Papers by Mircea Ariel Schoenfeld
Brain, 2003
Brain atrophy as determined by quantitative MRI can be used to characterize disease progression i... more Brain atrophy as determined by quantitative MRI can be used to characterize disease progression in multiple sclerosis. Many studies have addressed white matter (WM) alterations leading to atrophy, while changes of the cerebral cortex have been studied to a lesser extent. In vivo, the cerebral cortex has been difficult to study due to its complex structure and regional variability. Measurement of cerebral cortex thickness at different disease stages may provide new insights into grey matter (GM) pathology. In the present investigation, we evaluated in vivo cortical thickness and its relationship to disability, disease duration, WM T2 hyper-intense and T1 hypo-intense lesion volumes. High-resolution MRI brain scans were obtained in 20 patients with clinically definite multiple sclerosis and 15 age-matched normal subjects. A novel method of automated surface reconstruction yielded measurements of the cortical thickness for each subject's entire brain and computed cross-subject statistics based on the cortical anatomy. Statistical thickness difference maps were generated by performing t-tests between patient and control groups and individual thickness measures were submitted to analyses of variance to investigate the relationship between cortical thickness and clinical variables. The mean overall thickness of the cortical ribbon was reduced in multiple sclerosis patients compared with controls [2.30 mm (SD 0.14) versus 2.48 mm (SD 0.11)], showing a significant main effect of group (controls versus patients). In patients, we found significant main effects for disability, disease duration, T2 and T1 lesion volumes. The visualization of statistical difference maps of the cortical GM thickness on inflated brains across the cortical surface revealed a distinct distribution of significant focal thinning of the cerebral cortex in addition to the diffuse cortical atrophy. Focal cortical thinning in frontal [2.37 mm (SD 0.17) versus 2.73 mm (SD 0.25)] and in temporal [2.65 mm (SD 0.15) versus 2.95 mm (SD 0.11)] brain regions was observed, even early in the course of the disease or in patients with mild disability. Patients with longstanding disease or severe disability, however, presented additionally with focal thinning of the motor cortex area [2.35 mm (SD 0.19) versus 2.74 mm (SD 0.15)]. We conclude that in vivo measurement of cortical thickness is feasible in patients suffering from multiple sclerosis. The data provide new insight into the cortical pathology in multiple sclerosis patients, revealing focal cortical thinning beside an overall reduction of the cortical thickness with disease progression.
The modulatory impact of reward and attention on global feature selection in human visual cortex
Visual Cognition, 2014
ABSTRACT Reward powerfully influences human behaviour and perception, with reward effects being o... more ABSTRACT Reward powerfully influences human behaviour and perception, with reward effects being observed already on the level of basic sensory processing. Although reward-related modulations generally resemble those related to attentional selection, it is debated whether these effects indeed reflect the same selection operations. Here we focus on neuromagnetic indices of global colour-based attention in visual cortex, and ask whether reward elicits the same or separable underlying modulation effects. Observers performed a colour/orientation selection task where colour served to define the target as well as reward prospect. On each trial a target containing the target colour and one other colour was presented in the left visual field (VF) together with a bicoloured distractor in the right VF. Reward was delivered on correctly performed trials when the reward colour appeared in the target but not when it appeared in the distractor. The effect of global colour selection was assessed by comparing the brain response to the distractor depending on whether it contained the target colour, the reward colour, both, or neither. We observed that both the reward and target colour led to similar increases of the neuromagnetic response between ~200-260 ms originating from the same ventral extrastriate visual cortex areas, albeit slightly temporally lagged. Importantly, the response to the target and reward colour alone always added up to match the response size of their combined presentation. These results suggest that while reward and attention recruit the same global feature selection effects in extrastriate visual cortex, they are likely controlled by independent top-down influences.
