Humans engaged in monotonous tasks are susceptible to occasional errors that may lead to serious ... more Humans engaged in monotonous tasks are susceptible to occasional errors that may lead to serious consequences, but little is known about brain activity patterns preceding errors. Using functional MRI and applying independent component analysis followed by deconvolution of hemodynamic responses, we studied error preceding brain activity on a trial-by-trial basis. We found a set of brain regions in which the temporal evolution of activation predicted performance errors. These maladaptive brain activity changes started to evolve 30 sec before the error. In particular, a coincident decrease of deactivation in default mode regions of the brain, together with a decline of activation in regions associated with maintaining task effort, raised the probability of future errors. Our findings provide insights into the brain network dynamics preceding human performance errors and suggest that monitoring of the identified precursor states may help in avoiding human errors in critical real-world situations.
Concurrent event-related EEG-fMRI recordings pick up volume-conducted and hemodynamically convolu... more Concurrent event-related EEG-fMRI recordings pick up volume-conducted and hemodynamically convoluted signals from latent neural sources that are spatially and temporally mixed across the brain, i.e. the observed data in both modalities represent multiple, simultaneously active, regionally overlapping neuronal mass responses. This mixing process decreases the sensitivity of voxel-by-voxel prediction of hemodynamic activation by the EEG when multiple sources contribute to either the predictor and/or the response variables. In order to address this problem, we used independent component analysis (ICA) to recover maps from the fMRI and timecourses from the EEG, and matched these components across the modalities by correlating their trial-to-trial modulation. The analysis was implemented as a group-level ICA that extracts a single set of components from the data and directly allows for population inferences about consistently expressed function-relevant spatiotemporal responses. We illustrate the utility of this method by extracting a previously undetected but relevant EEG-fMRI component from a concurrent auditory target detection experiment.
Alzheimer's disease (AD) is a neurodegenerative disorder that prominently affects cerebral connec... more Alzheimer's disease (AD) is a neurodegenerative disorder that prominently affects cerebral connectivity. Assessing the functional connectivity at rest, recent functional MRI (fMRI) studies reported on the existence of resting-state networks (RSNs). RSNs are characterized by spatially coherent, spontaneous fluctuations in the blood oxygen level-dependent signal and are made up of regional patterns commonly involved in functions such as sensory, attention, or default mode processing. In AD, the default mode network (DMN) is affected by reduced functional connectivity and atrophy. In this work, we analyzed functional and structural MRI data from healthy elderly (n = 16) and patients with amnestic mild cognitive impairment (aMCI) (n = 24), a syndrome of high risk for developing AD. Two questions were addressed: (i) Are any RSNs altered in aMCI? (ii) Do changes in functional connectivity relate to possible structural changes? Independent component analysis of resting-state fMRI data identified eight spatially consistent RSNs. Only selected areas of the DMN and the executive attention network demonstrated reduced network-related activity in the patient group. Voxel-based morphometry revealed atrophy in both medial temporal lobes (MTL) of the patients. The functional connectivity between both hippocampi in the MTLs and the posterior cingulate of the DMN was present in healthy controls but absent in patients. We conclude that in individuals at risk for AD, a specific subset of RSNs is altered, likely representing effects of ongoing early neurodegeneration. We interpret our finding as a proof of principle, demonstrating that functional brain disorders can be characterized by functional-disconnectivity profiles of RSNs.
