Many efforts are making science more open and accessible; they are mostly concentrated on issues that appear before and after experiments are performed: open access journals, open databases, and many other tools to increase reproducibility of science and access to information. However, these initiatives do not promote access to scientific equipment necessary for experiments. Mostly due to monetary constraints, equipment availability has always been uneven around the globe, affecting predominantly low-income countries and institutions. Here, a case is made for the use of free open source hardware in research and education, including countries and institutions where funds were never the biggest problem.

Debates continue over whether the prevailing neuroscientific model of addiction as a brain disease informs questions around moral and criminal responsibility, but little empirical work has been conducted with those tasked to address this question in practical terms on a daily basis. We have explored this point over two studies, respectively sampling 110 and 276 Magistrates active in the UK. In the first study we asked them to consider a criminal sentencing scenario in which evidence of a defendant’s brain damage and impaired impulse control was presented. This neurological damage was attributed to either a (fictional) disease or to addiction. When the same neuropsychiatric profile resulted from disease, rather than heroin use and addiction, custodial sentences were significantly reduced. The pivotal factor denying addiction the mitigating power of disease was perceived choice in the initial acquisition; removing choice from addiction dramatically increased the odds of sentence reduction, while attaching choice to disease tended to aggravate or reverse earlier leniency. The second study presented another criminal sentencing scenario in which the defendant exhibited similar neurological impairment, but additionally included ‘mixed’ aetiologies in which either disease led to addiction or addiction led to disease. Our results confirm the dramatic effect which the aetiology of impairment can have on judgements of criminal responsibility, whilst moreover give suggestion that drug-use tips the balance in favour of the punitive element when weighing criminal sentencing decisions.

Spontaneous otoacoustic emissions (SOAEs) recorded from the ear canal in the absence of sound reflect cochlear amplification, an outer-hair-cell (OHC) process required for the extraordinary sensitivity and frequency selectivity of mammalian hearing. Although wild-type mice rarely emit, those with mutations that influence the tectorial membrane (TM) show an incidence of SOAEs similar to that in humans. In this report, we characterized mice with a missense mutation in Tecta, a gene required for the formation of the striated-sheet matrix within the core of the TM. Mice heterozygous for the Y1870C mutation (TectaY1870C/+) are prolific emitters, despite a moderate hearing loss. Additionally, Kimura’s membrane, into which the OHC stereocilia insert, separates from the main body of the TM, except at apical cochlear locations. Multimodal SOAEs are also observed in TectaY1870C/+ mice where energy is present at frequencies that are integer multiples of a lower-frequency SOAE (the primary). Second-harmonic SOAEs, at twice the frequency of a lower-frequency primary, are the most frequently observed. These secondary SOAEs are found in spatial regions where stimulus-evoked OAEs are small or in the noise floor. Introduction of high-level suppressors just above the primary SOAE frequency reduce or eliminate both primary and second-harmonic SOAEs. In contrast, second-harmonic SOAEs are not affected by suppressors, either above or below the second-harmonic SOAE frequency, even when they are much larger in amplitude. Hence, second-harmonic SOAEs do not appear to be spatially separated from their primaries, a finding that has implications for cochlear mechanics and the consequences of changes to TM structure.

Sensory processing can be tuned by a neuron’s integration area, the types of inputs, and the proportion and number of connections with those inputs. Integration areas often vary topographically to sample space differentially across regions. Here, we highlight two visual circuits in which topographic changes in the postsynaptic retinal ganglion cell (RGC) dendritic territories and their presynaptic bipolar cell (BC) axonal territories are either matched or unmatched. Despite this difference, in both circuits, the proportion of inputs from each BC type, i.e., synaptic convergence between specific BCs and RGCs, remained constant across varying dendritic territory sizes. Furthermore, synapse density between BCs and RGCs was invariant across topography. Our results demonstrate a wiring design, likely engaging homotypic axonal tiling of BCs, that ensures consistency in synaptic convergence between specific BC types onto their target RGCs while enabling independent regulation of pre- and postsynaptic territory sizes and synapse number between cell pairs.

Purpose: To determine whether the oxygen toxicity hypothesis can explain the distinctive spatio-temporal patterns of retinal degeneration associated with human retinitis pigmentosa (RP) and to predict the effects of antioxidant and trophic factor treatments under this hypothesis.

Methods: Three mathematical models were derived to describe the evolution of the retinal oxygen concentration and photoreceptor density over time. The first model considers only hyperoxia-induced degeneration, while the second and third models include mutation-induced rod and cone loss respectively. The models were formulated as systems of partial differential equations, defined on a two-dimensional domain spanning the region between the foveal center and the ora serrata, and were solved numerically using the finite element method.

Results: The mathematical models recapitulate patterns of retinal degeneration which involve preferential loss of photoreceptors in the parafoveal/perifoveal and far-peripheral retina, while those which involve a preferential loss of midperipheral photoreceptors cannot be reproduced. Treatment with antioxidants or trophic factors is predicted to delay, halt, or partially reverse retinal degeneration, depending upon the strength and timing of treatment and disease severity.

Conclusions: The model simulations indicate that while the oxygen toxicity hypothesis is sufficient to explain some of the patterns of retinal degeneration observed in human RP, additional mechanisms are necessary to explain the full range of behaviors. The models further suggest that antioxidant and trophic factor treatments have the potential to reduce hyperoxia-induced disease severity and that, where possible, these treatments should be targeted at retinal regions with low photoreceptor density to maximize their efficacy.

