Anterior Cortical Areas Research Articles

Gender differences in dynamic changes in the anterior cortical activity under negative emotional strain

Dynamic changes of anterior cortical areas activity under negative emotional strain at male and female teenage examinees were investigated. Dependence of anterior cortical activity changes on gender and initial conflictness level of examinees is determined, which is also confirmed by detected shifts in phychoemotional sphere.

Enhanced frontocentral EEG connectivity in photosensitive generalized epilepsies: A partial directed coherence study

Photosensitive epilepsy (PSE) is the most common form of reflex epilepsy presenting with electroencephalography (EEG) paroxysms elicited by intermittent photic stimulation (IPS). To investigate whether the neuronal network undergoes dynamic changes before and during the transition to an EEG epileptic discharge, we estimated EEG connectivity patterns in photosensitive (PS) patients with idiopathic generalized epilepsy. EEG signals were evaluated under resting conditions and during 14 Hz IPS, a frequency that consistently induces photoparoxysmal responses (PPRs) in PS patients. Partial directed coherence (PDC), a linear measure of effective connectivity based on multivariate autoregressive models, was used in 10 PS patients and 10 controls. Anterior versus posterior (F3, F4, C3, C4, and P3, P4, O1, O2) and interhemispheric connectivity patterns (F4, C4, P4, O2, and F3, C3, P3, O1) were estimated with focus on beta and gamma band activity. PDC analysis revealed an enhanced connectivity pattern in terms of both the number and strength of outflow connections in the PS patient group. Under resting condition, the greater connectivity in the PS patients occurred in the beta band, whereas it mainly involved the gamma band during IPS (i.e., the frequencies ranging from 40-60 Hz that include the higher harmonics of the stimulus frequency). Both at rest and during IPS, the differences between the PS patients and controls were due primarily to clearly increased connectivity involving the anterior cortical regions. Our findings indicate that PS patients are characterised by abnormal EEG hyperconnectivity, primarily involving the anterior cortical regions under resting conditions and during IPS. This suggests that, even if the occipital cortical regions are the recipient zone of the stimulus and probably hyperexcitable, the anterior cortical areas are prominently involved in generating the hypersynchronization underlying the spike-and wave discharges elicited by IPS.

Neuroanatomical profiles of personality change in frontotemporal lobar degeneration

BackgroundThe neurobiological basis of personality is poorly understood. Frontotemporal lobar degeneration (FTLD) frequently presents with complex behavioural changes, and therefore potentially provides a disease model in which to investigate brain substrates of personality.AimsTo assess neuroanatomical correlates of personality change in a cohort of individuals with FTLD using voxel-based morphometry (VBM).MethodThirty consecutive individuals fulfilling consensus criteria for FTLD were assessed. Each participant’s carer completed a Big Five Inventory (BFI) questionnaire on five key personality traits; for each trait, a change score was derived based on current compared with estimated premorbid characteristics. All participants underwent volumetric brain magnetic resonance imaging. A VBM analysis was implemented regressing change score for each trait against regional grey matter volume across the FTLD group.ResultsThe FTLD group showed a significant decline in extraversion, agreeableness, conscientiousness and openness and an increase in neuroticism. Change in particular personality traits was associated with overlapping profiles of grey matter loss in more anterior cortical areas and relative preservation of grey matter in more posterior areas; the most robust neuroanatomical correlate was identified for reduced conscientiousness in the region of the posterior superior temporal gyrus.ConclusionsQuantitative measures of personality change in FTLD can be correlated with changes in regional grey matter. The neuroanatomical profiles for particular personality traits overlap brain circuits previously implicated in aspects of social cognition and suggest that dysfunction at the level of distributed cortical networks underpins personality change in FTLD.

