Modulation of attention in healthy children using a course of EEG-feedback sessions

We studied changes in the power spectra of EEG in the course of sessions of feedback by EEG characteristics (neurofeedback sessions) and estimated the effects of neurofeedback on psychological and EEG correlates of voluntary attention. Indices of the latter were estimated using Bourdon’s test (a correcture test) and Schulte’s tables. Twenty-nine reasonably healthy 10-to 13-year-old children took part in the study; they were divided into two groups, an experimental group (n = 12) and a control group (n = 15). The results obtained support the statement on noticeable changes in the functional state of the brain both immediately in the course of a neurofeedback session and after a course of such trainings. Changes in the ratios of the spectral powers of the beta₁ vs theta rhythms and the low-frequency beta vs theta rhythms were found in EEG recorded from the sensorimotor zone of the right hemisphere (C4). The observed changes in the spectral characteristics of EEG induced by the course of neurofeedback sessions were accompanied by the improvement of a few indices of voluntary attention. Neirofiziologiya/Neurophysiology, Vol. 38, Nos. 5/6, pp. 458–465, September–December, 2006.     

Correlations between characteristics of evoked EEG potentials recorded in a go/no-go paradigm and indices of attention in children

We studied correlations of the parameters of evoked EEG potentials (EPs) with the indices of attention in 30 children (12 years old). The EP were recorded in a two-stimulus go/no-go paradigm; the time of reaction was also measured. The indices of attention were measured using a Burdone test (correction trial) and Schulte’s tables. Optimum characteristics of attention were found in children with high amplitudes of the P2 component, P300 wave, and contingent negative deviation, low amplitudes of the N2 component, and small values of the latencies of the P1-N1-P2 complex. Neirofiziologiya/Neurophysiology, Vol. 37, Nos. 5/6, pp. 452–458, September–December, 2005.     

Peculiarities of EEG in hard-of-hearing children of primary school age

Electroencephalographic examination of 7-to 9-year-old children with sensorineural deafness of degrees II and III included EEG recording in the resting state, in the course of reaction of activation (at opening of the eyes), under conditions of rhythmic photostimulation with frequencies of 4, 6, 9, and 12 sec⁻¹ and under those of the hyperventilation test. The results allow us to conclude that systems responsible for generation of EEG in hard-of-hearing children demonstrate some functionally immaturity. The following facts confirm the above conclusion. As compared with the norm, greater normalized spectral powers (SPs) of the delta and theta rhythms, a higher intensity of electrogenesis (integral power of oscillations) within all frequency ranges, and a smaller mean frequency of the dominant rhythm were typical of hard-of-hearing children. In these children, the reaction of activation in the majority of cases looked like incomplete suppression of the alpha rhythm. Upon rhythmic photostimulation, hard-of-hearing boys and girls demonstrated following of the rhythm at frequencies of 4 and 6 sec⁻¹ while children with normal hearing demonstrated that at 9 and 12 sec⁻¹ frequencies. The characteristics of EEG reactions under the conditions of the hyperventilation test reflected the immaturity of the fronto-thalamic controlling system, as well as certain dysfunction of lower brainstem regions in children with disorders of hearing. Neirofiziologiya/Neurophysiology, Vol. 40, No. 2, pp. 137–146, March–April, 2008.     

EEG Correlates of the Psychological Adaptation Potential of a Personality

In a group of 68 adults of both sexes, we examined correlations between estimates of the psychological adaptability of an individual (diagnosed using a multilevel personality questionnaire, MPQ) and spectral powers, SPs, of the frequency components (rhythms) of background EEG recorded in the resting state (leads C3 and C4 according to the 10–20 system). Despite high individual variability within the group, indices by the scale “communicative potential” demonstrated significant correlation with the SP of the θ rhythm, while estimates of the moral normativity correlated with the SPs of the α and β1 rhythms. Subgroups of the persons classified according to the level of the integral adaptation capability (personality’s adaptation potential) differed from each other in the mean estimates of interhemisphere asymmetry of the α rhythm; this index was higher in subjects with the medium/high level of adaptability. The correlations observed are, most probably, determined by the fact that both the level of psychological adaptability of the personality and the EEG amplitude parameters depend significantly on genetic (neurochemical, in particular) factors. Such peculiarities of the neurodynamic constitution of the individual are probably determined, to a considerable extent, by the specificities of organization and functioning of a few neurotransmitter (aminergic, in particular) and neurohumoral systems.     

