Christian Rummel - Academia.edu (original) (raw)

Uploads

Papers by Christian Rummel

Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society, 2011

We suggest a procedure to identify those parts of the spectrum of the equal-time correlation matr... more We suggest a procedure to identify those parts of the spectrum of the equal-time correlation matrix C where relevant information about correlations of a multivariate time series is induced. Using an ensemble average over each of the distances between eigenvalues, all nearest-neighbor distributions can be calculated individually. We present numerical examples, where ͑a͒ information about cross correlations is found in the so-called "bulk" of eigenvalues ͑which generally is thought to contain only random correlations͒ and where ͑b͒ the information extracted from the lower edge of the spectrum of C is statistically more significant than that extracted from the upper edge. We apply the analysis to electroencephalographic recordings with epileptic events.

Epilepsia, 2012

Purpose: Epileptic seizures are associated with a dysregulation of electrical brain activity on m... more Purpose: Epileptic seizures are associated with a dysregulation of electrical brain activity on many different spatial scales. To better understand the dynamics of epileptic seizures, that is, how the seizures initiate, propagate, and terminate, it is important to consider changes of electrical brain activity on different spatial scales. Herein we set out to analyze periictal electrical brain activity on comparatively small and large spatial scales by assessing changes in single intracranial electroencephalography (EEG) signals and of averaged interdependences of pairs of EEG signals. Methods: Single and multiple EEG signals are analyzed by combining methods from symbolic dynamics and information theory. This computationally efficient approach is chosen because at its core it consists of analyzing the occurrence of patterns and bears analogy to classical visual EEG reading. Symbolization is achieved by first mapping the EEG signals into bit strings, that is, long sequences of zeros and ones, depending solely on whether their amplitudes increase or decrease. Bit strings reflect relational aspects between consecutive values of the original EEG signals, but not the values themselves. For each bit string the relative frequencies of the different constituent short bit patterns are then determined and used to compute two information theoretical measures: (1) redundancy (R) of single bit strings characterizes electri-cal brain activity on a comparatively small spatial scale represented by a single EEG signal and (2) averaged pairwise mutual information with all other bit strings (M), which allows tracking of larger-scale EEG dynamics. Key Findings: We analyzed 20 periictal intracranial EEG recordings from five patients with pharmacoresistant temporal lobe epilepsy. At seizure onset, R first strongly increased and then decreased toward seizure termination, whereas M gradually increased throughout the seizure. Bit strings with maximal R were always derived from EEG signals recorded from the visually identified seizure-onset zone. When compared to the bit strings derived from other EEG signals, their M was relatively smaller. These findings are consistent with a strong but transient occurrence of information-poor, that is, redundant electrical brain activity on a smaller spatial scale, which is particularly pronounced in the seizure-onset zone. On a larger spatial scale, a progressively more collective state emerges, as revealed by increasing amounts of mutual information. Significance: Information theoretical analysis of bit patterns derived from EEG signals helps to characterize periictal brain activity on different spatial scales in a quantitative and efficient way and may provide clinically relevant results.

ABSTRACT During epileptic seizures a large number of neurons are recruited into a collective dyna... more ABSTRACT During epileptic seizures a large number of neurons are recruited into a collective dynamics. Rather than being simply monolithic “hyper-synchronous states” seizures show a complex and often patient specific evolution in multichannel EEG. Here, we summarize recent approaches to a multivariate description of the whole interacting network by diagonalization of interrelation matrices. Equal-time cross-correlation and mutual information are used to estimate linear and nonlinear interrelations and appropriate surrogates are employed for hypothesis testing. It has been found that focal onset seizures stop after an increase of crosscorrelation on the largest spatial scale accessible by intracranial EEG. On smaller scales a pronounced rearrangement of correlation patterns is observed during seizures. Ictogenic brain tissue may differ from the non-ictogenic one with respect to its degree of significantly nonlinear interrelations that cannot be explained by linear correlation alone. Nonlinear interrelation tends to be higher during seizures than inter-ictally. We conclude that multivariate methods and a separation of nonlinear from linear effects may give new insights into spatio-temporal seizure dynamics. These approaches might contribute to a better understanding of seizure generation and termination as well as to a better delineation of ictogenic brain tissue. Thus, they may ultimately be relevant for novel diagnostic and therapeutic approaches.

