Burden of acute kidney injury in HIV patients under deoxycholate amphotericin B therapy for cryptococcal meningitis and cost-minimization analysis of amphotericin B lipid complex.

Deoxycholate amphotericin B (d-AMB) has a higher rate of acute kidney injury (AKI) in comparison of lipid formulations. However, lipid amphotericin B has high costs in developing countries. The aim of this study is to assemble a model of cost-minimization of amphotericin B lipid complex (ABLC) in patients with cryptococcal meningitis. This is a retrospective study done in a cohort of patients with cryptococcal meningitis to study the economic impact of its use in developing countries. Cost analysis were based on direct cost of different antifungal therapies, chronic dialysis after discharge, and survival of patients based on a retrospective cohort of 102 patients infected with human immunodeficiency virus with confirmed diagnosis of cryptococcal meningitis. From 102 patients treated with d-AMB, 60.78% developed any grade of AKI and 10.78% developed AKI demanding hemodialysis. The percentage of patients with meningeal cryptococcosis treated with d-AMB that requeired chronic HD was 2.39%. The same model was performed for patient that would be treated with ABLC, which resulted in 0.20% of patients demanding chronic HD due to its lower nephrotoxicity. When the model is applied in 100 patients, the total costs with d-AMB would be US$ 184,543 and with ABLC would be US$ 1,640,109 in 5 years. Treatment with ABLC would be cost saving in comparison to d-AMB treatment, if early switch of treatment occurred in patients presenting AKI. The change should be as soon as possible to avoid further complication, like dialysis, which is associated with a lower life expectancy.

Microbiological profile and susceptibility pattern of surgical site infections related to orthopaedic trauma.

BACKGROUND: Understanding the epidemiology of microorganisms associated with surgical site infections related to orthopaedic trauma (SSI-ROT) is important in establishing treatment protocols. The aim of this study was to evaluate the etiology and susceptibility pattern of SSIs related to orthopaedic trauma in a Brazilian reference hospital for trauma. METHODS: Patients with SSI-ROT in a Brazilian reference hospital for trauma were retrospectively analyzed. All patients with orthopaedic trauma who underwent a surgical procedure and developed SSI within one year were included. All patients had culture samples from the surgical site obtained from biopsy of bone or soft tissue. Clinical and epidemiological data of the patients were collected. RESULTS: A total of 147 patients with trauma-related infection were included in the analysis. The mean time to infection was 55.5 days, and the mean duration of hospitalization was 20.0 days. The in-hospital mortality rate after infection was 5.4%. Cultures were obtained from all patients, with 104 samples obtained from soft tissues and 43 samples from bone. The positivity rate was 93.2%. Among the isolates, 56.5% (77 patients) were gram-negative bacteria and 43.8% (60 patients) were gram-positive bacteria. Staphylococcus aureus was identified in 34%, Enterobacter spp. in 14.9%, and Pseudomonas aeruginosa in 11.6%. Staphylococcus aureus presented a higher positivity in bone samples (odds ratio, 1.29; 95% CI, 1.01-1.70; p = 0.04). Few microorganisms were multi-resistant. CONCLUSION: SSI in orthopaedic trauma can be associated with gram-negative bacilli, the susceptibility profile of which suggested that most infections occur after discharge. Staphylococcus aureus infections were commonly caused by methicillin-susceptible isolates, and this susceptibility to oral antibiotic options helps in the dehospitalization of patients.

Pharmacological aspects and spectrum of action of ceftazidime-avibactam: a systematic review.

PURPOSE: Ceftazidime-avibactam is an antimicrobial association active against several Enterobacteriaceae species, including those resistant to carbapenem. Considering the importance of this drug in the current panorama of multidrug-resistant bacteria, we performed a systematic review about ceftazidime-avibactam with emphasis on clinical and pharmacological published data. METHODS: A systematic search of the medical literature was performed. The databases searched included MEDLINE, EMBASE and Web of Science (until September 2017). The search terms used were 'avibactam', 'NXL104' and 'AVE1330A'. Bibliographies from those studies were also reviewed. Ceftazidime was not included as a search term, once relevant studies about avibactam in association with other drugs could be excluded. Only articles in English were selected. No statistical analysis or quality validation was included in this review. RESULTS: A total of 151 manuscripts were included. Ceftazidime-avibactam has limited action against anaerobic bacteria. Avibactam is a potent inhibitor of class A, class C, and some class D enzymes, which includes KPC-2. The best pharmacodynamic profile of ceftazidime-avibactam is ƒT > MIC, validated in an animal model of soft tissue infection. Three clinical trials showed the efficacy of ceftazidime-avibactam in patients with intra-abdominal and urinary infections. Ceftazidime-avibactam has been evaluated versus meropenem/doripenem in hospitalized adults with nosocomial pneumonia, neutropenic patients and pediatric patients. CONCLUSION: Ceftazidime-avibactam has a favorable pharmacokinetic profile for severe infections and highly active against carbapenemases of KPC-2 type.

