype. Covariates of D-PTSD were included, to understand additional symptoms, risk factors and comorbidities. The search was performed on PubMed, EBSCOHost, and PTSDPubs according to 2020 PRISMA guidelines. Eligible articles assessed trauma exposure, PTSD symptoms and diagnosis, and dissociation, in adult samples. 13 of 165 articles met the inclusion criteria. All identified a dissociative subtype of PTSD, mainly characterized by higher levels of depersonalization and derealization. D-PTSD profile sometimes presented other dissociative symptoms, such as gaps in awareness and memory, other comorbid disorders, and a history of abuse. Despite some limitations, this review supports the existence of a dissociative subgroup of individuals among those with PTSD. More rigorous studies are needed to clarify these findings and their clinical implications.

A novel integrated approach to estimate the mitochondrial content of neuronal cells and brain tissues.

BACKGROUND: Mitochondria and their dynamics fuel most cellular processes both in physiological and pathological conditions. In the central nervous system, mitochondria sustain synaptic transmission and plasticity via multiple mechanisms which include their redistribution and/or expansion to higher energy demanding sites, sustaining activity changes and promoting morphological circuit adaptations. NEW METHOD: To be able to evaluate changes in mitochondrial number and protein phenotype, we propose a novel methodological approach where the simultaneous analysis of both mitochondrial DNA and protein content is performed on each individual microsample, avoiding non-homogeneous loss of material. RESULTS: We validated this method on neuronal-like cells and tissue samples and obtained estimates for the mitochondrial/genomic DNA ratio as well as for the abundance of protein counterparts. When the mitochondrial content per cell was evaluated in different brain areas, our results matched the known regional variation in aerobic-anaerobic metabolism. When long-term potentiation (LTP) was induced on hippocampal neurons, we detected increases in the abundance of mitochondria that correlated with the degree of synaptic enhancement. CONCLUSIONS: Our approach can be effectively used to study the mitochondrial content andits changes in different brain cells and tissues.

Neuronal Cells Confinement by Micropatterned Cluster-Assembled Dots with Mechanotransductive Nanotopography.

Artificially grown neuronal cultures of brain cells have been used for decades in the attempt to reproduce and study in vitro the complexity of brain circuits. It soon became evident that this alone was insufficient, because of the random architecture of these artificial networks. Important groundwork therefore resulted in the development of methods to confine neuronal adhesion at specific locations to match predefined network topologies and connectivity. Despite this notable progress in neural circuitry engineering, there is still need for micropatterned substrates that recapitulate better biophysical cues of the neuronal microenvironment, taking into account recent findings of their significance for neuronal differentiation and functioning. Here, we report the development and characterization of a novel approach that, by using supersonic cluster beam deposition of zirconia nanoparticles, allows the patterning of small nanostructured cell-adhesive areas according to predefined geometries onto elsewhere nonadhesive antifouling glass surfaces. As distinguishing features, compared to other micropatterning approaches in this context, the integrated nanostructured surfaces possess extracellular matrix-like nanotopographies of predetermined roughness; previously shown to be able to promote neuronal differentiation due to their impact on mechanotransductive processes, and can be used in their original state without any coating requirements. These micropatterned substrates were validated using (i) a neuron-like PC12 cell line and (ii) primary cultures of rat hippocampal neurons. After initial uniform plating, both neuronal cells types were found to converge and adhere specifically to the nanostructured regions. The cell-adhesive areas effectively confined cells, even when these were highly mobile and repeatedly attempted to cross boundaries. Inside these small permissive islands, cells grew and differentiated, in the case of the hippocampal neurons, up to the formation of mature, functionally active, and highly connected synaptic networks. In addition, when spontaneous instances of axon bridging between nearby dots occurred, a functional interdot communication between these subgroups of cells was observed.