We report on oxygenation changes noninvasively recorded by multichannel continuous-wave near infr... more We report on oxygenation changes noninvasively recorded by multichannel continuous-wave near infrared spectroscopy (CW-NIRS) during endovascular neuroradiologic interventions requiring temporary balloon occlusion of arteries supplying the cerebral circulation. Digital subtraction angiography (DSA) provides reference data on the site, timing, and effectiveness of the flow stagnation as well as on the amount and direction of collateral circulation. This setting allows us to relate CW-NIRS findings to brain specific perfusion changes. We focused our analysis on the transition from normal perfusion to vessel occlusion, i.e., before hypoxia becomes clinically apparent. The localization of the maximal response correlated either with the core (occlusion of the middle cerebral artery) or with the watershed areas (occlusion of the internal carotid artery) of the respective vascular territories. In one patient with clinically and angiographically confirmed insufficient collateral flow during carotid artery occlusion, the total hemoglobin concentration became significantly asymmetric, with decreased values in the ipsilateral watershed area and contralaterally increased values. Multichannel CW-NIRS monitoring might serve as an objective and early predictive marker of critical perfusion changes during interventions-to prevent hypoxic damage of the brain. It also might provide valuable human reference data on oxygenation changes as they typically occur during acute stroke.

Artikel basiert auf Antrittsvorlesung gleichen Titels des Erstautors vom 30.06.2010 im Rahmen des... more Artikel basiert auf Antrittsvorlesung gleichen Titels des Erstautors vom 30.06.2010 im Rahmen des Epilepsiechirurgiesymposiums der Universitäten Bern und Basel Bei Patienten, die an pharmakoresistenter Epilepsie mit fokal beginnenden Anfällen leiden, sollte möglichst früh im Krankheitsverlauf die Möglichkeit eines epilepsiechirurgischen Eingriffes abgeklärt werden. Hauptziele der prä-chirurgischen Epilepsiediagnostik sind 1) die Anfallsursprungszone genau zu lokalisieren und 2) festzustellen, ob diese ohne unzumutbare neurologische Folgeschäden entfernt werden kann. Zur Erreichung dieser Ziele stellt das EEG, die Aufzeichnung cerebral generierter elektrischer Potentiale, neben der Bildgebung mittels Magnetresonanztomographie (MRT) die wichtigste technische Methode dar. In eindeutigen Fällen genügt in der prä-chirurgischen Abklärung die EEG Registrierung mit extrakraniellen Elektroden. Wenn aber die Resultate nicht invasiver Methoden nicht übereinstimmende Befunde ergeben, wird häufig eine EEG Aufzeichnung mit intrakraniellen Elektroden notwendig. Wir beschreiben in diesem Artikel -auch anhand von Fallbeispielen -EEG Aufzeichnungen mit extrakraniellen und mit intrakraniellen Elektroden während der prä-chirurgischen Epilepsiediagnostik. Es wird insbesondere auch demonstriert wie mit Hilfe quantitativer Signalanalyse klinisch und pathophysiologisch relevante EEG Informationen erkannt und dargestellt werden können. Worrell GA, So EL, Kazemi J, O'Brien TJ, Mosewich RK, Cascino GD, Meyer FB, Marsh WR. Focal ictal beta discharge on scalp EEG predicts excellent outcome of frontal lobe epilepsy surgery. Epilepsia, 43:277-282, 2002 Danksagung Die hier ausschnittweise beschriebene Forschung wird unterstützt durch den Schweizerischen Nationalfonds (SNF 320030_122010) und durch die Deutsche Forschungsgemeinschaft (RU 1401/2-1) Anmerkung

Cerebral electrical activity is highly nonstationary because the brain reacts to ever changing ex... more Cerebral electrical activity is highly nonstationary because the brain reacts to ever changing external stimuli and continuously monitors internal control circuits. However, a large amount of energy is spent to maintain remarkably stationary activity patterns and functional inter-relations between different brain regions. Here we examine linear EEG correlations in the peri-ictal transition of focal onset seizures, which are typically understood to be manifestations of dramatically changing inter-relations. Contrary to expectations we find stable correlation patterns with a high similarity across different patients and different frequency bands. This skeleton of spatial correlations may be interpreted as a signature of standing waves of electrical brain activity constituting a dynamical ground state. Such a state could promote the formation of spatiotemporal neuronal assemblies and may be important for the integration of information stemming from different local circuits of the functional brain network.