Peculiarities of EEG in Subjects with Coronary-Prone (Type A) Behavior

In a group including 72 adults of both sexes, we studied correlations between the estimates of the so-called coronary-prone personality type (type A) diagnosed using the Jenkins questionnaire and the spectral powers (SPs) of the frequency components (rhythms) of background EEGs recorded in the resting state (leads C3 and C4 according to the 10-20 system). Despite natural high interindividual variability, estimates that characterized the subject as belonging to the behavioral type A corresponded, on average, to relatively low SPs of the δ, θ, and α EEG components, intermediate values of the β₁ rhythm SP and coefficient of reactivity of the α rhythm, and higher SPs of the high-frequency (β₂ and γ) rhythms. Estimates characterizing type B personality corresponded to significantly higher δ-rhythm SPs, intermediate SPs of the θ and α rhythms, and smaller SPs of the β and γ rhythms. The interhemisphere asymmetry coefficient for the α rhythm was usually negative in type-A individuals and positive in the cases of types B and AB. The peculiarities observed are probably determined, to a certain extent, by the fact that both the characteristics of the behavioral types of the personality and the amplitude parameters of EEG rhythms depend significantly on inherited (in particular neurochemical) factors. Such peculiarities of the neurodynamic constitution of the individual are determined, to a considerable extent, by the specificity of organization and functioning of a few neurotransmitter (in particular aminergic) and neurohumoral systems.     

Interrelations between Peculiarities of the Motivational Sphere of a Personality and Characteristics of the Current EEG

In a group of 70 adult subjects of both sexes, we estimated the levels of the need for achievement and its motivation (interpreted as generalized characteristics of the state of the motivational sphere of a personality and diagnosed using questionnaires of Orlov and Mehrabian) and examined the correlations of these estimates with spectral powers (SPs) of the frequency components (rhythms) of the current background EEG (С3 and С4 leads according to the 10–20 system). Despite the fact that naturally high interindividual variability exists, high estimates of the need for achievement correlated with medium values of the SPs of most EEG frequency components (δ, θ, α, and β₁ rhythms), low SPs of the β₂ and γ rhythms, and higher values of the coefficient of reactivity (CR) of the α rhythm. A high level of the need for achievement corresponded to higher SPs of the θ and γ rhythms and high CR of the α rhythm, a medium SP of this EEG component, and lower SPs of the δ and β rhythms. The coefficient of interhemisphere asymmetry of the α rhythm was the highest at low values of the studied psychological indices. Interrelations that we found in our study can be explained as follows: both the characteristics of the need for achievement and motivation typical of a certain personality and the amplitude parameters of the EEG rhythms observed in this individual depend significantly on genetically determined factors (in particular, on neurochemical ones). These peculiarities of neurodynamic constitution of the individual are, to a considerable extent, due to the specificity of organization and functioning of a few neurotransmitter (aminergic, in particular) and neurohumoral systems. Neirofiziologiya/Neurophysiology, Vol. 41, No. 1, pp. 61–69, January–February, 2009.     

EEG Correlates of Anxiety and Emotional Stability in Adult Healthy Subjects

We studied peculiarities of the spectral characteristics of EEG in 111 healthy adult subjects of both sexes. The levels of situative anxiety (anxiety state) and personal anxiety were estimated using the Spielberger–Khanin test system. To estimate anxiety-related properties of the personality, Cattel’s technique 16 PF (form А) was used. Estimates of situative anxiety demonstrated only two cases of positive correlation with the spectral power density (SPD) of EEG rhythms (SPDs of the beta2 rhythm in the right-hemisphere temporal and occipital regions; recording with the eyes open). Estimates of personal anxiety positively correlated with the SPDs of the beta1 and (especially) beta2 EEG rhythms. Under conditions with the eyes open, the number of significant correlations was greater, and correlations themselves were tighter than with the eyes closed. The closest correlations of the estimates of personal anxiety with the SPDs of the beta rhythm were found in frontal and central leads of both hemispheres and in parietal and occipital loci of the right hemisphere. Only a single case of correlation of the alpha rhythm SPD with personal anxiety (negative correlation, a parietal lead in the left hemisphere) was found. At the same time, rather numerous correlations of the alpha rhythm expression with an index congeneric to anxiety, the C factor by the Cattel’s questionnaire (emotional stability/instability), were found. Thus, the intense beta EEG rhythm can be considered an electrographic correlate of high situative and personal anxieties. At the same time, the alpha rhythm power correlates with the emotional stability of the individual. We suppose that persons with a well-developed alpha rhythm are characterized by active and stable functioning of the cerebral dopaminergic system; this simultaneously serves as a pre-requisite of high emotional stability and social adaptability.     