As the development of new classes of antibiotics slows, bacterial resistance to existing antibiotics is becoming an increasing problem. A potential solution is to develop treatment strategies with an alternative mode of action. We consider one such strategy: anti-adhesion therapy. Whereas antibiotics act directly upon bacteria, either killing them or inhibiting their growth, anti-adhesion therapy impedes the binding of bacteria to host cells. This prevents bacteria from deploying their arsenal of virulence mechanisms, while simultaneously rendering them more susceptible to natural and artificial clearance. In this paper, we consider a particular form of anti-adhesion therapy, involving biomimetic multivalent adhesion molecule 7 coupled polystyrene microbeads, which competitively inhibit the binding of bacteria to host cells. We develop a mathematical model, formulated as a system of ordinary differential equations, to describe inhibitor treatment of a Pseudomonas aeruginosa burn wound infection in the rat. Benchmarking our model against in vivo data from an ongoing experimental programme, we use the model to explain bacteria population dynamics and to predict the efficacy of a range of treatment strategies, with the aim of improving treatment outcome. The model consists of two physical compartments: the host cells and the exudate. It is found that, when effective in reducing the bacterial burden, inhibitor treatment operates both by preventing bacteria from binding to the host cells and by reducing the flux of daughter cells from the host cells into the exudate. Our model predicts that inhibitor treatment cannot eliminate the bacterial burden when used in isolation; however, when combined with regular or continuous debridement of the exudate, elimination is theoretically possible. Lastly, we present ways to improve therapeutic efficacy, as predicted by our mathematical model.

Impulsivity refers to both a stable personality trait and a set of behaviours which undergo momentary changes depending on the current circumstances. Impulsivity plays a vital role in daily life as well as clinical practice as it is associated with drug misuse and certain neuropsychiatric conditions. Because of its great health and well-being importance, it is crucial to understand factors which modulate impulsive behaviours. The current studies investigated the role of emotions and physiological arousal as modulators of impulsive actions and decisions in healthy individuals.

A set of experiments was conducted using a variety of methods including behavioural testing, physiological recordings, psychopharmacology and neuroimaging. Studies 1 and 2 clarified the influence of emotional states on distinct dimensions of impulsive behaviours. Study 3 investigated the neural correlates behind the impact of emotions on impulsive actions. Finally, studies 4 and 5 focused on the relationship between physiological arousal and behavioural and trait impulsivity.

Our findings demonstrate that a degree to which one’s internal (emotional or physiological) state changes, is associated with behavioural impulsivity level. Importantly, distinct dimensions of impulsivity are differentially sensitive to those changes. Namely, increased state level of physiological arousal is associated with decreased motor ‘stopping’ impulsivity, enhanced subjective ratings and objective measurements of arousal are also related to decreased temporal impulsivity. Increased ratings of stress and increased physiological arousal, however, are associated with higher reflection impulsivity. At the neural level, successful response inhibition requires enhanced activation of prefrontal and parietal areas in impulsive individuals, particularly in negative emotional context, suggesting that behavioural control might be more effortful for highly impulsive individuals.

In conclusion, changes in internal bodily state are related to behavioural impulsivity level. Staying more attuned to those changes and finding adaptive ways to adjust behaviour according to bodily needs might be vital to reducing impulsivity levels.

In Alzheimer’s disease (AD) and other tauopathies, soluble tau protein self-assembles into insoluble aggregates. In AD, tau is deposited as neurofibrillary tangles (NFTs) composed mainly of paired helical filaments (PHFs). The structural core of PHFs is made up of two protofilaments with C-shaped subunits. There is a need for a relevant model of tau aggregation that does not require non-physiological inducers of aggregation, to permit the study of inhibition of tau aggregation and tau seeding in a physiological environment. The tau protein fragment, dGAE (amino acids 297-391) maps onto the proteolytically-stable PHF-core tau sequence and represents a model system with which to understand the cellular effects of misfolded tau.
In this thesis, dGAE self-assembly was characterised in vitro, to investigate changes to dGAE size and morphology over the course of assembly and the role of disulphide bonds in this process. Here, we show that dGAE assembles into filaments that resemble PHFs from AD brain, but this process does not depend on Cys-322. The effect of the small molecule, MT, on dGAE self-assembly was investigated, showing that MT must be reduced to LMT to efficiently inhibit dGAE self-assembly and forms species with an alternative conformation. The effect of exogenously-applied dGAE on cell viability, internalisation and seeding capabilities were examined in differentiated SH-SY5Y human neuroblastoma cells, which do not overexpress aggregation prone mutant tau or tau fragments. These cells can internalise dGAE in a soluble form and accumulates within the cytoplasm. Exposure to exogenous dGAE induces changes to endogenously expressed tau, namely a redistribution and increase in phosphorylated endogenous tau.
The results presented in this thesis characterise the self-assembly of the PHF core under physiological conditions and aids in understanding the process leading to PHF formation. This approach will provide a useful tool to facilitate the study of tau aggregation and ultimately to study the potential of tau aggregation inhibitors to target tau seeding activity.

