Visual evoked potentials and event related potentials in congenitally deaf subjects

The purpose was to test parameters of visual evoked potentials (VEPs) and of event-related potentials (ERPs) in deaf subjects to verify visual and cognitive CNS functions in a handicapped group of the population. Three types of visual stimuli (with dominating parvocellular or magnocellular system activation or with cognitive tasks) were used in the study. Six deaf persons (4 women, 2 men, mean age 17 years) and 6 persons with normal hearing (sex- and age-matched) were included in this pilot study. In all types of stimulation, latencies and amplitudes of main VEPs and ERPs components were evaluated. No significant latency differences were found. However, significantly reduced amplitudes were found in the occipital area for responses to motion and cognitive stimuli which might be interpreted as a part of functional reorganization of the extrastriate and cognitive cortical areas of deaf subjects.     

Visual event related potentials modulated by contextually relevant and irrelevant olfactory primes.

Visual evoked potentials were recorded from 16 scalp locations on 10 young subjects during presentation of a series of high-quality photographs on a computer screen. The photographs consisted of equal numbers of pictures of fruit (citrus and non-citrus fruits), flowers (roses and other flowers) and objects (e.g. buildings, vehicles, animals etc.). Every picture was different in order to avoid repetition effects. The pictures were presented under four odour conditions: no odour, rose odour, jasmine odour and citrus odour. In order to keep the subjects alert they were asked to make categorizing decisions for the visual stimuli (e.g. flower or fruit). No decision was required concerning the relationship between the visual stimulus and the odour. As expected, the N400 peak was more negative when the picture stimulus did not match the odour. It is hypothesized that the N400 peak can be used as a measure of relatedness of a sensory stimulus to a previous or on-going prime, irrespective of the mode of the stimuli.     

The P300 event-related potentials in dementia of the Alzheimer type. Correlations between P300 and monoamine metabolites

We studied auditory event-related potentials (ERPs) in 40 patients with dementia of the Alzheimer type (DAT). Peak latencies and amplitudes of N100, P200 and P300 components were measured. To study the possible relationships between the ERPs and monoaminergic neurotransmitter functions, CSF neurotransmitter metabolites were also analyzed. In patients with DAT, the P300 amplitude was significantly reduced and the P300 latency was prolonged. CSF concentrations of 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) were decreased. The P300 amplitude was significantly correlated with the 5-HIAA concentration. There were no correlations between the P300 components and the HVA concentration. These findings suggest that the serotonergic system modulates the P300 component of ERPs in patients with DAT.     

The estimation of event related potentials affected by random shifts and scalings

There is considerable evidence for trial to trial variability of the event related potentials (ERPs) within a given subject's recording. This variability influences the outcome of usual procedures in ERP analysis. Better results may be obtained if the sources of variability are explicitly taken into account in an appropriate model. This paper considers a probabilistic model, the random shift and scaling (RSS) model, where the response is modified by a random time shift and a random scale factor. In addition to this, an additional random scale factor which affects both the response and the background noise is taken into account. This time shift and these scale factors are handled as nuisance parameters. Maximum likelihood and least squares estimators of these parameters and the waveform of response are derived for the RSS model. It is shown that the Woody estimate of the ERP reported in earlier work can be derived by restricting the assumptions for the RSS model. Test statistics for hypotheses on means are obtained for the RSS model and a new type of discriminant function. The usefulness of the method is illustrated by means of simulation studies. Receiver operating characteristic (ROC) curves are used to demonstrate that the new type of discriminant performs better than the usual Fisher's Linear Discriminant.     

Influence of instructions in multi-discrimination experiments on event related potentials

The purpose of the experiment was to study the effects of psychological factors on slow brain potentials in relation to information processing and strategy establishment. Subjects were subjected to paired stimuli: A) two identical tone bursts (50 ms, 5000 Hz); B) two different stimuli the second (unconditioned) was a low pitched tone burst (50 ms, 500 Hz); C) only the warning stimulus was delivered to the subjects. In a first experiment, subjects (N = 10) were asked to detect and signal by a motor act the low pitched click (B); in a second experiment, subjects (N = 8) were to detect and signal in the same way the unconditioned tone burst omission (C). Results showed that the auditory event-related potentials (ERP) obtained in the two experiments presented two components: a negative wave (N150) followed by a positive one (P270). Solely, the late positive component differed in topography during the two situations. A fronto-central Contingent Negative Variation (CNV) appeared in all the conditions for the two experiments while a Post Imperative Negative Variation was often obvious in the first experiment.     