The ontogeny of the neurophysiological mechanisms of stereognosis: An EEG study

Age-related characteristics of the systemic organization of intra- and interhemispheric interactions during a stereognostic task (tactile shape recognition with the right or left hand) were studied in adults and children aged five to six, seven to eight, and nine to ten years. A combined pattern of cortical interactions was found in adults. It was expressed in a considerable enhancement of relationships between cortical bioelectric potentials compared to the baseline accompanied by a substantial increase in the intensity of the systemic interactions between anterior and posterior cortical areas. This pattern was revealed by both coherence and cross-correlation analyses of the electroencephalogram (EEG). In the EEGs of children, the enhancement of interhemispheric relationships was observed at an age as early as five to six years and was the highest in seven- to eight-year-old children, whereas the increase in the cross-correlation of cortical bioelectric potentials in the frontal—occipital direction developed gradually, approaching the definitive level typical of adults by the age of nine to ten years. The results suggest that the central mechanisms of stereognosis, a function important for manual and occupational activities, gradually develop during postnatal ontogeny. Heterochronic involvement of intra- and interhemispheric interactions in the performance of stereognostic task may be related to gradual, heterochronic myelination of commissural and associative pathways.

Does EMX2 directly interfere with glutamatergic versus GABAergic phenotype decision?

Event Abstract Back to Event Does EMX2 directly interfere with glutamatergic versus GABAergic phenotype decision? Nóra Hádinger1*, B. Varga1, K. Barabas1 and Emilia Madarasz1 1 IEM-HAS, Hungary For proper development of the mammalian cerebral cortex, region-specific transcription factors should be activated on schedule. EMX2 is expressed early (8th day) in mouse embryos, in the anterior neural plate. At the time of anterior tube closure, Emx2 is expressed in the dorsal part of the forebrain vesicles with increasing intensity to caudo-medial direction. Lack of EMX2 results in a rearrangement of the anterior cortical areas, and impairs the development of the whole dorsal forebrain. The target genes of EMX2 transcription factor are not known. In healthy developing mice, Emx2 is uniformly expressed in the ventricular zone of the entire dorsal forebrain, which is the birthplace of cortical glutamatergic neurons. Its expression, however, is maintained in the subventricular zone of adult mice. In the present work, the effects of EMX2 on neuronal cell fate decision and on the choice of neurotransmitter phenotype were investigated by comparing wild type and EMX2 overexpressing neural stem cells and differentiated progenies. The results demonstrated that continuous expression of EMX2 did not inhibit the in vitro differentiation of neural stem cells. Moreover, the expression of EMX2 was not sufficient to suppress some GABAergic features (VGAT1) in stem cell derived post-mitotic neurons or to increase markedly the proportion of neurons with VGLUT2 immunoreactivity. Conference: 12th Meeting of the Hungarian Neuroscience Society, Budapest, Hungary, 22 Jan - 24 Jan, 2009. Presentation Type: Poster Presentation Topic: Developmental neurobiology and subcortical functions Citation: Hádinger N, Varga B, Barabas K and Madarasz E (2009). Does EMX2 directly interfere with glutamatergic versus GABAergic phenotype decision?. Front. Syst. Neurosci. Conference Abstract: 12th Meeting of the Hungarian Neuroscience Society. doi: 10.3389/conf.neuro.01.2009.04.235 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 13 Mar 2009; Published Online: 13 Mar 2009. * Correspondence: Nóra Hádinger, IEM-HAS, Budapest, Hungary, hadinger@koki.hu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Nóra Hádinger B. Varga K. Barabas Emilia Madarasz Google Nóra Hádinger B. Varga K. Barabas Emilia Madarasz Google Scholar Nóra Hádinger B. Varga K. Barabas Emilia Madarasz PubMed Nóra Hádinger B. Varga K. Barabas Emilia Madarasz Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Enhanced metabolic capacity of the frontal cerebral cortex after Pavlovian conditioning

