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.

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.

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.

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.

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.

Non-human animal models continue to be indispensable in neuroscience research for the foreseeable future. In recent years, animal-right activists have been increasing the pressure on politicians and policymakers to phase out animal research. To address this pressure, we should adapt our communication habits, to be more open and transparent about (our) animal research and most importantly to expand the methods we use to communicate about our research and increase the extend of this outreach. In this editorial we discuss the why and how of animal research communication.

In the context of an aging population, concerns surrounding memory function become increasingly prevalent, particularly as individuals transition into middle age and beyond. This study investigated neurofeedback (NFB) as a potential early therapeutic intervention to address subjective cognitive decline in aging populations. NFB, a biofeedback technique utilizing a brain-computer interface, has demonstrated promise in the treatment of various neurological and psychological conditions. Here, we evaluated the efficacy of individualized NFB training, tailored to each participant’s EEG profile, compared to a standard NFB training protocol aimed at upregulating peak alpha frequency, in enhancing cognitive function among individuals experiencing subjective cognitive decline (SCD). Our NFB protocol incorporated innovative elements, including the implementation of a criterion for learning success to ensure consistent achievement levels by the conclusion of the training sessions. Additionally, we introduced a non-learners group to account for individuals who do not demonstrate the expected proficiency in NFB regulation. Analysis of electroencephalographic (EEG) signals during NFB sessions, as well as before and after training, provides insights into the modulatory effects of NFB on EEG frequencies. Contrary to expectations, our rigorous analysis revealed that the ability of individuals with SCD to modulate EEG signal power and duration at specific frequencies was not exclusive to the intended frequency target. Furthermore, examination of EEG signals recorded using a high-density EEG showed no discernible alteration in signal power between pre- and post-NFB training sessions. Similarly, no significant effects were observed on questionnaire scores when comparing pre- and post-NFB training assessments.

Actions are rarely devoid of emotional content. Thus, a more complete picture of the neural mechanisms underlying mental simulation of observed actions requires more research using emotion information. The present study used high-density electroencephalography to investigate mental simulation associated with facial emotion categorisation. Alpha-mu rhythm modulation was measured at each frequency, from 8 Hz to 13 Hz, to infer the degree of sensorimotor simulation. Results suggest the sensitivity of the sensorimotor activity to emotional information, because (1) categorising static images of neutral faces as happy or sad was associated with stronger suppression in the central region than categorising clearly happy faces, (2) there was preliminary evidence indicating that the strongest suppression in the central region was in response to neutral faces, followed by sad and then happy faces, and (3) in the control task, which required categorising images with the head oriented right, left, or forward as right or left, differences between conditions showed a pattern more indicative of task difficulty rather than sensorimotor engagement. Dissociable processing of emotional information in facial expressions and directionality information in head orientations was further captured in beta band activity (14-20 Hz). Stronger mu suppression to neutral faces indicates that sensorimotor simulation extends beyond crude motor mimicry. We propose that mu rhythm responses to facial expressions may serve as a biomarker for empathy circuit activation. Future research should investigate whether atypical or inconsistent mu rhythm responses to facial expressions indicate difficulties in understanding or sharing emotions.

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is a standard treatment for advanced Parkinson’s disease (PD). The precise positioning of the electrode can significantly influence the results of DBS and the overall improvement in the quality of life for PD patients receiving this therapy. We hypothesize that single unit activity (SUA) features can serve as a valid marker of the optimal DBS-electrode insertion trajectory, leading to the most favorable outcome of STN-DBS surgery. We analyzed spontaneous SUA data recorded during Microelectrode Recording (MER) for 21 patients with PD who underwent DBS surgery. We compared 29 linear and 6 nonlinear characteristics of the STN neural activity recorded along different microelectrode insertion paths to determine features corresponding to favorable stimulation outcomes. Our research indicated that the SUA features of pause neurons in a dorsal STN region significantly affected stimulation outcomes. For the trajectories chosen for lead insertion, firing rate, burst rate, and oscillatory activity at 8-12 and 12-20 bands were significantly decreased. Moreover, nonlinear feature analysis showed a significant increase in mutual information for the chosen trajectories. Our findings highlight the significance of specific indicators, such as the activity of pause neurons in the dorsal region and numerous linear SUA characteristics, in determining the optimal lead installation trajectory. Furthermore, our findings emphasize the importance of investigating paths rejected during test-stimulation to understand motor impairment in Parkinson’s disease and its treatment mechanisms.

This paper uses suicidality in bipolar disorder (BD) as a case study demonstrating the preferability of multidimensional over reductionist frameworks in accounting for complex phenomena with cognitive, psychological, socio-environmental, and physiological components. Suicidality, or behaviors and thoughts concerning an intention to end one’s life, illustrates the interplay between diverse factors. This multidimensionality is reflected in the heterogeneous strategies for managing suicidality, which range from psychosocial and cognitive to pharmaceutical and technological interventions. Suicidality in BD is a multi-dimensional phenomenon whose study has been productive through the methods of several disciplines. For instance, suicidality in BD is partly genetic and can be aggravated by symptomatic periods, suggesting physiological causal factors. However, some features of suicidality in BD underscore the causal roles of cognitions. Notably, suicidality can persist beyond depressive periods, and is sometimes experienced during mania. This may be due to persistent suicidal ideation, highlighting the need to account for cognitive or psychological causal factors. Models of suicidality in BD typically adopt a pluralistic approach that does not reduce one dimension to another. Rather, they are treated as different facets of a complex phenomenon that interact and influence each other. Moreover, recent studies have shown the promise of physical interventions, e.g., electroconvulsive therapy and deep-brain stimulation, in the treatment of suicidality in BD. Socio-environmental interventions have been successful in suicide prevention more generally. This demonstrates how multidisciplinary, multidimensional explanations are most likely to productively account for how diverse factors contribute to suicidality along with genetic and physiological determinants.