Changes in Evoked Potentials Depending on Attention Level in Performance of Visual Tasks

Evoked potentials (EPs) in the parietal and temporal leads were recorded in 14 young subjects in response to successively administered right- and left-side simple visual symbols, squares and circles, during passive viewing and reactions to randomly presented target stimuli. Depending on task conditions and context, the stimuli were divided into four groups: (1) passively perceived stimuli, (2) irrelevant stimuli administered on the side opposite to the target, (3) irrelevant stimuli on the side of the target, and (4) target stimuli. The EPs were averaged over the groups. With an increase in the demands of attention from the first to the fourth groups of stimuli, a linear increase in activation, estimated by the total amplitude of the N1–P3 component, was observed in the parietal leads. The P3b component was mainly responsible for the growth of the EP amplitude. In the temporal leads, the activation was substantially weaker than in the parietal leads and displayed lower between-group differences. The results support the idea that the parietal cortex in humans is of primary importance in tasks involving visual attention and stimuli selection.     

Neurophysiological Indicators of Voluntary and Involuntary Visual Attention in a Human

The visual evoked potentials (EPs) in response to lateralized and central visual symbols under the conditions of involuntary (passive viewing) and selective attention (when one of the symbols was a target and required a rapid and precise motor reaction) are considered. The evoked potentials in the occipital, parietal, and frontal derivations were recorded in 20 healthy subjects. It was shown that the EP during selective attention are most pronounced and more alike in the parietal derivations. A strong positive correlation was revealed between the EP amplitude ([N1–P3] component) and the EP stability (correlation between the repeated EP). The involuntary and voluntary forms of attention supplement each other: the more expressed the involuntary attention (assessed by the [N1–P3] component) the higher the EP to target stimuli during voluntary attention and the shorter the reaction time. It is suggested that the role of visual attention consists in the increase and stabilization of cortical activity (primarily, the parietal regions) engaged in solving a visual task.     

Health-Related Quality of Life in Children and Adolescents with Nonclassic Congenital Adrenal Hyperplasia

Objective: Nonclassic congenital adrenal hyperplasia (NCCAH) is a late-onset milder form of congenital adrenal hyperplasia that differs dramatically from the classic form. Health-related quality of life (HRQOL) in pediatric patients with the sole diagnosis of NCCAH has not been determined; therefore, in this study, we aimed to determine whether HRQOL is compromised in comparison to the general population.Methods: Single-center, cross-sectional, case-control study. Twenty-three hydrocortisone-treated children and adolescents (7 males) diagnosed with NCCAH by cosyntropin stimulation test and CYP21A2 gene mutation analysis were recruited to this study; 6 healthy siblings were also recruited. HRQOL was assessed by the child and parent-proxy PedsQL Inventory and compared between NCCAH subjects and healthy siblings. HRQOL scores of NCCAH subjects were compared with known standards from the U.S. and Israeli general healthy populations. Anthropometric measurements of children and parents were performed and compared between NCCAH subjects and healthy siblings. Pearson correlation coefficients were calculated.Results: HRQOL scores of the participants and parents did not differ between NCCAH subjects and healthy siblings. The HRQOL emotional domain scores of the NCCAH patients and parent were significantly lower than the healthy U.S. pediatric population (P = .046) but not different from established standards of the healthy Israeli population (P = .583). Anthropometric measurements were within the normal range and did not differ between NCCAH subjects and their siblings. Total, school functioning, and psychosocial HRQOL domain scores were positively correlated with body mass index–standard deviation score in NCCAH subjects.Conclusion: HRQOL was not adversely affected by NCCAH among adequately treated children and adolescents.Abbreviations: BMI = body mass index; CAH = congenital adrenal hyperplasia; HRQOL = health-related quality of life; NCCAH = nonclassic congenital adrenal hyperplasia; PedsQL = Pediatric Quality of Life Inventory; SDS = standard deviation score     

Activation of Extrastriate Cortical Areas in a Human during Selection of Visual Stimuli by Their Shape and Localization: Analysis of Evoked Potentials

