Causal Contribution Research Articles

Immune Activation Promotes Cardiac Remodeling in a Mouse Model of Takotsubo Cardiomyopathy

Takotsubo Cardiomyopathy (TCM) is an acute, life-threatening condition characterized by a drop in ejection fraction (EF) and apical ballooning of the left ventricle (LV). TCM is most frequently observed in women and is associated with an emotional or physical stressor. Importantly, with medical intervention, cardiac dysfunction is transient, and EF is often restored over weeks to months. Despite this, patients who experience TCM are at an increased risk of additional cardiovascular events and premature mortality. The precise etiology of TCM is unknown but a wave of excess circulating catecholamines is thought to be a trigger. Furthermore, the cause for increased cardiovascular risk post-TCM is unknown. The goal of this study is to understand how the immune system may contribute to TCM and the associated cardiovascular event risk. To induce TCM, mice were given a single dose of 200mg/kg isoproterenol (ISO), i.p. and cardiac function was assessed by conscious echocardiography (ECG). An initial study compared the effect of ISO between sexes (n=4-6). Though ISO induced a drop in EF in both sexes after 24 hours (p<0.001 compared to vehicle (Veh)), females exhibited lower EF (46.64±3.11%) than males (68.36±2.62%, p<0.0001). This mirrors the increased prevalence of clinically defined TCM in females in human populations. For this reason, female mice were used for the following experiments. A time course study demonstrated that EF begins to normalize by Day 3 (78.78±2.70 v 90.80±1.00%, p<0.001) and is restored to baseline levels by Day 7 (90.65±1.17%). Flow cytometry was used to identify changes in immune cell populations in the heart on Days 0, 1, 3 and 7 (n=4-5). Neutrophils and inflammatory monocytes increased on Day 1, returning to baseline by Day 3. Dendritic cells and macrophages were elevated on Day 3 post-ISO, with a specific increase in CCR2+ TIM4- recruited inflammatory macrophages (p<0.0001). Across all subsets, the number of immune cells returned to baseline levels by Day 7. Due to the robust immune response observed, we tested the specific hypothesis that transfer of immune cells from mice who have experienced TCM would induce cardiac dysfunction in naïve recipient mice. Donor mice were treated with either Veh or ISO and 1 day later splenocyte isolation and transfer was performed. Importantly, transfer of splenocytes from mice who had TCM induced a significant drop in EF the following day in the recipient mice (86.30±1.08%, p=0.001, n=10) concurrent with an increase in LV inner diameter and volume during systole. A final study tested the hypothesis that a history of TCM would increase risk for future cardiovascular disease. Veh or ISO-treated mice were allowed to recover for 10 days. Tail-cuff plethysmography showed no significant difference in baseline blood pressure and minipumps were implanted to deliver a constant infusion of Angiotensin II (Ang II, 140ng/kg/min). Mice with a history of TCM exhibited higher blood pressures compared to controls (135.11±3.32 v 116.9±6.41mmhg, n=6/9, p<0.05) by week 2 of Ang II infusion. These results together demonstrated that TCM is associated with a robust immune response and points to a possible causal contribution of immune activation to the cardiac dysfunction observed in TCM. Furthermore, a history of TCM promotes a hypertensive phenotype, but additional studies are needed to test whether this is through immunological mechanisms. AHAPOST837441 DJF, 19EIA34480023-MSM, and 1R01 HL161212-MSM. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

SGLT2 inhibition, plasma proteins, and heart failure: a proteome-wide Mendelian Randomization and colocalization study.