While Pavlovian conditioning alters stimulus-evoked metabolic activity in the cerebral cortex, less is known about the effects of Pavlovian conditioning on neuronal metabolic capacity. Pavlovian conditioning may increase prefrontal cortical metabolic capacity, as suggested by evidence of changes in cortical synaptic strengths, and evidence for a shift in memory initially processed in subcortical regions to more distributed prefrontal cortical circuits. Quantitative cytochrome oxidase histochemistry was used to measure cumulative changes in brain metabolic capacity associated with both cued and contextual Pavlovian conditioning in rats. The cued conditioned group received tone–foot-shock pairings to elicit a conditioned freezing response to the tone conditioned stimulus, while the contextually conditioned group received pseudorandom tone–foot-shock pairings in an excitatory context. Untrained control group was handled daily, but did not receive any tone presentations or foot shocks. The cued conditioned group had higher cytochrome oxidase activity in the infralimbic and anterior cingulate cortex, and lower cytochrome oxidase activity in dorsal hippocampus than the other two groups. A significant increase in cytochrome oxidase activity was found in anterior cortical areas (medial, dorsal and lateral frontal cortex; agranular insular cortex; lateral and medial orbital cortex and prelimbic cortex) in both conditioned groups, as compared with the untrained control group. In addition, no differences in cytochrome oxidase activity in the somatosensory regions and the amygdala were detected among all groups. The findings indicate that cued and contextual Pavlovian conditioning induces sustained increases in frontal cortical neuronal metabolic demand resulting in regional enhancement in the metabolic capacity of anterior cortical regions. Enhanced metabolic capacity of these anterior cortical areas after Pavlovian conditioning suggests that the frontal cortex may play a role in the retention and regulation of learned associations.

A large-scale neurocomputational model of emotional decision making

There is growing interest in exploring the neurological activity underlying valuation and decision making. Recent findings have greatly enriched behavioral investigations of the psychology of preference and choice by revealing the specific biological substrates of reward encoding, trust, risky choice, and other relevant phenomena. Neurocomputational modeling allows for precise integrations of empirical findings into detailed mechanisms for how specific brain operations can produce complex cognitions and behaviors. We present a biologically realistic spiking neural model of affective choice and judgment that demonstrates this important explanatory role for computational neuroscience. Our model proposes a fundamental interplay between an emotional arousal state encoded by the amygdala and judgments of reward value and valuation changes computed in orbitofrontal cortex. Inspired by findings from attention research, we model a multiplicative modulation of reward valuation by affective arousal, whereby highly emotive events or contexts cause an amplification of positive or negative subjective judgments. This modulated signal feeds into interacting opponent systems for computing positive and negative reward prediction errors, which we have respectively encoded through dopaminergic and serotonergic activity. The degree to which an obtained outcome was positively or negatively unexpected induces activity in our modeled anterior cingulate and dorsolateral prefrontal cortical areas regarding the behavioral relevance of the outcome, with negative surprises indicating current behavior may need to be modified. A consolidation of encoded valuation, saliency and relative surprise is proposed to drive the planning of stimulus-appropriate behavior. Finally, information regarding behavioral saliency and prediction error feeds back to modulate emotional arousal level itself. These modeled mechanisms help to explain several important findings of behavioral decision research. In particular, the model provides a rigorous biological account of prospect theoretic loss aversion by encoding an asymmetric influence of the effects of positive and negative outcomes on emotional arousal, which produces disparities in subjective valuations of equivalent losses and gains. Mechanisms for relative valuations and neural firing saturation effects in orbitofrontal cortex further contribute to an explanation of the shape of the observed value function from prospect theory. The model also suggests multiple distinct neurological mechanisms by which information framing may affect choices, including ones involving anticipated pleasure. This allows for the proposal of a detailed neural basis for observed interactions between affect, prior expectations and counterfactual comparisons considered at the behavioral level in decision affect theory. Simulations of these important emotional decision phenomena lend support to the specific mechanisms of cognitive-affective interaction implemented in our model, and show the valuable role computational neuroscience can play in developing richer and more complete explanations in cognitive psychology.

Anatomical Asymmetries of Anterior Perisylvian Speech-Language Regions

Anterior cortical perisylvian areas important for speech and language functions include the pars triangularis (PTR), comprised of heteromodal association cortex, and the pars opercularis (POP), comprised of motor association cortex. The anatomy of these frontal language regions has not been well studied in large samples, however in smaller samples, leftward asymmetry of these regions has been found. Sex-linked differences have also been suggested, with bilateral activation of frontal language areas in women and leftward activation in men. We used volumetric MRI methods to measure the gray matter volume of the PTR, POP, and diagonal sulcus (DS) in 60 healthy right-handed adults and examined the distribution of asymmetry of these regions. Sex-linked differences in volume and asymmetry of anterior speech regions were also examined. For the PTR, there was a slight leftward asymmetry, however for the POP+DS, there was a slight rightward asymmetry. The DS was present slightly more often in the right hemisphere than in the left hemisphere and its frequency was similar in men and women. There were no significant sex-linked differences in volume or asymmetry for any of these frontal areas. More studies are necessary, looking at the anatomy of anterior language regions in large samples and examining the relationship between anatomy and function.