Moderation of Increased Anxiety in Children and Teenagers with the Use of Neurotherapy: Estimation of the Efficacy

We estimated the efficacy of using the technique of feedback (FB) by EEG characteristics (EEG-FB, neurotherapy) with the aim of reducing increased anxiety levels in healthy 10- to 14-year-old children. The anxiety level was estimated using the Prikhojan anxiety test, the Spielberger–Khanin questionnaire, and the House–Tree–Person projective drawing technique. Positive effects of series of neurotherapy sessions were obvious. After training was completed, we observed significant increases in the ratios of the amplitudes of alpha and theta rhythms, semsorimotor and theta rhythms, as well as of the modal frequency of the EEG alpha rhythm in tested persons of the experimental group (n = 7). In the control group (n = 10), changes in these values did not reach the significance level. In the experimental group of tested persons subjected to EEG-FB sessions, the anxiety level decreased appreciably; in addition, the indices “feeling of inferiority” and “frustration” decreased significantly. In the control group, alterations of these psychological indices were not unidirectional. Therefore, modifications of the EEG pattern, which occurred in the course of training and were accompanied by a decrease in the anxiety level in the experimental group, can be indicative of the expediency of EEG-FB for the reduction of high anxiety levels in children and teenagers.     

Correlations between the psychological peculiarities of an individual and the efficacy of a single neurofeedback session (by the EEG characteristics)

Modifications of different EEG rhythms induced by a single neurofeedback session (by the EEG characteristics) directed toward an increase in the ratio of the spectral powers (SPs) of the α vs θ oscillations were compared with the psychological characteristics of the tested subjects (the group included 30 persons). A generally accepted neurofeedback technique was used; the intensity of acoustic white noise served as the feedback signal. EEG potentials were recorded from the C3 and C4 leads. Psychological testing was carried out using Eysenck’s (EPQ), Rusalov’s (OST), and (16 PF) questionnaires. The directions of changes in the SPs of EEG frequency components were found to significantly correlate with some individuality-related peculiarities of the tested subjects. The SP of the δ rhythm correlated with the EPQ scale “neuroticism,” OST scale “social plasticity,” and 16 PF factors H (“parmia”), I (“premsia”), and Q₃ (“self-control of behavior”). The SP of the θ component demonstrated correlations with the OST scales “ergisity,” “plasticity,” and “social temp” and with 16 PF factors M (“autia”), Q₄ (“frustration”), and Q1 (“exvia”). The SP of the α rhythm correlated with 16 PF factors Q₃ (“self-control of behavior”), G (“strength of superEgo”), O (“hypothymia”), L (“protension”), and N (“shrewdness”). The SP of the β rhythm correlated with the OST scale “emotionality,” while that of the γ rhythm showed correlations with the 16 PF indices L (“protension”) and M (“autia”). Changes in the ratio of the α vs θ SPs correlated with the EPQ scale “neuroticism.” Thus, our data confirm the statement that a high individual variability of the results of a single (first in the series) neurofeedback session is to a great extent related to peculiarities of the individual psychological pattern of the subject. Neirofiziologiya/Neurophysiology, Vol. 38, No. 3, pp. 239–247, May–June, 2006.     

Correlation between the Activity of Dopaminergic Neurons of the Ventral Tegmentum and Spectral Power of the EEG Rhythms in Awake Cats

