Ezrin-Radixin-Moesin (ERM) proteins are actin-binding proteins that contribute to morphological changes in dendritic spines. Despite their significant role in regulating spine structure, the role of ERM proteins in the n...Ezrin-Radixin-Moesin (ERM) proteins are actin-binding proteins that contribute to morphological changes in dendritic spines. Despite their significant role in regulating spine structure, the role of ERM proteins in the nucleus accumbnes (NAcc) is not well known, especially in in the context of risk-reward decision-making. Here, we measured the relationship between synaptic excitation and inhibition (E/I ratio) from medium spiny neurons in the NAcc core obtained in the rat after a rat gambling task (rGT). Then, after surgery of a phosphomimetic pseudo-active mutant form of radixin (Rdx-T564D) in the NAcc core, we examined its role in synaptic plasticity and the accompanying risk-choice behavior in rGT. We found that basal E/I ratio in the NAcc core was higher in risk-averse rats than risk-seeking rats. However, it was significantly reduced in risk-averse rats similar to that in risk-seeking rats in the presence of Rdx-T564D in the NAcc core. Furthermore, the head sizes of spines were shifted in risk-averse rats expressing Rdx-T564D in the NAcc core, similar to those observed in risk-seeking rats. The effects of Rdx-T564D in risk-averse rats were again manifested as behavioral changes, with reduced selection of optimal choices and increased selection of disadvantageous ones. In this study, we demonstrated that manipulation of radixin phosphorylation status in the NAcc core can alter glutamatergic synaptic transmission and spine structure at this site, as well as risk choice behaviors in the rGT. These novel findings illustrate that radixin in the NAcc core plays a significant role in determining risk preference during the rGT.
Modulating the ER stress pathway holds therapeutic promise for neurodegenerative diseases; however, identifying optimal targets remains challenging. In this study, we conducted an unbiased screening to systematically sea...Modulating the ER stress pathway holds therapeutic promise for neurodegenerative diseases; however, identifying optimal targets remains challenging. In this study, we conducted an unbiased screening to systematically search for commonly up-regulated proteins in ER stress-related neurodegenerative conditions, with endoplasmic reticulum oxidoreductase 1 alpha (ERO1A) emerging as a significant hit. Further experiments conducted in the model organism Drosophila melanogaster demonstrated that elevated levels of Drosophila ERO1A (ERO1L) were indeed detrimental to neurons. Conversely, genetic suppression or pharmacological inhibition of ERO1L activity provided neuroprotection under ER stress and extended the lifespan of flies. To translate these findings, we performed a genetic modifier screening and underscored significant neuroprotective effects against UBQLN2 pathology. Additionally, administration of the chemical probe inhibitor of ERO1A, known as EN460, enhanced locomotive functions and neuromuscular junction (NMJ) morphology in Drosophila UBQLN2 model. Mechanistically, targeting ERO1L during environmental or pathological ER stress mitigated proteotoxic stress by lowering either the PERK or IRE1 branches of the unfolded protein response (UPR). These findings suggest ERO1A as a promising therapeutic target in UBQLN2 and other ER stress-related conditions.
Prog Neurobiol
· 2024 Nov · PMID 39389338
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Synaptic networks determine brain function. Highly complex interconnected brain synaptic networks provide output even under fluctuating or pathological conditions. Relevant to the treatment of brain disorders, understand...Synaptic networks determine brain function. Highly complex interconnected brain synaptic networks provide output even under fluctuating or pathological conditions. Relevant to the treatment of brain disorders, understanding the limitations of such functional networks becomes paramount. Here we use the example of Parkinson's Disease (PD) as a system disorder, with PD symptomatology emerging only when the functional reserves of neurons, and their interconnected networks, are unable to facilitate effective compensatory mechanisms. We have denoted this the "threshold theory" to account for how PD symptoms develop in sequence. In this perspective, threshold functions are delineated in a quantitative, synaptic, and cellular network context. This provides a framework to discuss the development of specific symptoms. PD includes dysfunction and degeneration in many organ systems and both peripheral and central nervous system involvement. The threshold theory accounts for and explains the reasons why parallel gradually emerging pathologies in brain and peripheral systems generate specific symptoms only when functional thresholds are crossed, like tipping points. New and mounting evidence demonstrate that PD and related neurodegenerative diseases are multisystem disorders, which transcends the traditional brain-centric paradigm. We believe that representation of threshold functions will be helpful to develop new medicines and interventions that are specific for both pre- and post-symptomatic periods of neurodegenerative disorders.
