Papers by Camila Sardeto Deolindo
bioRxiv (Cold Spring Harbor Laboratory), Mar 30, 2024
The human brain has a remarkable ability to learn and update its beliefs about the world. Here, w... more The human brain has a remarkable ability to learn and update its beliefs about the world. Here, we investigate how thermosensory learning shapes our subjective experience of temperature and the misperception of pain in response to harmless thermal stimuli. Through computational modeling, we demonstrate that the brain uses a probabilistic predictive coding scheme to update beliefs about temperature changes based on their uncertainty. We find that these expectations directly modulate the perception of pain in the thermal grill illusion. Quantitative microstructural brain imaging revealed that the myeloarchitecture and iron content of the somatosensory cortex, the posterior insula and the amygdala reflect inter-individual variability in computational parameters related to learning and the degree to which uncertainty modulates illusory pain perception. Our findings offer a new framework to explain how the brain infers pain from innocuous thermal inputs. Our model has important implications for understanding the etiology of thermosensory symptoms in chronic pain conditions.
bioRxiv (Cold Spring Harbor Laboratory), Mar 14, 2024
In the thermal grill illusion (TGI), the spatial alternation of non-noxious warm and cold tempera... more In the thermal grill illusion (TGI), the spatial alternation of non-noxious warm and cold temperatures elicits burning sensations that resemble the presence of noxious stimuli. Previous research has largely relied on the use of specific temperature values (i.e., 20°C and 40°C) to study this phenomenon in both healthy individuals and patient populations. However, this methodology fails to account for inter-individual differences in thermal sensitivity, limiting the precision with which TGI responses can be evaluated across diverse populations. To address this gap, we created a Two-Dimensional Thermal Grill Calibration (2D-TGC) protocol, enabling an efficient and precise estimation of the combinations of warm and cold temperatures needed to elicit burning sensations tailored to each individual. By applying the 2D-TGC protocol in 43 healthy participants, we demonstrated key findings: (1) The TGI can be thresholded using an adaptive psychophysical method. (2) Multiple combinations of warm and cold temperatures can elicit this phenomenon. (3) The protocol facilitated the identification of temperature combinations that elicit TGI with varying levels of probability, intensity, and perceived quality ranging from freezing cold to burning hot. (4) TGI responsivity can be quantified as a continuous variable, moving beyond the conventional classification of individuals as responders vs. non-responders based on arbitrary temperature values. The 2D-TGC offers a comprehensive approach to investigate the TGI across populations with altered thermal sensitivity, and can be integrated with other methods (e.g., neuroimaging) to elucidate the mechanisms responsible for perceptual illusions in the thermo-nociceptive system.
bioRxiv (Cold Spring Harbor Laboratory), Aug 23, 2023
Paradoxical Heat Sensation (PHS) is the remarkable feeling of warmth or heat pain while the skin ... more Paradoxical Heat Sensation (PHS) is the remarkable feeling of warmth or heat pain while the skin is cooling . Despite its initial documentation over 100 years ago (Goldscheider, 1884), a unified explanation for this perplexing experience remains elusive, defying traditional models of thermosensation. Here, we apply contrast enhancement principles, known for their instrumental role in understanding visual illusions, to the domain of thermosensation. Contrast enhancement describes the amplification of two contrasting visual features , such as the enhanced perception of an edge between a light and dark bar. We extend this concept to thermosensation, which encompasses an enhancement of the difference between sequential warming and cooling of the skin and predict that this mechanism underlies the experience of PHS. Remarkably, thermal contrast, defined as the normalised difference between successive temporal warm and cold temperatures, predicts the occurrence of PHS. Our findings reveal compelling evidence supporting the role of thermal contrast in the generation of PHS, shedding light on its underlying mechanism and offering a framework for understanding broader encoding principles in thermosensation.
Communications psychology, Apr 24, 2024
Paradoxical Heat Sensation (PHS) is the remarkable feeling of warmth or heat pain while the skin ... more Paradoxical Heat Sensation (PHS) is the remarkable feeling of warmth or heat pain while the skin is cooling. Despite its initial documentation over 100 years ago, a unified explanation for this perplexing experience remains elusive. Here we apply contrast enhancement principles, known for their instrumental role in understanding visual illusions, to the domain of thermosensation. Contrast enhancement describes the amplification of two contrasting visual features, such as the enhanced perception of an edge between a light and dark bar. In thermosensation, this encompasses an enhancement of the difference between sequential warming and cooling of the skin, and is defined as the normalised difference between successive temporal warm and cold temperatures. Remarkably, thermal contrast predicts the occurrence of PHS. Our findings reveal compelling evidence supporting the role of thermal contrast in the generation of PHS, shedding light on its underlying mechanism and offering a framework for broader encoding principles in thermosensation and pain.