Stochastic transitions into silence cause noise correlations in cortical circuits.

The spiking activity of cortical neurons is highly variable. This variability is generally correlated among nearby neurons, an effect commonly interpreted to reflect the coactivation of neurons due to anatomically shared inputs. Recent findings, however, indicate that correlations can be dynamically modulated, suggesting that the underlying mechanisms are not well understood. Here, we investigate the hypothesis that correlations are dominated by neuronal coinactivation: the occurrence of brief silent periods during which all neurons in the local network stop firing. We recorded spiking activity from large populations of neurons in the auditory cortex of anesthetized rats across different brain states. During spontaneous activity, the reduction of correlation accompanying brain state desynchronization was largely explained by a decrease in the density of the silent periods. The presentation of a stimulus caused an initial drop of correlations followed by a rebound, a time course that was mimicked by the instantaneous silence density. We built a rate network model with fluctuation-driven transitions between a silent and an active attractor and assumed that neurons fired Poisson spike trains with a rate following the model dynamics. Variations of the network external input altered the transition rate into the silent attractor and reproduced the relation between correlation and silence density found in the data, both in spontaneous and evoked conditions. This suggests that the observed changes in correlation, occurring gradually with brain state variations or abruptly with sensory stimulation, are due to changes in the likeliness of the microcircuit to transiently cease firing.

Endoscopic transluminal debridement of the pancreas.

Most patients with acute pancreatitis will develop edematous pancreatitis with a mild course and spontaneous resolution within several days to a few weeks. However, about 20% of patients will develop necrotizing pancreatitis, which carries a high mortality. This case report focuses on a patient with infected necrosis of the pancreas, which is managed with endoscopic transluminal debridement, a safe alternative to open surgery.

Stroke and cardiac papillary fibroelastoma: mechanical thrombectomy after thrombolytic therapy.

We describe a case of a 34-year-old man with a sudden development of right hemiparesis and aphasia because of infarction of the left middle cerebral artery that was submitted to intravenous (IV) recombinant tissue plasminogen activator and mechanical thrombectomy. Transesophageal echocardiogram showed a small mass on the anterior leaflet of the mitral valve. Cardiac surgery was performed, and histological examination of the removed material was consistent with cardiac papillary fibroelastoma (CPF). Experience in using IV thrombolysis for the treatment of embolic stroke because of CPF is limited. To the best of our knowledge, only 3 patients are reported in literature in whom acute ischemic stroke and associated CPF were treated with thrombolytic therapy. A discussion of the efficacy of IV thrombolysis and the possible superiority of mechanical thrombectomy is included.

Economic and budgetary impact evaluation of isavuconazole (Cresemba®) versus voriconazole (Vfend®) for the treatment of patients with possible invasive aspergillosis from the perspective of the Brazilian supplementary health system.

OBJECTIVES: This study aims to evaluate the cost-utility and the budgetary impact of isavuconazole compared to voriconazole in patients with suspected invasive aspergillosis (IA) from the perspective of the Brazilian supplementary health system (SHS). METHODS: In this model, a decision tree was developed and included patients with possible IA. Efficacy parameters were extracted from the clinical studies. Drug acquisition, hospitalization costs and adverse events were also collected. Alternative 3- and 10-year time horizon scenarios were used. In addition, deterministic and probabilistic sensitivity analyses were simulated. A budget impact analysis of isavuconazole versus voriconazole was performed, assuming a time horizon of 5 years. In addition, sensitivity analyses were conducted to assess the robustness of the model. Results are reported in Brazilian Real (BRL), year values 2022. RESULTS: The economic analysis of the base case showed that isavuconazole is associated with a saving of 95,174.00 BRL per patient compared to voriconazole. All other simulated scenarios showed that isavuconazole is dominant versus comparators when considering a willingness to pay 40,688.00 BRL/Quality-Adjusted Life Years (QALY). The results were considered robust by the sensitivity analyses. The budget impact analysis showed that the incorporation of isavuconazole generates savings to the SHS, compared to voriconazole, of approximately 20.5 million BRL in the first year. This reaches about 54 million BRL in the fifth incorporation year, considering the market penetration of 20% in the first year, and 50% in the fifth year. CONCLUSION: Compared with voriconazole, isavuconazole is regarded as a dominant treatment strategy for patients with suspected IA and generates savings for the SHS.

