Browsing by Author "Ruiz, S."
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- ItemAbnormal Neural Connectivity in Schizophrenia and fMRI-Brain-Computer Interface as a Potential Therapeutic Approach(2013) Ruiz, S.; Birbaumer, N.; Sitaram, RanganathaConsidering that single locations of structural and functional abnormalities are insufficient to explain the diverse psychopathology of schizophrenia, new models have postulated that the impairments associated with the disease arise from a failure to integrate the activity of local and distributed neural circuits: the “abnormal neural connectivity hypothesis.” In the last years, new evidence coming from neuroimaging have supported and expanded this theory. However, despite the increasing evidence that schizophrenia is a disorder of neural connectivity, so far there are no treatments that have shown to produce a significant change in brain connectivity, or that have been specifically designed to alleviate this problem. Brain-Computer Interfaces based on real-time functional Magnetic Resonance Imaging (fMRI-BCI) are novel techniques that have allowed subjects to achieve self-regulation of circumscribed brain regions. In recent studies, experiments with this technology have resulted in new findings suggesting that this methodology could be used to train subjects to enhance brain connectivity, and therefore could potentially be used as a therapeutic tool in mental disorders including schizophrenia. The present article summarizes the findings coming from hemodynamics-based neuroimaging that support the abnormal connectivity hypothesis in schizophrenia, and discusses a new approach that could address this problem.
- ItemClassifying brain states and pupillary responses associated with the processing of old and new information(2022) Campos-Arteaga, G.; Araneda, A.; Ruiz, S.; Rodriguez, E.; Sitaram, R.Memory retrieval of consolidated memories has been extensively studied using "old-new tasks", meaning tasks in which participants are instructed to discriminate between stimuli they have experienced before and new ones. Significant differences in the neural processing of old and new elements have been demonstrated using different techniques, such as electroencephalography and pupillometry. In this work, using the data from a previously published study (Campos-Arteaga, Forcato et al. 2020), we investigated whether machine learning methods can classify, based on single trials, the brain activity and pupil responses associated with the processing of old and new information. Specifically, we used the EEG and pupillary information of 39 participants who completed an associative recall old-new task in which they had to discriminate between previously seen or new pictures and, for the old ones, to recall an associated word. Our analyses corroborated the differences in neural processing of old and new items reported in previous studies. Based on these results, we hypothesized that the application of machine learning methods would allow an optimal classification of old and new conditions.Using a Windowed Means approach (WM) and two different machine learning algorithms -Logistic Regression (WM-LR) and Linear Discriminant Analysis (WM-LDA) -mean classification performances of 0.75 and 0.74 (AUC) were achieved when EEG and pupillary signals were combined to train the models, respectively. In both cases, when the EEG and pupillary data were merged, the performance was significantly better than when they were used separately. In addition, our results showed similar classification performances when fused classification models (i.e., models created with the concatenated information of 38 participants) were applied to individuals whose EEG and pupillary information was not considered for the model training. Similar results were found when alternative preprocessing methods were used.Taken together, these findings show that it is possible to classify the neurophysiological activity associated with the processing of experienced and new stimuli using machine learning techniques. Future research is needed to determine how this knowledge might have potential implications for memory research and clinical practice.
- ItemEEG subject-dependent neurofeedback training selectively impairs declarative memories consolidation process(2024) Campos-Arteaga, G.; Flores-Torres, J.; Rojas-Thomas, F.; Morales-Torres, R.; Poyser, D.; Sitaram, R.; Rodriguez, E.; Ruiz, S.The process of stabilization and storage of memories, known as consolidation, can be modulated by different interventions. Research has shown that self-regulation of brain activity through Neurofeedback (NFB) during the consolidation phase significantly impacts memory stabilization. While some studies have successfully modulated the consolidation phase using traditional EEG-based Neurofeedback (NFB) that focuses on general parameters, such as training a specific frequency band at particular electrodes, they often overlook the unique and complex neurodynamics that underlie each memory content in different individuals, potentially limiting the selective modulation of memories. The main objective of this study is to investigate the effects of a Subject-Dependent NFB (SD-NFB), based on individual models created from the brain activity of each participant, on long-term declarative memories. Participants underwent an experimental protocol involving three sessions. In the first session, they learned images of faces and houses while their brain activity was recorded. This EEG data was used to create individualized models to identify brain patterns related to learning these images. Participants were then divided into three groups, with one group receiving SD-NFB to enhance brain activity linked to faces, another to houses, and a CONTROL sham group that did not receive SD-NFB. Memory performance was evaluated 24 h and seven days later using an 'old-new' recognition task, where participants distinguished between 'old' and 'new' images. The results showed that memory contents (faces or houses) whose brain patterns were trained via SD-NFB scored lower in recognition compared to untrained contents, as evidenced 24 h and seven days post-training. In summary, this study demonstrates that SD-NFB can selectively impact the consolidation of specific declarative memories. This technique could hold significant implications for clinical applications, potentially aiding in the modulation of declarative memory strength in neuropsychiatric disorders where memories are pathologically exacerbated.
