Stefan P Koch

Publications

• 1.93

  Impact points

  The human execution/observation matching system investigated with a complex everyday task: a functional near-infrared spectroscopy (fNIRS) study.

  Saskia Koehler, Johanna Egetemeir, Prisca Stenneken, Stefan P Koch, Paul Pauli, Andreas J Fallgatter, Martin J Herrmann

  Neuroscience letters. 12/2011; 508(2):73-7.

  The investigation of brain areas involved in the human execution/observation matching system (EOM) has been limited to restricted motor actions when using common neuroimaging techniques such as functional magnetic resonance imaging (fMRI). A method which overcomes this limitation is functional near-... [more] The investigation of brain areas involved in the human execution/observation matching system (EOM) has been limited to restricted motor actions when using common neuroimaging techniques such as functional magnetic resonance imaging (fMRI). A method which overcomes this limitation is functional near-infrared spectroscopy (fNIRS). In the present study, we explored the cerebral responses underlying action execution and observation during a complex everyday task. We measured brain activation of 39 participants during the performance of object-related reaching, grasping and displacing movements, namely setting and clearing a table, and observation of the same task from different perspectives. Observation of the table-setting task activated parts of a network matching those activated during execution of the task. Specifically, observation from an egocentric perspective led to a higher activation in the inferior parietal cortex than observation from an allocentric perspective, implicating that the viewpoint also influences the EOM during the observation of complex everyday tasks. Together these findings suggest that fNIRS is able to overcome the restrictions of common imaging methods by investigating the EOM with a naturalistic task.
• 5.74

  Impact points

  Somatosensory activation of two fingers can be discriminated with ultrahigh-density diffuse optical tomography.

  Christina Habermehl, Susanne Holtze, Jens Steinbrink, Stefan P Koch, Hellmuth Obrig, Jan Mehnert, Christoph H Schmitz

  NeuroImage. 12/2011; 59(4):3201-11.

  Topographic non-invasive near infrared spectroscopy (NIRS) has become a well-established tool for functional brain imaging. Applying up to 100 optodes over the head of a subject, allows achieving a spatial resolution in the centimeter range. This resolution is poor compared to other functional imagi... [more] Topographic non-invasive near infrared spectroscopy (NIRS) has become a well-established tool for functional brain imaging. Applying up to 100 optodes over the head of a subject, allows achieving a spatial resolution in the centimeter range. This resolution is poor compared to other functional imaging tools. However, recently it was shown that diffuse optical tomography (DOT) as an extension of NIRS based on high-density (HD) probe arrays and supplemented by an advanced image reconstruction procedure allows describing activation patterns with a spatial resolution in the millimeter range. Building on these findings, we hypothesize that HD-DOT may render very focal activations accessible which would be missed by the traditionally used sparse arrays. We examined activation patterns in the primary somatosensory cortex, since its somatotopic organization is very fine-grained. We performed a vibrotactile stimulation study of the first and fifth finger in eight human subjects, using a 900-channel continuous-wave DOT imaging system for achieving a higher resolution than conventional topographic NIRS. To compare the results to a well-established high-resolution imaging technique, the same paradigm was investigated in the same subjects by means of functional magnetic resonance imaging (fMRI). In this work, we tested the advantage of ultrahigh-density probe arrays and show that highly focal activations would be missed by classical next-nearest neighbor NIRS approach, but also by DOT, when using a sparse probe array. Distinct activation patterns for both fingers correlated well with the expected neuroanatomy in five of eight subjects. Additionally we show that activation for different fingers is projected to different tissue depths in the DOT image. Comparison to the fMRI data yielded similar activation foci in seven out of ten finger representations in these five subjects when comparing the lateral localization of DOT and fMRI results.
• 10.99

  Impact points

  Dreamed movement elicits activation in the sensorimotor cortex.

  Martin Dresler, Stefan P Koch, Renate Wehrle, Victor I Spoormaker, Florian Holsboer, Axel Steiger, Philipp G Sämann, Hellmuth Obrig, Michael Czisch

  Current biology : CB. 11/2011; 21(21):1833-7.