Journal fur Neurologie, Neurochirurgie und Psychiatrie
Medica/Elsevier BIOBASE P . b . b . 0 2 Z 0 3 1 1 1 7 M , V e r l a g s p o s t a m t : 3 0 0 2 P... more Medica/Elsevier BIOBASE P . b . b . 0 2 Z 0 3 1 1 1 7 M , V e r l a g s p o s t a m t : 3 0 0 2 P u r k e r s d o r f , E r s c h e i n u n g s o r t : 3 0 0 3 G a b l i t z ; P r e i s : E U R 1 0 , -Krause & Pachernegg GmbH . VERLAG für MEDIZIN und WIRTSCHAFT . A-3003 Gablitz
Basal ganglia pathology in ALS is associated with neuropsychological deficits
Neurology, Jan 18, 2015
To evaluate basal ganglia changes along the amyotrophic lateral sclerosis (ALS)-ALS-frontotempora... more To evaluate basal ganglia changes along the amyotrophic lateral sclerosis (ALS)-ALS-frontotemporal dementia (FTD) continuum using multiple, complementary imaging techniques. Sixty-seven C9orf72-negative patients with ALS and 39 healthy controls were included in a cross-sectional quantitative MRI study. Seven patients with ALS met criteria for comorbid behavioral variant FTD (ALS-FTD), 18 patients met the Strong criteria for cognitive and/or behavioral impairment (ALS-Plus), and 42 patients had no cognitive impairment (ALS-Nci). Volumetric, shape, and density analyses were performed for the thalamus, amygdala, nucleus accumbens, hippocampus, caudate nucleus, pallidum, and putamen. Significant basal ganglia volume differences were identified between the study groups. Shape analysis revealed distinct atrophy patterns in the amygdala in patients with ALS-Nci and in the hippocampus in patients with ALS-Plus in comparison with controls. Patients with ALS-FTD exhibited pathologic changes i...
Journal of Neurology, 2015
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive l... more Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive limb and/or bulbar muscular weakness and atrophy. Although ALS-related alterations of motor and extra-motor neuronal networks have repeatedly been reported, their temporal dynamics during disease progression are not well understood. Recently, we reported a decline of motor system activity and a concurrent increase of hippocampal noveltyevoked modulations across 3 months of ALS progression. To address whether these functional changes are associated with structural ones, the current study employed probabilistic fiber tractography on diffusion tensor imaging (DTI) data using a longitudinal design. Therein, motor network integrity was assessed by DTI-based tracking of the intracranial corticospinal tract, while connectivity estimates of occipito-temporal tracts (between visual and entorhinal, perirhinal or parahippocampal cortices) served to assess structural changes that could be related to the increased novelty-evoked hippocampal activity across time described previously. Complementing these previous functional observations, the current data revealed an ALSrelated decrease in corticospinal tract structural connectivity compared to controls, while in contrast, visuoperirhinal connectivity was relatively increased in the patient group. Importantly, beyond these between-group differences, a rise in the patients' occipito-temporal tract strengths occurred across a 3-month interval, while at the same time no changes in corticospinal tract connectivity were observed. In line with previously identified functional alterations, the dynamics of these structural changes suggest that the affection of motor-and memory-related networks in ALS emerges at distinct disease stages: while motor network degeneration starts primarily during early (supposedly pre-symptomatic) phases, the hippocampal/medial temporal lobe dysfunctions arise at later stages of the disease.
Neural correlates of multiple object tracking strategies
NeuroImage, Jan 6, 2015
Amazingly, human observers can track four independently moving targets. The present study investi... more Amazingly, human observers can track four independently moving targets. The present study investigated the neural correlates of multiple-object tracking (MOT). Based on previous work we used a modified MOT-task to which subjects exhibited different behaviors. One half of the subjects showed slower RTs and higher error rates with increasing correspondence between tracked items and a probe consisting of 4 highlighted items presented after the tracking. The other half of the subjects had better performance when the probe fully matched the tracked items. Here we sought to investigate the neural representation of the two divergent behavior types. Using multivariate pattern analysis we observed two partly overlapping functional networks associated with the different behaviors. Subjects that responded fast and accurate to full-congruity trials predominantly showed a functional pattern for the full-congruity condition that was very different from patterns associated with any of the partly c...
TheNeuralSiteofAttentionMatchestheSpatialScaleof Perception
Impact of left versus right hemisphere subcortical stroke on the neural processing of action observation and imagery
Restorative neurology and neuroscience, Jan 2, 2015
Mental training appears to be an attractive tool in stroke rehabilitation. The objective of this ... more Mental training appears to be an attractive tool in stroke rehabilitation. The objective of this study was to investigate whether any differences in the processing of action observation and imagery might exist between patients with left and right hemisphere subcortical strokes. Eighteen patients with strictly subcortical stroke (nine right-hemispheric) underwent a functional magnetic resonance imaging (fMRI) study with an experimental paradigm in which motor acts had to be observed and/or imagined from a first person perspective. Changes in hemodynamic activity were measured using fMRI. The activity level was found to be higher in the non-lesioned compared to the lesioned hemisphere. Patients with lesions in the left hemisphere had a higher activation level in visual (fusiform and lingual gyri), superior temporal areas and dorsal premotor regions across all performed comparisons than those with right hemisphere lesions. Furthermore they had more vivid imagery experiences and lower s...