The rank-based nonlinear predictability score was recently introduced as a test for determinism i... more The rank-based nonlinear predictability score was recently introduced as a test for determinism in point processes. We here adapt this measure to time series sampled from time-continuous flows. We use noisy Lorenz signals to compare this approach against a classical amplitude-based nonlinear prediction error. Both measures show an almost identical robustness against Gaussian white noise. In contrast, when the amplitude distribution of the noise has a narrower central peak and heavier tails than the normal distribution, the rank-based nonlinear predictability score outperforms the amplitude-based nonlinear prediction error. For this type of noise, the nonlinear predictability score has a higher sensitivity for deterministic structure in noisy signals. It also yields a higher statistical power in a surrogate test of the null hypothesis of linear stochastic correlated signals. We show the high relevance of this improved performance in an application to electroencephalographic (EEG) recordings from epilepsy patients. Here the nonlinear predictability score again appears of higher sensitivity to nonrandomness. Importantly, it yields an improved contrast between signals recorded from brain areas where the first ictal EEG signal changes were detected (focal EEG signals) versus signals recorded from brain areas that were not involved at seizure onset (nonfocal EEG signals).

The analysis of short segments of noise-contaminated, multivariate real world data constitutes a ... more The analysis of short segments of noise-contaminated, multivariate real world data constitutes a challenge. In this paper we compare several techniques of analysis, which are supposed to correctly extract the amount of genuine cross-correlations from a multivariate data set. In order to test for the quality of their performance we derive time series from a linear test model, which allows the analytical derivation of genuine correlations. We compare the numerical estimates of the four measures with the analytical results for different correlation pattern. In the bivariate case all but one measure performs similarly well. However, in the multivariate case measures based on the eigenvalues of the equal-time cross-correlation matrix do not extract exclusively information about the amount of genuine correlations, but they rather reflect the spatial organization of the correlation pattern. This may lead to failures when interpreting the numerical results as illustrated by an application to three electroencephalographic recordings of three patients suffering from pharmacoresistent epilepsy.

While analysis and interpretation of structural epileptogenic lesion is an essential task for the... more While analysis and interpretation of structural epileptogenic lesion is an essential task for the neuroradiologist in clinical practice, a substantial body of epilepsy research has shown that focal lesions influence brain areas beyond the epileptogenic lesion, across ensembles of functionally and anatomically connected brain areas. In this review article, we aim to provide an overview about altered network compositions in epilepsy, as measured with current advanced neuroimaging techniques to characterize the initiation and spread of epileptic activity in the brain with multimodal noninvasive imaging techniques. We focus on resting-state functional magnetic resonance imaging (MRI) and simultaneous electroencephalography/fMRI, and oppose the findings in idiopathic generalized versus focal epilepsies. These data indicate that circumscribed epileptogenic lesions can have extended effects on many brain systems. Although epileptic seizures may involve various brain areas, seizure activity does not spread diffusely throughout the brain but propagates along specific anatomic pathways that characterize the underlying epilepsy syndrome. Such a functionally oriented approach may help to better understand a range of clinical phenomena such as the type of cognitive impairment, the development of pharmacoresistance, the propagation pathways of seizures, or the success of epilepsy surgery.

Cortical gray matter thinning occurs during childhood due to pruning of inefficient synaptic conn... more Cortical gray matter thinning occurs during childhood due to pruning of inefficient synaptic connections and an increase in myelination. Preterms show alterations in brain structure, with prolonged maturation of the frontal lobes, smaller cortical volumes and reduced white matter volume. These findings give rise to the question if there is a differential influence of age on cortical thinning in preterms compared to controls. To investigate the relationship between age and cortical thinning in school-aged preterms compared to controls. The automated surface reconstruction software FreeSurfer was applied to obtain measurements of cortical thickness based on T1-weighted MRI images. Forty-one preterms (<32weeks gestational age and/or <1500g birth weight) and 30 controls were included in the study (7-12years). In preterms, age correlated negatively with cortical thickness in right frontal, parietal and inferior temporal regions. Furthermore, young preterms showed a thicker cortex compared to old preterms in bilateral frontal, parietal and temporal regions. In controls, age was not associated with cortical thickness. In preterms, cortical thinning still seems to occur between the age of 7 and 12years, mainly in frontal and parietal areas whereas in controls, a substantial part of cortical thinning appears to be completed before they reach the age of 7years. These data indicate slower cortical thinning in preterms than in controls.

Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society, 2011

We suggest a procedure to identify those parts of the spectrum of the equal-time correlation matr... more We suggest a procedure to identify those parts of the spectrum of the equal-time correlation matrix C where relevant information about correlations of a multivariate time series is induced. Using an ensemble average over each of the distances between eigenvalues, all nearest-neighbor distributions can be calculated individually. We present numerical examples, where ͑a͒ information about cross correlations is found in the so-called "bulk" of eigenvalues ͑which generally is thought to contain only random correlations͒ and where ͑b͒ the information extracted from the lower edge of the spectrum of C is statistically more significant than that extracted from the upper edge. We apply the analysis to electroencephalographic recordings with epileptic events.

Epilepsia, 2012

Purpose: Epileptic seizures are associated with a dysregulation of electrical brain activity on m... more Purpose: Epileptic seizures are associated with a dysregulation of electrical brain activity on many different spatial scales. To better understand the dynamics of epileptic seizures, that is, how the seizures initiate, propagate, and terminate, it is important to consider changes of electrical brain activity on different spatial scales. Herein we set out to analyze periictal electrical brain activity on comparatively small and large spatial scales by assessing changes in single intracranial electroencephalography (EEG) signals and of averaged interdependences of pairs of EEG signals. Methods: Single and multiple EEG signals are analyzed by combining methods from symbolic dynamics and information theory. This computationally efficient approach is chosen because at its core it consists of analyzing the occurrence of patterns and bears analogy to classical visual EEG reading. Symbolization is achieved by first mapping the EEG signals into bit strings, that is, long sequences of zeros and ones, depending solely on whether their amplitudes increase or decrease. Bit strings reflect relational aspects between consecutive values of the original EEG signals, but not the values themselves. For each bit string the relative frequencies of the different constituent short bit patterns are then determined and used to compute two information theoretical measures: (1) redundancy (R) of single bit strings characterizes electri-cal brain activity on a comparatively small spatial scale represented by a single EEG signal and (2) averaged pairwise mutual information with all other bit strings (M), which allows tracking of larger-scale EEG dynamics. Key Findings: We analyzed 20 periictal intracranial EEG recordings from five patients with pharmacoresistant temporal lobe epilepsy. At seizure onset, R first strongly increased and then decreased toward seizure termination, whereas M gradually increased throughout the seizure. Bit strings with maximal R were always derived from EEG signals recorded from the visually identified seizure-onset zone. When compared to the bit strings derived from other EEG signals, their M was relatively smaller. These findings are consistent with a strong but transient occurrence of information-poor, that is, redundant electrical brain activity on a smaller spatial scale, which is particularly pronounced in the seizure-onset zone. On a larger spatial scale, a progressively more collective state emerges, as revealed by increasing amounts of mutual information. Significance: Information theoretical analysis of bit patterns derived from EEG signals helps to characterize periictal brain activity on different spatial scales in a quantitative and efficient way and may provide clinically relevant results.

ABSTRACT During epileptic seizures a large number of neurons are recruited into a collective dyna... more ABSTRACT During epileptic seizures a large number of neurons are recruited into a collective dynamics. Rather than being simply monolithic “hyper-synchronous states” seizures show a complex and often patient specific evolution in multichannel EEG. Here, we summarize recent approaches to a multivariate description of the whole interacting network by diagonalization of interrelation matrices. Equal-time cross-correlation and mutual information are used to estimate linear and nonlinear interrelations and appropriate surrogates are employed for hypothesis testing. It has been found that focal onset seizures stop after an increase of crosscorrelation on the largest spatial scale accessible by intracranial EEG. On smaller scales a pronounced rearrangement of correlation patterns is observed during seizures. Ictogenic brain tissue may differ from the non-ictogenic one with respect to its degree of significantly nonlinear interrelations that cannot be explained by linear correlation alone. Nonlinear interrelation tends to be higher during seizures than inter-ictally. We conclude that multivariate methods and a separation of nonlinear from linear effects may give new insights into spatio-temporal seizure dynamics. These approaches might contribute to a better understanding of seizure generation and termination as well as to a better delineation of ictogenic brain tissue. Thus, they may ultimately be relevant for novel diagnostic and therapeutic approaches.

