Through the lens of preclinical research on substance use disorders (SUD), I propose a reflection aimed at reevaluating animal models in neuroscience, with a focus on ecological relevance. While rodent models have provided valuable insights into the neurobiology of SUD, the field currently faces a validation crisis, with findings often failing to translate into effective human treatments. Originally designed to address the lack of reproducibility in animal studies, the current global gold standard of rigorous standardization has led to increasingly controlled environments. This growing disconnection between laboratory settings and real-world scenarios exacerbates the validation crisis. Rodent models have also revealed various environmental influences on drug use and its neural mechanisms, highlighting parallels with human behavior and underscoring the importance of ecological relevance in behavioral research. Drawing inspiration from inquiries in ethology and evolutionary biology, I advocate for incorporating greater environmental complexity into animal models. In line with this idea, the neuroethological approach involves studying spontaneous behaviors in semi-natural habitats while utilizing advanced technologies to monitor neural activity. Although this framework offers new insights into human neuroscience, it does not adequately capture the complex human conditions that lead to neuropsychiatric diseases. Therefore, preclinical research should prioritize understanding the environmental factors that shape human behavior and neural architecture, integrating these insights into animal models. By emphasizing ecological relevance, we can achieve deeper insights into neuropsychiatric disorders and develop more effective treatment strategies. This approach highlights significant benefits for both scientific inquiry and ethical considerations.

The use of animals in scientific research has sparked productive and important debates. To encourage an informed exchange of ideas and prevent misinformation, this literary work presents arguments in favor of animal research, particularly in the field of neuroscience. Through a literary approach, it supports the premise that animal research is essential for advancing medical science, offering crucial insights into biological and cognitive processes that cannot be replicated otherwise, ensuring both safety and efficacy---while also acknowledging the ethical and moral dilemmas that researchers may face.

Are animal models necessary? Exploring (dis)advantages and alternativesAna Isabel Guimarães1,21Pharmacology and Neurobiology Laboratory of the Immunophysiology and Pharmacology Department and2Center for Drug Discovery and Innovative Medicines (MedInUP), School of Medicine and Biomedical Sciences(ICBAS), University of Porto, Portugal

Runner up in the FENS Care Writing Competition - Literary Category

This is a mentoring statement submitted in context of the FENS-Kavli Network of Excellence Mentoring Prize evaluation process.

The misfolding and aggregation of TAR DNA binding protein-43 (TDP-43), leading to the formation of cytoplasmic inclusions, emerge as a key pathological feature in a spectrum of neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and frontotemporal lobar dementia (FTLD). TDP-43 shuttles between the nucleus and cytoplasm but forms nuclear bodies (NBs) in response to stress. These NBs partially colocalize with nuclear speckles and paraspeckles that sequester RNAs and proteins, thereby regulating many cellular functions. The laboratory of Steven Brown has recently found that the non-POU domain-containing octamer-binding protein (NONO), a component of paraspeckles, forms novel nuclear speckle-like structures in mouse cortical neurons in response to stress and sleep deprivation. These findings suggest the possibility of a functional link between NONO and TDP-43, potentially contributing to TDP-43 proteinopathy. Here, we demonstrate that loss of function in the Drosophila homolog of NONO, no on or off transient A (NonA), exacerbates pathological phenotypes caused by TDP-43 gain of function, leading to locomotor defects and life span shortening. These results provide supporting evidence for the functional link between NONO and TDP-43 and lay the foundation for dissecting underlying mechanisms.

The brain’s ability to integrate sensory and motor information allows us to maintain a sense of orientation in space, a process in which head-direction cells play a key role. While these neurons have been studied extensively in mammals, their presence and function in non-mammalian species remain less understood. Here, I summarise the research work for my PhD thesis, where we explore the interpeduncular nucleus (IPN) in zebrafish, a lesser-known brain region, using whole-brain electron microscopy and calcium imaging techniques. We identified a novel population of unipolar neurons, with their activity exhibiting a dynamic, rotational pattern during head movements, even in the absence of sensory cues. This population mirrors the functionality of head-direction cells observed in mammals, suggesting a conserved mechanism for spatial orientation across vertebrates. Our findings reveal the potential of the zebrafish IPN as a vertebrate model for studying ring attractor networks, a theoretical framework previously used to explain head-direction cell activity. These results pave the way for future research on how motor and sensory signals converge in the vertebrate brain to maintain spatial orientation.