Performance of Metarhizium rileyi Nm017: nutritional supplementation to improve production and quality conidia.

This study aimed to analyze the effect of nutritional supplements on improving conidia production of Metarhizium rileyi Nm017 at laboratory scale (yields of conidia/substrate and biomass/substrate, and substrate consumption). Also, the influence on quality parameters were evaluated (germination at 36 and 48 h, enzymatic activity, and insecticidal activity on Helicoverpa zea). Six treatments (T1-T6) were assessed and all of them reached maximum conidia concentration after 7 days fermentation, a feasible production timetable. Yields from treatment T6 (yeast extract + V8 juice) were 1.5-threefold higher than the other treatments. Conidia from T6 reached germinations of 56% and 12% at 36 and 48 h, respectively, higher than T1 (without supplements), which had the lowest values found. M. rileyi conidia obtained from treatment T6 had the highest enzymatic activity (0.45 U chitinase g-1, 0.28 U lipase g-1, and 1.29 U protease g-1). However, treatments with the highest conidia yields and enzymatic activity were not positively correlated to the efficacy against H. zea. When M. rileyi was produced on T5 (yeast hydrolysate + V8 juice), conidia were 35% more virulent than treatment T6. The findings evidenced the noticeable impact of nutritional substrate amended for conidia production and quality. This work showed the relevance of insecticidal activity assessment as a selection criterion in the mass production development of a biocontrol agent.

Rapid, systematic updating of movement by accumulated decision evidence.

Acting in the natural world requires not only deciding among multiple options but also converting decisions into motor commands. How the dynamics of decision formation influence the fine kinematics of response movement remains, however, poorly understood. Here we investigate how the accumulation of decision evidence shapes the response orienting trajectories in a task where freely-moving rats combine prior expectations and auditory information to select between two possible options. Response trajectories and their motor vigor are initially determined by the prior. Rats movements then incorporate sensory information as early as 60 ms after stimulus onset by accelerating or slowing depending on how much the stimulus supports their initial choice. When the stimulus evidence is in strong contradiction, rats change their mind and reverse their initial trajectory. Human subjects performing an equivalent task display a remarkably similar behavior. We encapsulate these results in a computational model that, by mapping the decision variable onto the movement kinematics at discrete time points, captures subjects' choices, trajectories and changes of mind. Our results show that motor responses are not ballistic. Instead, they are systematically and rapidly updated, as they smoothly unfold over time, by the parallel dynamics of the underlying decision process.

Correlation between neural spike trains increases with firing rate.

Populations of neurons in the retina, olfactory system, visual and somatosensory thalamus, and several cortical regions show temporal correlation between the discharge times of their action potentials (spike trains). Correlated firing has been linked to stimulus encoding, attention, stimulus discrimination, and motor behaviour. Nevertheless, the mechanisms underlying correlated spiking are poorly understood, and its coding implications are still debated. It is not clear, for instance, whether correlations between the discharges of two neurons are determined solely by the correlation between their afferent currents, or whether they also depend on the mean and variance of the input. We addressed this question by computing the spike train correlation coefficient of unconnected pairs of in vitro cortical neurons receiving correlated inputs. Notably, even when the input correlation remained fixed, the spike train output correlation increased with the firing rate, but was largely independent of spike train variability. With a combination of analytical techniques and numerical simulations using 'integrate-and-fire' neuron models we show that this relationship between output correlation and firing rate is robust to input heterogeneities. Finally, this overlooked relationship is replicated by a standard threshold-linear model, demonstrating the universality of the result. This connection between the rate and correlation of spiking activity links two fundamental features of the neural code.

COVID-19 in real world: Survival and medical costs of hospitalized patients in Brazil´s first wave.