OBJECTIVE: The main aim was to track the dynamics of pattern-learning using single-trial event-re... more OBJECTIVE: The main aim was to track the dynamics of pattern-learning using single-trial event-related potentials (ERPs). A new 'learning-oddball' paradigm was employed presenting eight random targets (the 'no-pattern') followed by eight regular targets (the 'pattern'). In total, six repetitions of the 'no-pattern' followed by the 'pattern' were presented. METHODS: We traced the dynamics of learning by measuring responses to 16 (eight random-eight regular) targets. Since this alternation of the 'no-pattern' followed by the 'pattern' was repeated six times, we extracted single-trial responses to all 96 targets to determine if learning occurred more rapidly with each repetition of the 'pattern.' RESULTS: Following random targets, ERPs contained a marked P3-N2 component that decreased to regular targets, whereas a contingent negative variation (CNV) appeared. ERP changes could be best described by sigmoid 'learning' curves. Single-trial analyses showed that learning occurred more rapidly over repetitions and suggested that the CNV developed prior to the decay of the N2-P3 component. CONCLUSIONS: We show a new paradigm-analysis methodology to track learning processes directly from brain signals. SIGNIFICANCE: Single-trial ERPs analyses open a wide range of applications. Tracking the dynamic structure of cognitive functions may prove crucial in the understanding of learning and in the study of different pathologies.
The brain acts as an integrated information processing system, which methods in cognitive neurosc... more The brain acts as an integrated information processing system, which methods in cognitive neuroscience have so far depicted in a fragmented fashion. Here, we propose a simple and robust way to integrate functional MRI (fMRI) with single trial event-related potentials (ERP) to provide a more complete spatiotemporal characterization of evoked responses in the human brain. The idea behind the approach is to find brain regions whose fMRI responses can be predicted by paradigm-induced amplitude modulations of simultaneously acquired single trial ERPs. The method was used to study a variant of a two-stimulus auditory target detection (odd-ball) paradigm that manipulated predictability through alternations of stimulus sequences with random or regular target-to-target intervals. In addition to electrophysiologic and hemodynamic evoked responses to auditory targets per se, single-trial modulations were expressed during the latencies of the P2 (170-ms), N2 (200-ms), and P3 (320-ms) components and predicted spatially separated fMRI activation patterns. These spatiotemporal matches, i.e., the prediction of hemodynamic activation by time-variant information from single trial ERPs, permit inferences about regional responses using fMRI with the temporal resolution provided by electrophysiology
In order to examine auditory lateralization of prelexical speech processing, a dichotic listening... more In order to examine auditory lateralization of prelexical speech processing, a dichotic listening task was performed with concurrent EEG measurement. Subjects were tested with dichotic pairs of six consonant-vowel (CV) syllables that initially started with a voiced (/ba/, /da/, /ga/) or a voiceless stop consonant (/pa/, /ta/, /ka/). Electrophysiological correlates were analyzed by a low resolution electromagnetic tomography (LORETA) approach to estimate the sources of N1 event-related potentials (ERP) in the 3D brain. Behavioral and electrophysiological measures revealed different ear advantages and ERP amplitude measures for voiced and voiceless syllables. Fronto-central N1 amplitudes were larger for syllables with voiced than voiceless initial consonants. LORETA source estimates revealed a lateralization effect, with stronger leftward lateralization for voiced than voiceless CV syllables. The present study demonstrates that auditory lateralization is affected by temporal cues in CV syllables. The lateralization effect suggests that functional hemispheric differences exist at an early prelexical level of speech processing.
2.3 Tom Eichele, Matthias Moosmann, Lei Wu, Ingmar Gutberlet, and Stefan Debener Removal of MRI A... more 2.3 Tom Eichele, Matthias Moosmann, Lei Wu, Ingmar Gutberlet, and Stefan Debener Removal of MRI Artifacts from EEG Recordings Introduction The simultaneous recording of electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) provides several advantages ...
Imaging research into age-related changes in episodic memory has mainly focused on changes in cor... more Imaging research into age-related changes in episodic memory has mainly focused on changes in cortical areas in the medial temporal lobe and the hippocampus. However, several lines of evidence indicate that subcortical structures such as the basal ganglia and the thalamus are also involved in episodic memory function. Recent studies have revealed age-related changes in functional connectivity between different brain areas, as measured by resting state fMRI. It remains to be shown whether functional connectivity measures in the basal ganglia and the thalamus can be associated with age-related changes in memory function. Here, we investigate this question by applying high model order spatial independent component analysis to resting state fMRI data in a cohort of 100 healthy elderly and relate connectivity features to verbal episodic memory function as assessed by the California Verbal Learning Test (CVLT). We identified five components that were located within different parts of the thalamus and the basal ganglia. Two of these components demonstrated negative correlations between their functional connectivity level and CVLT performance. We also found negative correlations between connectional strength within subcortical structures and CVLT performance. These results indicate a previously undocumented role for the putamen and the thalamus in verbal episodic memory function in aging.