Cannabinoid receptor 1 (CB1) regulates synaptic transmission through presynaptic receptors in nerve terminals, and its physiological roles are of clinical relevance. The cellular sources and synaptic targets of CB1-expressing terminals in the human cerebral cortex are undefined. We demonstrate a variable laminar pattern of CB1-immunorective axons and electron microscopically show that CB1-positive GABAergic terminals make type-2 synapses innervating dendritic shafts (69%), dendritic spines (20%) and somata (11%) in neocortical layers 2-3. Of the CB1-immunopositive GABAergic terminals, 25% were vesicular-glutamate-transporter-3 (VGLUT3)-immunoreactive, suggesting GABAergic/glutamatergic co-transmission on dendritic shafts. In vitro recorded and labelled VGLUT3 or CB1-positive GABAergic interneurons expressed cholecystokinin, vasoactive-intestinal-polypeptide and calretinin, had diverse firing, axons and dendrites, and included rosehip, neurogliaform and basket cells, but not double bouquet or axo-axonic cells. CB1-positive interneurons innervated pyramidal cells and GABAergic interneurons. Most glutamatergic synaptic terminals formed type-1 synapses and some were positive for CB1 receptor concentrated in the presynaptic active zone, unlike in GABAergic terminals. From the sampled VGLUT3-positive terminals, 60% formed type-1 synapses with dendritic spines (80%) or shafts (20%) and 52% were also positive for VGLUT1, suggesting intracortical origin. Some VGLUT3-positive terminals were immunopositive for vesicular-monoamine-transporter-2, suggesting 5-HT/glutamate co-transmission. Overall, the results show that CB1 regulates GABA release mainly to dendritic shafts of both pyramidal cells and interneurons, and predict CB1-regulated co-release of GABA and glutamate from single cortical interneurons. We also demonstrate the co-existence of multiple vesicular glutamate transporters in a select population of terminals probably originating from cortical neurons and innervating dendritic spines in the human cerebral cortex.

Good brain health plays a significant role in an individual’s well-being and profoundly impacts the collective economy and society. Brain development does not stop at birth and some aspects continue throughout childhood and adolescence, allowing the full development of cognitive functions. Different determinants related to physical health, healthy environments, safety and security, life-long learning, and social connection as well as access to quality services influence the way our brains develop, adapt, and respond to stress and adversity. Ongoing progress in neurobiology and cognitive neuroscience allow the design of better prevention and intervention strategies to help avoid brain deficits and/or limit their impact and maintain brain health. The European Brain Council (EBC) convened an expert meeting during the FENS Forum 2024 to address youth brain health challenges. In recent years, the importance of brain health has garnered significant attention across scientific, medical, and policy-making communities. While much focus has traditionally been on neurodegenerative conditions affecting the elderly, a paradigm shift towards prioritizing brain health in youth is both timely and necessary. This shift can profoundly impact individual lives and society, necessitating an interdisciplinary approach that brings neuroscience to the forefront of public health and informs evidence-based policy. The topic is of utmost importance as EBC launched this year a new campaign on No Health Without Brain Health rallying support with its member organisations and the wider brain community for the increased prioritization of brain health on EU health and research agendas.

The integration of optogenetic techniques with traditional behavioral paradigms has provided novel insights into the neural mechanisms underlying olfactory-based fear conditioning. Olfactory cues are potent triggers for fear responses, and understanding the intricate neural dynamics involved in olfactory fear learning is crucial for unraveling the complexities of aversive memory formation. In this study, a robust method is presented that combines optogenetic stimulation of olfactory bulb glomeruli with foot shock fear conditioning to investigate olfactory-based fear learning in mice. By merging optogenetic manipulation with behavioral assays, a comprehensive framework for studying the mechanisms of olfactory fear conditioning is provided. This method offers new avenues for exploring the neural dynamics of adaptive responses to olfactory threats and may have implications for understanding fear-related disorders.