Monopolar evoked potentials (EPs) in the parietal and temporal leads were recorded in 23 young, healthy subjects in the process of selection of visual stimuli by shape and localization. Two different central stimuli (selection by shape) and two similar right and left stimuli (selection by localization) were presented in the first series. Two simple right and left stimuli were presented in the second series, and a subject had to respond either to their shape or their localization. During spatial attention and shape recognition in both tasks, characteristics of the prestimulus negativity (contingent negative variation (CNV)) and negative–positive N1–P3 complex pointed to the predominant activation of the parietal areas. The greatest differences were observed in the late P3b component, associated with the late selection, rather than in the early EP components. The dominance of parietal activation as compared to temporal activation was associated with attention demands; i.e., the dominance was highest in the case of target stimuli and was least pronounced during passive perception of stimuli. It is suggested that the parietooccipital visual system leads in tasks demanding spatial and nonspatial attention to stimuli in a simple visual environment (without surrounding elements).     

Role of the Frontal Cortical Areas in the Analysis of Visual Stimuli at Conscious and Unconscious Levels

Event-related potentials (ERP) in response to complex target stimuli, which consisted of a central recognizable picture and a lateral masked image (analyzed at the unconscious level) were recorded in adult subjects and seven-year-old children. ERP components N200, N300, and P400/N400 had different topography and were differently pronounced in adults and children. In adult subjects, the N200 component that reflects the processing of a sensory stimulus was recorded in the temporo-parieto-occipital and occipital areas. In children, N200 was recorded in the caudal regions and the frontal areas of the cortex. Analysis of different waveforms obtained by subtraction of the ERP to the central stimulus from the ERP to the complex stimulus showed that unconscious stimulus processing in adult subjects is not reflected in the ERP structure. In children, an unconsciously processed image incorporated into a complex stimulus evokes processing negativity in the occipital and frontal cortical areas. Comparison of ERP in groups of children divided by their reflectivity/impulsivity showed that, predominantly, the left frontal area is involved in image analysis at the unconscious level in reflective children and, predominantly, the right frontal area participates in unconscious image analysis in impulsive children. It is suggested that the perfection of the visual recognition of a target stimulus, which contains additional unconsciously processed information, consists in growth of the involvement of the left-hemispheric mechanisms (with respective growth of significance of the left-hemispheric mechanisms) and in a decrease in the role of the frontal areas in analysis of sensory information.     

The role of the genotype in the variability of human evoked potentials at different stages of ontogeny]

The determinants of individual differences in visual EPs to stimuli of different type depending on the age of subjects were studied. EPs to flash, checkerboard pattern and some other stimuli with semantic aspect were recorded in three groups of MZ, DZ twins aged 8-9, 10-12, 18-25 years. The heritability of EPs parameters is not ontogenetically stable characteristic. It changes from one age group to another in different way for separate EPs components and parameters depending on their nature, type of stimulus, area of recording. Most of all genotypical influences are manifested in EPs parameters of 10-12 years old subjects, especially the middle latency components from vertex area and latent periods of EPs in comparison with their amplitudes.     

Systemic Organization of Perceptive Activity in Children with Different Levels of Mental Development

Visual evoked potentials (EPs) of the left and right hemispheres in response to relevant and irrelevant stimuli in the structures of the left and right hemispheres have been studied in healthy young schoolchildren, learning-disabled (LD) children, and mentally retarded (MR) children. In healthy children, the largest EP variations depending on the stimulus relevancy have been found in associative structures of the left hemisphere. In LD children of the same age, the amplitude and temporal characteristics of left-hemispheric EPs to target and nontarget stimuli are the same. In MR children, EPs to relevant and irrelevant stimuli do not differ from each other in either the left or the right hemisphere. EP latencies are significantly longer in MR children than in healthy children. The results of simultaneous recording of EPs in the left and right hemispheres during isolated stimulation of the right and left visual half-fields indicate that interhemispheric interaction is impaired in children with deviations in mental development. The results of the study are discussed in terms of the psychological characteristics and learning ability of children.     