Music perception with a cochlear implant (CI) can be unsatisfactory because current-day implants ... more Music perception with a cochlear implant (CI) can be unsatisfactory because current-day implants are primarily designed to enable speech discrimination. The present study aimed at evaluating electrophysiological correlates of musical sound perception in CI users to help achieve the long-term goal of improved restoration of hearing in those individuals. Auditory discrimination accuracy in adult CI users (n=12) and matched normal-hearing controls (n=12) was measured by behavioral discrimination tasks and mismatch negativity (MMN) recordings. Discrimination profiles were obtained by using a set of clarinet sounds (original/vocoded) varying along different acoustic dimensions (frequency/intensity/duration) and deviation magnitudes (four levels). Behavioral results and MMN recordings revealed reduced auditory discrimination accuracy in CI users. An inverse relationship was found between MMN amplitudes and duration of profound deafness. CI users have difficulties in discriminating small changes in the acoustic properties of musical sounds. The recently developed multi-feature MMN paradigm (Pakarinen et al., 2007) can be used to objectively evaluate discrimination abilities of CI users for musical sounds. Measuring auditory discrimination functions by means of a multi-feature MMN paradigm could be of substantial clinical value by providing a comprehensive profile of the extent of restored hearing in CI users.
… Eeg and Fmri: Recording, Analysis, and …, Jan 1, 2010
3.4 Vince D. Calhoun and Tom Eichele Fusion of EEG and fMRI by Parallel Group ICA Introduction an... more 3.4 Vince D. Calhoun and Tom Eichele Fusion of EEG and fMRI by Parallel Group ICA Introduction and Background Independent component analysis (ICA) is increasingly uti-lized as a tool for evaluating the hidden spatiotemporal structure contained within brain imaging data. In ...
Glutamate is critically involved in the regulation of cognitive functions in humans. There is, ho... more Glutamate is critically involved in the regulation of cognitive functions in humans. There is, however, sparse evidence regarding how blocking glutamate action at the receptor site during a cognitive task affects brain activation. In the current study, the effects of the glutamate antagonist memantine were examined with functional magnetic resonance imaging (fMRI). Thirty-one healthy adults were scanned twice in a counter-balanced design, either in a no-drug session or after administration of memantine for 21 days. The subjects performed a simple auditory perception task with consonant-vowel stimuli. Group-level spatial independent component analysis (ICA) was used to decompose the data and to extract task-related activations. The focus was on four task-related ICA components with frontotemporal localization. The results showed that glutamate-blockage resulted in a significant enhancement in one component, with no significant effect in the other three components. The enhanced effect of memantine was in the middle temporal gyrus, superior frontal gyrus, and middle frontal gyrus. It is suggested that the results reflect effects of glutamatergic processes primarily through non-N-methyl-D-aspartate (NMDA) receptor pathways. Moreover, the results demonstrate that memantine can be used as a probe which allows for studying the effect of excitatory neurotransmission on neuronal activation.
Humans engaged in monotonous tasks are susceptible to occasional errors that may lead to serious ... more Humans engaged in monotonous tasks are susceptible to occasional errors that may lead to serious consequences, but little is known about brain activity patterns preceding errors. Using functional MRI and applying independent component analysis followed by deconvolution of hemodynamic responses, we studied error preceding brain activity on a trial-by-trial basis. We found a set of brain regions in which the temporal evolution of activation predicted performance errors. These maladaptive brain activity changes started to evolve 30 sec before the error. In particular, a coincident decrease of deactivation in default mode regions of the brain, together with a decline of activation in regions associated with maintaining task effort, raised the probability of future errors. Our findings provide insights into the brain network dynamics preceding human performance errors and suggest that monitoring of the identified precursor states may help in avoiding human errors in critical real-world situations.