Frontiers in Human Neuroscience, 2009
The time course of local fi eld potentials (LFPs) displaying typical discharge frequencies in the... more The time course of local fi eld potentials (LFPs) displaying typical discharge frequencies in the gamma frequency range highly correlates with the blood oxygen level dependent (BOLD) signal in response to rotating checkerboard stimuli in animals. In humans, oscillatory gammaband responses (GBRs) show strong inter-individual variations in frequency and amplitude but considerable intra-individual reliability indicating that individual gamma activity refl ects a personal trait. While the functional role of these GBRs is still debated, investigations combining electroencephalography-functional magnetic resonance imaging (EEG-fMRI) measurements provide a tool to obtain further insights into the underlying functional architecture of the human brain and will shed light onto the understanding of the dynamic relation between the BOLD signal and the properties of the electrical activity recorded on the scalp. We investigated the relation between the hemodynamic response and evoked gamma-band response (eGBR) to visual stimulation. We tested the hypothesis that the amplitude of human eGBRs and BOLD responses covary intra-individually as a function of stimulation as well as inter-individually as a function of gamma-trait. Seventeen participants performed visual discrimination tasks during separate EEG and fMRI recordings. Results revealed that visual stimuli that evoked high GBRs also elicited strong BOLD responses in the human V1/V2 complex. Furthermore, inter-individual variations of BOLD responses to visual stimuli in the bilateral primary (Area 17) and secondary (Area V5/MT) visual cortex and the right hippocampal formation were correlated with the individual gamma-trait of the subjects. The present study further supports the notion that neural oscillations in the gamma frequency range are involved in the cascade of neural processes that underlie the hemodynamic responses measured with fMRI.
Action observation and imagery conducted with stroke patients stimulate both hemispheres: the affected and non-affected
ABSTRACT Objectives: The application of the mirror neuron system (MNS) has extended into the fiel... more ABSTRACT Objectives: The application of the mirror neuron system (MNS) has extended into the field of stroke rehabilitation through mirror- or video therapy. Current literature has demonstrated that action observation exclusively or predominantly stimulates the non-affected hemisphere [1, 2]. The aim of this study was to use the fMRI (functional magnetic imaging) to investigate whether the affected and non-affected hemispheres are stimulated to the same extent during action observation and imagery conducted in stroke patients. Methods: fMRI in block design applying action observation or action imagery with open eyes. Stimuli consisted of object-related, simple hand actions. Eight right hemispheric and eight left hemispheric stroke patients with incomplete hand pareses participated in the study. Results: Action observation as well as simultaneous action observation and imagery induced activation in a well known network of occipital, superior and inferior parietal and dorsolateral and ventrolateral premotor cortical areas. Cortical activation encompassed a symmetrical bilateral pattern: the affected hemispheres were stimulated to the same degree as the non-affected hemisphere. Conclusion: This study confirms that action observation has facilitatory effects in the affected and non-affected hemispheres, respectively. Data support applicability of video-therapy in stroke patients. 1. Kimberley TJ et al (2006) Neurorehabilitation and Neural Repair 20:268277 2. Stinear CM et al (2007) Clin Neurophysiol 118:17941801
The time course of local fi eld potentials (LFPs) displaying typical discharge frequencies in the... more The time course of local fi eld potentials (LFPs) displaying typical discharge frequencies in the gamma frequency range highly correlates with the blood oxygen level dependent (BOLD) signal in response to rotating checkerboard stimuli in animals. In humans, oscillatory gammaband responses (GBRs) show strong inter-individual variations in frequency and amplitude but considerable intra-individual reliability indicating that individual gamma activity refl ects a personal trait. While the functional role of these GBRs is still debated, investigations combining electroencephalography-functional magnetic resonance imaging (EEG-fMRI) measurements provide a tool to obtain further insights into the underlying functional architecture of the human brain and will shed light onto the understanding of the dynamic relation between the BOLD signal and the properties of the electrical activity recorded on the scalp. We investigated the relation between the hemodynamic response and evoked gamma-band response (eGBR) to visual stimulation. We tested the hypothesis that the amplitude of human eGBRs and BOLD responses covary intra-individually as a function of stimulation as well as inter-individually as a function of gamma-trait. Seventeen participants performed visual discrimination tasks during separate EEG and fMRI recordings. Results revealed that visual stimuli that evoked high GBRs also elicited strong BOLD responses in the human V1/V2 complex. Furthermore, inter-individual variations of BOLD responses to visual stimuli in the bilateral primary (Area 17) and secondary (Area V5/MT) visual cortex and the right hippocampal formation were correlated with the individual gamma-trait of the subjects. The present study further supports the notion that neural oscillations in the gamma frequency range are involved in the cascade of neural processes that underlie the hemodynamic responses measured with fMRI.