Distribution of Spatial Complexity of EEG in Idiopathic Generalized Epilepsy and Its Change After Chronic Valproate Therapy

The objective of this study was to investigate the global and regional spatial synchrony of the EEG background activity, and to assess the effect of chronic valproate therapy on spatial synchrony. 15 idiopathic generalized epilepsy (IGE) patients were examined and compared to 16 normal controls. Resting EEG with 19 channels was investigated before and during chronic administration of valproate (VPA). Omega, a single-valued measure of spatial covariance complexity, was calculated to assess the degree of spatial synchrony of EEG. Furthermore, a new parameter was defined to characterize the distribution of spatial synchrony (Antero-Posterior Complexity Ratio, APCR). Global Omega complexity was significantly lower in IGE compared to controls, while regional complexity showed significant differences only in the anterior region: the IGE group showed lower complexity. APCR was significantly lower in IGE. VPA therapy (1) lowered the global complexity, (2) increased regional complexity in the anterior region, but decreased it in the posterior region, and (3) increased APCR. In IGE lower complexity, i.e. enhanced spatial synchrony, was found, especially in the anterior cortical area. VPA modified the distribution of spatial synchrony in IGE patients towards that of normal controls, although the effect is not identical with full normalization of cortical bioelectric activity. Whether the observed change of spatial synchrony distribution may reflect the normalizing effect of valproate on the brain state is worth further investigation.

Altered quinpirole-induced local cerebral glucose utilization in anterior cortical regions in rats after sensitization to quinpirole

Dopaminergic psychostimulants produce behavioral responses of greater magnitude with repeated, intermittent administration, than a single, acute dose, a phenomenon known as “sensitization.” Most studies of sensitization have focused on the “motive circuit”; however, some additional anterior cortical regions also appear to be affected. In this study, alterations in regional neuronal activity in anterior cortical brain areas produced by quinpirole, a D 2/D 3 agonist, were assessed on the basis of local cerebral glucose utilization (LCGU) using the [ 14C]-2-deoxyglucose (2-DG) method. Adult, male Long-Evans rats (180–200 g, n = 7–9/group) were subjected to ten injections of quinpirole (0.5 mg/kg, s.c.) administered every third day; controls and drug-naive rats received saline. Locomotor activity was quantitated after injections one and ten to confirm sensitization. The 2-DG procedure was initiated 60 min after an 11th injection in freely moving rats. LCGU was determined in 11 anterior cortical brain regions by quantitative autoradiography. In drug-naive rats, quinpirole decreased LCGU in the cingulate cortex-area 3 (−16%) and infralimbic cortex (−16%). In sensitized rats, quinpirole decreased LCGU in the cingulate cortex-area 1 (−19%), frontal cortex-area 3 (−19%), lateral orbital cortex (−18%), medial/ventral orbital cortex (−17%), and parietal cortex (−17%) as well as in the cingulate cortex-area 3 (−19%) and infralimbic cortex (−20%); (all P < 0.05 v. control). This suggests that decreased neuronal activity in the cingulate cortex-area 1, frontal cortex-area 3, lateral orbital cortex, medial/ventral orbital cortex, and parietal cortex, in addition to altered activity in the motive circuit, may underlie the augmented behavioral response to quinpirole in sensitized animals.

Antero-posterior functional coupling at sleep onset: changes as a function of increased sleep pressure