To investigate the causal contributions of Sodium-glucose cotransporter 2 (SGLT2) inhibition on Heart Failure (HF) and identify the circulating proteins that mediate SGLT2 inhibition's effects on HF. Applying a two-sample, two-step Mendelian Randomization (MR) analysis, we aimed to estimate: (1) the causal impact of SGLT2 inhibition on HF; (2) the causal correlation of SGLT2 inhibition on 4,907 circulating proteins; (3) the causal association of SGLT2 inhibition-driven plasma proteins on HF. Genetic variants linked to SGLT2 inhibition derived from the previous studies. The 4,907 circulating proteins were derived from the deCODE study. Genetic links to HF were obtained through the Heart Failure Molecular Epidemiology for Therapeutic Targets (HERMES) consortium. SGLT2 inhibition demonstrated a lower risk of HF (odds ratio [OR] = 0.44, 95% CI [0.26, 0.76], P = 0.003). Among 4,907 circulating proteins, we identified leucine rich repeat transmembrane protein 2 (LRRTM2), which was related to both SGLT2 inhibition and HF. Mediation analysis revealed that the impact of SGLT2 inhibition on HF operates indirectly through LRRTM2 [β = -0.20, 95% CI (-0.39, -0.06), P = 0.02] with a mediation proportion of 24.6%. Colocalization analysis provided support for the connections between LRRTM2 and HF. The study indicated a causative link between SGLT2 inhibition and HF, with plasma LRRTM2 potentially serving as a mediator.

Graded causation and moral responsibility

AbstractTheories of graded causation attract growing attention in the philosophical debate on causation. An important field of application is the controversial relationship between causation and moral responsibility. However, it is still unclear how exactly the notion of graded causation should be understood in the context of moral responsibility. One question is whether we should endorse a proportionality principle, according to which the degree of an agent’s moral responsibility is proportionate to their degree of causal contribution. A second question is whether a theory of graded causation should measure closeness to necessity or closeness to sufficiency. In this paper, we argue that we should indeed endorse a proportionality principle and that this principle supports a notion of graded causation relying on closeness to sufficiency rather than closeness to necessity. Furthermore, we argue that this insight helps to provide a plausible analysis of the so-called ‘Moral Difference Puzzle’ recently described by Bernstein.

Decreased Circulating Very Small Low-Density Lipoprotein is Likely Causal for Age-Related Macular Degeneration

Abnormal changes in metabolite levels in serum or plasma have been highlighted in several studies in age-related macular degeneration (AMD), the leading cause of irreversible vision loss. Specific changes in lipid profiles are associated with an increased risk of AMD. Metabolites could thus be used to investigate AMD disease mechanisms or incorporated into AMD risk prediction models. However, whether particular metabolites causally affect the disease has yet to be established. A 3-tiered analysis of blood metabolites in the United Kingdom (UK) Biobank cohort to identify metabolites that differ in AMD patients with evidence for a putatively causal role in AMD. A total of 72376 donors from the UK Biobank cohort including participants with AMD (N=1353) and non-AMD controls (N=71023). We analyzed 325 directly measured or derived blood metabolites from the UK Biobank for 72376 donors to identify AMD-associated metabolites. Genome-wide association studies for 325 metabolites in 98316 European participants from the UK Biobank were performed. The causal effects of these metabolites in AMD were tested using a 2-sample Mendelian randomization approach. The predictive value of these measurements together with sex and age was assessed by developing a machine learning classifier. Evaluating metabolic biomarkers associated with AMD susceptibility and investigating their potential causal contribution to the development of the disease. This study noted age to be the prominent risk factor associated with AMD development. While accounting for age and sex, we identified 84 metabolic markers as significantly (false discovery rate-adjusted P value < 0.05) associated with AMD. Lipoprotein subclasses comprised the majority of the AMD-associated metabolites (39%) followed by several lipoprotein to lipid ratios. Nineteen metabolites showed a likely causative role in AMD etiology. Of these, 6 lipoproteins contain very small, very low-density lipoprotein (VLDL), and phospholipids to total lipid ratio in medium VLDL. Based on this we postulate that depletion of circulating very small VLDLs is likely causal for AMD. The risk prediction model constructed from the metabolites, age and sex, identified age as the primary predictive factor with a much smaller contribution by metabolites to AMD risk prediction. This study underscores the pronounced role of lipids in AMD susceptibility and the likely causal contribution of particular subclasses of lipoproteins to AMD. Our study provides valuable insights into the metabopathological mechanisms of AMD disease development and progression.