Sleep constitutes a brain state of disengagement from the external world that supports memory consolidation and restores cognitive resources. The precise mechanisms how sleep and its varied stages support information pro...Sleep constitutes a brain state of disengagement from the external world that supports memory consolidation and restores cognitive resources. The precise mechanisms how sleep and its varied stages support information processing remain largely unknown. Synaptic scaling models imply that daytime learning accumulates neural information, which is then consolidated and downregulated during sleep. Currently, there is a lack of in-vivo data from humans and rodents that elucidate if, and how, sleep renormalizes information processing capacities. From an information-theoretical perspective, a consolidation process should entail a reduction in neural pattern variability over the course of a night. Here, in a cross-species intracranial study, we identify a tradeoff in the neural population code during sleep where information coding efficiency is higher in the neocortex than in hippocampal archicortex in humans than in rodents as well as during wakefulness compared to sleep. Critically, non-REM sleep selectively reduces information coding efficiency through pattern repetition in the neocortex in both species, indicating a transition to a more robust information coding regime. Conversely, the coding regime in the hippocampus remained consistent from wakefulness to non-REM sleep. These findings suggest that new information could be imprinted to the long-term mnemonic storage in the neocortex through pattern repetition during sleep. Lastly, our results show that task engagement increased coding efficiency, while medically-induced unconsciousness disrupted the population code. In sum, these findings suggest that neural pattern variability could constitute a fundamental principle underlying cognitive engagement and memory formation, while pattern repetition reflects robust coding, possibly underlying the consolidation process.
Executive control of behaviour entails keeping a fine balance between response execution and action inhibition. The most anterior part of the prefrontal cortex (frontopolar cortex) is highly developed in anthropoids; how...Executive control of behaviour entails keeping a fine balance between response execution and action inhibition. The most anterior part of the prefrontal cortex (frontopolar cortex) is highly developed in anthropoids; however, no previous study has examined its essential (indispensable) role in regulating the interplay between action execution and inhibition. In this cross-species study, we examine the performance of humans and macaque monkeys in the context of a stop-signal task and then assess the consequence of selective and bilateral damage to frontopolar cortex on monkeys' behaviour. Humans and monkeys showed significant within-session practice-related adjustments in both response execution (increase in response time (RT) and decrease in response variabilities) and action inhibition (enhanced inhibition). Furthermore, both species expressed context-dependent (post-error and post-stop) behavioral adjustments. In post-lesion testing, frontopolar-damaged monkeys had a longer RT and lower percentage of timeout trials, compared to their pre-lesion performance. The practice-related changes in mean RT and in RT variability were significantly heightened in frontopolar-damaged monkeys. They also showed attenuated post-error, but exaggerated post-stop, behavioural adjustments. Importantly, frontopolar damage had no significant effects on monkeys' inhibition ability. Our findings indicate that frontopolar cortex plays a critical role in allocation of control to response execution, but not action inhibition.
To encode allocentric space information of a viewing object, it is important to relate perceptual information in the first-person perspective to the representation of an entire scene which would be constructed before. A...To encode allocentric space information of a viewing object, it is important to relate perceptual information in the first-person perspective to the representation of an entire scene which would be constructed before. A substantial number of studies investigated the constructed scene information (e.g., cognitive map). However, only few studies have focused on its influence on perceptual processing. Therefore, we designed a visually guided saccade task requiring monkeys to gaze at objects in different locations on different backgrounds clipped from large self-designed mosaic pictures (parental pictures). In each trial, we presented moving backgrounds prior to object presentations, indicating a frame position of the background image on a parental picture. We recorded single-unit activities from 377 neurons in the posterior inferotemporal (PIT) cortex of two macaques. Equivalent numbers of neurons showed space-related (119 of 377) and object-related (125 of 377) information. The space-related neurons coded the gaze locations and background images jointly rather than separately. These results suggest that PIT neurons represent a particular location within a particular background image. Interestingly, frame positions of background images on parental pictures modulated the space-related responses dependently on parental pictures. As the frame positions could be acquired by only preceding visual experiences, the present results may provide neuronal evidence of a mnemonic effect on current perception, which might represent allocentric object location in a scene beyond the current view.