OBJECTIVE: To evaluate survival and direct medical costs of patients admitted in private hospitals with COVID-19 during the first wave. METHODS: A retrospective, observational study analyzing survival and the economic data retrieved on hospitalized patients with COVID-19. Data from March 2020 to December 2020. The direct cost of hospitalization was estimated using the microcosting method with each individual hospitalization. RESULTS: 342 cases were evaluated. Median age of 61.0 (95% CI 57.0‒65.0). 194 (56.7%) were men. The mortality rate was higher in the female sex (p = 0.0037), ICU (p < 0.001), mechanical ventilation (p<0.001) and elderly groups. 143 (41.8%) patients were admitted to the ICU (95% CI 36.6%-47.1%), of which 60 (41.9%) required MV (95% CI 34.0%-50.0%). Global LOS presented median of 6.7 days (95% CI 6.0-7.2). Mean costs were US$ 7,060,00 (95% CI 5,300.94-8,819,00) for each patient. Mean cost for patients discharged alive and patients deceased was US$ 5,475.53 (95% CI 3,692.91-7,258.14) and US$ 12,955.19 (95% CI 8,106.61-17,803.76), respectively (p < 0.001). CONCLUSIONS: Patients admitted with COVID-19 in these private hospitals point to great economic impact, mainly in the elderly and high-risk patients. It is key to better understand such costs in order to be prepared to make wise decisions during the current and future global health emergencies.

Recurrent networks endowed with structural priors explain suboptimal animal behavior.

The strategies found by animals facing a new task are determined both by individual experience and by structural priors evolved to leverage the statistics of natural environments. Rats quickly learn to capitalize on the trial sequence correlations of two-alternative forced choice (2AFC) tasks after correct trials but consistently deviate from optimal behavior after error trials. To understand this outcome-dependent gating, we first show that recurrent neural networks (RNNs) trained in the same 2AFC task outperform rats as they can readily learn to use across-trial information both after correct and error trials. We hypothesize that, although RNNs can optimize their behavior in the 2AFC task without any a priori restrictions, rats' strategy is constrained by a structural prior adapted to a natural environment in which rewarded and non-rewarded actions provide largely asymmetric information. When pre-training RNNs in a more ecological task with more than two possible choices, networks develop a strategy by which they gate off the across-trial evidence after errors, mimicking rats' behavior. Population analyses show that the pre-trained networks form an accurate representation of the sequence statistics independently of the outcome in the previous trial. After error trials, gating is implemented by a change in the network dynamics that temporarily decouple the categorization of the stimulus from the across-trial accumulated evidence. Our results suggest that the rats' suboptimal behavior reflects the influence of a structural prior that reacts to errors by isolating the network decision dynamics from the context, ultimately constraining the performance in a 2AFC laboratory task.

Temporal integration is a robust feature of perceptual decisions.

Making informed decisions in noisy environments requires integrating sensory information over time. However, recent work has suggested that it may be difficult to determine whether an animal's decision-making strategy relies on evidence integration or not. In particular, strategies based on extrema-detection or random snapshots of the evidence stream may be difficult or even impossible to distinguish from classic evidence integration. Moreover, such non-integration strategies might be surprisingly common in experiments that aimed to study decisions based on integration. To determine whether temporal integration is central to perceptual decision-making, we developed a new model-based approach for comparing temporal integration against alternative 'non-integration' strategies for tasks in which the sensory signal is composed of discrete stimulus samples. We applied these methods to behavioral data from monkeys, rats, and humans performing a variety of sensory decision-making tasks. In all species and tasks, we found converging evidence in favor of temporal integration. First, in all observers across studies, the integration model better accounted for standard behavioral statistics such as psychometric curves and psychophysical kernels. Second, we found that sensory samples with large evidence do not contribute disproportionately to subject choices, as predicted by an extrema-detection strategy. Finally, we provide a direct confirmation of temporal integration by showing that the sum of both early and late evidence contributed to observer decisions. Overall, our results provide experimental evidence suggesting that temporal integration is an ubiquitous feature in mammalian perceptual decision-making. Our study also highlights the benefits of using experimental paradigms where the temporal stream of sensory evidence is controlled explicitly by the experimenter, and known precisely by the analyst, to characterize the temporal properties of the decision process.

Postsurgical pyoderma gangrenosum complicating reduction mammaplasty.