  Since the discovery of the close association between rapid eye movement (REM) sleep and dreaming, much effort has been devoted to link physiological signatures of REM sleep to the contents of associated dreams [1-4]. Due to the impossibility of experimentally controlling spontaneous dream activity, ... [more] Since the discovery of the close association between rapid eye movement (REM) sleep and dreaming, much effort has been devoted to link physiological signatures of REM sleep to the contents of associated dreams [1-4]. Due to the impossibility of experimentally controlling spontaneous dream activity, however, a direct demonstration of dream contents by neuroimaging methods is lacking. By combining brain imaging with polysomnography and exploiting the state of "lucid dreaming," we show here that a predefined motor task performed during dreaming elicits neuronal activation in the sensorimotor cortex. In lucid dreams, the subject is aware of the dreaming state and capable of performing predefined actions while all standard polysomnographic criteria of REM sleep are fulfilled [5, 6]. Using eye signals as temporal markers, neural activity measured by functional magnetic resonance imaging (fMRI) and near-infrared spectroscopy (NIRS) was related to dreamed hand movements during lucid REM sleep. Though preliminary, we provide first evidence that specific contents of REM-associated dreaming can be visualized by neuroimaging.
• 13.26

  Impact points

  The developmental origins of voice processing in the human brain.

  Tobias Grossmann, Regine Oberecker, Stefan Paul Koch, Angela D Friederici

  Neuron. 03/2010; 65(6):852-8.

  In human adults, voices are processed in specialized brain regions in superior temporal cortices. We examined the development of this cortical organization during infancy by using near-infrared spectroscopy. In experiment 1, 7-month-olds but not 4-month-olds showed increased responses in left and ri... [more] In human adults, voices are processed in specialized brain regions in superior temporal cortices. We examined the development of this cortical organization during infancy by using near-infrared spectroscopy. In experiment 1, 7-month-olds but not 4-month-olds showed increased responses in left and right superior temporal cortex to the human voice when compared to nonvocal sounds, suggesting that voice-sensitive brain systems emerge between 4 and 7 months of age. In experiment 2, 7-month-old infants listened to words spoken with neutral, happy, or angry prosody. Hearing emotional prosody resulted in increased responses in a voice-sensitive region in the right hemisphere. Moreover, a region in right inferior frontal cortex taken to serve evaluative functions in the adult brain showed particular sensitivity to happy prosody. The pattern of findings suggests that temporal regions specialize in processing voices very early in development and that, already in infancy, emotions differentially modulate voice processing in the right hemisphere.

• High-resolution optical functional mapping of the human somatosensory cortex.

  Stefan P Koch, Christina Habermehl, Jan Mehnert, Christoph H Schmitz, Susanne Holtze, Arno Villringer, Jens Steinbrink, Hellmuth Obrig

  Frontiers in neuroenergetics. 01/2010; 2:12.

  Non-invasive optical imaging of brain function has been promoted in a number of fields in which functional magnetic resonance imaging (fMRI) is limited due to constraints induced by the scanning environment. Beyond physiological and psychological research, bedside monitoring and neurorehabilitation ... [more] Non-invasive optical imaging of brain function has been promoted in a number of fields in which functional magnetic resonance imaging (fMRI) is limited due to constraints induced by the scanning environment. Beyond physiological and psychological research, bedside monitoring and neurorehabilitation may be relevant clinical applications that are yet little explored. A major obstacle to advocate the tool in clinical research is insufficient spatial resolution. Based on a multi-distance high-density optical imaging setup, we here demonstrate a dramatic increase in sensitivity of the method. We show that optical imaging allows for the differentiation between activations of single finger representations in the primary somatosensory cortex (SI). Methodologically our findings confirm results in a pioneering study by Zeff et al. (2007) and extend them to the homuncular organization of SI. After performing a motor task, eight subjects underwent vibrotactile stimulation of the little finger and the thumb. We used a high-density diffuse-optical sensing array in conjunction with optical tomographic reconstruction. Optical imaging disclosed three discrete activation foci one for motor and two discrete foci for vibrotactile stimulation of the first and fifth finger, respectively. The results were co-registered to the individual anatomical brain anatomy (MRI) which confirmed the localization in the expected cortical gyri in four subjects. This advance in spatial resolution opens new perspectives to apply optical imaging in the research on plasticity notably in patients undergoing neurorehabilitation.
• 7.18

  Impact points

  Sensitivity of newborn auditory cortex to the temporal structure of sounds.

  Silke Telkemeyer, Sonja Rossi, Stefan P Koch, Till Nierhaus, Jens Steinbrink, David Poeppel, Hellmuth Obrig, Isabell Wartenburger

  The Journal of neuroscience : the official journal of the Society for Neuroscience. 11/2009; 29(47):14726-33.