- ItemLaparoscopic Liver Resection: A South American Experience with 2887 Cases(2020) Pekolj, J.; Claria Sanchez, R.; Salceda, J.; Maurette, R. J.; Schelotto, P. B.; Pierini, L.; Canepa, E.; Moro, M.; Stork, G.; Resio, N.; Neffa, J.; Mc Cormack, L.; Quinonez, E.; Raffin, G.; Obeide, L.; Fernandez, D.; Pfaffen, G.; Salas, C.; Linzey, M.; Schmidt, G.; Ruiz, S.; Alvarez, F.; Buffaliza, J.; Maroni, R.; Campi, O.; Bertona, C.; de Santibanes, M.; Mazza, O.; Belotto de Oliveira, M.; Diniz, A. L.; Enne de Oliveira, M.; Machado, M. A.; Kalil, A. N.; Pinto, R. D.; Rezende, A. P.; Ramos, E. J. B.; Talvane T. Oliveira, A.; Torres, O. J. M.; Jarufe Cassis, N.; Buckel, E.; Quevedo Torres, R.; Chapochnick, J.; Sanhueza Garcia, M.; Munoz, C.; Castro, G.; Losada, H.; Vergara Suarez, F.; Guevara, O.; Davila, D.; Palacios, O.; Jimenez, A.; Poggi, L.; Torres, V.; Fonseca, G. M.; Kruger, J. A. P.; Coelho, F. F.; Russo, L.; Herman, P.Background Laparoscopic liver resections (LLR) have been increasingly performed in recent years. Most of the available evidence, however, comes from specialized centers in Asia, Europe and USA. Data from South America are limited and based on single-center experiences. To date, no multicenter studies evaluated the results of LLR in South America. The aim of this study was to evaluate the experience and results with LLR in South American centers. Methods From February to November 2019, a survey about LLR was conducted in 61 hepatobiliary centers in South America, composed by 20 questions concerning demographic characteristics, surgical data, and perioperative results. Results Fifty-one (83.6%) centers from seven different countries answered the survey. A total of 2887 LLR were performed, as follows: Argentina (928), Brazil (1326), Chile (322), Colombia (210), Paraguay (9), Peru (75), and Uruguay (8). The first program began in 1997; however, the majority (60.7%) started after 2010. The percentage of LLR over open resections was 28.4% (4.4-84%). Of the total, 76.5% were minor hepatectomies and 23.5% major, including 266 right hepatectomies and 343 left hepatectomies. The conversion rate was 9.7%, overall morbidity 13%, and mortality 0.7%. Conclusions This is the largest study assessing the dissemination and results of LLR in South America. It showed an increasing number of centers performing LLR with the promising perioperative results, aligned with other worldwide excellence centers.
- ItemPrevalence and determinants of misreporting of energy intake among Latin American populations: results from ELANS study(2019) Previdelli, A. N.; Gómez, G.; Kovalskys, I.; Fisberg, M.; Cortés, L. Y.; Parej, R. G.; Liria, M. R.; García, M. C. Y.; Herrera Cuenca, M.; Rigotti Rivera, Attilio; Guajardo, V.; Zimberg, I. Z.; Murillo, A. G.; Fisberg, M.; Kovalskys, I.; Salas, G. G.; Sanabria, L. Y. C.; García, M. C. Y.; Torres, R. G. P.; Koletzko, B.; Moreno, L. A.; Pratt, M.; Guajardo, V.; Zimberg, I. Z.; Amigo, M. P.; Janezic, X.; Cardini, F.; Echeverry, M.; Langsman, M.; Fisberg, M.; Zimberg, I. Z.; De Franca, N. A. G.; Echeverría, G.; Landaeta, L.; Castillo Valenzuela, Oscar; Vargas, L. N.; Tobar, L. F.; Castillo, Y. M.; Rojas, R. M.; Chinnock, A.; Cáceres, M. V.; Torres, R. P.; Liria, M. R.; Meza, K.; Abad, M.; Penny, M.; Vasquez, M.; Rivas, O.; Meza, C.; Ruiz, S.; Ramírez, G.; Hernández, P.; Goncalves, P. B.; Alberico, C.; Ferrari, G. L. D. M.
- ItemWeighted neurofeedback facilitates greater self-regulation of functional connectivity between the primary motor area and cerebellum(2021) Vargas, P.; Sitaram, R.; Sepúlveda, P.; Montalba, C.; Rana, M.; Torres, R.; Tejos Nunez, Cristian Andres; Ruiz, S.