Navegando por Autor "Castellano, Gabriela"
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Item Channel capacity in brain-computer interfaces.(2020) Costa, Thiago Bulhões da Silva; Suarez Uribe, Luisa Fernanda; Leite, Sarah Negreiros de Carvalho; Soriano, Diogo Coutinho; Castellano, Gabriela; Suyama, Ricardo; Attux, Romis Ribeiro de Faissol; Panazio, Cristiano MagalhãesObjective. Adapted from the concept of channel capacity, the information transfer rate (ITR) has been widely used to evaluate the performance of a brain–computer interface (BCI). However, its traditional formula considers the model of a discrete memoryless channel in which the transition matrix presents very particular symmetries. As an alternative to compute the ITR, this work indicates a more general closed-form expression—also based on that channel model, but with less restrictive assumptions—and, with the aid of a selection heuristic based on a wrapper algorithm, extends such formula to detect classes that deteriorate the operation of a BCI system. Approach. The benchmark is a steady-state visually evoked potential (SSVEP)-based BCI dataset with 40 frequencies/classes, in which two scenarios are tested: (1) our proposed formula is used and the classes are gradually evaluated in the order of the class labels provided with the dataset; and (2) the same formula is used but with the classes evaluated progressively by a wrapper algorithm. In both scenarios, the canonical correlation analysis (CCA) is the tool to detect SSVEPs. Main results. Before and after class selection using this alternative ITR, the average capacity among all subjects goes from 3.71 1.68 to 4.79 0.70 bits per symbol, with p -value <0.01, and, for a supposedly BCI-illiterate subject, her/his capacity goes from 1.53 to 3.90 bits per symbol. Significance. Besides indicating a consistent formula to compute ITR, this work provides an efficient method to perform channel assessment in the context of a BCI experiment and argues that such method can be used to study BCI illiteracy.Item Evaluation of a protocol for fMRI assessment associated with augmented reality rehabilitation of stroke subjects.(2019) Assis, Gilda Aparecida de; Brandão, Alexandre Fonseca; Corrêa, Ana Grasielle Dionísio; Castellano, GabrielaNew technologies for rehabilitation involving Augmented Reality (AR) as a complement to conventional therapy have appeared in recent years. An earlier study for shoulder rehabilitation using the AR NeuroR computer system showed improved clinical outcomes for stroke patients. This study aims to analyze a proposed protocol to measure possible changes in functional brain connectivity associated with the use of the NeuroR system in the context of shoulder motor rehabilitation of post-stroke subjects. A pilot study was conducted with a poststroke patient, using resting-state functional magnetic resonance imaging (RS-fMRI). RS-fMRI signals were acquired pre and post use of the NeuroR system (pre-test and post-test), integrated into the patient’s rehabilitation program. Functional connectivity analysis of RS-fMRI was performed using the motor area as seed. he maximum connectivity value in the pre-test occurred in the ipsilesional parietal region while the maximum in the post-test was located in the ipsilesional frontal region. It was observed that the regions strongly associated with motor activity had higher connectivity values at post-test compared to pre-test. The proposed protocol is suitable and safe for verifying if functional brain connectivity was changed after the rehabilitation program with NeuroR training, indicating a possible neuroplasticity effect. Tests with a larger number of patients are still necessary.Item Investigation of fMRI protocol for evaluation of gestural interaction applied to upper-limb motor improvement.(2019) Brandão, Alexandre Fonseca; Casseb, Raphael Fernandes; Almeida, Sara Regina Meira; Assis, Gilda Aparecida de; Camargo, Alline Fernanda de Barros; Min, Li Li; Castellano, GabrielaThe use of Virtual Reality (VR) systems for rehabilitation treatment as a complement to conventional therapy has grown in recent years. Upper limbs therapy using VR has already been shown useful for stroke patients. In this work, we present a pilot study aiming to investigate the use of a functional magnetic resonance imaging (fMRI) protocol to analyze brain connectivity changes in subjects undergoing upper limb training through a VR environment. Thirteen healthy subjects underwent resting-state fMRI exams before and after a VR session. Although no significant changes are expected in healthy subjects performing only one training session, this study could pave the way for future studies performed with both stroke patients or athletes performing more sessions. Indeed, no significant changes in motor cortex connectivity were found. Nonetheless, an evaluation protocol for this type of VR rehabilitation procedure was successfully established, to be used in further studies with patients or athletes.