Brain Topography
Over the last decade, EEG resting-state microstate analysis has evolved from a niche existence to... more Over the last decade, EEG resting-state microstate analysis has evolved from a niche existence to a widely used and well-accepted methodology. The rapidly increasing body of empirical findings started to yield overarching patterns of associations of biological and psychological states and traits with specific microstate classes. However, currently, this cross-referencing among apparently similar microstate classes of different studies is typically done by “eyeballing” of printed template maps by the individual authors, lacking a systematic procedure. To improve the reliability and validity of future findings, we present a tool to systematically collect the actual data of template maps from as many published studies as possible and present them in their entirety as a matrix of spatial similarity. The tool also allows importing novel template maps and systematically extracting the findings associated with specific microstate maps from ongoing or published studies. The tool also allows...
Limitations of principal component analysis as a method to detect neuronal assemblies
2014 IEEE 16th International Conference on e-Health Networking, Applications and Services (Healthcom), 2014
The anatomical and functional characterization of neuronal assemblies (NAs) is a major challenge ... more The anatomical and functional characterization of neuronal assemblies (NAs) is a major challenge in neuroscience. Principal component analysis (PCA) is a widely used method for feature detection, however, when dealing with neuronal data analysis, its limitations have not yet been fully understood. Our work complements previous PCA studies which, in general, characterise NAs based solely on excitatory neuronal interactions. We analysed the performance of PCA in two neglected scenarios: assemblies containing patterns of neural interactions (1) with inhibition and (2) with delays. The analyses considered two types of artificially generated data, one drawn from a traditional Poissonian model, and the other drawn from a latent multivariate Gaussian model; in both models, data from a behaving Wistar rat was used for parameter tuning. Our results highlight scenarios in which neglecting complex interactions between neurons can lead to false conclusions when using PCA to detect NAs. Also, we reinforce the importance of more realistic simulations in the evaluation of neuronal signal processing algorithms.
Method for the Synchronization of Data Recorders by Coupling Accelerometer Data
2021 IEEE International Symposium on Inertial Sensors and Systems (INERTIAL)
This paper presents a method to synchronize data acquisition devices that are mechanically couple... more This paper presents a method to synchronize data acquisition devices that are mechanically coupled, having attached an accelerometer to each device. A common time base for the accelerometer signals are obtained through the identification of pairing salient peaks and applying line-fitting through the potential matches. Aligning data recorded from different sources is important to precisely provide an observation of the state of a system in time (sensor fusion), to estimate the correlation between its variables and to correlate variables to time-based events. A data link between devices is not always possible or convenient. If the acquisition devices are mechanically coupled, such as being in the same body or vehicle, we propose to synchronize the data recorded from both by using the accelerometers signals to bridge. The provided solution is an automated process to find the temporal reference between accelerometer signals. Several signal processing steps are taken after data collection and storage: inconsistency removal and filtering, detection of maxima and minima, selection of saliencies, description through a characteristic pair of numbers: the interval lengths between it and its successor and its predecessor, listing possible matches between salient points, selection of the topmost relevant matches and line fitting with consensus. We discuss qualitative similarities of related work. Quantitative results are also presented by using the multidisciplinary study that motivated this work, with simultaneous data from the instrumentation of a helicopter and pilot physiological data. To conclude, we discuss the limitations of the presented approach and future work.
Method for the Synchronization of Data Recorders by Coupling Accelerometer Data
2021 IEEE International Symposium on Inertial Sensors and Systems (INERTIAL)
This paper presents a method to synchronize data acquisition devices that are mechanically couple... more This paper presents a method to synchronize data acquisition devices that are mechanically coupled, having attached an accelerometer to each device. A common time base for the accelerometer signals are obtained through the identification of pairing salient peaks and applying line-fitting through the potential matches. Aligning data recorded from different sources is important to precisely provide an observation of the state of a system in time (sensor fusion), to estimate the correlation between its variables and to correlate variables to time-based events. A data link between devices is not always possible or convenient. If the acquisition devices are mechanically coupled, such as being in the same body or vehicle, we propose to synchronize the data recorded from both by using the accelerometers signals to bridge. The provided solution is an automated process to find the temporal reference between accelerometer signals. Several signal processing steps are taken after data collection and storage: inconsistency removal and filtering, detection of maxima and minima, selection of saliencies, description through a characteristic pair of numbers: the interval lengths between it and its successor and its predecessor, listing possible matches between salient points, selection of the topmost relevant matches and line fitting with consensus. We discuss qualitative similarities of related work. Quantitative results are also presented by using the multidisciplinary study that motivated this work, with simultaneous data from the instrumentation of a helicopter and pilot physiological data. To conclude, we discuss the limitations of the presented approach and future work.