We report on oxygenation changes noninvasively recorded by multichannel continuous-wave near infr... more We report on oxygenation changes noninvasively recorded by multichannel continuous-wave near infrared spectroscopy (CW-NIRS) during endovascular neuroradiologic interventions requiring temporary balloon occlusion of arteries supplying the cerebral circulation. Digital subtraction angiography (DSA) provides reference data on the site, timing, and effectiveness of the flow stagnation as well as on the amount and direction of collateral circulation. This setting allows us to relate CW-NIRS findings to brain specific perfusion changes. We focused our analysis on the transition from normal perfusion to vessel occlusion, i.e., before hypoxia becomes clinically apparent. The localization of the maximal response correlated either with the core (occlusion of the middle cerebral artery) or with the watershed areas (occlusion of the internal carotid artery) of the respective vascular territories. In one patient with clinically and angiographically confirmed insufficient collateral flow during carotid artery occlusion, the total hemoglobin concentration became significantly asymmetric, with decreased values in the ipsilateral watershed area and contralaterally increased values. Multichannel CW-NIRS monitoring might serve as an objective and early predictive marker of critical perfusion changes during interventions-to prevent hypoxic damage of the brain. It also might provide valuable human reference data on oxygenation changes as they typically occur during acute stroke.

Artikel basiert auf Antrittsvorlesung gleichen Titels des Erstautors vom 30.06.2010 im Rahmen des... more Artikel basiert auf Antrittsvorlesung gleichen Titels des Erstautors vom 30.06.2010 im Rahmen des Epilepsiechirurgiesymposiums der Universitäten Bern und Basel Bei Patienten, die an pharmakoresistenter Epilepsie mit fokal beginnenden Anfällen leiden, sollte möglichst früh im Krankheitsverlauf die Möglichkeit eines epilepsiechirurgischen Eingriffes abgeklärt werden. Hauptziele der prä-chirurgischen Epilepsiediagnostik sind 1) die Anfallsursprungszone genau zu lokalisieren und 2) festzustellen, ob diese ohne unzumutbare neurologische Folgeschäden entfernt werden kann. Zur Erreichung dieser Ziele stellt das EEG, die Aufzeichnung cerebral generierter elektrischer Potentiale, neben der Bildgebung mittels Magnetresonanztomographie (MRT) die wichtigste technische Methode dar. In eindeutigen Fällen genügt in der prä-chirurgischen Abklärung die EEG Registrierung mit extrakraniellen Elektroden. Wenn aber die Resultate nicht invasiver Methoden nicht übereinstimmende Befunde ergeben, wird häufig eine EEG Aufzeichnung mit intrakraniellen Elektroden notwendig. Wir beschreiben in diesem Artikel -auch anhand von Fallbeispielen -EEG Aufzeichnungen mit extrakraniellen und mit intrakraniellen Elektroden während der prä-chirurgischen Epilepsiediagnostik. Es wird insbesondere auch demonstriert wie mit Hilfe quantitativer Signalanalyse klinisch und pathophysiologisch relevante EEG Informationen erkannt und dargestellt werden können. Worrell GA, So EL, Kazemi J, O'Brien TJ, Mosewich RK, Cascino GD, Meyer FB, Marsh WR. Focal ictal beta discharge on scalp EEG predicts excellent outcome of frontal lobe epilepsy surgery. Epilepsia, 43:277-282, 2002 Danksagung Die hier ausschnittweise beschriebene Forschung wird unterstützt durch den Schweizerischen Nationalfonds (SNF 320030_122010) und durch die Deutsche Forschungsgemeinschaft (RU 1401/2-1) Anmerkung

Cerebral electrical activity is highly nonstationary because the brain reacts to ever changing ex... more Cerebral electrical activity is highly nonstationary because the brain reacts to ever changing external stimuli and continuously monitors internal control circuits. However, a large amount of energy is spent to maintain remarkably stationary activity patterns and functional inter-relations between different brain regions. Here we examine linear EEG correlations in the peri-ictal transition of focal onset seizures, which are typically understood to be manifestations of dramatically changing inter-relations. Contrary to expectations we find stable correlation patterns with a high similarity across different patients and different frequency bands. This skeleton of spatial correlations may be interpreted as a signature of standing waves of electrical brain activity constituting a dynamical ground state. Such a state could promote the formation of spatiotemporal neuronal assemblies and may be important for the integration of information stemming from different local circuits of the functional brain network.

