Effect of stimulation shapes on the Steady-State Visual-Evoked response
04 Jun 2015-pp 1-2
TL;DR: Results indicate that there might exist a subject-dependent connection between the elicited SSVEP and choice of shapes for the stimulation paradigm, and investigate the potential for a novel shape switching based stimulation paradigm forSSVEP elicitation.
Abstract: The strength of Steady-State Visual-Evoked Potentials (SSVEPs) have been observed to greatly depend on the stimulation source and paradigm. Orientation and size specific neurons have been discovered in the occipital cortex, which activate only when excited with specific patterns. Different shapes have different orientation and size aspects that eventually lead to activation of different neuronal groups. In this study, we investigate the potential for a novel shape switching based stimulation paradigm for SSVEP elicitation. Pattern reversal stimuli was found to elicit stronger SSVEP relative to single graphic stimuli. Results indicate that there might exist a subject-dependent connection between the elicited SSVEP and choice of shapes for the stimulation paradigm.
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01 Jan 2019
TL;DR: Combined PSD and MSE can be taken as a potential measure to detect AD in early state and the combined feature from alpha/theta and long scale entropy in the left frontal central area can discriminate AD from NC group.
Abstract: To assist effective and precise diagnosis for mild cognitive impairment (MCI) and Alzheimer’s disease (AD), Electroencephalograph (EEG) has been widely used in clinical research of patients with AD at MCI state. To study the linear and nonlinear abnormality of EEG in AD and MCI patients, multiple characteristics was applied to distinguish AD and MCI patients from the normal controls (NC). EEG signals was recorded from 28 subjects, including 10 AD patients, 8 MCI subjects and 10 healthy elderly people. EEG signals in all channels was computed by auto-regressive model and multi scale entropy (MSE) to obtain relative power spectral density (PSD) value of each frequency band and entropy value in different time scales. Area under Receiver operating characteristic curve (AUC) was used to compare the classification ability of the two method. The ratio Alpha/theta of MCI group in left frontal area can distinguish MCI from NC subjects. Also the long scale entropy value in left frontal-central area manifests a better accuracy in distinguish AD and MCI from NC group. In addition, the combined feature from alpha/theta and long scale entropy in the left frontal central area can discriminate AD from NC group with higher AUC reaching 0.89. This indicated that combined PSD and MSE can be taken as a potential measure to detect AD in early state.
10 citations
TL;DR: The results indicate an enhancement in performance of SSVEP based BCI with clockwise rotating stimuli and may be considered for communication and or control applications.
6 citations
Proceedings Article•
13 Jul 2018TL;DR: In this article, a steady-state motion visual evoked potential (SSMVEP) stimulation-the square's ring motion was proposed, and compared with the visual stimulation which are commonly used in BCI system both in objective and subjective aspects.
Abstract: In this study, a steady-state motion visual evoked potential (SSMVEP) stimulation-the square's ring motion was proposed, and compared with the visual stimulation which are commonly used in BCI system (oscillatory Newton's ring, square flicker and circular flicker) both in objective and subjective aspects. Eight healthy subjects were asked to gaze at those four simulations. For each stimulation, eight targets varying at different frequencies were presented on a LCD screen. Canonical Correlation Analysis (CCA) was used to identify SSVEPs, and subjective questionnaire was used to measure the comfort of the stimulations. The experimental results showed that the accuracy of the square's ring motion was 85±13.2% which has no significant difference with the oscillatory Newton's ring (85.9±9.1%). Meanwhile the accuracy of the square flicker was 98.1±4.38%, and the accuracy of the circular flicker was 99.1±1.9%. The subjective questionnaire reported that the square's ring motion was the most comfortable, followed by the Newton's ring motion, the circular flicker and the square flicker. Taken together, these results suggest that the square's ring motion equaling to the newton's ring can elicit SSVEP accurately and reduce the discomfort caused by flickering of targets. Though there is no obvious improvement in the accuracy of the square's ring motion compared with oscillatory Newton's ring, subjective score of the square's ring is a bit higher than the oscillatory Newton's ring. Under the premise of controlling the incorrect operation, the square's ring motion can be used as a visual stimulation in long-term SSMVEP-based BCI system.