TDP-43-mediated proteinopathy is a key factor in the pathology of amyotrophic lateral sclerosis (ALS). A potential underlying mechanism is dysregulation of the cytoskeleton. Here we investigate the effects of expressing TDP-43 wild-type and M337V and Q331K mutant isoforms on cytoskeletal integrity and function, using rat cortical neurons in vitro. We find that TDP-43 protein becomes mislocalised in axons over 24–72 hours in culture, with protein aggregation occurring at later timepoints (144 hours). Quantitation of cell viability showed toxicity of both wild-type and mutant constructs which increased over time, especially of the Q331K mutant isoform. Analysis of the effects of TDP-43 on axonal integrity showed that TDP-43-transfected neurons had shorter axons than control cells, and that growth cone sizes were smaller. Axonal transport dynamics were also impaired by transfection with TDP-43 constructs. Taken together these data show that TDP-43 mislocalisation into axons precedes cell death in cortical neurons, and that cytoskeletal structure and function is impaired by expression of either TDP-43 wild-type or mutant constructs in vitro. These data suggest that dysregulation of cytoskeletal and neuronal integrity is an important mechanism for TDP-43-mediated proteinopathy.

Understanding how neurons encode and compute information is fundamental to our study of the brain, but opportunities for hands-on experience with neurophysiological techniques on live neurons are scarce in science education. Here, we present Spikeling, an open source in silico implementation of a spiking neuron that costs £25 and mimics a wide range of neuronal behaviours for classroom education and public neuroscience outreach. Spikeling is based on an Arduino microcontroller running the computationally efficient Izhikevich model of a spiking neuron. The microcontroller is connected to input ports that simulate synaptic excitation or inhibition, to dials controlling current injection and noise levels, to a photodiode that makes Spikeling light sensitive, and to a light-emitting diode (LED) and speaker that allows spikes to be seen and heard. Output ports provide access to variables such as membrane potential for recording in experiments or digital signals that can be used to excite other connected Spikelings. These features allow for the intuitive exploration of the function of neurons and networks mimicking electrophysiological experiments. We also report our experience of using Spikeling as a teaching tool for undergraduate and graduate neuroscience education in Nigeria and the United Kingdom.

In clinical populations, olfactory abilities parallel executive function, implicating shared
neuroanatomical substrates within the ventral prefrontal cortex. In healthy individuals, the relationship
between olfaction and personality traits or certain cognitive and behavioural characteristics remains
unexplored. We therefore tested if olfactory function is associated with trait and behavioural impulsivity
in nonclinical individuals. Eighty-three healthy volunteers (50 females) underwent quantitative
assessment of olfactory function (odour detection threshold, discrimination, and identifcation). Each
participant was rated for trait impulsivity index using the Barratt Impulsiveness Scale and performed
a battery of tasks to assess behavioural impulsivity (Stop Signal Task, SST; Information Sampling
Task, IST; Delay Discounting). Lower odour discrimination predicted high ratings in non-planning
impulsivity (Barratt Non-Planning impulsivity subscale); both, lower odour discrimination and detection
threshold predicted low inhibitory control (SST; increased motor impulsivity). These fndings extend
clinical observations to support the hypothesis that defcits in olfactory ability are linked to impulsive
tendencies within the healthy population. In particular, the relationship between olfactory abilities and
behavioural inhibitory control (in the SST) reinforces evidence for functional overlap between neural
networks involved in both processes. These fndings may usefully inform the stratifcation of people at
risk of impulse-control-related problems and support planning early clinical interventions.

We assessed here functional connectivity changes in the locus coeruleus (LC) and ventral tegmental area (VTA) of patients with Alzheimer's disease (AD). We recruited 169 patients with either AD or amnestic mild cognitive impairment due to AD and 37 elderly controls who underwent cognitive and neuropsychiatric assessments and resting-state functional magnetic resonance imaging at 3T. Connectivity was assessed between LC and VTA and the rest of the brain. In amnestic mild cognitive impairment patients, VTA disconnection was predominant with parietal regions, while in AD patients, it involved the posterior nodes of the default-mode network. We also looked at the association between neuropsychiatric symptoms (assessed by the neuropsychiatric inventory) and VTA connectivity. Symptoms such as agitation, irritability, and disinhibition were associated with VTA connectivity with the parahippocampal gyrus and cerebellar vermis, while sleep and eating disorders were associated with VTA connectivity to the striatum and the insular cortex. This suggests a contribution of VTA degeneration to AD pathophysiology and to the occurrence of neuropsychiatric symptoms. We did not find evidence of LC disconnection, but this could be explained by the size of this nucleus, which makes it difficult to isolate. These results are consistent with animal findings and have potential implications for AD prognosis and therapies.

Disruptions of normal Hox gene expression can lead to severe morphological defects revealing a link between the regulation of Hox expression and pattern formation. Here we explore these links focusing on the impact of microRNA regulation on the expression of the Drosophila Hox gene Ultrabithorax (Ubx) during haltere development. Through the combination of bioinformatic and transcriptomic analyses we identify the miR-310/313 cluster (miR-310C) as a candidate regulator of Ubx. Several experiments confirm this. First, miR-310C and Ubx protein show complementary expression patterns in haltere imaginal discs; second, artificial activation of miR-310C expression in haltere discs leads to Ubx-like phenotypes. Third, expression of a fluorescent reporter bearing Ubx 3'UTR sequences is reduced when co-expressed with miR-310C Fourth, deletion of miR-310C leads to Ubx upregulation and changes the array of mechanosensory sensilla at the base of the haltere. Fifth, artificial increase of Ubx levels within the miR-310C expression domain phenocopies the mechanosensory defects observed in miR-310C mutants. We propose that miR-310C-mediated repression delimits Ubx fine-grain expression contributing to the sculpting of complex morphologies in the Drosophila haltere. Our work reveals a novel role of microRNA regulation in the control of Hox gene expression with impact on morphology.