Perceptography unveils the causal contribution of inferior temporal cortex to visual perception

Neurons in the inferotemporal (IT) cortex respond selectively to complex visual features, implying their role in object perception. However, perception is subjective and cannot be read out from neural responses; thus, bridging the causal gap between neural activity and perception demands independent characterization of perception. Historically, though, the complexity of the perceptual alterations induced by artificial stimulation of IT cortex has rendered them impossible to quantify. To address this old problem, we tasked male macaque monkeys to detect and report optical impulses delivered to their IT cortex. Combining machine learning with high-throughput behavioral optogenetics, we generated complex and highly specific images that were hard for the animal to distinguish from the state of being cortically stimulated. These images, named “perceptograms” for the first time, reveal and depict the contents of the complex hallucinatory percepts induced by local neural perturbation in IT cortex. Furthermore, we found that the nature and magnitude of these hallucinations highly depend on concurrent visual input, stimulation location, and intensity. Objective characterization of stimulation-induced perceptual events opens the door to developing a mechanistic theory of visual perception. Further, it enables us to make better visual prosthetic devices and gain a greater understanding of visual hallucinations in mental disorders.

A chronometric study of the posterior cerebellum’s function in emotional processing

The posterior cerebellum is a recently discovered hub of the affective and social brain, with different subsectors contributing to different social functions. However, very little is known about when the posterior cerebellum plays a critical role in social processing. Due to its location and anatomy, it has been difficult to use traditional approaches to directly study the chronometry of the cerebellum. To address this gap in cerebellar knowledge, here we investigated the causal contribution of the posterior cerebellum to social processing using a chronometric transcranial magnetic stimulation (TMS) approach. We show that the posterior cerebellum is recruited at an early stage of emotional processing (starting from 100ms after stimulus onset), simultaneously with the posterior superior temporal sulcus (pSTS), a key node of the social brain. Moreover, using a condition-and-perturb TMS approach, we found that the recruitment of the pSTS in emotional processing is dependent on cerebellar activation. Our results are the first to shed light on chronometric aspects of cerebellar function and its causal functional connectivity with other nodes of the social brain.

No evidence for a causal contribution of bioavailable testosterone to ADHD in sex-combined and sex-specific two-sample Mendelian randomization studies.

The higher prevalence of attention-deficit/hyperactivity disorder (ADHD) in males raises the question of whether testosterone is implicated in ADHD risk. However, cross-sectional studies did not identify an association between ADHD and testosterone levels. Mendelian randomization (MR) studies can overcome limitations inherent to association studies, especially of reverse causation and residual confounding. In the current study, sex-combined and sex-specific two-sample MR analyses were conducted to address whether testosterone has a causal influence on ADHD risk. Sex-combined as well as sex-specific target-genetic variants for bioavailable testosterone were derived from a large genome-wide association study (GWAS) on up to 382,988 adult white European UK Biobank study participants. In our sex-specific analyses for ADHD, including data from 14,154 males and 4,945 females with ADHD (17,948 and 16,246 controls respectively), no association between bioavailable testosterone and ADHD risk was found, neither in males (inverse-variance weighted (IVW): beta = 0.09, 95%-CI [-0.10, 0.27]) nor in females (IVW: beta=-0.01, 95%-CI [-0.20, 0.19]). However, in the sex-combined analysis, including 38,691 cases and 186,843 controls, genetically predicted bioavailable testosterone was associated with ADHD risk (IVW: beta = 0.24, 95%-CI [0.09, 0.39]). The inclusion of birth weight and/or SHBG as additional variables in multivariable MR analyses did not alter this result. However, when correcting for potential BMI-driven pleiotropy by a multivariable MR study, all effect estimates for testosterone showed non-significant results. Taken together, no robust evidence for a causal effect of bioavailable testosterone on the risk for ADHD was found.

Somatic mutations in aging and disease.