2 citations
References
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TL;DR: The striate cortex was studied in lightly anaesthetized macaque and spider monkeys by recording extracellularly from single units and stimulating the retinas with spots or patterns of light, with response properties very similar to those previously described in the cat.
Abstract: 1. The striate cortex was studied in lightly anaesthetized macaque and spider monkeys by recording extracellularly from single units and stimulating the retinas with spots or patterns of light. Most cells can be categorized as simple, complex, or hypercomplex, with response properties very similar to those previously described in the cat. On the average, however, receptive fields are smaller, and there is a greater sensitivity to changes in stimulus orientation. A small proportion of the cells are colour coded.
2. Evidence is presented for at least two independent systems of columns extending vertically from surface to white matter. Columns of the first type contain cells with common receptive-field orientations. They are similar to the orientation columns described in the cat, but are probably smaller in cross-sectional area. In the second system cells are aggregated into columns according to eye preference. The ocular dominance columns are larger than the orientation columns, and the two sets of boundaries seem to be independent.
3. There is a tendency for cells to be grouped according to symmetry of responses to movement; in some regions the cells respond equally well to the two opposite directions of movement of a line, but other regions contain a mixture of cells favouring one direction and cells favouring the other.
4. A horizontal organization corresponding to the cortical layering can also be discerned. The upper layers (II and the upper two-thirds of III) contain complex and hypercomplex cells, but simple cells are virtually absent. The cells are mostly binocularly driven. Simple cells are found deep in layer III, and in IV A and IV B. In layer IV B they form a large proportion of the population, whereas complex cells are rare. In layers IV A and IV B one finds units lacking orientation specificity; it is not clear whether these are cell bodies or axons of geniculate cells. In layer IV most cells are driven by one eye only; this layer consists of a mosaic with cells of some regions responding to one eye only, those of other regions responding to the other eye. Layers V and VI contain mostly complex and hypercomplex cells, binocularly driven.
5. The cortex is seen as a system organized vertically and horizontally in entirely different ways. In the vertical system (in which cells lying along a vertical line in the cortex have common features) stimulus dimensions such as retinal position, line orientation, ocular dominance, and perhaps directionality of movement, are mapped in sets of superimposed but independent mosaics. The horizontal system segregates cells in layers by hierarchical orders, the lowest orders (simple cells monocularly driven) located in and near layer IV, the higher orders in the upper and lower layers.
6,388 citations
"Effect of stimulation shapes on the..." refers background in this paper
...the visual cortex have been observed to be sensitive to lines of particular orientation only [7]....
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TL;DR: An experiment, where ten human subjects were presented flickering light at frequencies from 1 to 100 Hz in 1-Hz steps, and the event-related potentials exhibited steady-state oscillations at all frequencies up to at least 90 Hz, which could be a potential neural basis for gamma oscillations in binding experiments.
Abstract: The individual properties of visual objects, like form or color, are represented in different areas in our visual cortex. In order to perceive one coherent object, its features have to be bound together. This was found to be achieved in cat and monkey brains by temporal correlation of the firing rates of neurons which code the same object. This firing rate is predominantly observed in the gamma frequency range (approx. 30-80 Hz, mainly around 40 Hz). In addition, it has been shown in humans that stimuli which flicker at gamma frequencies are processed faster by our brains than when they flicker at different frequencies. These effects could be due to neural oscillators, which preferably oscillate at certain frequencies, so-called resonance frequencies. It is also known that neurons in visual cortex respond to flickering stimuli at the frequency of the flickering light. If neural oscillators exist with resonance frequencies, they should respond more strongly to stimulation with their resonance frequency. We performed an experiment, where ten human subjects were presented flickering light at frequencies from 1 to 100 Hz in 1-Hz steps. The event-related potentials exhibited steady-state oscillations at all frequencies up to at least 90 Hz. Interestingly, the steady-state potentials exhibited clear resonance phenomena around 10, 20, 40 and 80 Hz. This could be a potential neural basis for gamma oscillations in binding experiments. The pattern of results resembles that of multiunit activity and local field potentials in cat visual cortex.