Differences in semantic event-related potentials in learning-disabled,normal, and gifted children

Cortical event-related potentials (ERP) were recorded over FZ, CZ, and PZ scalp sites in 15 learning-disabled (LD), 14 gifted (G), and 13 normal control (N) children of ages 8–12. The common stimulus consisted of nouns presented 80 percent of the time; the target stimulus of animal names presented 20 per cent of the time. ERPs were averaged over subjects from 180 msec pre-stimulus to 900 msec post-stimulus. Principal components analysis was used to determine if there were amplitude differences at different post-stimulus latencies as a function of condition. Differences in ERP's between groups (LD, gifted, and controls), scalp locations, and common versus target stimuli were analyzed by ANOVAs. P ₃ , Late, P ₂ , and N ₁ components represented by four factors were identified. Significant differences between G and LD and the N and LD groups were found target stimulus at all central locations for the P ₃ component. Differences were found centrally between G and LD, G and N, and N and LD groups for the P ₂ component centrally. Other differences were found for the N ₁ and late components. These differences could be interpreted as a deficit in either attentional mechanisms or information processing for the LD group.     

Different numbers of maternal and paternal siblings of cystic fibrosis patients

Summary When 458 parents of children suffering from cystic fibrosis (CF) from all over the German Democratic Republic were interviewed to determine the number of their siblings, it was found that the maternal families had a total of 1369 children and the paternal, 1220. While the fathers of CF patients tended to originate from families with one or two children, more mothers than fathers came from families with three to twelve children (P=0.01). The average number of children in the maternal families was 2.99; in the paternal families, only 2.66. To rule out any methodological errors, sibs of mothers and fathers of various control groups were studied. We found that the number of siblings in these groups was balanced. The differences in our findings are probably due to CF heterozygosity. The underlying mechanism is unknown.     

Gender Differences in Spontaneous and Evoked Activities of the Human Brain

The purpose of this study was to analyze sex-related differences in spontaneous and evoked brain activity. The study included 11 women and 10 men aged between 18 and 27 years; the subjects were adapted to the conditions of electrophysiological experiment. Differences in spontaneous activity were estimated by EEG spectral characteristics in frequency ranges corresponding to θ, α, β₁, β₂, γ₁, and γ₂ rhythms at rest with the eyes open and closed. The differences in evoked activity were estimated by the parameters of evoked potentials (EP) recorded upon the presentation of different types of stimuli (images and words) and categories (“fruits” and “vessels”). Behavioral differences were estimated by the efficiency of stimuli recognition. No gender differences were observed in the efficiency of stimuli recognition (number of errors, time of reaction). In the EEG of male subjects at rest, fast frequencies (β and γ) were less marked than in the female subjects, which may indicate a higher level of activation of CNS structures in women. Regardless of stimuli type and category, the amplitude of EP components in men is lower than that in women, which may be caused by lower level of CNS activation. However, the difference in the latency of EP components depended on the type of stimuli used. During the recognition of visual images, the latency of earlier EP components (N1, P2) in men was longer mostly on back and/or right electrodes. The latencies of the later EP components (P3, N3) in male subjects were longer on the back electrodes and shorter on the front electrodes than those in female ones. During the recognition of words, the latency of P1, N1, P2 and N2 components in men were shorter on temporal and temporoparietal electrodes of the left hemisphere. This may indicate that visual image in men are perceived slower but comprehended faster than in women. On the other hand, verbal stimuli in men were perceived faster but comprehended slower than in women.     

Extended incubation recesses by alpine‐breeding Horned Larks: a strategy for dealing with inclement weather?

ABSTRACT Incubating birds can incur high energetic costs and, when faced with a trade‐off between incubation and foraging, parents may neglect their eggs in favor of their own somatic needs. Extended incubation recesses are an example of neglect, but they are often treated as outliers and largely overlooked in studies of incubation behavior. We studied incubation rhythms of Horned Larks (Eremophila alpestris) on Hudson Bay Mountain, British Columbia, Canada, during four breeding seasons. Incubation recesses averaged 10.92 ± 0.38 min (N= 4076 2‐h periods), but we observed 70 extended recesses, ranging from 59 to 387 min in duration, at 35 nests. Although rare (<1% of all daytime recesses), extended recesses occurred in all 4 yr, were longer and more frequent in colder years (60% occurred in the two coldest years), and often occurred during inclement weather (39% occurred during three storm events). Extended recesses did not appear to compensate for long attendance periods because extended recess duration was not correlated with the duration of previous on‐bouts (P= 0.10, N= 70) or the mean on‐bout duration of the previous 2‐h period (P= 0.36, N= 70). Rather, extended recesses seemed to reflect a shift in parental investment away from their eggs and toward self‐maintenance when faced with energetically stressful conditions. Extended recesses may have reduced embryo viability; egg‐hatching rates were 91 ± 2.4% for nests where females did not take extended recesses and 81 ± 4.2% for nests where females did take extended recesses (P= 0.02, N= 56 nests). Extended recesses during incubation are rare events, but they may represent an important mechanism that allows birds to breed successfully in energetically challenging conditions.     