Time always leaves its mark, and our genome is no exception. Mutations in the genome of somatic cells were first hypothesized to be the cause of aging in the 1950s, shortly after the molecular structure of DNA had been described. Somatic mutation theories of aging are based on the fact that mutations in DNA as the ultimate template for all cellular functions are irreversible. However, it took until the 1990s to develop the methods to test if DNA mutations accumulate with age in different organs and tissues and estimate the severity of the problem. By now, numerous studies have documented the accumulation of somatic mutations with age in normal cells and tissues of mice, humans, and other animals, showing clock-like mutational signatures that provide information on the underlying causes of the mutations. In this review, we will first briefly discuss the recent advances in next-generation sequencing that now allow quantitative analysis of somatic mutations. Second, we will provide evidence that the mutation rate differs between cell types, with a focus on differences between germline and somatic mutation rate. Third, we will discuss somatic mutational signatures as measures of aging, environmental exposure, and activities of DNA repair processes. Fourth, we will explain the concept of clonally amplified somatic mutations, with a focus on clonal hematopoiesis. Fifth, we will briefly discuss somatic mutations in the transcriptome and in our other genome, i.e., the genome of mitochondria. We will end with a brief discussion of a possible causal contribution of somatic mutations to the aging process.

Analyses of potential causal contributors to increased waist/hip ratio-associated cardiometabolic disease: A combined and sex-stratified Mendelian randomization study.

Increased waist/hip ratio (WHR) contributes to type 2 diabetes, fatty liver, dyslipidaemia, hypertension and coronary artery disease, with potential sex-differential effects. Postulated mediators include increased lipid flux, branched-chain amino acids, glycine and glycoprotein acetyl, but their relative contributions and sex-specific impact on WHR-associated cardiometabolic disease (CMD) are not established. We therefore undertook combined and sex-stratified Mendelian randomization (MR) to assess the relative causal contributions of these mediators to WHR-associated CMD using summary statistics from the largest genome-wide association studies in European ancestries. In sex-combined MR analyses, increased WHR significantly reduces high-density lipoprotein (beta = -0.416, SE = 0.029, p = 2.87E-47), increases triglyceride (beta = 0.431, SE = 0.029, p = 1.87E-50), type 2 diabetes (odds ratio = 2.747, SE = 0.09, p = 26E-23), coronary artery disease (odds ratio = 1.478, SE = 0.045, p = 6.96E-18), alanine transaminase (beta = 0.062, SE = 0.004, p = 6.88E-67), and systolic (beta = 0.134, SE = 0.022, p = 7.81E-10) and diastolic blood pressure (beta = 0.162, SE = 0.026, p = 5.38E-10). Adjustment for the mediators attenuated WHR's effects, but the associations remained significant with concordant results in females. In males, a similar pattern was seen, except after adjusting for the effect of the ratio of monounsaturated fatty acid to total free fatty acid, the potential causal effect of WHR was no longer significant: high-density lipoprotein (beta = -0.117, SE = 0.069, p = .09) and triglyceride (beta = 0.051, SE = 0.068, p = .459). MR suggests WHR increases the risk of CMD independent of these mediators, with the exception of dyslipidaemia in males, which is largely driven by the monounsaturated fatty acid to total free fatty acid ratio.

Recurrent Neural Circuits Overcome Partial Inactivation by Compensation and Re-learning.

Technical advances in artificial manipulation of neural activity have precipitated a surge in studying the causal contribution of brain circuits to cognition and behavior. However, complexities of neural circuits challenge interpretation of experimental results, necessitating new theoretical frameworks for reasoning about causal effects. Here, we take a step in this direction, through the lens of recurrent neural networks trained to perform perceptual decisions. We show that understanding the dynamical system structure that underlies network solutions provides a precise account for the magnitude of behavioral effects due to perturbations. Our framework explains past empirical observations by clarifying the most sensitive features of behavior, and how complex circuits compensate and adapt to perturbations. In the process, we also identify strategies that can improve the interpretability of inactivation experiments.

RNA Sequencing in Disease Diagnosis.

