ABSTRACT
Studies have shown that spatial attention remarkably affects the trial-to-trial response variability shared between neurons. Difficulty in the attentional task adjusts how much concentration we maintain on what is currently important and what is filtered as irrelevant sensory information. However, how task difficulty mediates the interactions between neurons with separated receptive fields (RFs) that are attended to or attended away is still not clear. We examined spike count correlations between single-unit activities recorded simultaneously in the primary visual cortex (V1) while monkeys performed a spatial attention task with two levels of difficulty. Moreover, the RFs of the two neurons recorded were non-overlapping to allow us to study fluctuations in the correlated responses between competing visual inputs when the focus of attention was allocated to the RF of one neuron. While increasing difficulty in the spatial attention task, spike count correlations were either decreased to become negative between neuronal pairs, implying competition among them, with one neuron (or none) exhibiting attentional enhancement of firing rate, or increased to become positive, suggesting inter-neuronal cooperation, with one of the pair showing attentional suppression of spiking responses. Besides, the modulation of spike count correlations by task difficulty was independent of the attended locations. These findings provide evidence that task difficulty affects the functional interactions between different neuronal pools in V1 when selective attention resolves the spatial competition.
Subject(s)
Animals , Attention/physiology , Macaca mulatta , Neurons/physiology , Photic Stimulation , Primary Visual Cortex , Visual Cortex/physiologyABSTRACT
Anxiety is usually generated because of the threatened feeling. The data of electrocardio, respiration, blood volume pulse and skin conductance signals were collected. The arithmetic of Relief were used for the feature selection and combined with k-Nearest Neighbor (kNN) arithmetic and Support Vector Machine (SVM) arithmetic for classification. The results show that the combination of Relief-SVM is better than combination of Relief-kNN on the recognition of anxiety state. The emotion recognition based on multi-physiological signals is superior to that based on one single signal.
Subject(s)
Humans , Algorithms , Anxiety , Artificial Intelligence , Pattern Recognition, Automated , Support Vector MachineABSTRACT
Visual prostheses have the potential to restore partial vision for the blinds. The stimulating electrodes generate reproducible phosphenes. Still limited by the low resolution vision used in visual prostheses nowadays, it is important to optimize the image processing strategies in order to deliver better visual information to the patients. This paper presents a review of the current research progress on the image processing strategies based on visual attention models under simulated prosthetic vision and related psychophysics.
Subject(s)
Computer Simulation , Image Processing, Computer-Assisted , Methods , Visual ProsthesisABSTRACT
The paper proposed a new method to design and fabricate a flexible neural microelectrode arrays (MEA) for retinal prosthesis, the ion-beam technology was introduced to decrease the width of conductive wires and the distances between wires, a high density MEA (120 microelectrodes with a matrix of 10 x 12) was fabricated on a single layer of polymer from this. The MEA was proved to possess a fine electrochemical property. In vitro test, the average impedance of MEA on 1 kHz was 16 k omega +/- 2 k omega and the average phase difference was -85 degrees +/-30 degrees.
Subject(s)
Micro-Electrical-Mechanical Systems , Microelectrodes , Prosthesis Design , Visual ProsthesisABSTRACT
Boosting spatial resolution of visual prostheses is an effective method to improve implant subjects' visual perception. However, power consumption of visual implants greatly rises with the increasing number of implanted electrodes. In respond to this trend, visual prostheses need to develop high-efficiency wireless power transmission and high-speed data transmission. This paper presents a review of current research progress on wireless power and data transmission for visual prostheses, analyzes relative principles and requirement, and introduces design methods of power and data transmission.
Subject(s)
Electric Power Supplies , Prosthesis Design , Visual Prosthesis , Wireless TechnologyABSTRACT
Three-electrode testing method was used to investigate the effect of temperature on electrode impedance, and the pH shifts in saline solution resulting from the electrical stimulation were also determined. Experiments in PBS (phosphate buffered solution) solution showed that the electrode impedance was almost invariable at the human body temperature range (35 degrees C-40 degrees C). And the experiments in unbuffered saline solution showed that pH shifts decreased from 0.03 to 0.005 when the frequency of biphasic charged-balanced pulses increased from 1 Hz to 100 Hz. Even stimulated by monophasic pulses (frequency is 15 Hz, amplitude is 50 microA), the stimulus-induced pH shift of electrode only varies 0.15 (anodic pulse current increased 0.15 and cathodic pulse current decreased 0.15).
Subject(s)
Electrochemistry , Eye, Artificial , Materials Testing , Microelectrodes , Prostheses and ImplantsABSTRACT
According to analyses of the real-time performance of the visual prosthesis image processing system, down-sampling is a key factor which influences the processing speed. Based on these analyses, the algorithm of grid sampled averaging was proposed for down-sampling. Then the effect of grid parameters on the result and algorithm complexity was evaluated by using the regional-averaging algorithm as a reference. Our research shows that the grid-averaging algorithm could reduce the computation burden by 90% or more, with no significant difference from the regional-averaging algorithm.