Hunger state can substantially alter the perceived value of a stimulus, even to the extent that the same sensory cue can trigger antagonistic behaviors. How the nervous system uses these graded perceptual shifts to select between opposed motor patterns remains enigmatic. Here, we challenged food-deprived and satiated Lymnaea to choose between two mutually exclusive behaviors, ingestion or egestion, produced by the same feeding central pattern generator. Decoding the underlying neural circuit reveals that the activity of central dopaminergic interneurons defines hunger state and drives network reconfiguration, biasing satiated animals toward the rejection of stimuli deemed palatable by food-deprived ones. By blocking the action of these neurons, satiated animals can be reconfigured to exhibit a hungry animal phenotype. This centralized mechanism occurs in the complete absence of sensory retuning and generalizes across different sensory modalities, allowing food-deprived animals to increase their perception of food value in a stimulus-independent manner to maximize potential calorific intake.

Amyloid proteins feature in neurodegenerative diseases and functionally throughout many organisms. Furthermore, due to their structural properties, amyloid proteins have been developed as materials in biotechnology. This raises the question of what makes disease-related amyloid proteins toxic. β-amyloid 1-42 (Aβ42) is a self-assembling protein that goes through many structural changes before forming the extracellular plaques characteristic of Alzheimer's disease. We have studied the conformational changes of the Aβ42 peptide over time by combining a range of biophysical approaches including circular dichroism, and Thioflavin T fluorescence with Transmission Electron Microscopy. Aβ42 assembly is compared to a novel, rationally-designed, assembly-resistant Aβ42 peptide variant (vAβ42), as well as the two main Aβ42 controls, Aβ reversed (Aβ42-1)and Aβ scrambled (AβS). The vAβ42 differs in sequence by only two amino acids, however, does not self-assemble or form β-sheet structures, unlike Aβ42-1and AβS which both display a high propensity to form amyloid. All three variants of Aβ42 were non-toxic in primary hippocampal cultures, highlighting the importance of primary sequence in determining the toxic nature of an amyloid protein. Furthermore, the structure andtoxicity of the naturally functional amyloid protein, GNNQQNY,and the designedfunctional amyloid peptide, FEFKFEFKK (F9), have also been characterised. These show immediate assembly into mature fibrils, do not form intermediary species and are not cytotoxic. Together, this data suggests the ability to form oligomers and the time spent in this conformation is a requirement of amyloid toxicity. To further investigate the link between size, conformation and toxicity, we compared the cytotoxicity and internalisation of oligomeric, fibrillar and sonicated fibres of Aβ42 in primary hippocampal neurons using immunolabelling and live cell imaging. As expected, the oligomeric Aβ42 was highly neurotoxic in hippocampal cultures, however fibrillar and sonicated fibrils did not have the same effect. Finally, the necessity of internalisation in mediating cytotoxicity was investigated and showed a certain threshold of intracellular accumulation must be met to induce cytotoxicity. Overall, our data suggests primary sequence, the resultant self-assembly and intermediary species formed, and intracellular accumulation are vital in determining the pathogenic properties of amyloid proteins.

Lithium has long been used for the treatment of psychiatric disorders, due to its robust beneficial effect as a mood stabilizing drug. Lithium’s effectiveness for improving neurological function is therefore well-described, stimulating the investigation of its potential use in several neurodegenerative conditions including Alzheimer’s (AD), Parkinson’s (PD) and Huntington’s (HD) diseases. A narrow therapeutic window for these effects, however, has led to concerted efforts to understand the molecular mechanisms of lithium action in the brain, in order to develop more selective treatments that harness its neuroprotective potential whilst limiting contraindications. Animal models have proven pivotal in these studies, with lithium displaying advantageous effects on behavior across species, including worms (C. elegans), zebrafish (Danio rerio), fruit flies (Drosophila melanogaster) and rodents. Due to their susceptibility to genetic manipulation, functional genomic analyses in these model organisms have provided evidence for the main molecular determinants of lithium action, including inhibition of inositol monophosphatase (IMPA) and glycogen synthase kinase-3 (GSK-3). Accumulating pre-clinical evidence has indeed provided a basis for research into the therapeutic use of lithium for the treatment of dementia, an area of medical priority due to its increasing global impact and lack of disease-modifying drugs. Although lithium has been extensively described to prevent AD-associated amyloid and tau pathologies, this review article will focus on generic mechanisms by which lithium preserves neuronal function and improves memory in animal models of dementia. Of these, evidence from worms, flies and mice points to GSK-3 as the most robust mediator of lithium’s neuro-protective effect, but it’s interaction with downstream pathways, including Wnt/β-catenin, CREB/brain-derived neurotrophic factor (BDNF), nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and toll-like receptor 4 (TLR4)/nuclear factor-κB (NFκB), have identified multiple targets for development of drugs which harness lithium’s neurogenic, cytoprotective, synaptic maintenance, anti-oxidant, anti-inflammatory and protein homeostasis properties, in addition to more potent and selective GSK-3 inhibitors. Lithium, therefore, has advantages as a multi-functional therapy to combat the complex molecular pathology of dementia. Animal studies will be vital, however, for comparative analyses to determine which of these defense mechanisms are most required

In view of the prevalence of sensorineural hearing defects in an ageing population, the development of protocols to generate cochlear hair cells and their associated sensory neurons as tools to further our understanding of inner ear development are highly desirable. We report herein a robust protocol for the generation of both vestibular and cochlear hair cells from human pluripotent stem cells which represents an advance over currently available methods that have been reported to generate vestibular hair cells only. Generating otic organoids from human pluripotent stem cells using a three-dimensional culture system, we show formation of both types of sensory hair cells bearing stereociliary bundles with active mechano-sensory ion channels. These cells share many morphological characteristics with their in vivo counterparts during embryonic development of the cochlear and vestibular organs and moreover demonstrate electrophysiological activity detected through single-cell patch clamping. Collectively these data represent an advance in our ability to generate cells of an otic lineage and will be useful for building models of the sensory regions of the cochlea and vestibule.