How we combine minimal linguistic units into larger structures remains an unresolved topic in neuroscience. Language processing involves the abstract construction of 'vertical' and 'horizontal' information simultaneously...How we combine minimal linguistic units into larger structures remains an unresolved topic in neuroscience. Language processing involves the abstract construction of 'vertical' and 'horizontal' information simultaneously (e.g., phrase structure, morphological agreement), but previous paradigms have been constrained in isolating only one type of composition and have utilized poor spatiotemporal resolution. Using intracranial recordings, we report multiple experiments designed to separate phrase structure from morphosyntactic agreement. Epilepsy patients (n = 10) were presented with auditory two-word phrases grouped into pseudoword-verb ('trab run') and pronoun-verb either with or without Person agreement ('they run' vs. 'they runs'). Phrase composition and Person violations both resulted in significant increases in broadband high gamma activity approximately 300 ms after verb onset in posterior middle temporal gyrus (pMTG) and posterior superior temporal sulcus (pSTS), followed by inferior frontal cortex (IFC) at 500 ms. While sites sensitive to only morphosyntactic violations were distributed, those sensitive to both composition types were generally confined to pSTS/pMTG and IFC. These results indicate that posterior temporal cortex shows the earliest sensitivity for hierarchical linguistic structure across multiple dimensions, providing neural resources for distinct windows of composition. This region is comprised of sparsely interwoven heterogeneous constituents that afford cortical search spaces for dissociable syntactic relations.
Prog Neurobiol
· 2024 Oct · PMID 39303758
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Listening in complex sound environments requires rapid segregation of different sound sources, e.g., having a conversation with multiple speakers or other environmental sounds. Efficient processing requires fast encoding...Listening in complex sound environments requires rapid segregation of different sound sources, e.g., having a conversation with multiple speakers or other environmental sounds. Efficient processing requires fast encoding of inputs to adapt to target sounds and identify relevant information from past experiences. This adaptation process represents an early phase of implicit learning of the sound statistics to form auditory memory. The auditory cortex (ACtx) plays a crucial role in this implicit learning process, but the underlying circuits are unknown. In awake mice, we recorded neuronal responses in different ACtx subfields using in vivo 2-photon imaging of excitatory and inhibitory (parvalbumin; PV) neurons. We used a paradigm adapted from human studies that induced rapid implicit learning from passively presented complex sounds and imaged A1 Layer 4 (L4), A1 L2/3, and A2 L2/3. In this paradigm, a frozen spectro-temporally complex 'Target' sound randomly re-occurred within a stream of other random complex sounds. All ACtx subregions contained distinct groups of cells specifically responsive to complex acoustic sequences, indicating that even thalamocortical input layers (A1 L4) respond to complex sounds. Subgroups of excitatory and inhibitory cells in all subfields showed decreased responses for re-occurring Target sounds, indicating that ACtx is highly involved in the early implicit learning phase. At the population level, activity was more decorrelated to Target sounds independent of the duration of frozen token, subregions, and cell type. These findings suggest that ACtx and its input layers contribute to the early phase of auditory memory for complex sounds, suggesting a parallel strategy across ACtx areas and between excitatory and inhibitory neurons.