Psychophysiological Features of Somatosensory Disorders in Victims of the Chernobyl Accident

Participants of the Chernobyl clean-up (n = 145) teams exposed to radiation doses from 0.05 to 3.5 Gy who had for the first time complained of pathologic somatosensory sensations (ostealgic syndrome), 20 healthy subjects, and 50 veterans of the war in Afghanistan with posttraumatic stress disorder (PTSD) were examined by a neuropsychiatrist and presented with the MMPI test. Somatosensory evoked potentials (SSEPs) were recorded. Paresthesia and cenesthopathy were characteristic of the participants of the Chernobyl clean-up. Sensation disorders of the cerebral type, kinesthetic illusions, cenesthopathic hypochondriac disorders, and paroxysmal psychosensory states predominated in this group of subjects. They differed significantly from the veterans with PTSD in markedly increased scores on MMPI scales (hypochondriasis, schizophrenia, pure hypochondriasis, pure schizophrenia, emotional exclusion, and perception oddity), which closely correlated with clinical somatosensory symptoms. In clean-up workers, somatosensory disorders were significantly associated with hypochondriac and schizophrenic-like symptoms. The latencies (LPs) of main SSEP components—N ₂₀, P ₂₅, N ₁₄₀, P ₃₀₀, and N ₄₀₀—were increased and their amplitudes decreased in subjects exposed to radiation. Their SSEPs had significant topographical deviations in the left temporoparietal area: the contralateral LPs were increased, whereas the contralateral amplitudes of the thalamocortical N ₂₀ component and the cortical P ₂₅ component were decreased as compared to normal values. Somatosensory disorders and hypochondriac and schizophrenic symptoms were significantly correlated with changes in the SSEPs. The decrease in the N ₂₀ amplitude and increase in the P ₂₅ latency in the left temporoparietal area were dose-dependent. The results suggest cerebral rather than peripheral origin of ostealgic syndrome and other somatosensory disorders in the participants of the Chernobyl clean-up. These disorders are associated with radiation-induced dysfunction of the corticolimbic structures of the left—dominant—hemisphere. It is suggested that somatosensory disorders in patients exposed to low doses of radiation can be considered as manifestations of chronic fatigue syndrome /fibromyalgia, whereas schizoform organic brain lesions manifest themselves after exposure to a radiation dose of 0.3–0.5 Gy.     

High frequency of diabetes-specific autoantibodies in parents of children with type 1 diabetes. DENIS study group.

Strategies to identify subjects at risk for type 1 diabetes are largely based on the detection of autoantibodies directed to various beta cell autoantigens. Most previous studies only comprise siblings and children of patients with type 1 diabetes; only scare data are available on the antibody profile in older relatives. In this study, we examined the prevalence of cytoplasmic islet cell antibodies (ICA), antibodies to glutamic acid decarboxylase (GADA), antibodies to the protein tyrosine phosphatase IA-2 (IA-2A) and IA-2beta (IA-2betaA) in 531 unaffected parents of patients with type 1 diabetes, and compared the results with antibody frequencies in 2425 siblings. The frequency of ICA, GADA and IA-2A was substantially higher among siblings as compared to parents of patients with type 1 diabetes (8.0% vs. 4.5%, 8.0% vs. 4.3%, and 4.5% vs. 1.9%, respectively; p<0.01). However, subdividing the probands according to age revealed a high prevalence of ICA (5.5 %), GADA (5.9 %), and IA-2A (3.1%) among parents aged 31 -40 years which was similar to that observed in siblings above 20 years of age (6.4%, 6.4%, and 3.1%). In both cohorts, GADA and IA-2A were significantly associated with the presence of ICA. The combined screening for GADA and IA-2A identified 100% of parents and 91.9% of siblings at high risk for type 1 diabetes (>10 JDF-U). Furthermore, the analysis of antibody combinations revealed that among antibody positive individuals the percentage of subjects with two or three antibodies was even higher in parents (69.0%) than in siblings (58.2%). The present study shows a high frequency of single and multiple autoantibodies in unaffected parents of patients with type 1 diabetes. Our data indicate that GAD and IA-2 not only represent the major target of autoantibodies in young siblings but also in adult relatives. These findings may be important for the design of future intervention studies.     