In the adult auditory organ, mechanoelectrical transducer (MET) channels are essential for transducing acoustic stimuli into electrical signals. In the absence of incoming sound, a fraction of the MET channels on top of the sensory hair cells are open, resulting in a sustained depolarizing current. By genetically manipulating the in vivo expression of molecular components of the MET apparatus, we show that during pre-hearing stages the MET current is essential for establishing the electrophysiological properties of mature inner hair cells (IHCs). If the MET current is abolished in adult IHCs, they revert into cells showing electrical and morphological features characteristic of pre-hearing IHCs, including the re-establishment of cholinergic efferent innervation. The MET current is thus critical for the maintenance of the functional properties of adult IHCs, implying a degree of plasticity in the mature auditory system in response to the absence of normal transduction of acoustic signals.

Alzheimer's disease (AD) is a tauopathy characterised by pathological fibrillisation of tau protein to form the paired helical filaments (PHFs) which constitute neurofibrillary tangles. The methylthioninium (MT) moiety reverses the proteolytic stability of the PHF core and is in clinical development for treatment of AD in a stable reduced form as leuco-MT (LMT). It has been hypothesised that MT acts via oxidation of cysteine residues which is incompatible with activity in the predominantly reducing environment of living cells. We have shown recently that the PHF-core tau unit assembles spontaneously in vitro to form PHF-like filaments. Here we describe studies using circular dichroism, SDS-polyacrylamide gel electrophoresis, transmission electron microscopy and site-directed mutagenesis to elucidate the mechanism of action of the MT moiety. We show that MT inhibitory activity is optimal in reducing conditions, that the active moiety is the reduced LMT form of the molecule, and that its mechanism of action is cysteine-independent.

Single cell mass spectrometry (MS) is uniquely positioned for the sequencing and identification of peptides in rare cells. Small peptides can take on different roles in subcellular compartments. Whereas some peptides serve as neurotransmitters in the cytoplasm, they can also function as transcription factors in the nucleus. Thus, there is a need to analyze the subcellular peptide compositions in identified single cells. Here, we apply capillary microsampling MS with ion mobility separation for the sequencing of peptides in single neurons of the mollusk Lymnaea stagnalis, and the analysis of peptide distributions between the cytoplasm and nucleus of identified single neurons that are known to express cardioactive Phe-Met-Arg-Phe amide-like (FMRFamide-like) neuropeptides. Nuclei and cytoplasm of Type 1 and Type 2 F group (Fgp) neurons were analyzed for neuropeptides cleaved from the protein precursors encoded by alternative splicing products of the FMRFamide gene. Relative abundances of nine neuropeptides were determined in the cytoplasm. The nuclei contained six of these peptides at different abundances. Enabled by its relative enrichment in Fgp neurons, a new 28-residue neuropeptide was sequenced by tandem MS.

Alzheimer’s disease (AD) is the most common form of dementia and is distinguished from other dementias by observation of extracellular Amyloid-b (Ab) plaques and intracellular neurofibrillary tangles, comprised of fibrils of Ab and tau protein, respectively. At early stages, AD is characterized by minimal neurodegeneration, oxidative stress, nucleolar stress, and altered protein synthesis machinery. It is generally believed that Ab oligomers are the neurotoxic species and their levels in the AD brain correlate with the severity of dementia suggesting that they play a critical role in the pathogenesis of the disease. Here, we show that the incubation of differentiated human neuroblastoma cells (SHSY5Y) with freshly prepared Ab42 oligomers initially resulted in oxidative stress and subtle nucleolar stress in the absence of DNA damage or cell death. The presence of exogenous Ab oligomers resulted in altered nuclear tau levels as well as phosphorylation state, leading to altered distribution of nucleolar tau associated with nucleolar stress. These markers of cellular dysfunction worsen over time alongside a reduction in ribosomal RNA synthesis and processing, a decrease in global level of newly synthesized RNA and reduced protein synthesis. The interplay between Ab and tau in AD remains intriguing and Ab toxicity has been linked to tau phosphorylation and changes in localization. These findings provide evidence for the involvement of Ab42 effects on nucleolar tau and protein synthesis machinery dysfunction in cultured cells. Protein synthesis dysfunction is observed in mild cognitive impairment and early AD in the absence of significant neuronal death.