A cluster based model for brain activity data staging
Biomedical Signal Processing and Control
Frontiers in Neural Circuits, Jan 11, 2018
Accumulating evidence suggests that neural interactions are distributed and relate to animal beha... more Accumulating evidence suggests that neural interactions are distributed and relate to animal behavior, but many open questions remain. The neural assembly hypothesis, formulated by Hebb, states that synchronously active single neurons may transiently organize into functional neural circuits-neuronal assemblies (NAs)-and that would constitute the fundamental unit of information processing in the brain. However, the formation, vanishing, and temporal evolution of NAs are not fully understood. In particular, characterizing NAs in multiple brain regions over the course of behavioral tasks is relevant to assess the highly distributed nature of brain processing. In the context of NA characterization, active tactile discrimination tasks with rats are elucidative because they engage several cortical areas in the processing of information that are otherwise masked in passive or anesthetized scenarios. In this work, we investigate the dynamic formation of NAs within and among four different cortical regions in long-range fronto-parieto-occipital networks (primary somatosensory, primary visual, prefrontal, and posterior parietal cortices), simultaneously recorded from seven rats engaged in an active tactile discrimination task. Our results first confirm that task-related neuronal firing rate dynamics in all four regions is significantly modulated. Notably, a support vector machine decoder reveals that neural populations contain more information about the tactile stimulus than the majority of single neurons alone. Then, over the course of the task, we identify the emergence and vanishing of NAs whose participating neurons are shown to contain more information about animal behavior than randomly chosen neurons. Taken together, our results further support the role of multiple and distributed neurons as the functional unit of information processing in the brain (NA hypothesis) and their link to active animal behavior.
Microstates in complex and dynamical environments: Unraveling situational awareness in critical helicopter landing maneuvers
Human Brain Mapping
Scientific Reports
The procedures to be performed after sudden engine failure of a single-engine helicopter impose h... more The procedures to be performed after sudden engine failure of a single-engine helicopter impose high workload on pilots. The maneuver to regain aircraft control and safe landing is called autorotation. The safety limits to conduct this maneuver are based on the aircraft height versus speed diagram, which is also known as "Dead Man’s Curve”. Flight-test pilots often use subjective methods to assess the difficulty to conduct maneuvers in the vicinity of this curve. We carried out an extensive flight test campaign to verify the feasibility of establishing quantitative physiological parameters to better assess the workload endured by pilots undergoing those piloting conditions. Eleven pilots were fully instrumented with sensors and had their physiological reactions collected during autorotation maneuvers. Our analyses suggested that physiological measurements (heart rate and electrodermal activity) can be successfully recorded and useful to capture the most effort-demanding effects...
A Critical Analysis on Characterizing the Meditation Experience Through the Electroencephalogram
Frontiers in Systems Neuroscience
Measures for brain connectivity analysis: nodes centrality and their invariant patterns
The European Physical Journal Special Topics, 2017
Low drift and high sensitivity Fiber Optic Gyroscope using tunable VCSEL as optical source
2009 IEEE LEOS Annual Meeting Conference Proceedings, 2009
Accumulating evidence suggests that neural interactions are distributed and relate to animal beha... more Accumulating evidence suggests that neural interactions are distributed and relate to animal behavior, but many open questions remain. The neural assembly hypothesis, formulated by Hebb, states that synchronously active single neurons may transiently organize into functional neural circuits—neuronal assemblies (NAs)—and that would constitute the fundamental unit of information processing in the brain. However, the formation, vanishing, and temporal evolution of NAs are not fully understood. In particular, characterizing NAs in multiple brain regions over the course of behavioral tasks is relevant to assess the highly distributed nature of brain processing. In the context of NA characterization, active tactile discrimination tasks with rats are elucidative because they engage several cortical areas in the processing of information that are otherwise masked in passive or anesthetized scenarios. In this work, we investigate the dynamic formation of NAs within and among four different cortical regions in long-range fronto-parieto-occipital networks (primary somatosensory, primary visual, prefrontal, and posterior parietal cortices), simultaneously recorded from seven rats engaged in an active tactile discrimination task. Our results first confirm that task-related neuronal firing rate dynamics in all four regions is significantly modulated. Notably, a support vector machine decoder reveals that neural populations contain more information about the tactile stimulus than the majority of single neurons alone. Then, over the course of the task, we identify the emergence and vanishing of NAs whose participating neurons are shown to contain more information about animal behavior than randomly chosen neurons. Taken together, our results further support the role of multiple and distributed neurons as the functional unit of information processing in the brain (NA hypothesis) and their link to active animal behavior.
Limitations of principal component analysis as a method to detect neuronal assemblies
2014 IEEE 16th International Conference on e-Health Networking, Applications and Services (Healthcom), 2014
Low drift and high sensitivity Fiber Optic Gyroscope using tunable VCSEL as optical source
Page 1. Low Drift and High Sensitivity Fiber Optic Gyroscope Using Tunable VCSEL as Optical Sourc... more Page 1. Low Drift and High Sensitivity Fiber Optic Gyroscope Using Tunable VCSEL as Optical Source Carlos FR Mateus, Member, IEEE, Camila D. Sardeto and Carmem Lúcia Barbosa Instituto de Estudos Avançados IEAv/CTA Rod. ...
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Papers by Camila Sardeto Deolindo