Perinatal conditions and infant development in children with schizophrenic parents

Abstract

A twenty‐year study was begun in Denmark in 1962 of the differential effects of pregnancy and delivery complications on children of schizophrenic parents, on children of normal parents, and on children of parents with nonschizophrenic psychiatric disorders. This paper studies these children and their parents in 1971 utilizing data on pregnancy, delivery, and the physical and neurological examinations of the children at birth and at one year of age. Results include (1) a higher incidence of mildly low birth weight in children born to schizophrenics, also associated with developmental abnormalities at one year, (2) a higher incidence of infant females suffering from the effects of pregnancy complications, particularly where the schizophrenic parent was the father, and (3) a large number of results which involve the schizophrenic fathers.     

Characteristics of event-related potentials in response to symbolical and alphabetical stimulation matrices used in a P300-based brain-computer interface

In order to create a P300-based brain-computer interface (BCI) (the so-called Farwell-Donchin paradigm, FD) with a symbol matrix used as a stimulus, we compared characteristics of event-related potentials (ERPs) in response to stimulation by 6 × 6 matrices composed of either pictogram symbols or Cyrillic alphabet characters. Nine healthy adults were examined in 18 experiments, during which 28-channel EEGs were recorded in the course of stimulation with matrices of these two types. The obtained ERP data, i.e., amplitudes and peak latencies of the ERP components N1, P3 (with the P3a and P3b sub-components), and N4 were compared and analyzed for different types of stimulation matrices. In at least seven out of nine subjects, P3a, P3b, and N4 ERP amplitudes were larger in response to the symbol matrix than to the character matrix, while N1 amplitudes were larger for the character matrix. For N1 and P3a, the ERP latencies were shorter for the symbol matrix, while for P3b and N4, they were longer for the character matrix. The topography of differential ERP responses to the two types of stimuli was analyzed using a series of paired t-tests. Differences of ERP component amplitudes were determined individually for each of the 28 channels; next, for each site, absolute t-test values were summed for all nine subjects. For all ERP components studied, the t-test for peak amplitudes in response to target and non-target letters identified two separate areas with distinct lateralization. ERP responses to target and non-target symbols differed most in transversely extended areas. Finally, the yield surface of differential response to target letters and target symbols had a complex topography.     

Electrophysiological Correlates of Attentional Disorders in 12- to 13-Year-Old Adolescents

The EEG was recorded in 12- to 13-year-old adolescents with attention deficit hyperactivity disorder (ADHD). During the EEG recording, the subjects performed an attention test. Pairs of tone stimuli in the combinations low–low and low–high were presented in random order with equal probabilities with intervals of 2.3 s. Subjects had to press a button as soon as possible in response to low–low tone pair presentation (a go trial) and not to press the button when a pair consisting of low and high tones was presented (a no-go trial). On the basis of the results of the test performance (the numbers of omissions and false alarms), the subjects were divided into three groups characterized by the degree of severity of the attentional disorder. The evoked potentials in go and no-go trials were detected individually for the subject groups and each derivation. The components N1, N2, P2, P3-go, and P3-no-go were identified in the evoked potentials. These components had different latencies and were differently localized over the head surface. Only the amplitudes of P3-go and P3-no-go in the subjects were statistically significantly correlated with the severity of the attentional disorder.     