Tau is known for its pathological role in neurodegenerative diseases, including Alzheimer’s disease (AD) and other tauopathies. Tau is found in many subcellular compartments such as the cytosol and the nucleus. Although its normal role in microtubule binding is well established, its nuclear role is still unclear. Here, we reveal that tau localises to the nucleolus in undifferentiated and differentiated neuroblastoma cells (SHSY5Y), where it associates with TIP5, a key player in heterochromatin stability and ribosomal DNA (rDNA) transcriptional repression. Immunogold labelling on human brain sample confirms the physiological relevance of this finding by showing tau within the nucleolus colocalises with TIP5. Depletion of tau results in an increase in rDNA transcription with an associated decrease in heterochromatin and DNA methylation, suggesting that under normal conditions tau is involved in silencing of the rDNA. Cellular stress induced by glutamate causes nucleolar stress associated with the redistribution of nucleolar non-phosphorylated tau, in a similar manner to fibrillarin, and nuclear upsurge of phosphorylated tau (Thr231) which doesn’t colocalise with fibrillarin or nucleolar tau. This suggests that stress may impact on different nuclear tau species. In addition to involvement in rDNA transcription, nucleolar non-phosphorylated tau also undergoes stress-induced redistribution similar to many nucleolar proteins

Cytoplasmic dynein 1 (hereafter referred to simply as dynein) is a dimeric motor protein that walks and transports intracellular cargos towards the minus end of microtubules. In this article, we formulate, based on physical principles, a mechanical model to describe the stepping behaviour of cytoplasmic dynein walking on microtubules from the cell membrane towards the nucleus. Unlike previous studies on physical models of this nature, we base our formulation on the whole structure of dynein to include the temporal dynamics of the individual subunits such as the cargo ( for example, an endosome, vesicle or bead), two rings of six ATPase domains associated with diverse cellular activities (AAAþ rings) and the microtubule-binding domains which allow dynein to bind to microtubules. This mathematical framework allows us to examine experimental observations on dynein across a wide range of different species, as well as being able to make predictions on the temporal behaviour of the individual components of dynein not currently experimentally measured. Furthermore, we extend the model framework to include backward stepping, variable step size and dwelling. The power of our model is in its predictive nature; first it reflects recent experimental observations that dynein walks on microtubules using a weakly coordinated stepping pattern with predominantly not passing steps. Second, the model predicts that interhead coordination in the ATP cycle of cytoplasmic dynein is important in order to obtain the alternating stepping patterns and long run lengths seen in experiments.

The lateral line organ in fish and amphibians transforms fluid motion in the animal’s surroundings into a representation of its hydrodynamic environment. This sense is involved in complex behaviors, ranging from rheotaxis to schooling. The primary sensory neurons are hair cells, each of which can tonically transmit a graded ‘analog’ signal to afferent neurons, via highly specialized ‘ribbon’ synapses. Many questions about this first step in sensory coding remain to be answered. For example: What is the relationship between the biologically relevant stimulus and hair cell output? How do the synaptic properties of different hair cells contribute to the signal that is sent to the brain? And how are these signals modulated by top-down (efferent) projections? The first chapter of this thesis describes a newly established preparation including an overview of transgenic fish lines, some of which were newly generated, to study the processing of mechanical information in larval zebrafish at various stages, from the periphery to the hindbrain. The second chapter contains a detailed characterization of the relationship between cupula deflection and hair-cell glutamate release. We show that the population of hair cells in the lateral line is highly heterogeneous in terms of their sensitivity, dynamic range and adaptive properties and that this heterogeneity has functional implications for downstream processing. These results are unique because of how well the biophysical, anatomical and physiological context of the actual sensory transduction is maintained. The third chapter describes the effects of (fictive) locomotion on the processing of mechanical information. We show that an efferent signal, which is highly correlated with motor neuron activity, is present in the neuromast and leads to a strong suppression of mechanically induced activity of afferent neurons. This efference copy appears to selectively reduce the gain to hair cells sensitive to posterior cupula deflections.

In this study we investigated effects of the APOE ε4 allele (which confers an enhanced risk of poorer cognitive ageing, and Alzheimer’s Disease) on sustained attention (vigilance) performance in young adults using the Rapid Visual Information Processing (RVIP) task and event-related fMRI. Previous fMRI work with this task has used block designs: this study is the first to image an extended (6-minute) RVIP task. Participants were 26 carriers of the APOE ε4 allele, and 26 non carriers (aged 18–28). Pupil diameter was measured throughout, as an index of cognitive effort. We compared activity to RVIP task hits to hits on a control task (with similar visual parameters and response requirements but no working memory load): this contrast showed activity in medial frontal, inferior and superior parietal, temporal and visual cortices, consistent with previous work, demonstrating that meaningful neural data can be extracted from the RVIP task over an extended interval and using an event-related design. Behavioural performance was not affected by genotype; however, a genotype by condition (experimental task/control task) interaction on pupil diameter suggested that ε4 carriers deployed more effort to the experimental compared to the control task. fMRI results showed a condition by genotype interaction in the right hippocampal formation: only ε4 carriers showed downregulation of this region to experimental task hits versus control task hits. Experimental task beta values were correlated against hit rate: parietal correlations were seen in ε4 carriers only, frontal correlations in non-carriers only. The data indicate that, in the absence of behavioural differences, young adult ε4 carriers already show a different linkage between functional brain activity and behaviour, as well as aberrant hippocampal recruitment patterns. This may have relevance for genotype differences in cognitive ageing trajectories.

Animal eyes have evolved to process behaviourally important visual information, but how retinas deal with statistical asymmetries in visual space remains poorly understood. Using hyperspectral imaging in the field, in-vivo 2-photon imaging of retinal neurons and anatomy, here we show that larval zebrafish use a highly anisotropic retina to asymmetrically survey their natural visual world. First, different neurons dominate different parts of the eye, and are linked to a systematic shift in inner retinal function: Above the animal, there is little colour in nature and retinal circuits are largely achromatic. Conversely, the lower visual field and horizon are colour-rich and are predominately surveyed by chromatic and colour-opponent circuits that are spectrally matched to the dominant chromatic axes in nature. Second, in the horizontal and lower visual field bipolar cell terminals encoding achromatic and colour opponent visual features are systematically arranged into distinct layers of the inner retina. Third, above the frontal horizon, a high-gain ultraviolet-system piggy-backs onto retinal circuits, likely to support prey-capture.