Modulation of otolith MEG responses by change of gravitational force vector
Klinische Neurophysiologie, 2010
Neurophysiological correlates of preserved vision after a lesion of the primary visual cortex | Neurophysiologische korrelate von restwahrnehmung nach läsion des primär visuellen kortex
Klinische Neurophysiologie, 2004
... MA Schoenfeld 1 , D. Poggel 2 , T. Noesselt 1 , C. Tempelmann 1 , DB Sellner 1 , A. Szentkuti... more ... MA Schoenfeld 1 , D. Poggel 2 , T. Noesselt 1 , C. Tempelmann 1 , DB Sellner 1 , A. Szentkuti 1 , SA Hillyard 3 , H.-J ... Dieses Syndrom wurde nach dem Erstentdecker James Riddoch benannt [2]. Mehrere Studien wurden durchgeführt, um die neuralen Korrelate der ... Dr. med. ...
Restorative Neurology and Neuroscience, 2010
Purpose: Recent studies have found age-related BOLD signal changes in several areas of the human ... more Purpose: Recent studies have found age-related BOLD signal changes in several areas of the human brain. We investigated whether such changes also occur in brain areas involved in the processing of motor action observation and imagery. Methods: Functional magnetic resonance imaging with an experimental paradigm in which motor acts had to be observed and/or imagined from a first person perspective was performed in twenty-six subjects. Results: In line with previous work action observation and imagery induced BOLD signal increases in similar areas, predominantly in the premotor and parietal cortex. In contrast to young subjects the elderly displayed a stronger activity in most activated brain areas indicative of compensatory activity for the age-related decline of neural structures. Importantly, activity in the ventrolateral premotor cortex and inferior parietal cortex, seminal areas of the mirror neuron system, did not exhibit activity changes as a function of age. Conclusion: These findings suggest that activity within the mirror neuron system is not age dependent and provide a neural basis for therapeutical interventions and novel rehabilitation treatments such as video therapy.
Frontiers in Human Neuroscience, 2010
Being able to effectively explore our visual world is of fundamental importance, and it has been ... more Being able to effectively explore our visual world is of fundamental importance, and it has been suggested that the straight-ahead gaze (primary position) might play a special role in this context. We employed fMRI in humans to investigate how neural activity might be modulated for saccades relative to this putative default position. Using an endogenous cueing paradigm, saccade direction and orbital starting position were systematically manipulated, resulting in saccades toward primary position (centripetal) and away from primary position (centrifugal) that were matched in amplitude, directional predictability, as well as orbital starting position. In accord with earlier research, we found that fMRI activity in the superior colliculus (SC), as well as in the frontal eye fields and the intraparietal sulcus, was enhanced contralateral to saccade direction across all saccade conditions. Furthermore, the SC exhibited a relative activity decrease during re-centering relative to centrifugal saccades, a pattern that was paralleled by faster saccadic reaction times. In contrast, activity within the cortical eye fields was not significantly modulated during re-centering saccades as compared to other saccade types, suggesting that the re-centering bias is predominantly implemented at a subcortical rather than cortical processing stage. Such a modulation might reflect a special coding bias facilitating the return of gaze to a default position in the gaze space in which retinotopic and egocentric reference frames are aligned and from which the visual world can be effectively explored.
Journal of Neurologic Physical Therapy, 2012
Background and Purpose: Both action observation (AO) and action imagery have been proposed as the... more Background and Purpose: Both action observation (AO) and action imagery have been proposed as therapeutic options for stroke rehabilitation. Currently, it is not clear to what extent their underlying neuronal mechanisms differ from each other and whether one of these therapeutic options might be preferable for this purpose. Methods: Twenty-six healthy subjects were investigated using functional magnetic resonance imaging during AO alone and AO with ad-
Magneto- and electroencephalographic manifestations of reward anticipation and delivery
NeuroImage, 2012
The monetary incentive delay task was used to characterize reward anticipation and delivery with ... more The monetary incentive delay task was used to characterize reward anticipation and delivery with concurrently acquired evoked magnetic fields, EEG potentials and EEG/MEG oscillatory responses, obtaining a precise portrayal of their spatiotemporal evolution. In the anticipation phase, differential activity was most prominent over midline electrodes and parieto-occipital sensors. Differences between non-reward- and reward-predicting cues were localized in the cuneus and later in the dorsal PCC, suggesting a modulation by potential reward information during early visual processing, followed by a coarse emotional evaluation of the cues. Oscillatory analysis revealed increased theta power after non-reward cues over fronto-central sites. In the beta range, power decreased with the magnitude of the potential reward and increased with reaction time, probably reflecting the influence of the striatal response to potential reward on the sensorimotor cortex. At reward delivery, negative prediction errors led to a larger mediofrontal negativity. The spatiotemporal evolution of reward processing was modulated by prediction error: whereas differences were located in PCC and putamen in the prediction error comparison, in the case of expected outcomes they were located in PCC, ACC and parahippocampal gyrus. In the oscillatory realm, theta power was largest following rewards and, in the case of non-rewards, was largest when these were unexpected. Higher beta activity following rewards was also observed in both modalities, but MEG additionally showed a significant power decrease for this condition over parieto-occipital sensors. Our results show how visual, limbic and striatal structures are involved in the different stages of reward anticipation and delivery, and how theta and beta oscillations have a prominent role in the processing of these stimuli.