Anderson TL, Keady JV, Songrady J
… +5 more, Tavakoli NS, Asadipooya A, Neeley RE, Turner JR, Ortinski PI
Prog Neurobiol
· 2024 Sep · PMID 39218140
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Recent evidence indicates that neuronal activity within the claustrum (CLA) may be central to cellular and behavioral responses to psychedelic hallucinogens. The CLA prominently innervates many cortical targets and displ...Recent evidence indicates that neuronal activity within the claustrum (CLA) may be central to cellular and behavioral responses to psychedelic hallucinogens. The CLA prominently innervates many cortical targets and displays exceptionally high levels of serotonin (5-HT) binding. However, the influence of serotonin receptors, prime targets of psychedelic drug action, on CLA activity remains unexplored. We characterize the CLA expression of all known 5-HT subtypes and contrast the effects of 5-HT and the psychedelic hallucinogen, 2,5-dimethoxy-4-iodoamphetamine (DOI), on excitability of cortical-projecting CLA neurons. We find that the CLA is particularly enriched with 5-HT2C receptors, expressed predominantly on glutamatergic neurons. Electrophysiological recordings from CLA neurons that project to the anterior cingulate cortex (ACC) indicate that application of 5-HT inhibits glutamate receptor-mediated excitatory postsynaptic currents (EPSCs). In contrast, application of DOI stimulates EPSCs. We find that the opposite effects of 5-HT and DOI on synaptic signaling can both be reversed by inhibition of the 5-HT2C, but not 5-HT2A, receptors. We identify specific 5-HT receptor subtypes as serotonergic regulators of the CLA excitability and argue against the canonical role of 5-HT2A in glutamatergic synapse response to psychedelics within the CLA-ACC circuit.
Accurate definition of the borders of cortical visual areas is essential for the study of neuronal processes leading to perception. However, data used for definition of areal boundaries have suffered from issues related...Accurate definition of the borders of cortical visual areas is essential for the study of neuronal processes leading to perception. However, data used for definition of areal boundaries have suffered from issues related to resolution, uniform coverage, or suitability for objective analysis, leading to ambiguity. Here, we present a novel approach that combines widefield optical imaging, presentation of naturalistic movies, and encoding model analysis, to objectively define borders in the primate extrastriate cortex. We applied this method to test conflicting hypotheses about the third-tier visual cortex, where areal boundaries have remained controversial. We demonstrate pronounced tuning preferences in the third-tier areas, and an organizational structure in which the dorsomedial area (DM) contains representations of both the upper and lower contralateral quadrants, and is located immediate anterior to V2. High-density electrophysiological recordings with a Neuropixels probe confirm these findings. Our encoding-model approach offers a powerful, objective way to disambiguate areal boundaries.
Our understanding of how otoferlin, the major calcium sensor in inner hair cells (IHCs) synaptic transmission, contributes to the overall dynamics of synaptic vesicle (SV) trafficking remains limited. To address this que...Our understanding of how otoferlin, the major calcium sensor in inner hair cells (IHCs) synaptic transmission, contributes to the overall dynamics of synaptic vesicle (SV) trafficking remains limited. To address this question, we generated a knock-in mouse model expressing an otoferlin-GFP protein, where GFP was fused to its C-terminal transmembrane domain. Similar to the wild type protein, the GFP-tagged otoferlin showed normal expression and was associated with IHC SV. Surprisingly, while the heterozygote Otof mice exhibited a normal hearing function, homozygote Otof mice were profoundly deaf attributed to severe reduction in SV exocytosis. Fluorescence recovery after photobleaching revealed a markedly increased mobile fraction of the otof-GFP-associated SV in Otof IHCs. Correspondingly, 3D-electron tomographic of the ribbon synapses indicated a reduced density of SV attached to the ribbon active zone. Collectively, these results indicate that otoferlin requires a free intravesicular C-terminal end for normal SV docking and fusion.
The orientation map is one of the most well-studied functional maps of the visual cortex. However, results from the literature are of different qualities. Clear boundaries among different orientation domains and blurred...The orientation map is one of the most well-studied functional maps of the visual cortex. However, results from the literature are of different qualities. Clear boundaries among different orientation domains and blurred uncertain distinctions were shown in different studies. These unclear imaging results will lead to an inaccuracy in depicting cortical structures, and the lack of consideration in experimental design will also lead to biased depictions of the cortical features. How we accurately define orientation domains will impact the entire field of research. In this study, we test how spatial frequency (SF), stimulus size, location, chromatic, and data processing methods affect the orientation functional maps (including a large area of dorsal V4, and parts of dorsal V1) acquired by intrinsic signal optical imaging. Our results indicate that, for large imaging fields, large grating stimuli with mixed SF components should be considered to acquire the orientation map. A diffusion model image enhancement based on the difference map could further improve the map quality. In addition, the similar outcomes of achromatic and chromatic gratings indicate two alternative types of afferents from LGN, pooling in V1 to generate cue-invariant orientation selectivity.