RNA sequencing (RNA-seq) enables the accurate measurement of multiple transcriptomic phenotypes for modeling the impacts of disease variants. Advances in technologies, experimental protocols, and analysis strategies are rapidly expanding the application of RNA-seq to identify disease biomarkers, tissue- and cell-type-specific impacts, and the spatial localization of disease-associated mechanisms. Ongoing international efforts to construct biobank-scale transcriptomic repositories with matched genomic data across diverse population groups are further increasing the utility of RNA-seq approaches by providing large-scale normative reference resources. The availability of these resources, combined with improved computational analysis pipelines, has enabled the detection of aberrant transcriptomic phenotypes underlying rare diseases. Further expansion of these resources, across both somatic and developmental tissues, is expected to soon provide unprecedented insights to resolve disease origin, mechanism of action, and causal gene contributions, suggesting the continued high utility of RNA-seq in disease diagnosis.

REEP4 variant analysis in blepharospasm and other neurological disorders.

In preceding work, a deleterious REEP4 variant [GRCh38/hg38, NC_000008.11:g.22140245G>A, NM_025232.4:c.109C>T, p.Arg37Trp] was found to co-segregate with blepharospasm (BSP) in a large African-American pedigree. Other REEP4 variants have been reported in genetic screening studies of dystonia. The REEP4 paralogs, REEP1 and REEP2, are associated with spastic paraplegia. The causal contributions of REEP4 variants to dystonia and other neurological disorders remains indecisive. Sanger sequencing was used to screen subjects (N = 307) with BSP and BSP-plus dystonia affecting additional anatomical segments (BSP+) phenotypes for variants in REEP4. In silico tools were used to examine the deleteriousness of reported (ClinVar) and previously published REEP4 variants. No highly deleterious variant was identified in coding or contiguous splice site regions of REEP4 in our cohort of 307 subjects. In silico analysis identified numerous deleterious REEP4 variants in published screening studies of dystonia and several highly deleterious single nucleotide REEP4 variants in ClinVar. Highly deleterious REEP4 variants are rare in BSP and BSP+ phenotypes.

Downstream network transformations dissociate neural activity from causal functional contributions

Neuroscientists rely on distributed spatio-temporal patterns of neural activity to understand how neural units contribute to cognitive functions and behavior. However, the extent to which neural activity reliably indicates a unit's causal contribution to the behavior is not well understood. To address this issue, we provide a systematic multi-site perturbation framework that captures time-varying causal contributions of elements to a collectively produced outcome. Applying our framework to intuitive toy examples and artificial neural networks revealed that recorded activity patterns of neural elements may not be generally informative of their causal contribution due to activity transformations within a network. Overall, our findings emphasize the limitations of inferring causal mechanisms from neural activities and offer a rigorous lesioning framework for elucidating causal neural contributions.

Inactivation of face-selective neurons alters eye movements when free viewing faces.

During free viewing, faces attract gaze and induce specific fixation patterns corresponding to the facial features. This suggests that neurons encoding the facial features are in the causal chain that steers the eyes. However, there is no physiological evidence to support a mechanistic link between face-encoding neurons in high-level visual areas and the oculomotor system. In this study, we targeted the middle face patches of the inferior temporal (IT) cortex in two macaque monkeys using an functional magnetic resonance imaging (fMRI) localizer. We then utilized muscimol microinjection to unilaterally suppress IT neural activity inside and outside the face patches and recorded eye movements while the animals free viewing natural scenes. Inactivation of the face-selective neurons altered the pattern of eye movements on faces: The monkeys found faces in the scene but neglected the eye contralateral to the inactivation hemisphere. These findings reveal the causal contribution of the high-level visual cortex in eye movements.