We studied correlations between the frequency of background impulse activity (BIA) of dopaminergic (DAergic) neurons of the ventral tegmentum (VT) and spectral power (SP) of the frequency components of EEG samples recorded in awake cats. The EEG was recorded monopolarly (electrodes were fixed in the cranial bones) from the frontal, occipital, and right and left temporal regions of the cortex. In a great majority of the cases, the BIA frequency of VT DA-ergic neurons demonstrated significant positive correlations with changes in the SPs of the alpha and beta EEG rhythms. The closest correlations of the spiking frequency of DA-ergic cells with the SP of the alpha rhythm was observed in the occipital region, while those with the beta SP were found in the frontal area. Correlations of the activity of DA-ergic neurons with the SPs of the alpha and beta rhythms in the left temporal cortical zone were closer, as compared with those in the symmetrical right zone. Correlations of the SPs of the delta, theta, and gamma EEG components with the discharge frequency of VT DA neurons were of opposite directions, and in most cases such correlations did not reach the level of significance. The results of this study show that, in some cases, specific EEG patterns can be considered indicators of the state of the cerebral VT DA-ergic system. Neirofiziologiya/Neurophysiology, Vol. 40, No. 4, pp. 359–367, July–August, 2008.     

Complex estimation of adaptation abilities of the organism in children using the indices of responsiveness of the cardiovascular system and characteristics of EEG

Based on the complex analysis of the data of cardiointervalographic (CIG) and rheoencephalographic (REG) examination of 37 healthy children and 63 children suffering from bronchial asthma (BA), we identified the most informative indices characterizing reactions of the cardiovascular system under conditions of an active orthostatic test (coefficient of autonomic responsiveness and index of responsiveness of the vessels). We conclude that the relation between the values of these indices allows one to identify the level of strain of the regulatory mechanisms and the state of the adaptation systems of the organism, which determine the adequacy of control of the autonomic sphere. The following gradations can be classified: an optimum level, compensated adaptation disorders (strain and overstrain of the regulatory mechanisms), and decompensated adaptation disorders (exhaustion of the regulatory mechanisms and failure of adaptation). Among clinically healthy children, we found a risk group (about 30%) with manifestations of lowering of the organism’s adaptive abilities. It is shown that groups of healthy children and children suffering from BA differ from each other in the shares of different patterns of EEG and variants of EEG responses to a hyperventilation test. Qualitative and quantitative characteristics of EEG in children, despite high interindividual variability, clearly correlate with the state of adaptation processes. The expedience of a complex approach in estimating the adaptation ability of the child based on the data of CIG, REG and EEG examinations is discussed. Neirofiziologiya/Neurophysiology, Vol. 38, No. 1, pp. 72–84, January–February, 2006.     

A comparative electrophysiological study of regulatory components of working memory in adults and seven- to eight-year-old children: An analysis of coherence of EEG rhythms

Coherence at the frequency of θ, α, and β EEG rhythms was analyzed in 14 adults and 23 children of 7–8 years old while they performed cognitive tasks requiring an involvement of working memory (WM). We used the pair matching paradigm in which subjects had to match a pair of stimuli shown in succession in the central visual field. The pairs of verbal and visuo-spatial stimuli were mixed together and presented in a pseudo random order. Each pair was preceded by a warning signal that did not specify a modality of upcoming stimuli. We analyzed EEG segments recorded (i) in the rest condition, (ii) prior to the first (reference) stimulus (maintenance of nonspecific voluntary attention), and (iii) prior to the second (test) stimulus (retention of information in WM). In the present study we focused on the regulatory functional components of WM, and therefore, the stimulus modality has not been taken into account. In adults, maintaining nonspecific voluntary attention was accompanied by an increase of the strength of θ-related functional coupling between medial areas of the frontal cortex and temporal cortical zones and by a strengthening of local β-related functional connectivity in the fronto-central areas of the cortex. In children, no such increase was found for θ rhythm; for β rhythm the increase was limited to several short-range functional links. In adults, the retention of information in WM was accompanied by the growth in α coherence in distant fronto-parietal links, predominantly in the right hemisphere, while in children information retention was accompanied by the growth of θ coherence in the inferio-temporal and parietal cortical regions. The results of the study point to a relative immaturity of the mechanisms of executive control of WM in children of 7–8 years old.     