Concurrent event-related EEG-fMRI recordings pick up volume-conducted and hemodynamically convolu... more Concurrent event-related EEG-fMRI recordings pick up volume-conducted and hemodynamically convoluted signals from latent neural sources that are spatially and temporally mixed across the brain, i.e. the observed data in both modalities represent multiple, simultaneously active, regionally overlapping neuronal mass responses. This mixing process decreases the sensitivity of voxel-by-voxel prediction of hemodynamic activation by the EEG when multiple sources contribute to either the predictor and/or the response variables. In order to address this problem, we used independent component analysis (ICA) to recover maps from the fMRI and timecourses from the EEG, and matched these components across the modalities by correlating their trial-to-trial modulation. The analysis was implemented as a group-level ICA that extracts a single set of components from the data and directly allows for population inferences about consistently expressed function-relevant spatiotemporal responses. We illustrate the utility of this method by extracting a previously undetected but relevant EEG-fMRI component from a concurrent auditory target detection experiment.
Alzheimer's disease (AD) is a neurodegenerative disorder that prominently affects cerebral connec... more Alzheimer's disease (AD) is a neurodegenerative disorder that prominently affects cerebral connectivity. Assessing the functional connectivity at rest, recent functional MRI (fMRI) studies reported on the existence of resting-state networks (RSNs). RSNs are characterized by spatially coherent, spontaneous fluctuations in the blood oxygen level-dependent signal and are made up of regional patterns commonly involved in functions such as sensory, attention, or default mode processing. In AD, the default mode network (DMN) is affected by reduced functional connectivity and atrophy. In this work, we analyzed functional and structural MRI data from healthy elderly (n = 16) and patients with amnestic mild cognitive impairment (aMCI) (n = 24), a syndrome of high risk for developing AD. Two questions were addressed: (i) Are any RSNs altered in aMCI? (ii) Do changes in functional connectivity relate to possible structural changes? Independent component analysis of resting-state fMRI data identified eight spatially consistent RSNs. Only selected areas of the DMN and the executive attention network demonstrated reduced network-related activity in the patient group. Voxel-based morphometry revealed atrophy in both medial temporal lobes (MTL) of the patients. The functional connectivity between both hippocampi in the MTLs and the posterior cingulate of the DMN was present in healthy controls but absent in patients. We conclude that in individuals at risk for AD, a specific subset of RSNs is altered, likely representing effects of ongoing early neurodegeneration. We interpret our finding as a proof of principle, demonstrating that functional brain disorders can be characterized by functional-disconnectivity profiles of RSNs.
OBJECTIVE: The main aim was to track the dynamics of pattern-learning using single-trial event-re... more OBJECTIVE: The main aim was to track the dynamics of pattern-learning using single-trial event-related potentials (ERPs). A new 'learning-oddball' paradigm was employed presenting eight random targets (the 'no-pattern') followed by eight regular targets (the 'pattern'). In total, six repetitions of the 'no-pattern' followed by the 'pattern' were presented. METHODS: We traced the dynamics of learning by measuring responses to 16 (eight random-eight regular) targets. Since this alternation of the 'no-pattern' followed by the 'pattern' was repeated six times, we extracted single-trial responses to all 96 targets to determine if learning occurred more rapidly with each repetition of the 'pattern.' RESULTS: Following random targets, ERPs contained a marked P3-N2 component that decreased to regular targets, whereas a contingent negative variation (CNV) appeared. ERP changes could be best described by sigmoid 'learning' curves. Single-trial analyses showed that learning occurred more rapidly over repetitions and suggested that the CNV developed prior to the decay of the N2-P3 component. CONCLUSIONS: We show a new paradigm-analysis methodology to track learning processes directly from brain signals. SIGNIFICANCE: Single-trial ERPs analyses open a wide range of applications. Tracking the dynamic structure of cognitive functions may prove crucial in the understanding of learning and in the study of different pathologies.