  Understanding the rapidly developing building blocks of speech perception in infancy requires a close look at the auditory prerequisites for speech sound processing. Pioneering studies have demonstrated that hemispheric specializations for language processing are already present in early infancy. Ho... [more] Understanding the rapidly developing building blocks of speech perception in infancy requires a close look at the auditory prerequisites for speech sound processing. Pioneering studies have demonstrated that hemispheric specializations for language processing are already present in early infancy. However, whether these computational asymmetries can be considered a function of linguistic attributes or a consequence of basic temporal signal properties is under debate. Several studies in adults link hemispheric specialization for certain aspects of speech perception to an asymmetry in cortical tuning and reveal that the auditory cortices are differentially sensitive to spectrotemporal features of speech. Applying concurrent electrophysiological (EEG) and hemodynamic (near-infrared spectroscopy) recording to newborn infants listening to temporally structured nonspeech signals, we provide evidence that newborns process nonlinguistic acoustic stimuli that share critical temporal features with language in a differential manner. The newborn brain preferentially processes temporal modulations especially relevant for phoneme perception. In line with multi-time-resolution conceptions, modulations on the time scale of phonemes elicit strong bilateral cortical responses. Our data furthermore suggest that responses to slow acoustic modulations are lateralized to the right hemisphere. That is, the newborn auditory cortex is sensitive to the temporal structure of the auditory input and shows an emerging tendency for functional asymmetry. Hence, our findings support the hypothesis that development of speech perception is linked to basic capacities in auditory processing. From birth, the brain is tuned to critical temporal properties of linguistic signals to facilitate one of the major needs of humans: to communicate.
• 7.18

  Impact points

  Stimulus-induced and state-dependent sustained gamma activity is tightly coupled to the hemodynamic response in humans.

  Stefan P Koch, Peter Werner, Jens Steinbrink, Pascal Fries, Hellmuth Obrig

  The Journal of neuroscience : the official journal of the Society for Neuroscience. 11/2009; 29(44):13962-70.

  A prompt behavioral response to a stimulus depends both on the salience of the stimulus as well as the subject's preparedness. Thus, both stimulus properties and cognitive factors, such as attention, may determine the strength of neuronal synchronization in the gamma range. For a comprehensive i... [more] A prompt behavioral response to a stimulus depends both on the salience of the stimulus as well as the subject's preparedness. Thus, both stimulus properties and cognitive factors, such as attention, may determine the strength of neuronal synchronization in the gamma range. For a comprehensive investigation of stimulus-response processing through noninvasive imaging, it is, however, a crucial issue whether both kinds of gamma modulation elicit a hemodynamic response. Here, we show that, in the human visual cortex, stimulus strength and internal state modulate sustained gamma activity and hemodynamic response in close correspondence. When participants reported velocity changes of gratings varying in contrast, gamma activity (35-70 Hz) increased systematically with contrast. For stimuli of constant contrast, the amplitude of gamma activity before the behaviorally relevant velocity change was inversely correlated to the behavioral response latency. This indicates that gamma activity also reflects an overall attentive state. For both sources of variance, gamma activity was tightly coupled to the hemodynamic response measured through optical topography. Because of the close relationship between high-frequency neuronal activity and the hemodynamic signal, we conclude that both stimulus-induced and state-dependent gamma activity trigger a metabolic demand and are amenable to vascular-based imaging.
• 1.95

  Impact points

  Electrophysiological evidence for cognitive control during conflict processing in visual spatial attention.

  Stefanie Kehrer, Antje Kraft, Kerstin Irlbacher, Stefan Koch, Herbert Hagendorf, Norbert Kathmann, Stephan Brandt

  Psychological research. 01/2009;

  Event-related potentials were measured to investigate the role of visual spatial attention mechanisms in conflict processing. We suggested that a more difficult target selection leads to stronger attentional top-down control, thereby reducing the effects of arising conflicts. This hypothesis was tes... [more] Event-related potentials were measured to investigate the role of visual spatial attention mechanisms in conflict processing. We suggested that a more difficult target selection leads to stronger attentional top-down control, thereby reducing the effects of arising conflicts. This hypothesis was tested by varying the selection difficulty in a location negative priming (NP) paradigm. The difficult task resulted in prolonged responses as compared to the easy task. A behavioral NP effect was only evident in the easy task. Psychophysiologically the easy task was associated with reduced parietal N1, enhanced frontocentral N2 and N2pc components and a prolonged P3 latency for the conflict as compared to the control condition. The N2pc effect was also obvious in the difficult task. Additionally frontocentral N2 amplitudes increased and latencies of N2pc and P3 were delayed compared to the easy task. The differences at frontocentral and parietal electrodes are consistent with previous studies ascribing activity in the prefrontal and parietal cortex as the source of top-down attentional control. Thus, we propose that stronger cognitive control is involved in the difficult task, resulting in a reduced behavioral NP conflict.
• 5.74