Reflection of Anxiety in the Characteristics of Evoked EEG Potentials in 10- to 11-Year-Old Children

We studied the peculiarities of the amplitude/time parameters of evoked EEG potentials (EPs) and event-related potentials (ERPs) in 10- to 11-year-old children characterized by low and high anxiety levels. The latter levels were estimated using the scale of the manifest anxiety test of Prikhozhan and projective techniques (“House–Tree–Person,” HTP, and the Lüscher color test). For children with a high anxiety level, the amplitudes of the following EP components and ERPs were lower than those in low-anxiety children of the same age: P1 (predominantly in the occipital region of the left hemisphere), P2 (in the right occipital region), and Р300 wave (in different loci of both hemispheres). In high-anxiety children, we also more frequently observed increased amplitudes of the N2 component in the left parietal and right occipital regions. High-anxiety individuals were characterized by longer latencies of component P1 (mostly in the right frontal and left central regions) and, at the same time, shorter latencies of component N1 (in the parietal and occipital regions of the left hemisphere and also in the right temporal region). Thus, we found that the amplitude/time characteristics of a few EP components and ERPs in children with high anxiety levels differ statistically significantly from the parameters of corresponding EPs/ERPs in individuals of the same age but with low anxiety levels.     

Modifications of the EEG frequency pattern in humans related to a single neurofeedback session

We studied changes in the frequency pattern of EEG related to a single session of biological feedback by the EEG characteristics (neurofeedback, NFB) directed toward an increase in the ratio of α/θ spectral powers (SPs) (an experimental group; 30 subjects) and to a session of the supposedly indifferent acoustic influence (listening to a musical background; 30 persons). A standard technique of EEG recording was used; the loudness of white noise overlapping the musical background served as an NFB signal. EEG was recorded from the C3 and C4 leads. Within the examined experimental group, an NFB session elicited a trend toward statistically insignificant decreases in the SPs of δ, α, and β rhythms and increases in the SPs of θ and γ EEG components. Listening to a supposedly neutral musical background by the control group, with no attempts at self-control of the SPs of EEG rhythms, was followed by rather clear unidirectional (partially significant) decreases in the SPs of θ, α, β, and γ components; the δ activity in the left hemisphere decreased, while in the right hemisphere it increased. In general, results of the single NFB session were characterized by a high interindividual variability, which can be related mostly to the specificities of psychophysiological characteristics of the personality of the tested subject. Neirofiziologiya/Neurophysiology, Vol. 37, Nos. 5/6, pp. 443–451, September–December, 2005.     

Modulation of High-Frequency EEG Rhythms under Conditions of the Activation Reaction: Dependence on Psychological Characteristics of Personality

In a group of 118 adults of both sexes, we studied modulation of high-frequency EEG rhythms (β and γ components) under conditions of EEG activation related to opening of the eyes. Typical changes in the α rhythm (significant depression in the overwhelming majority of the tested subjects) was accompanied by different (in direction and intensity) shifts of the spectral powers (SPs) of the β and γ components in different subjects. The power of the β1 subcomponent under conditions of the activation reaction increased in 6 persons and dropped in 109 persons; changes in this index in two hemispheres were opposite in their directions in 3 subjects. Thus, changes in the β1 SP upon opening of the eyes were nearly parallel to those of the α rhythm but less intense. The subgroups differentiated according to the pattern of reactivity of the β2 subcomponent included 23, 85, and 10 subjects; for the γ rhythm, the corresponding numbers were 31, 72, and 8. In other words, the patterns of reactivity of β2 and γ oscillations were rather similar to each other but differed significantly from the pattern for the β1 rhythm. Values of the differential coefficients of reactivity (DCRs) of the β1, β2, and γ rhythms demonstrated significant correlations that were especially close for the β2 and γ activity. Within the entire examined group, we found significant negative correlations of the DCR values for β and γ activities with the estimates of some psychological characteristics of the subjects (levels of neuroticism, psychoticism, plasticity, self-control of behavior, and some others) measured using the RTS (Strelau), EPQ (Eysenck), OST (Rusalov), and 16PF (Kettel) questionnaires. The dispersion analysis demonstrated that the above-mentioned subgroups of the subjects (with increase and decrease in the SPs of the β and γ rhythms in both hemispheres and opposite changes of these indices in the right and left hemisphere) showed significant or close to significant specific intergroup differences of a few mean values of the psychological characteristics estimated according to the above questionnaires. Possible mechanisms of modulation of high-frequency EEG components under conditions of the reaction of EEG activation and relations of such changes to the psychological characteristics of the personality are discussed.     