Warring the increasing incidence of Parkinson’s disease (PD) requires better characterized animal models, in particular of the PD prodrome. Since pesticide are well-established triggers of Parkinsonism, we now undertook a detailed characterization of the time dependent onset of behavioral and neurochemical alterations after the repeated daily i.p. administration to adult male rats of a low dose of rotenone (2.75 mg/kg) during weekdays for 21 days. The onset of motor (bradykinesia in the open field test) and coordination deficits (balance in the rotarod and rearing in the open field) occurred after 14 days of exposure to rotenone, linked to a nigrostriatal dopaminergic degeneration and increased accumulation of alpha-synuclein, which are key features of PD. Moreover, we identified several modifications pre-dating the onset of PD-like motor symptoms, encompassing gastrointestinal alterations and a modified whole-body composition together with olfactory dysfunction and memory and emotional impairments, which were typified by: i) a delayed gastric emptying of liquids (13CO2 analysis), which was evident from the third day of rotenone administration and was aggravated over subsequent days; ii) a loss of total, visceral and subcutaneous body fat and dehydration (bioimpedance spectroscopy); iii) olfactory dysfunction (discrimination test and food buried test). The characterization of this prodrome period in this robust model of PD offers a unique window of opportunity to investigate the pathophysiological mechanisms of PD onset and to devise and test novel neuroprotective strategies.

Inconsistent results are observed in the effects of transcranial direct current stimulation (tDCS) with different montages on motor learning. This study aimed to compare the effects of anodal and cathodal tDCS over primary motor cortex (M1) at different intensities (1 and 2 mA) on motor learning in healthy young adults. The participants were randomly divided to five groups: 1) 1mA M1 c-tDCS, 2) 1mA M1 a-tDCS, 3) 2 mA M1 c-tDCS, 4) 2 mA M1 a-tDCS and 5) M1 sham tDCS. The groups received 20-minute stimulation concurrent with serial response time test (SRTT) implicitly, while the tDCS was turned off after 30 seconds in the sham tDCS group. Response time (RT) and error rate (ER) during SRTT were assessed prior, during and 72 hours after the intervention. The results indicated that online learning occurred in all groups (P < 0.05), except in M1 c-tDCS (1 mA) (P>0.05). In addition, offline learning was observed in 1 mA M1 a-tDCS, 2mA M1 a-tDCS and 2 mA M1 c-tDCS as compared to sham tDCS and M1 c-tDCS (1 mA) groups (P < 0.05). On the other hand, 1 mA M1 c-tDCS group did not indicate any consolidation effect and even a trend toward negative offline learning. M1 a-tDCS with different intensities and also 2 mA M1 c-tDCS may be helpful for the enhancement of motor learning in young adults. Considering the deterioration effect of 1 mA M1 c-tDCS, it seems that caution should be applied in using it to improve motor learning.

This editorial focuses on the issue of data misuse which is increasingly evidenced in social media as well as some premiere scientific journals like yours. This issue is of critical importance to open science projects in general, and ABCD in particular, given the broad array of biological, behavioral and environmental information collected on this American sample of 12.000 youth and parents. ABCD data are already widely used with over 1000 publications and twice as many citations per year as expected (relative citation index based on year, field and journal). However, the adverse consequences of misuse of data, and inaccurate interpretation of emergent findings from this precedent setting study may have profound impact on disadvantaged populations and perpetuate biases and societal injustices. This editorial contains recommendations and references which may guide authors and assist reviewers alike in avoiding misleading scientific interpretations not only with use of ABCD data but other large scale data sets as well.

We at EJN are delighted to introduce Dr. Laurel Trainor as the latest scientist for our series of Women in Neuroscience. We began this series to bring visibility and recognition to the superb women scientists working in our community (Helmreich et al., 2017). You can find all of the previous profiles at: https://onlinelibrary.wiley.com/doi/toc/10.1111/(ISSN)1460-9568.women-in-science I had the honor of speaking with Dr. Trainor in May 2024.

In recent decades, neuroscience has advanced with increasingly sophisticated strategies for recording and analyzing brain activity, enabling detailed investigations into the roles of functional units, such as individual neurons, brain regions, and their interactions. Recently, new strategies for the investigation of cognitive functions regard the study of higher-order interactions---that is, the interactions involving more than two brain regions or neurons. While methods focusing on individual units and their interactions at various levels offer valuable and often complementary insights, each approach comes with its own set of limitations. In this context, a conceptual map to categorize and locate diverse strategies could be crucial to orient researchers and guide future research directions. To this end, we define the spectrum of orders of interaction, namely a framework that categorizes the interactions among neurons or brain regions based on the number of elements involved in these interactions. We use a simulation of a toy model and a few case studies to demonstrate the utility and the challenges of the exploration of the spectrum. We conclude by proposing future research directions aimed at enhancing our understanding of brain function and cognition through a more nuanced methodological framework.