The influence of emotionally significant visual stimuli on cortical evoked potentials

Electrophysiological correlates of the perception of emotional stimuli were studied by means of recording the visual evoked potentials (EP) in 20 derivations (Fz, Cz, Pz, Oz, Fp _1/2,F _3/4,F _7/8,C _3/4,P _3/4,T _3/4,T _5/6, andO _1/2) during the emotional test performance. The performance of a special task by subjects was assessed positively or negatively (by administering emotionally positive or negative stimuli, respectively). Factor analysis revealed seven factors, which described the EP component structure. Analysis of variance demonstrated the influence of the emotional stimuli sign on the factorsP ₁₀₀,P ₁₄₀,N ₁₆₀,P ₂₂₀,P ₃₄₀, and “slow wave.” Hemispheric difference in reactions to the stimuli of a different emotional sign were recorded. During presentation of the positive and negative assessments, the amplitudes of the factorsP ₁₀₀,P ₃₄₀, and “slow wave” were maximally different in the left hemisphere, while the factorsN ₁₆₀ andP ₂₂₀ were maximally different in the right hemisphere.     

Age changes in latent periods of the human slow auditory evoked potential

With age regular changes take place in the latent periods of spikes of the slow auditory evoked potential. In particular, the latencies of the comparatively early waves (P₁, N₁, and P₂) become progressively shortened. Between 3–7 and 8–13 years the decrease is 50–60 msec, and later it is 25–35 msec. The latencies of the latest waves, especially P₃, N₃, and P₄, increase from 3–7 to 8–13 years by 35–65 msec. Later the latent period of the P₃ spike remains unchanged but the N₃ and P₄ waves disappear completely. Of all the components of the slow auditory evoked potential the most stable is the N₂ wave, the latent period of which decreases only very slightly with age. In children aged 3–7 years two wave complexes (P₁N₁P₂ and P₂N₂P₃) overlap frequently to form a single undifferentiated wave. This splits up into its components by 8 years of age. Long age changes in the shape and parameters of the slow auditory evoked potential are examined from the standpoint of the predominantly extralemniscal origin of this potential. On the basis of correlation discovered between the late waves of the evoked potential and the level of EEG synchronization it is postulated that the late waves of the slow evoked potential are formed with the participation of the nonspecific synchronizing system.Tbilisi State Postgraduate Medical Institute. Translated from Neirofiziologiya, Vol. 9, No. 1, pp. 3–10, January–February, 1977.     

Influence of genetic variants modulating dopamine activity on the brain processing of auditory information (the <Emphasis Type="Italic">P</Emphasis>300 paradigm)

We studied the influence of catechol-O-methyl transferase gene (COMT) polymorphism on the parameters of components of auditory evoked potentials (EPs) recorded under the conditions of selective attention in mentally healthy relatives of patients with endogenous psychosis. A smaller N100 latency of the EP in response to an insignificant stimulus, smaller N100 amplitude of the EP in response to a significant stimulus, smaller N200 latency, and larger P300 amplitude were found in subjects with the Met/Met genotype (with a higher dopamine activity), and a larger P200 latency was found in Val/Val genotype carriers. There was no influence of MMN gene polymorphism on the mismatch negativity.     

Functional brain organization of global and local visual perception: Analysis of event-related potentials

Event-related potentials (ERP) of the brain and psychometric indices (reaction time and percentage of correct responses) were studied in adult subjects during recognizing hierarchical visual stimuli (letters), while the subject’s attention was drawn to either the global or the local level of the stimulus. The psychophysical indices demonstrated the global precedence effect, i.e., an increased recognition time of a small letter, which was a part of an incongruent stimulus. The ERP component analysis demonstrated that differences in the regulatory mechanisms of attention and timing and topography of brain organization during processing of visual information depended on the level of recognizing the hierarchical stimulus (global vs. local). Visual recognition at the local level was accompanied by a stronger activation of visual associative areas (P _z and T ₆) at the stage of sensory feature analysis (P1 ERP component), as well as by the predominant involvement of the temporal inferior cortex of the right hemisphere (T ₆) at the stage of sensory categorization (the P2 ERP component) and of the frontal cortex of the right hemisphere at the stage of selection for the relevant target features (the N2 ERP component). Visual recognition at the global level was accompanied by significant involvement of the early sensory selection (the N1 ERP component) and predominant activation of the parietal cortex of the right hemisphere (P ₄) at the stage of sensory categorization (the P2 ERP component), as well as at the stage of identification of the target stimulus (the P3 ERP component). Perception of a stimulus at the global level is assumed to depend mostly on the analysis of its spatial features in the dorsal visual system, whereas perception at the local level involves analysis of the object-related features in the ventral visual system.