The use of the directed transfer function (DTF), an advanced computational analysis of electroencephalogaphic (EEG) data, which provides an estimation of the direction of the information flow underlying cortico-cortical functional coupling, has shown that the presleep period is characterized by posterior-to-anterior functional cortical coupling, while at sleep onset there is an inversion of that direction. This finding supported the idea that anterior cortical areas first synchronize sleep EEG activity. The aim of the present study was to assess the changes of functional coupling between anterior and posterior midline cortical areas during the sleep onset process when sleep pressure is heightened by a selective slow-wave sleep (SWS) deprivation. The hypothesis was that the anterior-to-posterior direction of the cortical functional coupling at sleep onset is enhanced by SWS deprivation. Ten normal right-handed male students slept for six consecutive nights in the laboratory (1: adaptation, 2: baseline, 3: baseline with awakenings, 4 and 5: SWS deprivations, 6: recovery), with standard polysomnographic recordings. The DTF was computed on data recorded during nights two and six from anterior (Fz A1) and posterior (Pz A1, Oz A1) derivations. Results showed that, during the recovery night, the anterior-to-posterior direction of functional cortical coupling is already present in the presleep period, indicating that SWS deprivation advances the shift to an anterior-to-posterior directionality of functional cortical coupling, possibly as a consequence of heightened sleep pressure. These findings support the notion that a spread of synchronizing signals from associative prefrontal to posterior areas play a role in the wake–sleep transition.

Changes in cortical activity during altered state of consciousness: study of meditation by high resolution EEG

The specific features of the topology of spectral powers and coherent interregional interrelation- ships in the narrow, individually determined δ -, θ -, α 1 -, α 2 - , and α 3 -frequency bands were studied by means of high-resolution EEG (62 channels) in novice and experienced meditators (NMs and EMs) at rest and under the conditions of generation of an altered state of consciousness characterized by inactivation of cognitive activity and the occurrence of a positive emotional experience of happiness. EMs in the meditation-free state were found to be characterized by a shift in the values of the individual α frequency to a lower-frequency region of the spectrum, along with higher, compared to NMs, θ -, α 1 -, α 2 - , and α 3 -band power values, which probably reflects the cumulative character of the influence of long-term meditative practice. The effective achievement of altered states of consciousness in EMs was associated with an increase in the local θ - and α 1 powers in the anterior cortical areas, as well as long-distance coherence between the prefrontal and posterior associative cor- tex with the formation of a center of gravity in the left prefrontal region (lead AF 3 ). According to the data of the correlation analysis of the EEG power values and the data of subjective scaling of the meditation state, the θ - power values were positively associated with positive emotional experiences and negatively associated with the level of mental activity. The results of this study are consistent with current concepts that the θ and α activities in narrow frequency bands reflect the activity of multifunctional neuronal networks selectively associated with processes of cognitive and affective activity.

Split-second sequential selective activation in human secondary visual cortex.

This work addressed early selection based on nonspatial visual features, using event-related potentials (ERPs) with high temporal resolution and dipole-source modeling. Subjects were presented rapid sequences of gratings varying in spatial frequency and orientation, and were instructed to attend to gratings with one spatial frequency and ignore those with another. Attention effects started at 120-msec latency as anterior positivity and proceeded as posterior negativity (200 msec) and anterior negativity (265 msec). Dipole-source modeling suggested that these effects reflect the sequential selective activation of, on average, posterior dorsal-medial, posterior ventral-lateral, and anterior medial cortical areas. In contrast, stimulus-specific activity was observed well before 100-msec latency and characterized by dipoles with locations significantly posterior to those of the attention-modulated activity. These results indicate that even with highly discriminable spatial frequencies, selection is not as early as before the 100-msec latency, unlike what is often found for location selection. It is also separated in time and anatomically from the earliest stimulus-specific cortical activity. Reducing discriminability of the selection feature resulted in longer selection latencies, becoming manifest only at 175 msec as an apparent combination of posterior and anterior negativities, and in an elevated criterion for overt responding.

Brief causal relations in EEG based on adaptive Granger causality

Commonly, coherence and correlation are used to describe interrelations between EEG signals. But, on this basis, the investigation of causality or direction of interrelations is not possible. The general idea of causality between two signals may be expressed in terms of upgrading the predictability of one signal bye the knowledge of the past of the other signal. The best established approach in this context is the so-called Granger causality. The study present an adaptive estimation of Granger causality, which allows to detect dynamic causal relations within time intervals of less 100 ms. The time-variant Granger causality is applied to EEG data of the Stroop task. It could be shown, that conflict situation generates a dense web of directed interactions from posterior to anterior cortical areas.