Action potential shape is a major determinant of synaptic transmission and mechanisms of spike-tuning are therefore of key functional significance. Here we demonstrate that synaptic activity itself modulates future spikes in the same neuron via a rapid feedback pathway. Using Ca2+ imaging and targeted uncaging approaches in layer 5 neocortical pyramidal neurons we show that the single spike-evoked Ca2+ rise occurring in one proximal bouton or first node of Ranvier drives a significant sharpening of subsequent action potentials recorded at the soma. This form of intrinsic modulation, mediated by the activation of large conductance Ca2+/voltage-dependent K+ channels (BK channels), acts to maintain high-frequency firing and limit runaway spike broadening during repetitive firing, preventing an otherwise significant escalation of synaptic transmission. Our findings identify a novel short-term presynaptic plasticity mechanism that utilizes the activity-history of a bouton or adjacent axonal site to dynamically tune ongoing signalling properties.

Motor actions can be facilitated or hindered by psychophysiological states of readiness, to guide rapid adaptive action. Cardiovascular arousal is communicated by cardiac signals conveying the timing and strength of individual heartbeats. Here, we tested how these interoceptive signals facilitate control of motor impulsivity. Participants performed a stop signal task, in which stop cues were delivered at different time points within the cardiac cycle: at systole when the heart contracts (T-wave peak, approximately 300 ms following the R-wave), or at diastole between heartbeats (R-wave peak). Response inhibition was better at systole, indexed by a shorter stop signal reaction time (SSRT), and longer stop signal delay (SSD). Furthermore, parasympathetic control of cardiovascular tone, and subjective sensitivity to interoceptive states, predicted response inhibition efficiency, although these cardiovascular and interoceptive correlations did not survive correction for multiple comparisons. This suggests that response inhibition capacity is influenced by interoceptive physiological cues, such that people are more likely to express impulsive actions during putative states of lower cardiovascular arousal, when frequency and strength of cardiac afferent signalling is reduced.

Wood ants are a model system for studying visual learning and navigation. They can forage for food and navigate to their nests effectively by forming memories of visual features in their surrounding environment. Previous studies of freely behaving ants have revealed many of the behavioural strategies and environmental features necessary for successful navigation. However, little is known about the exact visual properties of the environment that animals learn or the neural mechanisms that allow them to achieve this. As a first step towards addressing this, we developed a classical conditioning paradigm for visual learning in harnessed wood ants that allows us to control precisely the learned visual cues. In this paradigm, ants are fixed and presented with a visual cue paired with an appetitive sugar reward. Using this paradigm, we found that visual cues learnt by wood ants through Pavlovian conditioning are retained for at least one hour. Furthermore, we found that memory retention is dependent upon the ants’ performance during training. Our study provides the first evidence that wood ants can form visual associative memories when restrained. This classical conditioning paradigm has the potential to permit detailed analysis of the dynamics of memory formation and retention, and the neural basis of learning in wood ants.

Parkinson’s disease (PD) is conventionally seen as resulting from single-system neurodegeneration affecting nigrostriatal dopaminergic neurons. However, accumulating evidence indicates a multi-system degeneration and neurotransmitter deficiencies, including cholinergic neurons which degenerate in a brainstem nucleus, the pedunculopontine nucleus (PPN), resulting in motor- and cognitive impairments. The neuropeptide galanin can inhibit cholinergic transmission, whilst being upregulated in degenerating brain regions associated with cognitive decline. Here we determined the temporal-spatial profile of progressive expression of endogenous galanin within degenerating cholinergic neurons, across the rostro-caudal axis of the PPN, by utilising the lactacystin-induced rat model of PD. First, we show progressive neuronal death affecting nigral dopaminergic and PPN cholinergic neurons, reflecting that seen in PD patients, to facilitate use of this model for assessing the therapeutic potential of bioactive peptides. Next, stereological analyses of the lesioned brain hemisphere found that the number of PPN cholinergic neurons expressing galanin increased by 11%, compared to sham-lesioned controls, increasing by a further 5% as the neurodegenerative process evolved. Galanin upregulation within cholinergic PPN neurons was most prevalent closest to the intra-nigral lesion site, suggesting that galanin upregulation in such neurons adapt intrinsically to neurodegeneration, to possibly neuroprotect. This is the first report on the extent and pattern of galanin expression in cholinergic neurons across distinct PPN subregions in both the intact rat CNS and lactacystin lesioned rats. The findings pave the way for future work to target galanin signaling in the PPN, to determine the extent to which upregulated galanin expression could offer a viable treatment strategy for ameliorating PD symptoms associated with cholinergic degeneration.

To compare information and reach decisions effectively, our brain uses multiple heuristics, which can, however, induce biases in behavior. An elegant study by Akrami et al. (2018) finds evidence for one such heuristic in a sensory-based comparison task and identifies its location to the posterior parietal cortex.