Subject(s)
Algorithms , Image Processing, Computer-Assisted , Methods , Visual ProsthesisABSTRACT
In this paper, experiments were designed for inducing neutral, terrified, excited, annoying emotions, and also low, middle, high, three levels of tension emotions of stress state, respectively. Based on the multi physiological signals generated by the subjects in emotions, such as heart rate and respiration rate and so on, we extracted features from these data which had been eliminated the baseline. Then the Particle Swarm Optimization method was adopted to optimize the features selection from the features of multi physiological signals, and combined with k-Nearest Neighbor algorithm, different emotions and varying degree tensions were classified. The result shows that the classification accuracy of the kNN method with SPO and baseline eliminated is better than the traditional kNN method.
Subject(s)
Humans , Algorithms , Behavioral Research , Methods , Emotions , Stress, PsychologicalABSTRACT
Induced by a variety of retinopathy, visual loss has become the most serious form of disability, which influences the quality of human life. With the rapid development and crossing among the information science, microelectronics, material science and biomedical disciplines, the visual prosthesis makes reparation possible for the visual blindness caused by retinitis pigmentosa, age-related macular degeneration, and other eye, retina, optic nerve and visual cortex lesions. With technology innovation, the prosthesis design, manufacturing and surgical technique are no longer the biggest obstacles to the future development of the visual prosthesis, but how to construct effective transmission of information between the brain and the prosthesis. However, due to the complex structure of the human visual system, the visual prosthesis manufacturing and visual information signal mapping are facing some difficulties. Thus, we can only study the representation strategy of image information and micro-electrode array stimulation basing on limited pixels of simulated prosthesis visual information. By studying the visual information processing of the visual prosthesis, we propose a visual prosthesis design which is based on biological, mechanical, and electronic integration.
Subject(s)
Humans , Blindness , Rehabilitation , Electric Stimulation , Electrodes, Implanted , Prosthesis Design , Visual Perception , Visual ProsthesisABSTRACT
This paper introduces the current research progress on effect factors of mobility performance based on simulated prosthetic vision.
Subject(s)
Phosphenes , Prostheses and Implants , Vision, OcularABSTRACT
The development of the integrated blood pressure system with bluetooth communication function is introduced. Experimental results show that the system can complete blood pressure measurement and data transmission wireless effectively, which can be used in m-Health in future.
Subject(s)
Humans , Blood Pressure Determination , Methods , TelemetryABSTRACT
This paper employed a DSP platform to create the real-time and portable image processing system, and introduced a series of commonly used algorithms for visual prostheses. The results of performance evaluation revealed that this platform could afford image processing algorithms to be executed in real time.
Subject(s)
Algorithms , Image Processing, Computer-Assisted , Methods , Signal Processing, Computer-Assisted , Visual ProsthesisABSTRACT
This review paper presents the current research progress on effect factors of image recognition, which was based on simulated artificial vision.
Subject(s)
Image Processing, Computer-Assisted , Methods , Prostheses and Implants , Vision, OcularABSTRACT
A wireless transmission system for visual prosthesis is introduced. Power and data are transmitted through inductive link between only one pair of coils, in order to reduce the size of the device. The transmitter is based on Class-E power amplifier due to its high efficiency, and a modulation circuit is added to control the dc supply of the Class-E amplifier to achieve ASK modulation of data with modulation depth of 25%. In addition, an experimental system is implemented, and test shows that it sufficiently supports a 16-channel micro-stimulator on power delivery and data transfer rate.
Subject(s)
Amplifiers, Electronic , Electronic Data Processing , Electric Power Supplies , Electronics, Medical , Prosthesis Design , Telemetry , Visual ProsthesisABSTRACT
In this paper, we used the eletrotactile vision substitution system designed by ourselves to display Chinese characters on the 16x16 electrode array through some simple image processing algorithms and multiplexing technology. Based on this, simple Chinese character recognition experiment was conducted. The result of the experiment shows that the electrotactile vision substitution is a feasible solution for the blind to read simple Chinese characters and the result also solidifies the foundation of further study about more complex real-time image electrotactile display.
Subject(s)
Algorithms , Communication Aids for Disabled , Image Processing, Computer-Assisted , Language , Touch , Vision, OcularABSTRACT
This review paper presents the current research progress, challenges and future development on microelectrode array of retinal prosthesis, including epi-retinal and sub-retinal implants.
Subject(s)
Microelectrodes , Prosthesis Design , Visual ProsthesisABSTRACT
This paper proposed a new design on multi-layer flexible microelectrode arrays (MEA) of epiretinal prosthesis, as well as a set of automatic testing system to evaluate and analyze the MEA. Experiment results showed that the MEA was satisfying on both flexibility and impedance and the multi-layer design didn't introduce significant differences.