Olfactory coding relies on primary information from olfactory receptor cells, that respond to volatile airborne substances. Despite of extensive efforts, our understanding of odor-response profiles across receptors is still poor, due to the vast number of possible ligands (odorants), the high sensitivity even to trace compounds (creating false positive responses), and the diversity of olfactory receptors. Here, we linked chemical purification with a gas chromatograph to single-receptor type recording with transgenic flies using calcium imaging to record olfactory responses to a large panel of chemicals in 7 Drosophila ORs: Or10a, Or13a, Or22a, Or42b, Or47a, Or56a, Or92a. We analyze the data using linear-non-linear modeling, and reveal that most receptors have “simple” response types (mostly positive: Or10a, Or13a, Or22a, Or47a, Or56a). However, two receptors (Or42b, Or92a) have, in addition to “simple” responses, “complex” response types to some ligands, either positive with a negative rebound, or negative with a positive rebound, suggesting the presence of multiple binding sites and/or transduction cascades. We show that some ligands reported in the literature are false positives, due to contaminations in the stimulus. We record all stimuli across concentrations, showing that at different concentrations different substances appear as best ligands. Our data show that studying combinatorial olfactory coding must consider temporal response properties, and is strongly influenced by the presence of trace amounts of ligands (contaminations) in the samples. These observations have important repercussions for our thinking about how animals navigate their olfactory environment.

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.

Body ownership—the perception that one’s body belongs to oneself—has been explored using a rubber hand illusion, in which individuals misperceive a fake hand as their own (i.e., embodiment of the fake hand) when an unseen real hand and a visible fake hand are stroked synchronously. Thus, the movement of an embodied fake body may be represented in one’s own sensorimotor system. Using a combination of the rubber hand illusion and a motor task, we investigated whether simple movement of the embodied fake hand influenced the subsequent movement of the participants’ hand. The participants lifted their own index finger immediately upon observing the index finger lifting on the embodied (rubber hand illusion) or non-embodied (non-rubber hand illusion) fake hand (Experiment 1), and a light-emitting diode turning on near the fake hand (Experiment 2). The reaction times, peak velocities, and peak acceleration were extracted from the participants’ finger-lifting movements. In Experiment 1, the reaction time was significantly shorter in the rubber hand illusion condition than in the non-rubber hand illusion condition, suggesting the rapid facilitation effect of embodied fake hand movement on actual movement. However, no such motor facilitation was observed in Experiment 2, confirming that the improved reaction time in Experiment 1 resulted from the visual movement of the fake hand rather than attention to the fake hand itself. In contrast to the reaction time, the peak velocity and acceleration did not differ significantly in either experiment. These findings reflect the shared sensorimotor representations of illusory and actual self-movement.

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.

The locus coeruleus (LC) neurons send extensive projections to the somatosensory cortex and release noradrenaline (NA) at synaptic terminals, which is thought to regulate the activation of sensory-related cells by acting on three types of receptors (α1, α2 and β). Although previous studies have examined the effects of LC stimulation on single-unit sensory neurons, their impact on somatosensory evoked potentials (SEPs) and their temporal variations, as well as the specific roles of NA receptors remain unclear. Herein, we investigated how SEPs are modulated by tonic LC stimulation at physiological frequencies (0.1, 1 and 4 Hz) and identified the receptors involved in these changes. Forepaw stimulation-induced amplitudes in SEP were enhanced in response to 1 Hz stimulation of the LC but not in response to 0.1 and 4 Hz stimulation. Interestingly, the enhancement of SEPs after LC stimulation persisted for tens of minutes following the cessation of stimulation. Optical imaging using a voltage-sensitive dye showed an increase in the depolarizing response in the somatosensory cortex after 1 Hz stimulation. Prazosin (α1 receptor antagonist) and propranolol (β receptor antagonist) inhibited SEP enhancement following 1 Hz LC stimulation, whereas yohimbine (α2 receptor antagonist) had no effect. This suggests that the observed enhancement in SEP observed is primarily mediated by the activation of cortical excitatory α1 and β receptors. These findings provide insight into the impact of the NA system on sensory information processing as well as the pathophysiology of sensory disorders related to the disruption of the NA system.

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.

Levodopa provides effective symptomatic treatment for Parkinson’s disease. However, non-motor symptoms are often insufficiently relieved, and its long-term use is complicated by motor fluctuations and dyskinesia. To clarify mechanisms of levodopa-induced dyskinesia and pharmacological interventions aimed at reducing dyskinetic symptoms, we have here characterized the neurophysiological activity patterns in sensorimotor and cognitive-limbic circuits in dyskinetic rats, comparing the effects of amantadine, pimavanserin and the novel prospective antidyskinetic and antipsychotic treatment mesdopetam. Parallel recordings of local field potentials from eleven cortical and sub-cortical regions revealed suppression of narrowband gamma oscillations (NBGs) in sensorimotor structures by amantadine and mesdopetam in conjunction with alleviation of dyskinetic signs. Concomitant gamma oscillations in cognitive-limbic circuits were not directly linked to dyskinesia and were not affected by antidyskinetic treatments to the same extent, although treatment-induced reductions in functional coupling was observed in both sensorimotor and cognitive-limbic circuits, in parallel. In a broad frequency spectrum (1-200Hz), mesdopetam treatment displayed greater similarities to pimavanserin than to amantadine. These findings point to reduction of NBGs as a valuable biomarker for characterization of antidyskinetic treatment effects and provide systems-level mechanistic insights into the antidyskinetic efficacy of mesdopetam, with potential additional benefits for the treatment of Parkinson’s-related psychosis.

Peripherin is a class III intermediate filament protein that has recently gained attention as a potential biomarker for axonal damage in the peripheral nervous system. This review examines peripherin gene expression, protein structure, and its functions in both healthy and diseased states. Peripherin is predominantly expressed in the peripheral nervous system, especially in motor and sensory neurons, and plays a critical role in neurite growth, stability, and axonal transport during myelination. Its expression is regulated by various cytokines and undergoes several post-transcriptional modifications. Peripherin interacts with multiple proteins, including neurofilaments and kinases, influencing cytoskeletal dynamics and neuronal functions. The review also explores peripherin involvement in several neurological disorders, such as Amyotrophic Lateral Sclerosis, where its abnormal expression and aggregation contribute to disease pathology. Additionally, peripherin has been linked to polyneuropathies, traumatic axonal injury, and diabetic neuropathy, suggesting its broader relevance as a biomarker in these conditions. The potential of peripherin as a biomarker is further supported by recent studies using ultrasensitive detection methods, which have identified elevated peripherin levels in the serum of patients with neurological diseases. Despite the promising findings, the application of peripherin as a biomarker in clinical settings remains limited, primarily due to challenges in its detection and the need for further validation in diverse patient populations. Future research directions include the development of more sensitive assays and the exploration of peripherin's role in non-neuronal tissues, which may expand its diagnostic and therapeutic potential.

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.