Time-locked and phase-locked features of P300 event-related potentials (ERPs) for brain–computer interface speller

The brain–computer interface P300 speller is aimed to help those patients unable to activate muscles to spell words by utilizing their brain activity. However, a problem associated with the use of this brain–computer interface paradigm is the generation mechanics of P300 related to responses to visual stimuli. Herein, we investigated the event-related potential (ERP) response for the P300-based brain–computer interface speller. A signal preprocessing method integrated coherent average, principal component analysis (PCA) and independent component analysis (ICA) to reduce the dimensions and noise in the raw data. The time–frequency analysis was based on wavelet and two characteristic parameters of event-related spectral perturbation (ERSP) and inter-trial coherence (ITC) were computed to indicate the evoked response (time-locked) and phase reset (phase-locked) activity, respectively. Results demonstrated that the proposed method was valid for the time-locked and phase-locked feature extraction and both the evoked response and phase reset contributed to the genesis of the P300 signal. These electrophysiological responses characteristics of ERPs would be used for BCI P300 speller design and its signal processing strategies.     

Preservation of auditory P300-like potentials in cortical deafness

The phenomenon of blindsight has been largely studied and refers to residual abilities of blind patients without an acknowledged visual awareness. Similarly, "deaf hearing" might represent a further example of dissociation between detection and perception of sounds. Here we report the rare case of a patient with a persistent and complete cortical deafness caused by damage to the bilateral temporo-parietal lobes who occasionally showed unexpected reactions to environmental sounds despite she denied hearing. We applied for the first time electrophysiological techniques to better understand auditory processing and perceptual awareness of the patient. While auditory brainstem responses were within normal limits, no middle- and long-latency waveforms could be identified. However, event-related potentials showed conflicting results. While the Mismatch Negativity could not be evoked, robust P3-like waveforms were surprisingly found in the latency range of 600-700 ms. The generation of P3-like potentials, despite extensive destruction of the auditory cortex, might imply the integrity of independent circuits necessary to process auditory stimuli even in the absence of consciousness of sound. Our results support the reverse hierarchy theory that asserts that the higher levels of the hierarchy are immediately available for perception, while low-level information requires more specific conditions. The accurate characterization in terms of anatomy and neurophysiology of the auditory lesions might facilitate understanding of the neural substrates involved in deaf-hearing.     

Prediction of Auditory and Visual P300 Brain-Computer Interface Aptitude

Objective

Brain-computer interfaces (BCIs) provide a non-muscular communication channel for patients with late-stage motoneuron disease (e.g., amyotrophic lateral sclerosis (ALS)) or otherwise motor impaired people and are also used for motor rehabilitation in chronic stroke. Differences in the ability to use a BCI vary from person to person and from session to session. A reliable predictor of aptitude would allow for the selection of suitable BCI paradigms. For this reason, we investigated whether P300 BCI aptitude could be predicted from a short experiment with a standard auditory oddball.

Methods

Forty healthy participants performed an electroencephalography (EEG) based visual and auditory P300-BCI spelling task in a single session. In addition, prior to each session an auditory oddball was presented. Features extracted from the auditory oddball were analyzed with respect to predictive power for BCI aptitude.

Results

Correlation between auditory oddball response and P300 BCI accuracy revealed a strong relationship between accuracy and N2 amplitude and the amplitude of a late ERP component between 400 and 600 ms. Interestingly, the P3 amplitude of the auditory oddball response was not correlated with accuracy.

Conclusions

Event-related potentials recorded during a standard auditory oddball session moderately predict aptitude in an audiory and highly in a visual P300 BCI. The predictor will allow for faster paradigm selection.

Significance

Our method will reduce strain on patients because unsuccessful training may be avoided, provided the results can be generalized to the patient population.     