930 citations
"Effect of stimulation shapes on the..." refers background in this paper
...SSVEPs have been hypothesized to be caused by a resonance phenomenon occurring in localized cortical sources [3]....
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TL;DR: The evoked potential in response to a grating alternating in phase at 8 c/s was recorded as a function of contrast from the occiput of man.
Abstract: 1 The evoked potential in response to a grating alternating in phase at 8 c/s was recorded as a function of contrast from the occiput of man
2 It was found that a linear relation exists between the log of contrast and the amplitude of the evoked potential
3 Extrapolation to zero amplitude voltage of the regression line between the amplitude of the evoked potential and log contrast predicts the psychophysical threshold This law was found to hold over the wide range of spatial frequencies tested
4 Below 3 c/deg the results are best fitted with two regression lines; one of these is generated from the foveal and the other from the parafoveal representation in the cortex
5 The slope of the regression lines was found to be almost independent of either the spatial frequency or the area of the stimulus grating
6 The slope of the regression lines could be markedly increased by using as a stimulus either two different spatial frequencies, or two different orientations, presented simultaneously
7 Using the evoked potential the selectivity to orientation was found to be so high that a channel was not influenced by another orientation 15° away
8 The channels selectively sensitive to spatial frequency were highly selective and were not influenced by another spatial frequency one octave removed in spatial frequency
9 It is concluded that in man there exist neurones highly selective to both orientation and spatial frequency
605 citations
"Effect of stimulation shapes on the..." refers background in this paper
...Further, neurons selectively sensitive to the orientation and size of retinal images have been observed [8]....
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TL;DR: This paper reviews the literature on SSVEP-based BCIs and comprehensively reports on the different RVS choices in terms of rendering devices, properties, and their potential influence on BCI performance, user safety and comfort.
Abstract: Brain-computer interface (BCI) systems based on the steady-state visual evoked potential (SSVEP) provide higher information throughput and require shorter training than BCI systems using other brain signals. To elicit an SSVEP, a repetitive visual stimulus (RVS) has to be presented to the user. The RVS can be rendered on a computer screen by alternating graphical patterns, or with external light sources able to emit modulated light. The properties of an RVS (e.g., frequency, color) depend on the rendering device and influence the SSVEP characteristics. This affects the BCI information throughput and the levels of user safety and comfort. Literature on SSVEP-based BCIs does not generally provide reasons for the selection of the used rendering devices or RVS properties. In this paper, we review the literature on SSVEP-based BCIs and comprehensively report on the different RVS choices in terms of rendering devices, properties, and their potential influence on BCI performance, user safety and comfort.
563 citations
"Effect of stimulation shapes on the..." refers background or methods in this paper
...SSVEP components have also been reported to exhibit significant variability across subjects [5], stimulation type [2], etc....
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...Apart from diagnosis of the human visual system [1], SSVEPs have been extensively exploited for use in Brain-Computer Interfaces [2]....
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TL;DR: The advantages of steady-state EP recording include speed in assessing sensory function in normal and sick infants, objective measurement at very high suprathreshold levels where psychophysical methods are difficult or ineffective, and proving a speedy objective equivalent to behavioral test in animals.
Abstract: The advantages of steady-state EP recording include (1) speed in assessing sensory function in normal and sick infants (e.g., in amblyopia) and in sick adults (e.g., in multiple sclerosis); (2) monitoring certain activities of sensory pathways that do not intrude into conscious perception; (3) rapidly assessing sensory function when a large number of subjects must be tested (e.g., in refraction); (4) objective measurement at very high suprathreshold levels where psychophysical methods are difficult or ineffective; (5) rapidly assessing sensory function in normal subjects when EP variability and nonstationarity preculde lengthy experiments; and (6) providing a speedy objective equivalent to behavioral test in animals.
275 citations
"Effect of stimulation shapes on the..." refers background or methods in this paper
...Steady-State Visual-Evoked Potentials (SSVEPs) are cortical exogenous manifestations of neuronal activity predominantly in the visual cortex in response to a visual flickering stimulus at frequencies greater than 4 Hz [1]....
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...Apart from diagnosis of the human visual system [1], SSVEPs have been extensively exploited for use in Brain-Computer Interfaces [2]....
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