Event-related potentials (ERPs) are one of the most popular control signals for brain-computer interfaces (BCIs). However, they are very weak and sensitive to the experimental settings including ...paradigms, stimulation parameters and even surrounding environments, resulting in a diversity of ERP patterns across different BCI experiments. It's still a challenge to develop a general decoding algorithm that can adapt to the ERP diversities of different BCI datasets with small training sets. This study compared a recently developed algorithm, i.e., discriminative canonical pattern matching (DCPM), with seven ERP-BCI classification methods, i.e., linear discriminant analysis (LDA), stepwise LDA, bayesian LDA, shrinkage LDA, spatial-temporal discriminant analysis (STDA), xDAWN and EEGNet for the single-trial classification of two private EEG datasets and three public EEG datasets with small training sets. The feature ERPs of the five datasets included P300, motion visual evoked potential (mVEP), and miniature asymmetric visual evoked potential (aVEP). Study results showed that the DCPM outperformed other classifiers for all of the tested datasets, suggesting the DCPM is a robust classification algorithm for assessing a wide range of ERP components.
Transient receptor potential (TRP) ankyrin 1 (TRPA1) is a Ca(2+)-permeant, nonselective cationic channel. It is predominantly expressed in the C afferent sensory nerve fibers of trigeminal and dorsal ...root ganglion neurons and is highly coexpressed with the nociceptive ion channel transient receptor potential vanilloid 1 (TRPV1). Several physical and chemical stimuli have been shown to activate the channel. In this study, we have used electrophysiological techniques and behavioral models to characterize the properties of TRPA1. Whole cell TRPA1 currents induced by brief application of lower concentrations of N-methyl maleimide (NMM) or allyl isothiocyanate (AITC) can be reversed readily by washout, whereas continuous application of higher concentrations of NMM or AITC completely desensitized the currents. The deactivation and desensitization kinetics differed between NMM and AITC. TRPA1 current amplitude increased with repeated application of lower concentrations of AITC, whereas saturating concentrations of AITC induced tachyphylaxis, which was more pronounced in the presence of extracellular Ca(2+). The outward rectification exhibited by native TRPA1-mediated whole cell and single-channel currents was minimal as compared with other TRP channels. TRPA1 currents were negatively modulated by protons and polyamines, both of which activate the heat-sensitive channel, TRPV1. Interestingly, neither protein kinase C nor protein kinase A activation sensitized AITC-induced currents, but each profoundly sensitized capsaicin-induced currents. Current-clamp experiments revealed that AITC produced a slow and sustained depolarization as compared with capsaicin. TRPA1 is also expressed at the central terminals of nociceptors at the caudal spinal trigeminal nucleus. Activation of TRPA1 in this area increases the frequency and amplitude of miniature excitatory or inhibitory postsynaptic currents. In behavioral studies, intraplantar and intrathecal administration of AITC induced more pronounced and prolonged changes in nociceptive behavior than those induced by capsaicin. In conclusion, the characteristics of TRPA1 we have delineated suggest that it might play a unique role in nociception.
The Schrödinger equation is solved exactly for some well known potentials. Solutions are obtained reducing the Schrödinger equation into a second order differential equation by using an appropriate ...coordinate transformation. The Nikiforov-Uvarov method is used in the calculations to get energy eigenvalues and the corresponding wave functions.
Key points
TMS is commonly used to study excitatory/inhibitory neurotransmission in cortical circuits.
Changes in cortical excitability following TMS are typically measured from hand (using EMG; ...limited to motor cortex) or scalp (using EEG); however, it is unclear whether these two measures represent the same activity when assessing motor cortex.
We found that TMS‐EMG and TMS‐EEG measures of motor cortex excitability are differentially affected by sensory confounds at different time points, masking any actual relationship between them in the time domain.
In the frequency domain, local high‐frequency oscillations in EEG recordings were minimally confounded by sensory artefacts and demonstrated strong correlations with EMG measures of cortical excitability across time, regardless of TMS intensity or waveform.
Therefore, despite the effects of sensory artefacts, the two measures of motor cortex excitability share a response component, suggesting that they index a similar cortical activity and perhaps the same neuronal population.