  Impact points

  Individual alpha-frequency correlates with amplitude of visual evoked potential and hemodynamic response.

  Stefan P Koch, Sophie Koendgen, Riad Bourayou, Jens Steinbrink, Hellmuth Obrig

  NeuroImage. 07/2008; 41(2):233-42.

  In a simultaneous electroencephalography (EEG) and near-infrared spectroscopy (NIRS) study, the predictive value of the individual alpha-frequency at rest (IAF) for the amplitude of neuronal and vascular responses to visual stimulation was investigated. Across subjects, we find (i) an inverse relati... [more] In a simultaneous electroencephalography (EEG) and near-infrared spectroscopy (NIRS) study, the predictive value of the individual alpha-frequency at rest (IAF) for the amplitude of neuronal and vascular responses to visual stimulation was investigated. Across subjects, we find (i) an inverse relationship between IAF and the amplitude of the alpha-rhythm at rest. The IAF also predicts (ii) the amplitude of the visual evoked potential (VEP), as well as (iii) the amplitude of the alpha-rhythm during stimulation. Most importantly, (iv) IAF correlates with the oxygenation response to visual stimulation: A high IAF predicts a low alpha-amplitude at rest, a small VEP amplitude and a small oxygenation response. Conversely, a low IAF predicts high alpha-amplitude and larger electrophysiological and vascular responses to stimulation. Based on these findings, we assume that the relationship between IAF and neuronal and vascular response stems from the size of the network recruited for visual processing. The relation between IAF, alpha-amplitude, evoked potential and vascular response is discussed in the framework of a simple heuristic model. The results may partly explain the large intersubject variability observed in recently published concurrent EEG-fMRI studies.
• 5.74

  Impact points

  The oxygenation response to functional stimulation: is there a physiological meaning to the lag between parameters?

  S Boden, H Obrig, C Köhncke, H Benav, S. P. Koch, J Steinbrink

  NeuroImage. 06/2007; 36(1):100-7.

  To investigate the regulation of the hemodynamic response to functional stimulation, functional near-infrared spectroscopy (fNIRS) has been used, due to its ability to assess the dynamics of oxygenated, deoxygenated and total hemoglobin concentration ([oxy-Hb], [deoxy-Hb] and [tot-Hb]). Concerning t... [more] To investigate the regulation of the hemodynamic response to functional stimulation, functional near-infrared spectroscopy (fNIRS) has been used, due to its ability to assess the dynamics of oxygenated, deoxygenated and total hemoglobin concentration ([oxy-Hb], [deoxy-Hb] and [tot-Hb]). Concerning the latency of these parameters, recent studies have returned a consistent picture when comparing the oxygenation response in the sensorimotor to the visual system: changes in [oxy-Hb] lead those in [deoxy-Hb] by 1.6+/-0.2 s (mean+/-SD) for the sensorimotor system but not for the visual system (0.1+/-0.3 s). A number of physiological differences between these cortical areas may account for such a discrepancy, however, the methodological properties of transcranial NIRS also have a relevant influence. Here we show that for the motor system the latency between changes in oxy- compared to deoxy-Hb vanishes once efforts are made to reduce the effects of a systemic response accompanying sensorimotor activity. We apply two independent approaches to reduce the systemic response and find a simultaneous change in [oxy-Hb] and [deoxy-Hb] even in response to a motor paradigm. The two approaches are: (i) an experimental paradigm with alternating contralateral and ipsilateral motor performance without interspersed rest periods designed to minimize systemic changes and (ii) a global correction scheme in an experiment, comparing a unilateral motor performance to rest. These data shed some doubt on the alleged fundamental physiological difference between cortical hemodynamic regulation in motor and visual cortex and highlight the relevance to respect contributions of the systemic hemodynamics.
• 7.18

  Impact points

  Synchronization between background activity and visually evoked potential is not mirrored by focal hyperoxygenation: implications for the interpretation of vascular brain imaging.