The brain acts as an integrated information processing system, which methods in cognitive neurosc... more The brain acts as an integrated information processing system, which methods in cognitive neuroscience have so far depicted in a fragmented fashion. Here, we propose a simple and robust way to integrate functional MRI (fMRI) with single trial event-related potentials (ERP) to provide a more complete spatiotemporal characterization of evoked responses in the human brain. The idea behind the approach is to find brain regions whose fMRI responses can be predicted by paradigm-induced amplitude modulations of simultaneously acquired single trial ERPs. The method was used to study a variant of a two-stimulus auditory target detection (odd-ball) paradigm that manipulated predictability through alternations of stimulus sequences with random or regular target-to-target intervals. In addition to electrophysiologic and hemodynamic evoked responses to auditory targets per se, single-trial modulations were expressed during the latencies of the P2 (170-ms), N2 (200-ms), and P3 (320-ms) components and predicted spatially separated fMRI activation patterns. These spatiotemporal matches, i.e., the prediction of hemodynamic activation by time-variant information from single trial ERPs, permit inferences about regional responses using fMRI with the temporal resolution provided by electrophysiology
In order to examine auditory lateralization of prelexical speech processing, a dichotic listening... more In order to examine auditory lateralization of prelexical speech processing, a dichotic listening task was performed with concurrent EEG measurement. Subjects were tested with dichotic pairs of six consonant-vowel (CV) syllables that initially started with a voiced (/ba/, /da/, /ga/) or a voiceless stop consonant (/pa/, /ta/, /ka/). Electrophysiological correlates were analyzed by a low resolution electromagnetic tomography (LORETA) approach to estimate the sources of N1 event-related potentials (ERP) in the 3D brain. Behavioral and electrophysiological measures revealed different ear advantages and ERP amplitude measures for voiced and voiceless syllables. Fronto-central N1 amplitudes were larger for syllables with voiced than voiceless initial consonants. LORETA source estimates revealed a lateralization effect, with stronger leftward lateralization for voiced than voiceless CV syllables. The present study demonstrates that auditory lateralization is affected by temporal cues in CV syllables. The lateralization effect suggests that functional hemispheric differences exist at an early prelexical level of speech processing.
2.3 Tom Eichele, Matthias Moosmann, Lei Wu, Ingmar Gutberlet, and Stefan Debener Removal of MRI A... more 2.3 Tom Eichele, Matthias Moosmann, Lei Wu, Ingmar Gutberlet, and Stefan Debener Removal of MRI Artifacts from EEG Recordings Introduction The simultaneous recording of electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) provides several advantages ...
Imaging research into age-related changes in episodic memory has mainly focused on changes in cor... more Imaging research into age-related changes in episodic memory has mainly focused on changes in cortical areas in the medial temporal lobe and the hippocampus. However, several lines of evidence indicate that subcortical structures such as the basal ganglia and the thalamus are also involved in episodic memory function. Recent studies have revealed age-related changes in functional connectivity between different brain areas, as measured by resting state fMRI. It remains to be shown whether functional connectivity measures in the basal ganglia and the thalamus can be associated with age-related changes in memory function. Here, we investigate this question by applying high model order spatial independent component analysis to resting state fMRI data in a cohort of 100 healthy elderly and relate connectivity features to verbal episodic memory function as assessed by the California Verbal Learning Test (CVLT). We identified five components that were located within different parts of the thalamus and the basal ganglia. Two of these components demonstrated negative correlations between their functional connectivity level and CVLT performance. We also found negative correlations between connectional strength within subcortical structures and CVLT performance. These results indicate a previously undocumented role for the putamen and the thalamus in verbal episodic memory function in aging.