A comparison study of two P300 speller paradigms for brain–computer interface

In this paper, a comparison of two existing P300 spellers is conducted. In the first speller, the visual stimuli of characters are presented in a single character (SC) paradigm and each button corresponding to a character flashes individually in a random order. The second speller is based on a region-based (RB) paradigm. In the first level, all characters are grouped and each button corresponding to a group flashes individually in a random order. Once a group is selected, the characters in it will appear on the flashing buttons of the second level for the selection of desired character. In a spelling experiment involving 12 subjects, higher online accuracy was obtained on the RB paradigm-based P300 speller than the SC paradigm-based P300 speller. Furthermore, we analyzed P300 detection performance, the P300 waveforms and Fisher ratios using the data collected by the two spellers. It was found that the stimuli display paradigm of the RB speller enhances P300 potential and is more suitable for P300 detection.     

The simulation of aerial movement--IV. A computer simulation model

A computer simulation model of human airborne movement is described. The body is modelled as 11 rigid linked segments with 17 degrees of freedom which are chosen with a view to modelling twisting somersaults. The accuracy of the model is evaluated by comparing the simulation values of the angles describing somersault, tilt and twist with the corresponding values obtained from film data of nine twisting somersaults. The maximum deviations between simulation and film are found to be 0.04 revolutions for somersault, seven degrees for tilt and 0.12 revolutions for twist. It is shown that anthropometric measurement errors, from which segmental inertia parameters are calculated, have a small effect on a simulation, whereas film digitization errors can account for a substantial part of the deviation between simulation and film values.     

P300 wave: a comparative study of impulsive aggressive criminals

Event-Related potentials are a simple non-invasive neurophysiological method enabling to comprehend certain aspects of the cognitive processing of information in humans. The best-known component of Event-Related Potentials is the so-called P3 wave. Alterations in the parameters of P300 wave have been discovered in certain personality disorders and in persons with impulsively aggressive behaviour. The purpose of this study is to investigate the changes of these parameters, especially an amplitude and latency in the place of Pz electrode. We examined 15 persons with the impulsive aggressive behaviour and compared them to a population comparable of normal age, gender and approximate degree of education. We used P300 auditory and a neuropsychological Eysenck IVE battery. The results showed that significantly lower amplitudes had been found in the aggressive impulsive subjects as compared to the control group. No statistically significant differences have been discovered in the latency. These results seem to confirm previous studies.     

A computer simulation of free-volume distributions and related structural properties in a model lipid bilayer.

A novel combined approach of molecular dynamics (MD) and Monte Carlo simulations is developed to calculate various free-volume distributions as a function of position in a lipid bilayer membrane at 323 K. The model bilayer consists of 2 x 100 chain molecules with each chain molecule having 15 carbon segments and one head group and subject to forces restricting bond stretching, bending, and torsional motions. At a surface density of 30 A2/chain molecule, the probability density of finding effective free volume available to spherical permeants displays a distribution with two exponential components. Both pre-exponential factors, p1 and p2, remain roughly constant in the highly ordered chain region with average values of 0.012 and 0.00039 A-3, respectively, and increase to 0.049 and 0.0067 A-3 at the mid-plane. The first characteristic cavity size V1 is only weakly dependent on position in the bilayer interior with an average value of 3.4 A3, while the second characteristic cavity size V2 varies more dramatically from a plateau value of 12.9 A3 in the highly ordered chain region to 9.0 A3 in the center of the bilayer. The mean cavity shape is described in terms of a probability distribution for the angle at which the test permeant is in contact with one of and does not overlap with anyone of the chain segments in the bilayer. The results show that (a) free volume is elongated in the highly ordered chain region with its long axis normal to the bilayer interface approaching spherical symmetry in the center of the bilayer and (b) small free volume is more elongated than large free volume. The order and conformational structures relevant to the free-volume distributions are also examined. It is found that both overall and internal motions have comparable contributions to local disorder and couple strongly with each other, and the occurrence of kink defects has higher probability than predicted from an independent-transition model.     

The origin of P elements in Drosophila melanogaster.

The P family of transposable genetic elements is thought to be a recent addition to the Drosophila melanogaster genome. New evidence suggests that the elements came from another Drosophila species, possibly carried by parasitic mites. The transposition mechanism of P elements involves DNA gap repair which may have facilitated their rapid spread through D. melanogaster worldwide. These results provide new insight into the process of a transposon's invasion into a new species and the potential risk of extinction such an invasion might entail.     