Neuroscience, 2004
The present study investigated the functional magnetic resonance tomography correlates of taste p... more The present study investigated the functional magnetic resonance tomography correlates of taste perception in the human primary taste cortex. There is conflicting evidence in the literature about chemotopical organization in this brain region. The topography of hemodynamic activity elicited by five taste stimuli (sweet, sour, salty, bitter and umami) was analyzed on the flattened cortical surfaces of six single subjects. A high inter-individual topographical variability had to be noted. The results showed different patterns of hemodynamic activity for the investigated tastes with some considerable overlap. However, the taste specific patterns were stable over time in each subject. Such an individual taste specific pattern was also found for the umami taste within the primary taste cortex of each subject. These results suggest that input from glutamate receptors on the tongue might be processed in an exclusive way in the primary taste cortex rather than as a combination of inputs from the classical taste receptors.
Journal of Neuroscience, 2012
Feature-based attention is known to operate in a spatially global manner, in that the selection o... more Feature-based attention is known to operate in a spatially global manner, in that the selection of attended features is not bound to the spatial focus of attention. Here we used electromagnetic recordings in human observers to characterize the spatiotemporal signature of such global selection of an orientation feature. Observers performed a simple orientation-discrimination task while ignoring taskirrelevant orientation probes outside the focus of attention. We observed that global feature-based selection, indexed by the brain response to unattended orientation probes, is composed of separable functional components. One such component reflects global selection based on the similarity of the probe with task-relevant orientation values ("template matching"), which is followed by a component reflecting selection based on the similarity of the probe with the orientation value under discrimination in the focus of attention ("discrimination matching"). Importantly, template matching occurs at ϳ150 ms after stimulus onset, ϳ80 ms before the onset of discrimination matching. Moreover, source activity underlying template matching and discrimination matching was found to originate from ventral extrastriate cortex, with the former being generated in more anterolateral and the latter in more posteromedial parts, suggesting template matching to occur in visual cortex higher up in the visual processing hierarchy than discrimination matching. We take these observations to indicate that the population-level signature of global feature-based selection reflects a sequence of hierarchically ordered operations in extrastriate visual cortex, in which the selection based on task relevance has temporal priority over the selection based on the sensory similarity between input representations.
Neural Mechanisms of Surround Attenuation and Distractor Competition in Visual Search
Journal of Neuroscience, 2011
Visual attention biases relevant processing in the visual system by amplifying relevant or attenu... more Visual attention biases relevant processing in the visual system by amplifying relevant or attenuating irrelevant sensory input. A potential signature of the latter operation, referred to as surround attenuation, has recently been identified in the electromagnetic brain response of human observers performing visual search. It was found that a zone of attenuated cortical excitability surrounds the target when the search required increased spatial resolution for item discrimination. Here we address the obvious hypothesis that surround attenuation serves distractor suppression in the vicinity of the target where interference from irrelevant search items is maximal. To test this hypothesis, surround attenuation was assessed under conditions when the target was presented in isolation versus when it was surrounded by distractors. Surprisingly, substantial and indistinguishable surround attenuation was seen under both conditions, indicating that it reflects an attentional operation independent of the presence of distractors. Adding distractors in the target's surround, however, increased the amplitude of the N2pc--an evoked response known to index distractor competition in visual search. Moreover, adding distractors led to a topographical change of source activity underlying the N2pc toward earlier extrastriate areas. In contrast, the topography of reduced source activity due to surround attenuation remained unaltered with and without distractors in the target's surround. We conclude that surround attenuation is not a direct consequence of the attenuation of distractors in visual search and that it dissociates from attentional operations reflected by the N2pc. A theoretical framework is proposed that links both operations in a common model of top-down attentional selection in visual cortex.
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Papers by Mircea Ariel Schoenfeld