The rank-based nonlinear predictability score was recently introduced as a test for determinism i... more The rank-based nonlinear predictability score was recently introduced as a test for determinism in point processes. We here adapt this measure to time series sampled from time-continuous flows. We use noisy Lorenz signals to compare this approach against a classical amplitude-based nonlinear prediction error. Both measures show an almost identical robustness against Gaussian white noise. In contrast, when the amplitude distribution of the noise has a narrower central peak and heavier tails than the normal distribution, the rank-based nonlinear predictability score outperforms the amplitude-based nonlinear prediction error. For this type of noise, the nonlinear predictability score has a higher sensitivity for deterministic structure in noisy signals. It also yields a higher statistical power in a surrogate test of the null hypothesis of linear stochastic correlated signals. We show the high relevance of this improved performance in an application to electroencephalographic (EEG) recordings from epilepsy patients. Here the nonlinear predictability score again appears of higher sensitivity to nonrandomness. Importantly, it yields an improved contrast between signals recorded from brain areas where the first ictal EEG signal changes were detected (focal EEG signals) versus signals recorded from brain areas that were not involved at seizure onset (nonfocal EEG signals).

The analysis of short segments of noise-contaminated, multivariate real world data constitutes a ... more The analysis of short segments of noise-contaminated, multivariate real world data constitutes a challenge. In this paper we compare several techniques of analysis, which are supposed to correctly extract the amount of genuine cross-correlations from a multivariate data set. In order to test for the quality of their performance we derive time series from a linear test model, which allows the analytical derivation of genuine correlations. We compare the numerical estimates of the four measures with the analytical results for different correlation pattern. In the bivariate case all but one measure performs similarly well. However, in the multivariate case measures based on the eigenvalues of the equal-time cross-correlation matrix do not extract exclusively information about the amount of genuine correlations, but they rather reflect the spatial organization of the correlation pattern. This may lead to failures when interpreting the numerical results as illustrated by an application to three electroencephalographic recordings of three patients suffering from pharmacoresistent epilepsy.

While analysis and interpretation of structural epileptogenic lesion is an essential task for the... more While analysis and interpretation of structural epileptogenic lesion is an essential task for the neuroradiologist in clinical practice, a substantial body of epilepsy research has shown that focal lesions influence brain areas beyond the epileptogenic lesion, across ensembles of functionally and anatomically connected brain areas. In this review article, we aim to provide an overview about altered network compositions in epilepsy, as measured with current advanced neuroimaging techniques to characterize the initiation and spread of epileptic activity in the brain with multimodal noninvasive imaging techniques. We focus on resting-state functional magnetic resonance imaging (MRI) and simultaneous electroencephalography/fMRI, and oppose the findings in idiopathic generalized versus focal epilepsies. These data indicate that circumscribed epileptogenic lesions can have extended effects on many brain systems. Although epileptic seizures may involve various brain areas, seizure activity does not spread diffusely throughout the brain but propagates along specific anatomic pathways that characterize the underlying epilepsy syndrome. Such a functionally oriented approach may help to better understand a range of clinical phenomena such as the type of cognitive impairment, the development of pharmacoresistance, the propagation pathways of seizures, or the success of epilepsy surgery.

Cortical gray matter thinning occurs during childhood due to pruning of inefficient synaptic conn... more Cortical gray matter thinning occurs during childhood due to pruning of inefficient synaptic connections and an increase in myelination. Preterms show alterations in brain structure, with prolonged maturation of the frontal lobes, smaller cortical volumes and reduced white matter volume. These findings give rise to the question if there is a differential influence of age on cortical thinning in preterms compared to controls. To investigate the relationship between age and cortical thinning in school-aged preterms compared to controls. The automated surface reconstruction software FreeSurfer was applied to obtain measurements of cortical thickness based on T1-weighted MRI images. Forty-one preterms (<32weeks gestational age and/or <1500g birth weight) and 30 controls were included in the study (7-12years). In preterms, age correlated negatively with cortical thickness in right frontal, parietal and inferior temporal regions. Furthermore, young preterms showed a thicker cortex compared to old preterms in bilateral frontal, parietal and temporal regions. In controls, age was not associated with cortical thickness. In preterms, cortical thinning still seems to occur between the age of 7 and 12years, mainly in frontal and parietal areas whereas in controls, a substantial part of cortical thinning appears to be completed before they reach the age of 7years. These data indicate slower cortical thinning in preterms than in controls.