Object recognition often involves the brain segregating objects from their surroundings. Neurophysiological studies of figure-ground texture segregation have yielded inconsistent results, particularly on whether V1 neuro...Object recognition often involves the brain segregating objects from their surroundings. Neurophysiological studies of figure-ground texture segregation have yielded inconsistent results, particularly on whether V1 neurons can perform figure-ground texture segregation or just detect texture borders. To address this issue from a population perspective, we utilized two-photon calcium imaging to simultaneously record the responses of large samples of V1 and V4 neurons to figure-ground texture stimuli in awake, fixating macaques. The average response changes indicate that V1 neurons mainly detect texture borders, while V4 neurons are involved in figure-ground segregation. However, population analysis (SVM decoding of PCA-transformed neuronal responses) reveal that V1 neurons not only detect figure-ground borders, but also contribute to figure-ground texture segregation, although requiring substantially more principal components than V4 neurons to reach a 75 % decoding accuracy. Individually, V1/V4 neurons showing larger (negative/positive) figure-ground response differences contribute more to figure-ground segregation. But for V1 neurons, the contribution becomes significant only when many principal components are considered. We conclude that V1 neurons participate in figure-ground segregation primarily by defining the figure borders, and the poorly structured figure-ground information V1 neurons carry could be further utilized by V4 neurons to accomplish figure-ground segregation.
We present here a view of the firing patterns of hippocampal cells that is contrary, both functionally and anatomically, to conventional wisdom. We argue that the hippocampus responds to efference copies of goals encoded...We present here a view of the firing patterns of hippocampal cells that is contrary, both functionally and anatomically, to conventional wisdom. We argue that the hippocampus responds to efference copies of goals encoded elsewhere; and that it uses these to detect and resolve conflict or interference between goals in general. While goals can involve space, hippocampal cells do not encode spatial (or other special types of) memory, as such. We also argue that the transverse circuits of the hippocampus operate in an essentially homogeneous way along its length. The apparently different functions of different parts (e.g. memory retrieval versus anxiety) result from the different (situational/motivational) inputs on which those parts perform the same fundamental computational operations. On this view, the key role of the hippocampus is the iterative adjustment, via Papez-like circuits, of synaptic weights in cell assemblies elsewhere.
Psychotic disorders entail intricate conditions marked by disruptions in cognition, perception, emotions, and social behavior. Notably, psychotic patients who use cannabis tend to show less severe deficits in social beha...Psychotic disorders entail intricate conditions marked by disruptions in cognition, perception, emotions, and social behavior. Notably, psychotic patients who use cannabis tend to show less severe deficits in social behaviors, such as the misinterpretation of social cues and the inability to interact with others. However, the biological underpinnings of this epidemiological interaction remain unclear. Here, we used the NMDA receptor blocker phencyclidine (PCP) to induce psychotic-like states and to study the impact of adolescent cannabinoid exposure on social behavior deficits and synaptic transmission changes in hippocampal area CA2, a region known to be active during social interactions. In particular, adolescent mice underwent 7 days of subchronic treatment with the synthetic cannabinoid, WIN 55, 212-2 (WIN) followed by one injection of PCP. Using behavioral, biochemical, and electrophysiological approaches, we showed that PCP persistently reduced sociability, decreased GAD67 expression in the hippocampus, and induced GABAergic deficits in proximal inputs from CA3 and distal inputs from the entorhinal cortex (EC) to CA2. Notably, WIN exposure during adolescence specifically restores adult sociability deficits, the expression changes in GAD67, and the GABAergic impairments in the EC-CA2 circuit, but not in the CA3-CA2 circuit. Using a chemogenetic approach to target EC-CA2 projections, we demonstrated the involvement of this specific circuit on sociability deficits. Indeed, enhancing EC-CA2 transmission was sufficient to induce sociability deficits in vehicle-treated mice, but not in animals treated with WIN during adolescence, suggesting a mechanism by which adolescent cannabinoid exposure rescues sociability deficits caused by enhanced EC-CA2 activity in adult mice.