Avaliação do envelhecimento do cristalino em olhos normais

Objetivo: Avaliar alterações do cristalino relacionadas à idade, em olhos normais, analisando-se sua densidade e espessura, além da profundidade da câmara anterior (PCA). Métodos: Foram estudados 120 olhos de 60 pacientes hígidos por meio do sistema Scheimpflug. Os pacientes foram distribuídos em 6 grupos: Grupo I, 10 a 19 anos; Grupo II, 20 a 29 anos; Grupo III, 30 a 39 anos; Grupo IV, 40 a 49 anos; Grupo V, 50 a 59 anos ; e Grupo VI, 60 a 69 anos. Foram analisadas as seguintes variáveis: profundidade da câmara anterior, densidade do cristalino (DC) e espessura do cristalino (EC). Para avaliação da densidade, o cristalino foi dividido em 5 áreas: cápsula anterior, córtex anterior, núcleo, córtex posterior e cápsula posterior. Estas variáveis foram correlacionadas com a idade. Resultados: A profundidade da câmara anterior diminuiu, ao passo que a espessura do cristalino aumentou com o envelhecimento. A densidade do cristalino aumentou com a idade em todas as áreas estudadas, exceto na cápsula posterior, onde ocorreu diminuição nos valores. Quando correlacionadas idade e densidade do cristalino observou-se forte correlação positiva nas seguintes áreas: cápsula anterior (r = 0,78; p<0,001), córtex anterior (r = 0,87; p<0,001), núcleo (r = 0,88; p<0,001) e córtex posterior (r = 0,70; p<0,001). A correlação entre idade e DC na área capsular posterior foi negativa (r = -0,62; p<0,001). Encontrou-se correlação significante entre idade e EC (r = 0,73; p<0,001). Os coeficientes de correlação para PCA e EC (r = -0,60; p<0,001) e PCA e idade (r = -0,34; p<0,001) foram negativos. Conclusões: Este estudo mostrou, por meio do sistema Scheimpflug, as alterações da profundidade da câmara anterior, densidade do cristalino e espessura do cristalino decorrentes do envelhecimento. Deve-se ter atenção com estas mudanças relacionadas à idade na realização de estudos envolvendo drogas anticataratogênicas, drogas tóxicas ao cristalino e pacientes com catarata.

The effects on auditory neurocognitive evoked responses and contingent negative variation activity of frontal cortex lesions or ablations in man: three new case studies

Our previous research in patients with extensive surgical ablations of the prefrontal cortex contradict the hypothesis of some authors that the generators of several auditory event-related potentials (ERPs) (N100; P200; N200; P300; SW), recordable in humans with depth/scalp electrodes and MEG over the prefrontal dorsolateral cortical areas, are essentially located in medial prefrontal and anterior cingulate–limbic cortices. Using a standard CNV paradigm, 21 EEG electrodes and topographic mapping analysis, the post-warning (S1) auditory N100a b c, P200, P300 (binaural clicks) and CNV activity were recorded in three additional patients after extensive dorsolateral and/or medial prefrontal cortex ablations, verified through CT/MRI examinations. No true post-S1/CNV components were recordable over the ablated frontal areas, only sporadic volume-conducted ERPs probably generated in the temporo-parietal lobes or posterior cingulate gyrus. For one of these patients, after excision of a vast right frontal epileptogenic cortical region (including extensive dorsolateral areas, but sparing the fronto-medial cortex and anterior/middle cingulate gyrus), no post-S1/CNV components were recordable over the ablated regions. These latest observations again indicate that independent neuronal generators of several post-S1 auditory and CNV components are located in the dorsolateral supramodal premotor/prefrontal cortical areas which are directly, ipsilaterally connected to the uni/multimodal temporo-parieto–occipital sensory and associative regions through the long, two-way, fairly superficial, superior arcuate-longitudinal and deeper superior and inferior occipito-frontal bundles. Clear and almost constant differences in the latency of some post-S1 N100 subcomponents (especially the time-lapses between onset and the highest amplitude of the N100 a and c) over various posterior, central and anterior cortical areas sequentially involved, roughly measured in 10 normal subjects along the scalp and with MRI cerebral imaging, may probably be accounted for by the transcortical homohemispheric conduction time, which varies in our scalp recordings from 1 cm/0.74–1.28 ms, mean ∼1 cm/1.02 ms (∼9.8 ms).