Counterfactual formulation of patient-specific root causes of disease

Objective:Root causes of disease intuitively correspond to root vertices of a causal model that increase the likelihood of a diagnosis. This description of a root cause nevertheless lacks the rigorous mathematical formulation needed for the development of computer algorithms designed to automatically detect root causes from data. We seek a definition of patient-specific root causes of disease that models the intuitive procedure routinely utilized by physicians to uncover root causes in the clinic. Methods:We use structural equation models, interventional counterfactuals and the recently developed mathematical formalization of backtracking counterfactuals to propose a counterfactual formulation of patient-specific root causes of disease matching clinical intuition. Results:We introduce a definition of patient-specific root causes of disease that climbs to the third rung of Pearl’s Ladder of Causation and matches clinical intuition given factual patient data and a working causal model. We then show how to assign a root causal contribution score to each variable using Shapley values from explainable artificial intelligence. Conclusion:The proposed counterfactual formulation of patient-specific root causes of disease accounts for noisy labels, adapts to disease prevalence and admits fast computation without the need for counterfactual simulation.

Stereotaxic Surgery as a Method to Deliver Epigenetic Editing Constructs in Rodent Brain.

Modern neuroscience research is increasingly discovering that alterations in epigenetic states within key brain cells is correlated with brain diseases. These epigenetic alterations may include changes in histone post-translational modifications and/or DNA modifications, all of which affect transcription and other gene expression programs within the brain cells that comprise central brain regions. However, the exact causal contribution of these epigenome changes to brain disease cannot be elucidated in the absence of direct in vivo manipulations in the implicated brain areas. Combining the design and creation of epigenetic editing constructs, gene delivery strategies, and stereotaxic surgery enables neuroscience researchers to target and manipulate the epigenetic state of the brain cells of laboratory rodents in a locus-specific manner and test its causal contribution to disease-related pathology and behaviors. Here, we describe the surgical protocol utilized by our group and others, which is optimized for herpes simplex virus delivery into the mouse brain, although the protocol outlined herein could be applied for delivery of adeno-associated viruses, lentiviruses, or nonviral gene-delivery methods in both mice and rats. The method allows for the overexpression of engineered DNA-binding proteins for direct and targeted epigenome editing in rodent brain with excellent spatiotemporal control. Nearly any brain region of interest can be targeted in rodents at every stage of postnatal life. Owing to the versatility, reproducibility, and utility of this technique, it is an important method for any laboratory interested in studying the cellular, circuit, and behavioral consequences of manipulating the brain epigenome in laboratory rodents.

Interpretation of Neurodegenerative GWAS Risk Alleles in Microglia and their Interplay with Other Cell Types.

Microglia have been implicated in numerous neurodegenerative and neuroinflammatory disorders; however, the causal contribution of this immune cell type is frequently debated. Genetic studies offer a unique vantage point in that they infer causality over a secondary consequence. Genome-wide association studies (GWASs) have identified hundreds of loci in the genome that are associated with susceptibility to neurodegenerative disorders. GWAS studies implicate microglia in the pathogenesis of Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), and to a lesser degree suggest a role for microglia in vascular dementia (VaD), frontotemporal dementia (FTD), and amyotrophic lateral sclerosis (ALS), and other neurodegenerative and neuropsychiatric disorders. The contribution and function of GWAS risk loci on disease progression is an ongoing field of study, in which large genomic datasets, and an extensive framework of computational tools, have proven to be crucial. Several GWAS risk loci are shared between disorders, pointing towards common pleiotropic mechanisms. In this chapter, we introduce key concepts in GWAS and post-GWAS interpretation of neurodegenerative disorders, with a focus on GWAS risk genes implicated in microglia, their interplay with other cell types and shared convergence of GWAS risk loci on microglia.

Unveiling the link between environmental management accounting, energy efficiency, and accountability in state-owned enterprises: An integrated analysis using PLS-SEM and fsQCA