Although single-trial induced long-term memories (LTM) have been of major interest in neuroscience, how LTM can form after a single episode of learning remains largely unknown. We hypothesized that the removal of molecular inhibitory constraints by microRNAs (miRNAs) plays an important role in this process. To test this hypothesis, first we constructed small non-coding RNA (sncRNA) cDNA libraries from the CNS of Lymnaea stagnalis subjected to a single conditioning trial. Then, by next generation sequencing of these libraries, we identified a specific pool of miRNAs regulated by training. Of these miRNAs, we focussed on Lym-miR-137 whose seed region shows perfect complementarity to a target sequence in the 3’ UTR of the mRNA for CREB2, a well-known memory repressor. We found that Lym-miR-137 was transiently up-regulated 1 h after single-trial conditioning, preceding a down-regulation of Lym-CREB2 mRNA. Furthermore, we discovered that Lym-miR-137 is co-expressed with Lym-CREB2 mRNA in an identified neuron with an established role in LTM. Finally, using an in vivo loss-of-function approach we demonstrated that Lym-miR-137 is required for single-trial induced LTM.

A technology abbreviated as DREADDs (designer receptors exclusively activated by designer drugs) uses synthetically derived receptors and selective, otherwise inert, exogenous ligands to transiently activate or inactivate targeted neuronal types within specific brain regions. A range of transfer strategies (but principally using viral vector infection methods) are used for delivering DREADD receptors into neural tissue, with stereotaxic microinjection of the virus into a particular location that refines spatial specificity of DREADD expression.
Designer Receptors Exclusively Activated by Designer Drugs section of the current chapter will serve readers with a basic overview of the principles underlying the workings of DREADDs (Fig. 24.1), but it does not intend to be exhaustive as to the cellular and molecular mechanisms underlying application of DREADDs. Interested readers seeking greater details pertaining to DREADDs' molecular mechanisms of action are referred to several excellent review articles, e.g., by Armbruster et al.1; Ferguson and Neumaier2; Rogan and Roth3; Sternson and Roth;4 and Roth.5 Designer Receptors Exclusively Activated by Designer Drugs section also reviews recent advances to the DREADD toolbox. Neurodegenerative Disease section seeks to highlight the tremendous potential held by the DREADD approach in many research areas relating to neurodegenerative disease, by highlighting recently developed approaches and applications. In particular, after an overview of the causes and features of two prominent neurodegenerative diseases, namely Alzheimer disease (AD) and Parkinson disease (PD), we review highlights from studies that have applied DREADD technologies to answer questions relating to both diseases, by making use of preclinical models, presented as a series of case studies. The findings from such studies pave the way toward use of DREADDs for relatively noninvasive, selective, reversible responses by neuronal populations and circuits, by means of a dose-responsive orally administered agonist that targets the human brain. Hence, the chapter ends (Translational Potential of Chemogenetics for Treating Neurodegenerative section) by reflecting on the potential that DREADDs offer to aid in the development of novel therapeutic treatments against neurodegenerative disease.

P2X4 is an ATP-gated cation channel that is widely expressed in most tissues in the body and at especially high levels within immune, endothelial, and epithelial cells. This channel plays a role in the secretion of inflammatory mediators, including brain-derived neurotrophic factor and prostaglandin E2, and as a regulator of cardiac contractility and vascular remodeling (Stokes et al., 2017; Suurväli et al., 2017). Within the P2X family, P2X4 has a unique subcellular distribution that is predominantly intracellular, within endolysosomal compartments (Bobanovic et al., 2002; Qureshi et al., 2007). This unusual distribution has sparked a debate about whether it might function at endolysosomal membranes in addition to its role at the plasma membrane. Patch-clamp recordings of ATP-evoked currents from enlarged vacuolar lysosomes have supported this view and revealed that lysosomal P2X4 receptors are under the dual regulation of intraluminal ATP and pH (Huang et al., 2014). The evidence to date suggests that P2X4 is one of several highly Ca2+-permeable lysosomal channels that control lysosomal Ca2+ fluxes and lysosome membrane trafficking events (Cao et al., 2015). Much of this evidence is based, however, on pharmacological manipulation of lysosome pH. In this issue of the Journal of General Physiology, Fois et al. provide a clearer description of the physiological role of lysosomal P2X4 receptors during the secretion of surfactant from alveolar type II (ATII) epithelial cells.

Our sensory receptors are faced with an onslaught of different environmental inputs. Each sensory event or encounter with an object involves a distinct combination of physical energy sources impinging upon receptors. In the rodent whisker system, each primary afferent neuron located in the trigeminal ganglion innervates and responds to a single whisker and encodes a distinct set of physical stimulus properties – features – corresponding to changes in whisker angle and shape and the consequent forces acting on the whisker follicle. Here we review the nature of the features encoded by successive stages of processing along the whisker pathway. At each stage different neurons respond to distinct features, such that the population as a whole represents diverse properties. Different neuronal types also have distinct feature selectivity. Thus, neurons at the same stage of processing and responding to the same whisker nevertheless play different roles in representing objects contacted by the whisker. This diversity, combined with the precise timing and high reliability of responses, enables populations at each stage to represent a wide range of stimuli. Cortical neurons respond to more complex stimulus properties – such as correlated motion across whiskers – than those at early subcortical stages. Temporal integration along the pathway is comparatively weak: neurons up to barrel cortex are sensitive mainly to fast (tens of milliseconds) fluctuations in whisker motion. The topographic organization of whisker sensitivity is paralleled by systematic organization of neuronal selectivity to certain other physical features, but selectivity to touch and to dynamic stimulus properties is distributed in “salt-and-pepper” fashion.