Theta phase coding in a network model of the entorhinal cortex layer II with entorhinal-hippocampal loop connections

We investigated successive firing of the stellate cells within a theta cycle, which replicates the phase coding of place information, using a network model of the entorhinal cortex layer II with loop connections. Layer II of the entorhinal cortex (ECII) sends signals to the hippocampus, and the hippocampus sends signals back to layer V of the entorhinal cortex (ECV). In addition to this major pathway, projection from ECV to ECII also exists. It is, therefore, inferred that reverberation activity readily appears if projections from ECV to ECII are potentiated. The frequency of the reverberation would be in a gamma range because it takes signals 20–30 ms to go around the entorhinal-hippocampal loop circuits. On the other hand, it has been suggested that ECII is a theta rhythm generator. If the reverberation activity appears in the entorhinal-hippocampal loop circuits, gamma oscillation would be superimposed on a theta rhythm in ECII like a gamma-theta oscillation. This is a reminiscence of the theta phase coding of place information. In this paper, first, a network model of ECII will be developed in order to reproduce a theta rhythm. Secondly, we will show that loop connections from one stellate cell to the other one are selectively potentiated by afferent signals to ECII. Frequencies of those afferent signals are different, and transmission delay of the loop connections is 20 ms. As a result, stellate cells fire successively within one cycle of the theta rhythm. This resembles gamma-theta oscillation underlying the phase coding. Our model also replicates the phase precession of stellate cell firing within a cycle of subthreshold oscillation (theta rhythm).     

Event-related synchronization and desynchronization of EEG during appraisal of threatening and pleasant visual stimuli in high anxious subjects

The 62-channel EEG was recorded while low (LA, n = 18) and high (HA, n = 18) trait-anxious subjects viewed sequentially presented neutral, threatening and pleasant IAPS stimuli. Event-related desynchronization (ERD) and synchronization (ERS) were studied in the delta, theta1, theta2, alpha1, alpha2, beta1, beta2, beta3, and gamma frequency bands. Between-group differences, related to stimulus emotionality, were linked to theta1 and theta2 bands. In the low theta at prefrontal sites in the test period of 100-700 ms after stimulus onset HA exhibited relative predominance of the left hemisphere in response to both threatening and pleasant stimuli, whereas LA yielded larger right than left hemisphere activity in response to all the three stimulus categories. In the upper theta band between group differences were associated with posterior cortical regions and the test period of 0-1000 ms after stimulus onset: HA exhibited the largest ERS to threatening, whereas LA prompted the largest ERS to pleasant stimuli. Finally, according to the ERD data, in the alpha1 band HA participants in comparison with LA revealed enhanced left hemisphere activation in response to all the stimulus categories. It is suggested that as it is indexed by theta-ERS relative predominance of the left hemisphere at prefrontal sites along with the largest bilateral activity of posterior cortical regions (i.e., enhanced higher order visual processing) to threatening stimuli could form the basis for general bias towards threatening information in HA at the very early stages of emotional processing.     

Electrophysiological indicators as endophenotypes of cognitive development

Parameters of the components of visual evoked potentials recorded in children aged 8 and 11 years make it possible to predict intelligence indices (according to Wechsler’s test) of the same individuals at the age of 22–23 years. The efficiency of this prediction exhibits dependence on the parameter of the evoked potential (EP), the type of the stimulus, site of recording, and the subject’s age. The presence of genetic correlations between the EP parameters and intelligence indices indicates the existence of common genetic factors involved in the formation of inter-age, inter-level phenotypic relationships of different indices of cognitive functions of a person.     

Cognitive tactics of Bengalese finch (<Emphasis Type="Italic">Lonchura striata </Emphasis>var. <Emphasis Type="Italic">domestica</Emphasis>) for song discrimination in a go/no-go operant task

Twelve Bengalese finches (Lonchura striata var. domestica) were trained to discriminate between a conspecific and a heterospecific song in a go/no-go operant task. Training the birds to go for the conspecifics song or to go for the heterospecific song required the same number of training sessions. Nine possible cognitive tactics could be used to solve this task, but probe tests revealed that the birds used only four. Six birds memorized only the “no-go” stimulus and responded to the rest of the stimuli (no-go memory), two birds classified songs according to the species category (open-ended categorization), one bird memorized both of the training stimuli but responded by chance to the probe stimuli (rote categorization), and two birds combined open-ended and rote categorization tactics (combined categorization). These tactics were related to the number of sessions needed to reach the species-discrimination criterion. Our results suggest that investigators should consider individual cognitive tactics and the pitfalls of go/no-go discrimination when interpreting the results of operant discrimination tasks.     

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.