UNLABELLED: Reduction mammaplasty is one of the most common surgeries performed by plastic surgeons. It relieves back and neck pain and improves the aesthetic contour of the ptotic breast. Postsurgical pyoderma gangrenosum (PSPG) is an unusual inflammatory disorder leading to rapidly progressive skin necrosis that can occur after any surgical procedure. The skin lesions have the characteristic appearance of ulcers with a purple-colored border and erythematous halo. Clinically, the patient has a low fever and severe local pain. In the majority of cases this disease is misdiagnosed as severe infection leading to improper debridement, exacerbating the problem. The mainstay of therapy for PSPG is still nonoperative and focuses on immunosuppressive medications and local wound care, which allows healing in the majority of the cases. It is important for plastic surgeons and infectologists to be cognizant of this entity, as a delay in diagnosis and management can be life-threatening and lead to considerable tissue loss and disfigurement of the breast. The authors report a case of reduction mammaplasty complicated with PSPG and its treatment. LEVEL OF EVIDENCE V: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Clinical trial and detection of SARS-CoV-2 by a commercial breath analysis test based on Terahertz technology.

Public health threats such as the current COVID-19 pandemics have required prompt action by the local, national, and international authorities. Rapid and noninvasive diagnostic methods may provide on-site detection and immediate social isolation, used as tools to rapidly control virus spreading. Accordingly, the aim of the present study was to evaluate a commercial breath analysis test (TERA.Bio®) and deterministic algorithm for detecting the SARS-CoV-2 spectral signature of Volatile Organic Compounds present in exhaled air samples of suspicious persons from southern Brazil. A casuistic total of 70 infected and 500 non-infected patients were sampled, tested, and results later compared to RT-qPCR as gold standard. Overall, the test showed 92.6% sensitivity and 96.0% specificity. No statistical correlation was observed between SARS-CoV-2 positivity and infection by other respiratory diseases. Further studies should focus on infection monitoring among asymptomatic persons. In conclusion, the breath analysis test herein may be used as a fast, on-site, and easy-to-apply screening method for diagnosing COVID-19.

Nationwide Access to Endovascular Treatment for Acute Ischemic Stroke in Portugal.

INTRODUCTION: Since the publication of endovascular treatment trials and European Stroke Guidelines, Portugal has re-organized stroke healthcare. The nine centers performing endovascular treatment are not equally distributed within the country, which may lead to differential access to endovascular treatment. Our main aim was to perform a descriptive analysis of the main treatment metrics regarding endovascular treatment in mainland Portugal and its administrative districts. MATERIAL AND METHODS: A retrospective national multicentric cohort study was conducted, including all ischemic stroke patients treated with endovascular treatment in mainland Portugal over two years (July 2015 to June 2017). All endovascular treatment centers contributed to an anonymized database. Demographic, stroke-related and procedure-related variables were collected. Crude endovascular treatment rates were calculated per 100 000 inhabitants for mainland Portugal, and each district and endovascular treatment standardized ratios (indirect age-sex standardization) were also calculated. Patient time metrics were computed as the median time between stroke onset, first-door, and puncture. RESULTS: A total of 1625 endovascular treatment procedures were registered. The endovascular treatment rate was 8.27/100 000 inhabitants/year. We found regional heterogeneity in endovascular treatment rates (1.58 to 16.53/100 000/year), with higher rates in districts closer to endovascular treatment centers. When analyzed by district, the median time from stroke onset to puncture ranged from 212 to 432 minutes, reflecting regional heterogeneity. DISCUSSION: Overall endovascular treatment rates and procedural times in Portugal are comparable to other international registries. We found geographic heterogeneity, with lower endovascular treatment rates and longer onset-to-puncture time in southern and inner regions. CONCLUSION: The overall national rate of EVT in the first two years after the organization of EVT-capable centers is one of the highest among European countries, however, significant regional disparities were documented. Moreover, stroke-onset-to-first-door times and in-hospital procedural times in the EVT centers were comparable to those reported in the randomized controlled trials performed in high-volume tertiary hospitals.