Differential changes of laser evoked potentials,late auditory evoked potentials and P300 under morphine in chronic pain patients

The present study investigates the differential behavior of laser evoked brain potentials (LEPs), late auditory evoked potentials (AEP) and the endogenous P300 in response to morphine treatment, examined in 6 chronic pain patients. The main result was that in parallel with marked clinical pain relief, amplitudes of the long latency LEP positivity (P400) were significantly reduced under morphine. One patient suffering from extremely painful osteoporosis for 20 years exhibited a large middle latency component (N170) which was prominently attenuated by morphine. In contrast to LEP amplitude reductions, auditory N1 and P2 potentials appeared either unchanged or even enlarged during morphine treatment. Also P300 amplitude was slightly increased under morphine. Reaction time and mood scales also failed to indicate any sedation. Obviously, LEPs reflected specifically the analgesic morphine effect in this study, while stability or enhancement of AEPs and P300 during morphine treatment indicated lack of sedation or even improved perception and concentration due to the removal of persistent pain as a disruptive perceptual-cognitive stressor.     

A subcortical correlate of P300 in man

Event-related potentials in visual and auditory target detection tasks were recorded simultaneously from the scalp, somatosensory thalamus and periaqueductal gray in a chronic pain patient with electrodes implanted subcortically for therapeutic purposes. Short latency tactile responses confirmed the location of the thalamic electrodes.Rare auditory stimuli which were detected by the subject were accompanied by a prominent P300 component at the scalp, and by negative activity at the subcortical sites with the same latency as the scalp positivity. This activity was not seen in responses to frequent non-target stimuli and was not dependent on an overt motor response.Similarly, rare visual stimuli generated a scalp P300 and negative activity subcortically; both scalp and subcortical waves had a longer latency than in the auditory experiment. The reaction time was similarly longer to visual targets.These data are inconsistent with a hippocampal generator for P300, but are consistent with a generator in the thalamus or more dorsally located structures.     

Event-related potentials recorded from the scalp and nasopharynx. II. N2, P3 and slow wave

Scalp and nasopharyngeal recordings of the N2, P3 and slow wave components were compared in a target-detection task. The effects of probability, interstimulus interval, intensity, discrimination difficulty, attention, stimulus omission and modality were evaluated. Waves of opposite polarity to the scalp N2 and P3 components were recorded in the nasopharynx. The scalp and nasopharyngeal N2 components showed different patterns of variation across experimental conditions. These findings indicate that there are two different cerebral processes occurring at the latency of the scalp N2. The scalp and nasopharyngeal P3 components consistently covaried across conditions, suggesting a single underlying process. The slow wave was observed only in the scalp recordings.     

The origin of modern humans: A cytogenetic model

A new model of the origin of man is proposed on the basis of recent studies on cytogenetics of chromosomal Q-heterochromatin regions (Q-HRs) in man and other higher primates. This model is based on the following facts: a) chromosomal Q-HRs were found in the genome of only three higher primates (man, the chimpanzee and the gorilla); b) chromosomal Q-HRs in the human genome, unlike those in apes, exhibit considerable quantitative variability; c) the number of human chromosomal Q-HRs in the genome has a selective value in the adaptation of human populations to various environmental conditions. According to this model, the three major morphofunctional distinctions of man—great physiological flexibility, characteristic morphological structure, and conceptual thinking—arose as a result of the capacity of our remote ancestors to broadly change their genome mass owing to features of chromosomal Q-HRs that are only intrinsic to man. We feel that genome-mass variability through chromosomal Q-HRs allowed man to adapt himself to various environments over such a short period of time.     

The origin of transfer of P307

The DNA fragment carrying the oriT region from the enterotoxin plasmid P307 was isolated and its polynucleotide sequence was determined. Using Southern hybridization assays with a synthetic oligonucleotide probe, the oriT region was identified on a 7.9-kb EcoRI fragment from P307. By ligating the fragment with the cloning vector pUC119, plasmid pAG10 was obtained. The physical map of the insert was determined and oriT was located on a 540-bp BglII/SalI fragment. After this fragment was subcloned into sequencing phages, the polynucleotide sequence was established. Part of the sequence proved to be almost identical to segments of the oriT regions of the plasmids F and R1; another neighboring region was very different among all three sequences. The polynucleotide sequence proximal to traM is highly similar to that of F but different from that of R1.