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This presentation is a report on the in situ characterization of stimulating microelectrodes in the context of multielectrode retinal prosthetic implants. The experimental system approximately replicates the geometric and electrical parameters of Second Sight® Medical Products' Argus™ II Retinal Implant. Topographic maps of electric potentials have been prepared for a 60 electrode structure in which...
This paper proposes a multiple model method that addresses the estimation of the EEG/MEG neural sources as a multihypothesis, multidimensional and dynamic estimation problem. The key aspect is the probabilistic integration of several neural models to simultaneously estimate and integrate the brain activity of different dynamic neural processes that are characterized by the number of sources, the dynamic...
Event-related potentials (ERPs) are one of the most informative and dynamic methods of monitoring cognitive processes, which are widely used in clinical research to deal a variety of psychiatric and neurological disorders as attention-deficit/hyperactivity disorder (ADHD). This work proposes an extraction and selection methodology for discriminating between normal and pathological patients with ADHD...
Exploration into electrical stimulation of the retina has thus far focussed primarily upon the development of prostheses targeted at one of two sites of intervention - the epi- and sub-retinal surfaces. These two approaches have sound, logical merit owing to their proximity to retinal neurons and their potential to deliver stimuli via the surviving retinal neural networks respectively. There is increasing...
This study aimed to explore the modulation of alpha rhythm in response to food pictures with distinct affection values. We examined the method to discriminate subject's state, i.e., whether he/she liked the article of food or not, from MEG signals detected over the head. Pictures of familiar foods were used as affective stimuli, while those pictures with complementary color phase were used as non-affective...
This article describes the development of a dual-monitor visual stimulus generator that is used in neuroscience experiments with invertebrates such as flies. The experiment consists in the visualization of two fixed images that are displaced horizontally according to the stimulus data. The system was developed using off-the-shelf FPGA kits and it is capable of displaying 640×480 pixels with 256 intensity...
This work proposes a clustering technique to analyze evoked potential signals. The proposed method uses an orthogonal subspace model to enhance the single-trial signals of a session and simultaneously a subspace measure to group the trials into clusters. The ensemble averages of the signals of the different clusters are compared with ensemble averages of visually selected trials which are free of...
Human-machine interaction (HMI) relies on pattern recognition algorithms that are not perfect. To improve the performance and usability of these systems we can utilize the neural mechanisms in the human brain dealing with error awareness. This study aims at designing a practical error detection algorithm using electroencephalogram signals that can be integrated in an HMI system. Thus, real-time operation,...
In this talk I will describe our work investigating sparse decoding of neural activity, given a realistic mapping of the visual scene to neuronal spike trains generated by a model of primary visual cortex (V1). We use a linear decoder which imposes sparsity via an L1 norm. The decoder can be viewed as a decoding neuron (linear summation followed by a sigmoidal nonlinearity) in which there are relatively...
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