The rising importance of sustainability and accountability in organizations has prompted the exploration of innovative approaches to enhance environmental performance and energy efficiency (ENE). The purpose of this research is to examine the extent to which environmental management accounting (EMA) and ENE practices contribute to accountability within state-owned enterprises (SOEs) in Bangladesh. This study employs both symmetrical (PLS-SEM) and asymmetrical (fsQCA) approaches. The study verifies internal consistency, reliability, validity, common method bias, and collinearity issues through measurement model analysis and conducts path analysis after testing model fitness in structural model analysis. Finally, the study uses fsQCA to conduct in-depth analyses of causal contributions from different conditions to a specific outcome of interest. The PLS-SEM analysis revealed significant positive relationships between EMA and ENE with transparency, responsibility, and answerability. These results indicate that organizations adopting EMA and ENE practices are more likely to exhibit higher levels of transparency, demonstrate greater responsibility towards environmental matters, and be more answerable to stakeholders for their accountability. Further, the study identified ENE as a mediator of EMA and accountability. Finally, the fsQCA analysis supported the importance of both EMA and ENE as necessary conditions for achieving accountability indicating the integration of EMA and ENE to foster transparency, responsibility, and answerability effectively. This study implies that by implementing EMA systems and focusing on energy-efficient operations, organizations can enhance transparency, responsibility, and answerability to stakeholders, fostering a positive image and reputation. Therefore, SOEs may consider integrating these practices into their overall sustainability strategies to maximize their impact on accountability and environmental performance.

Cross-species conservation in the regulation of parvalbumin by perineuronal nets.

Parvalbumin (PV) neurons play an integral role in regulating neural dynamics and plasticity. Therefore, understanding the factors that regulate PV expression is important for revealing modulators of brain function. While the contribution of PV neurons to neural processes has been studied in mammals, relatively little is known about PV function in non-mammalian species, and discerning similarities in the regulation of PV across species can provide insight into evolutionary conservation in the role of PV neurons. Here we investigated factors that affect the abundance of PV in PV neurons in sensory and motor circuits of songbirds and rodents. In particular, we examined the degree to which perineuronal nets (PNNs), extracellular matrices that preferentially surround PV neurons, modulate PV abundance as well as how the relationship between PV and PNN expression differs across brain areas and species and changes over development. We generally found that cortical PV neurons that are surrounded by PNNs (PV+PNN neurons) are more enriched with PV than PV neurons without PNNs (PV-PNN neurons) across both rodents and songbirds. Interestingly, the relationship between PV and PNN expression in the vocal portion of the basal ganglia of songbirds (Area X) differed from that in other areas, with PV+PNN neurons having lower PV expression compared to PV-PNN neurons. These relationships remained consistent across development in vocal motor circuits of the songbird brain. Finally, we discovered a causal contribution of PNNs to PV expression in songbirds because degradation of PNNs led to a diminution of PV expression in PV neurons. These findings reveal a conserved relationship between PV and PNN expression in sensory and motor cortices and across songbirds and rodents and suggest that PV neurons could modulate plasticity and neural dynamics in similar ways across songbirds and rodents.

Epistemic Complicity

AbstractThere is a widely accepted distinction between being directly responsible for a wrongdoing versus being somehow indirectly or vicariously responsible for the wrongdoing of another person or collective. Often this is couched in analyses of complicity, and complicity's role in the relationship between individual and collective wrongdoing. Complicity is important because, inter alia, it allows us to make sense of individuals who may be blameless or blameworthy to a relatively low degree for their immediate conduct, but are nevertheless blameworthy to a higher degree for their implication in some larger (or another person's) wrongdoing. In this paper, I argue that there is a distinctively epistemic kind of complicity. First, I motivate the distinction between direct and vicarious responsibility with three interlocking arguments, respectively appealing to: (i) the structure of rational agency; (ii) linguistic considerations; (iii) the role of ‘principal' vs. ‘accomplice’ in legal doctrine. I show how these arguments naturally extend to the epistemic domain, motivating an epistemic form of vicarious responsibility. I then examine complicity as a mechanism of vicarious epistemic responsibility. To fill this out, I engage with an epistemic analogue of the debate about the role of intention versus causal contribution in complicity. I propose a Casual Account of Epistemic Complicity, arguing that it accommodates a wide range of cases, and enables fine-grained explanations of degrees of culpability for epistemic complicity. With an adequate account of epistemic complicity on hand, we can explain what is objectionable about an important class of epistemic agent who, on an individual level, may be epistemically blameless or blameworthy to a relatively low degree, but whose relation to other individuals or collectives nevertheless makes them epistemically blameworthy to a higher degree. I explore some broader implications of this result.