Transcranial magnetic stimulation (TMS) is a powerful tool for investigating cortical circuits. Changes in cortical excitability following TMS are typically assessed by measuring changes in either conditioned motor‐evoked potentials (MEPs) following paired‐pulse TMS over motor cortex or evoked potentials measured with electroencephalography following single‐pulse TMS (TEPs). However, it is unclear whether these two measures of cortical excitability index the same cortical response. Twenty‐four healthy participants received local and interhemispheric paired‐pulse TMS over motor cortex with eight inter‐pulse intervals, sub‐ and suprathreshold conditioning intensities, and two different pulse waveforms, while MEPs were recorded from a hand muscle. TEPs were also recorded in response to single‐pulse TMS using the conditioning pulse alone. The relationships between TEPs and conditioned‐MEPs were evaluated using metrics sensitive to both their magnitude at each time point and their overall shape across time. The impacts of undesired sensory potentials resulting from TMS pulse and muscle contractions were also assessed on both measures. Both conditioned‐MEPs and TEPs were sensitive to re‐afferent somatosensory activity following motor‐evoked responses, but over different post‐stimulus time points. Moreover, the amplitude of low‐frequency oscillations in TEPs was strongly correlated with the sensory potentials, whereas early and local high‐frequency responses showed minimal relationships. Accordingly, conditioned‐MEPs did not correlate with TEPs in the time domain but showed high shape similarity with the amplitude of high‐frequency oscillations in TEPs. Therefore, despite the effects of sensory confounds, the TEP and MEP measures share a response component, suggesting that they index a similar cortical response and perhaps the same neuronal populations.
Key points
TMS is commonly used to study excitatory/inhibitory neurotransmission in cortical circuits.
Changes in cortical excitability following TMS are typically measured from hand (using EMG; limited to motor cortex) or scalp (using EEG); however, it is unclear whether these two measures represent the same activity when assessing motor cortex.
We found that TMS‐EMG and TMS‐EEG measures of motor cortex excitability are differentially affected by sensory confounds at different time points, masking any actual relationship between them in the time domain.
In the frequency domain, local high‐frequency oscillations in EEG recordings were minimally confounded by sensory artefacts and demonstrated strong correlations with EMG measures of cortical excitability across time, regardless of TMS intensity or waveform.
Therefore, despite the effects of sensory artefacts, the two measures of motor cortex excitability share a response component, suggesting that they index a similar cortical activity and perhaps the same neuronal population.
A Study of Evoked Potentials From Ear-EEG Kidmose, Preben; Looney, David; Ungstrup, Michael ...
IEEE transactions on biomedical engineering,
10/2013, Letnik:
60, Številka:
10
Journal Article
Recenzirano
A method for brain monitoring based on measuring the electroencephalogram (EEG) from electrodes placed in-the-ear (ear-EEG) was recently proposed. The objective of this study is to further ...characterize the ear-EEG and perform a rigorous comparison against conventional on-scalp EEG. This is achieved for both auditory and visual evoked responses, over steady-state and transient paradigms, and across a population of subjects. The respective steady-state responses are evaluated in terms of signal-to-noise ratio and statistical significance, while the qualitative analysis of the transient responses is performed by considering grand averaged event-related potential (ERP) waveforms. The outcomes of this study demonstrate conclusively that the ear-EEG signals, in terms of the signal-to-noise ratio, are on par with conventional EEG recorded from electrodes placed over the temporal region.
Highlights • Neuropathic pain is a chronic condition that represents a major health problem. • There is a need for new medications with greater efficacy and less adverse effects. • TRP channels are ...emerging targets for neuropathic pain therapeutics.
Two compact analytical models for the diatomic potential energy are presented and tested. The first (6-parameter) model represents a significant improvement on the extended Lennard-Jones (ELJ) ...function proposed by Hajigeorgiou J. Mol. Spectrosc.
263, 101 (2010), and the second (7-parameter) model is a modified Hulburt-Hirschfelder function. The adjustable parameters of the two functions can be determined either by an algebraic scheme that employs semiclassical expressions in terms of vibrational-rotational molecular constants, or by direct nonlinear least-squares fits to available numerical potential functions. Accuracy tests are carried out for a set of ground electronic states of 30 diatomic molecules. The two potential energy functions give accurate representations of the available numerical potential energy curves with average deviations over the 30 molecules of approximately 0.06% of D
e
, or 1 meV (∼ 8 cm
−1
). The best cases give average absolute deviations of 0.0002% of D
e
, or 0.007 meV (∼ 0.06 cm
−1
). Quantum-mechanical vibrational eigenvalues of the new potential representations are shown for selected molecules to agree very well with the experimental vibrational energies, with average absolute deviations of much less than 1 cm
−1
.
Intermolecular potentials are considered which were suggested between 1903 and 1971. These comprise the Mie potentials, the Lennard-Jones potentials, the Kihara potential, the numerically tabulated ...potential of Dymond and Alder and the multi-parameter potential of Barker, Fisher and Watts. Their origin is described as well as subsequent applications. An interesting item regarding the Mie potential is its twofold appearance as attractive mean field approximation and as n,m-potential. We also emphasize the big step forward made by London in 1930 who suggested an approximate solution of the Schrödinger equation leading to an attractive potential with inverse sixth power in the intermolecular distance. This work of London was the basis for the 12,6-Lennard-Jones potential which appeared in 1931. Results obtained in the literature for thermodynamic and transport properties with the considered potentials are shown and discussed.
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