Music perception with a cochlear implant (CI) can be unsatisfactory because current-day implants ... more Music perception with a cochlear implant (CI) can be unsatisfactory because current-day implants are primarily designed to enable speech discrimination. The present study aimed at evaluating electrophysiological correlates of musical sound perception in CI users to help achieve the long-term goal of improved restoration of hearing in those individuals. Auditory discrimination accuracy in adult CI users (n=12) and matched normal-hearing controls (n=12) was measured by behavioral discrimination tasks and mismatch negativity (MMN) recordings. Discrimination profiles were obtained by using a set of clarinet sounds (original/vocoded) varying along different acoustic dimensions (frequency/intensity/duration) and deviation magnitudes (four levels). Behavioral results and MMN recordings revealed reduced auditory discrimination accuracy in CI users. An inverse relationship was found between MMN amplitudes and duration of profound deafness. CI users have difficulties in discriminating small changes in the acoustic properties of musical sounds. The recently developed multi-feature MMN paradigm (Pakarinen et al., 2007) can be used to objectively evaluate discrimination abilities of CI users for musical sounds. Measuring auditory discrimination functions by means of a multi-feature MMN paradigm could be of substantial clinical value by providing a comprehensive profile of the extent of restored hearing in CI users.
… Eeg and Fmri: Recording, Analysis, and …, Jan 1, 2010
3.4 Vince D. Calhoun and Tom Eichele Fusion of EEG and fMRI by Parallel Group ICA Introduction an... more 3.4 Vince D. Calhoun and Tom Eichele Fusion of EEG and fMRI by Parallel Group ICA Introduction and Background Independent component analysis (ICA) is increasingly uti-lized as a tool for evaluating the hidden spatiotemporal structure contained within brain imaging data. In ...
Glutamate is critically involved in the regulation of cognitive functions in humans. There is, ho... more Glutamate is critically involved in the regulation of cognitive functions in humans. There is, however, sparse evidence regarding how blocking glutamate action at the receptor site during a cognitive task affects brain activation. In the current study, the effects of the glutamate antagonist memantine were examined with functional magnetic resonance imaging (fMRI). Thirty-one healthy adults were scanned twice in a counter-balanced design, either in a no-drug session or after administration of memantine for 21 days. The subjects performed a simple auditory perception task with consonant-vowel stimuli. Group-level spatial independent component analysis (ICA) was used to decompose the data and to extract task-related activations. The focus was on four task-related ICA components with frontotemporal localization. The results showed that glutamate-blockage resulted in a significant enhancement in one component, with no significant effect in the other three components. The enhanced effect of memantine was in the middle temporal gyrus, superior frontal gyrus, and middle frontal gyrus. It is suggested that the results reflect effects of glutamatergic processes primarily through non-N-methyl-D-aspartate (NMDA) receptor pathways. Moreover, the results demonstrate that memantine can be used as a probe which allows for studying the effect of excitatory neurotransmission on neuronal activation.
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RESULTS: Following random targets, ERPs contained a marked P3-N2 component that decreased to regular targets, whereas a contingent negative variation (CNV) appeared. ERP changes could be best described by sigmoid 'learning' curves. Single-trial analyses showed that learning occurred more rapidly over repetitions and suggested that the CNV developed prior to the decay of the N2-P3 component.
CONCLUSIONS: We show a new paradigm-analysis methodology to track learning processes directly from brain signals. SIGNIFICANCE: Single-trial ERPs analyses open a wide range of applications. Tracking the dynamic structure of cognitive functions may prove crucial in the understanding of learning and in the study of different pathologies.
RESULTS: Following random targets, ERPs contained a marked P3-N2 component that decreased to regular targets, whereas a contingent negative variation (CNV) appeared. ERP changes could be best described by sigmoid 'learning' curves. Single-trial analyses showed that learning occurred more rapidly over repetitions and suggested that the CNV developed prior to the decay of the N2-P3 component.
CONCLUSIONS: We show a new paradigm-analysis methodology to track learning processes directly from brain signals. SIGNIFICANCE: Single-trial ERPs analyses open a wide range of applications. Tracking the dynamic structure of cognitive functions may prove crucial in the understanding of learning and in the study of different pathologies.