The Kraepelinian Dichotomy: Evidence From Developmental and Neuroimaging Studies

The Kraepelinian Dichotomy: Evidence From Developmental and Neuroimaging Studies

Formation of the Interaction between the Wave Components of the Main EEG Rhythms in Children up to Five Years of Age

Using the analysis of the interaction between EEG components [1], the authors studied the regularities of the formation of the EEG wave structure in 36 children aged 4 to 7 months, 2 to 3 years, and 4 to 5 years. The EEG of 4- to 7-month-old children had a relatively organized temporal structure, whose components were connected mainly with those of the slow-wave range. This structure is reproduced in most of the leads and is more stable in the anterior cortical areas than in the posterior ones. The waking 2- to 5-year-old children had two “functional” nuclei in the relation structure of the EEG components characterized by statistically significant enhancement in the probability of the consecutive appearance of waves of certain ranges. These nuclei include a slow-wave nucleus in the range of the Δ2–θ1-frequencies and an “alpha”-nucleus in the α1- and α2-ranges (θ2 and α1 2- to 3-year-old children) of the EEG frequencies. The relations between the components of the slow-wave nucleus begin to form in infants, prevail in 2- to 3-year-old children, and weaken by the age of 4 to 5 years. A trend is observed in 2- to 5-year-old children towards an increase in the average frequency of the waves that form the slow-wave nucleus. The temporal (strengthening interaction between the waves) and spatial organization of the interaction between the wave components of the “alpha”-nucleus is accelerated at the age of 4 to 5 years. The average frequency of the components forming this nucleus gradually increases with the children's age from 4 to 7 months to 4 to 5 years. Competitive relations exist between the two nuclei, characterized by a significant decrease in the probability of transitions between the components of different nuclei. The θ2-component may play a special role of the connecting link between the nuclei at the age of 4 to 5 years, the interwave transition from the Δ- to θ-frequencies and from the latter to the α-range being effected by a leaplike rather than smooth frequency increase. The character of local and spatial rearrangements of the EEG temporal structure detected in this study reflects a gradual morphofunctional maturation of the brain as a system that maintains the specific features of self-regulation mechanisms and coordination of the intersystem interactions at various stages of a child's development.

Life Span Changes in Electrophysiological Measures of Inhibition

Three electrophysiological findings which provide suggestive evidence of weakened inhibition in children and the elderly are reviewed. First, compared to young adults, electrophysiological recordings from old adults show a greater incidence of EEG alpha in anterior cortical areas and of somatosensory evoked potentials in occipital areas, and a reduction in heterogeneity of EEG and ERP activity across recording sites. These findings suggest a relative weakening of central inhibition in old age and a loss of functional independence of cortical centers. Second, visually evoked potentials from children and the elderly demonstrate a relative lack of differentiation between patterned and unpatterned stimuli. Inhibition is known to be important within the visual system for the detection of lines and contours. Finally, children and the elderly do not dampen (inhibit) their electrophysiological responses to sensory stimuli as effectively as subjects of an intermediate age. These age-related differences in electrophysiological responsivity appear to parallel age changes in behavioral measures which are also believed to reflect weakened inhibition. The electrophysiological measures, which reflect maturity and health of CNS structural and chemical systems, indicate that inhibition plays an increasing role in the shaping of behavior as children approach late adolescence but a diminishing role as adults live beyond the fifth decade. Recent research, however, suggests that the magnitude of inhibitory loss in old age may be related to cardiovascular health. Older men who frequently participated in vigorous physical activity showed significantly less inhibitory loss than age-matched peers who seldom exercised.

Stimulus and Sex-Differences in Performance of Mental Rotation - Evidence from Event-Related Potentials

We examined stimulus and sex differences in reaction time (RT) and event-related potentials (ERPs) during mental rotation of letters and abstract designs (PMA figures). RTs replicated stimulus and angle effects found in previous studies, but no sex differences were found for either set of stimuli. ERP latency data showed women began stimulus evaluation earlier, and PMA rotations began later over smaller angles, whereas letter rotations began later over larger angles. ERP amplitude data replicated hemisphere, electrode, and angle effects found in earlier studies. Amplitude measures also showed greater involvement of anterior cortical areas for evaluation of letter figures and posterior right temporal lobe for PMA figures, and greater positivity of womens waveforms than mens over late evaluation and early rotation components.