Excessive beta oscillations in the subthalamic nucleus are established as a primary electrophysiological biomarker for motor impairment in Parkinson’s disease and are currently used as feedback signals in adaptive deep brain stimulation systems. However, there is still a need for optimization of stimulation parameters and the identification of optimal biomarkers that can accommodate varying patient conditions, such as ON and OFF levodopa medication. The precise boundaries of “pathological” oscillatory ranges, associated with different aspects of motor impairment, are still not fully clarified. In this study, we hypothesized that analyzing periodic and aperiodic components of subthalamic nucleus activity separately and identifying functionally distinct subranges within 8-35 Hz based on oscillatory properties may reveal robust biomarkers for specific aspects of motor impairment. We analyzed subthalamic nucleus activity of 14 patients with Parkinson’s disease. Local field potentials were recorded at rest from externalized electrodes postoperatively, both before and after levodopa administration. We showed that levodopa administration suppressed oscillations across a broad frequency range (11-32 Hz) and increased the slope of the aperiodic component. Changes in the aperiodic slope correlated with motor symptom alleviation. Periodic activity was linked to motor symptom severity: peak amplitude within the 14-20 Hz range correlated with overall motor impairment in the OFF state, while the 7-11 Hz range was associated with bradykinesia in the ON state. Our findings suggest that, in addition to low beta, alpha oscillations and the aperiodic component may serve as promising biomarkers for motor impairment and potential feedback signals in adaptive DBS systems.

Movement disorders such as Parkinson’s disease (PD) and cervical dystonia (CD) are associated with abnormal neuronal activity in the globus pallidus internus (GPi). Reduced firing rate and presence of spiking bursts are typical for CD, while PD is characterized by high frequency tonic activity. This research aims to identify the most important pallidal spiking parameters to classify these conditions. We analyzed the single unit activity of the external (GPe) and internal (GPi) segments of the globus pallidus in 11 CD and 10 PD patients who underwent standard DBS implantation. We compared firing rate, firing pattern and oscillatory characteristics of tonic, burst and pause cells and used logistic regression and random forest models to classify patients according to their pallidal activity. In the GPi we discovered prevalence of high firing rate tonic cells in patients with PD, while in dystonia burst neurons with high firing rate were predominant. GPi pause cells were mostly observed in CD patients and exhibited less spike variability compared to PD. Characteristics of neurons and their distribution in the GPe was similar. Logistic regression and random forest models identified spike variability and randomness as the key features for distinguishing between PD and CD, instead of firing rate or oscillation properties. Our study demonstrates that pallidal activity can predict Parkinson’s disease and cervical dystonia with high accuracy. Burst dynamics and characteristics of spiking randomness including entropy appear to be the most meaningful reflections of the neurophysiology of studied diseases.

The suprachiasmatic nucleus (SCN) is the master clock that orchestrates circadian clocks across the body to synchronize with and anticipate the earth’s light/dark cycles. Although post-transcriptional regulators called microRNAs have been implicated in physiological SCN function, how the absence of the entire mature miRNome impacts SCN output has not yet been explored. Here, we have generated an SCN-specific Dicer knockout mouse model by crossing Syt10Cre mice with Dicerflox mice to study behavioral consequences of miRNA depletion in the SCN. We show that loss of all mature miRNAs in the SCN shortens the circadian period length by ~40 minutes at the tissue level, and by ~50 minutes at the locomotor activity level. Knockout animals also showed arrythmicity or ultradian locomotor activities with no light masking under constant light, a condition which usually caused lengthening of the circadian period length and reduced activities, i.e. light masking, in nocturnal animals. Moreover, induction of Dicer knockout by Cre injection into the SCN of adult Dicerflox mice eventually resulted in loss of behavioral rhythms. Finally, we show suggestive evidence that SCN desynchronization might be one mechanism underlying the behavioral phenotypes of SCN-specific Dicer knockout animals.