Neuromyelitis optica (NMO) arises from primary astrocytopathy induced by autoantibodies targeting the astroglial protein aquaporin 4 (AQP4), leading to severe neurological sequelae such as vision loss, motor deficits, an...Neuromyelitis optica (NMO) arises from primary astrocytopathy induced by autoantibodies targeting the astroglial protein aquaporin 4 (AQP4), leading to severe neurological sequelae such as vision loss, motor deficits, and cognitive decline. Mounting evidence has shown that dysregulated activation of complement components contributes to NMO pathogenesis. Complement C3 deficiency has been shown to protect against hippocampal neurodegeneration and cognitive decline in neurodegenerative disorders (e.g., Alzheimer's disease, AD) and autoimmune diseases (e.g., multiple sclerosis, MS). However, whether inhibiting the C3 signaling can ameliorate cognitive dysfunctions in NMO remains unclear. In this study, we found that the levels of C3a, a split product of C3, significantly correlate with cognitive impairment in our patient cohort. In response to the stimulation of AQP4 autoantibodies, astrocytes were activated to secrete complement C3, which inhibited the development of cultured neuronal dendritic arborization. NMO mouse models exhibited reduced adult hippocampal newborn neuronal dendritic and spine development, as well as impaired learning and memory functions, which could be rescued by decreasing C3 levels in astrocytes. Mechanistically, we found that C3a engaged with C3aR to impair neuronal development by dampening β-catenin signalling. Additionally, inhibition of the C3-C3aR-GSK3β/β-catenin cascade restored neuronal development and ameliorated cognitive impairments. Collectively, our results suggest a pivotal role of the activation of the C3-C3aR network in neuronal development and cognition through mediating astrocyte and adult-born neuron communication, which represents a potential therapeutic target for autoimmune-related cognitive impairment diseases.
While it is well established that sensory cortical regions traditionally thought to be unimodal can be activated by stimuli from modalities other than the dominant one, functions of such foreign-modal activations are sti...While it is well established that sensory cortical regions traditionally thought to be unimodal can be activated by stimuli from modalities other than the dominant one, functions of such foreign-modal activations are still not clear. Here we show that visual activations in early auditory cortex can be related to whether or not the monkeys engaged in audio-visual tasks, to the time when the monkeys reacted to the visual component of such tasks, and to the correctness of the monkeys' response to the auditory component of such tasks. These relationships between visual activations and behavior suggest that auditory cortex can be recruited for visually-guided behavior and that visual activations can prime auditory cortex such that it is prepared for processing future sounds. Our study thus provides evidence that foreign-modal activations in sensory cortex can contribute to a subject's ability to perform tasks on stimuli from foreign and dominant modalities.
Identification of transient receptor potential cation channel, subfamily V member 1 (TRPV1), also known as capsaicin receptor, in 1997 was a milestone achievement in the research on temperature sensation and pain signall...Identification of transient receptor potential cation channel, subfamily V member 1 (TRPV1), also known as capsaicin receptor, in 1997 was a milestone achievement in the research on temperature sensation and pain signalling. Very soon after it became evident that TRPV1 is implicated in a wide array of physiological processes in different peripheral tissues, as well as in the central nervous system, and thereby could be involved in the pathophysiology of numerous diseases. Increasing evidence suggests that modulation of TRPV1 may also affect seizure susceptibility and epilepsy. This channel is localized in brain regions associated with seizures and epilepsy, and its overexpression was found both in animal models of seizures and in brain samples from epileptic patients. Moreover, modulation of TRPV1 on non-neuronal cells (microglia, astrocytes, and/or peripheral immune cells) may have an impact on the neuroinflammatory processes that play a role in epilepsy and epileptogenesis. In this paper, we provide a comprehensive and critical overview of currently available data on TRPV1 as a possible molecular target for epilepsy management, trying to identify research gaps and future directions. Overall, several converging lines of evidence implicate TRPV1 channel as a potentially attractive target in epilepsy research but more studies are needed to exploit the possible role of TRPV1 in seizures/epilepsy and to evaluate the value of TRPV1 ligands as candidates for new antiseizure drugs.