Introdução: A aprovação do tratamento endovascular para o acidente vascular cerebral isquémico obrigou à reorganização dos cuidados de saúde em Portugal. Os nove centros que realizam tratamento endovascular não estão distribuídos equitativamente pelo território, o que poderá causar acesso diferencial a tratamento. O principal objetivo deste estudo é realizar uma análise descritiva da frequência e métricas temporais do tratamento endovascular em Portugal continental e seus distritos. Material e Métodos: Estudo de coorte nacional multicêntrico, incluindo todos os doentes com acidente vascular cerebral isquémico submetidos a tratamento endovascular em Portugal continental durante um período de dois anos (julho 2015 a junho 2017). Foram colhidos dados demográficos, relacionados com o acidente vascular cerebral e variáveis do procedimento. Taxas de tratamento endovascular brutas e ajustadas (ajuste indireto a idade e sexo) foram calculadas por 100 000 habitantes/ano para Portugal continental e cada distrito. Métricas de procedimento como tempo entre instalação, primeira porta e punção foram também analisadas. Resultados: Foram registados 1625 tratamentos endovasculares, indicando uma taxa bruta nacional de tratamento endovascular de 8,27/100 000 habitantes/ano. As taxas de tratamento endovascular entre distritos variaram entre 1,58 e 16,53/100 000/ano, com taxas mais elevadas nos distritos próximos a hospitais com tratamento endovascular. O tempo entre sintomas e punção femural entre distritos variou entre 212 e 432 minutos. Discussão: A análise nacional a taxas de tratamento endovascular e tempos de atuação é comparável a outros registos internacionais. Verificaram-se heterogeneidades geográficas, com taxas de tratamento endovascular menores e maior tempo para tratamento nos distritos do sul e interior. Conclusão: Portugal continental apresenta uma taxa nacional de tratamento endovascular elevada, apresentando, contudo, assimetrias regionais no acesso. As métricas temporais foram comparáveis com as observadas nos ensaios clínicos piloto.

Flexible categorization in perceptual decision making.

Perceptual decisions rely on accumulating sensory evidence. This computation has been studied using either drift diffusion models or neurobiological network models exhibiting winner-take-all attractor dynamics. Although both models can account for a large amount of data, it remains unclear whether their dynamics are qualitatively equivalent. Here we show that in the attractor model, but not in the drift diffusion model, an increase in the stimulus fluctuations or the stimulus duration promotes transitions between decision states. The increase in the number of transitions leads to a crossover between weighting mostly early evidence (primacy) to weighting late evidence (recency), a prediction we validate with psychophysical data. Between these two limiting cases, we found a novel flexible categorization regime, in which fluctuations can reverse initially-incorrect categorizations. This reversal asymmetry results in a non-monotonic psychometric curve, a distinctive feature of the attractor model. Our findings point to correcting decision reversals as an important feature of perceptual decision making.

Proactive and reactive accumulation-to-bound processes compete during perceptual decisions.

Standard models of perceptual decision-making postulate that a response is triggered in reaction to stimulus presentation when the accumulated stimulus evidence reaches a decision threshold. This framework excludes however the possibility that informed responses are generated proactively at a time independent of stimulus. Here, we find that, in a free reaction time auditory task in rats, reactive and proactive responses coexist, suggesting that choice selection and motor initiation, commonly viewed as serial processes, are decoupled in general. We capture this behavior by a novel model in which proactive and reactive responses are triggered whenever either of two competing processes, respectively Action Initiation or Evidence Accumulation, reaches a bound. In both types of response, the choice is ultimately informed by the Evidence Accumulation process. The Action Initiation process readily explains premature responses, contributes to urgency effects at long reaction times and mediates the slowing of the responses as animals get satiated and tired during sessions. Moreover, it successfully predicts reaction time distributions when the stimulus was either delayed, advanced or omitted. Overall, these results fundamentally extend standard models of evidence accumulation in decision making by showing that proactive and reactive processes compete for the generation of responses.

Cortical state transitions and stimulus response evolve along stiff and sloppy parameter dimensions, respectively.

Previous research showed that spontaneous neuronal activity presents sloppiness: the collective behavior is strongly determined by a small number of parameter combinations, defined as 'stiff' dimensions, while it is insensitive to many others ('sloppy' dimensions). Here, we analyzed neural population activity from the auditory cortex of anesthetized rats while the brain spontaneously transited through different synchronized and desynchronized states and intermittently received sensory inputs. We showed that cortical state transitions were determined by changes in stiff parameters associated with the activity of a core of neurons with low responses to stimuli and high centrality within the observed network. In contrast, stimulus-evoked responses evolved along sloppy dimensions associated with the activity of neurons with low centrality and displaying large ongoing and stimulus-evoked fluctuations without affecting the integrity of the network. Our results shed light on the interplay among stability, flexibility, and responsiveness of neuronal collective dynamics during intrinsic and induced activity.