  Stefan P Koch, Jens Steinbrink, Arno Villringer, Hellmuth Obrig

  The Journal of neuroscience : the official journal of the Society for Neuroscience. 06/2006; 26(18):4940-8.

  We performed an electroencephalography and optical topography study simultaneously exploring electrophysiological and vascular response magnitude as a function of stimulus frequency. To elicit a response in the visual cortex, subjects were exposed to flicker frequencies varying from 1 to 25 Hz (1 Hz... [more] We performed an electroencephalography and optical topography study simultaneously exploring electrophysiological and vascular response magnitude as a function of stimulus frequency. To elicit a response in the visual cortex, subjects were exposed to flicker frequencies varying from 1 to 25 Hz (1 Hz steps, eyes closed). Extending the standard view to compare magnitudes of the evoked neuronal to the evoked vascular response, we additionally investigated modulations of alpha-power, a marker of "background" EEG activity. The results show two discrepancies between the electrophysiological and vascular response: (1) VEP and alpha-power exhibit a discontinuous peak when stimulating at the individual alpha-frequency (IAF) (approximately 10-11 Hz), indicating resonance between background oscillations and evoked response; this is not mirrored by the vascular response. (2) The vascular response, in contrast, steadily increases up to a maximum at 7-8 Hz and slightly decreases with higher frequencies. This continuous frequency dependence is partly reflected by the decrease in alpha-power up to frequencies of 8-9 Hz and a slight increase in alpha-power beyond the IAF resonance. Although indicating an inverse relationship between alpha-power and vascular response, the frequency dependence of the evoked response does not show such a correlation. Thus, electrophysiological resonance between an individual's alpha-frequency and isofrequent stimulation is not mirrored by the vascular response. Also, spontaneous background EEG activity is an important modulator of the vascular response magnitude. We discuss these deviations from a simple one-to-one translation between evoked potential and vascular response amplitude in the light of questions concerning synchronization, attenuation, and induction of background oscillations such as the alpha-rhythm.

• The oxygenation response to functional stimulation: Is there a physiological meaning to the lag between parameters?

  S. Boden, H. Obrig, C. Köhncke, H. Benav, S.P. Koch, J. Steinbrink

  NeuroImage.

  To investigate the regulation of the hemodynamic response to functional stimulation, functional near-infrared spectroscopy (fNIRS) has been used, due to its ability to assess the dynamics of oxygenated, deoxygenated and total hemoglobin concentration ([oxy-Hb], [deoxy-Hb] and [tot-Hb]). Concerning t... [more] To investigate the regulation of the hemodynamic response to functional stimulation, functional near-infrared spectroscopy (fNIRS) has been used, due to its ability to assess the dynamics of oxygenated, deoxygenated and total hemoglobin concentration ([oxy-Hb], [deoxy-Hb] and [tot-Hb]). Concerning the latency of these parameters, recent studies have returned a consistent picture when comparing the oxygenation response in the sensorimotor to the visual system: changes in [oxy-Hb] lead those in [deoxy-Hb] by 1.6 ± 0.2 s (mean ± SD) for the sensorimotor system but not for the visual system (0.1 ± 0.3 s).A number of physiological differences between these cortical areas may account for such a discrepancy, however, the methodological properties of transcranial NIRS also have a relevant influence. Here we show that for the motor system the latency between changes in oxy- compared to deoxy-Hb vanishes once efforts are made to reduce the effects of a systemic response accompanying sensorimotor activity. We apply two independent approaches to reduce the systemic response and find a simultaneous change in [oxy-Hb] and [deoxy-Hb] even in response to a motor paradigm. The two approaches are: (i) an experimental paradigm with alternating contralateral and ipsilateral motor performance without interspersed rest periods designed to minimize systemic changes and (ii) a global correction scheme in an experiment, comparing a unilateral motor performance to rest. These data shed some doubt on the alleged fundamental physiological difference between cortical hemodynamic regulation in motor and visual cortex and highlight the relevance to respect contributions of the systemic hemodynamics.

• Stimulus-induced and state-dependent sustained gamma activity is tightly coupled to the hemodynamic response in humans

  S. P. Koch, P. Werner, J Steinbrink, J. Fries, Hellmuth Obrig

  Journal of Neuroscience, v.29, 13962-13970 (2009).

• Sensitivity of newborn auditory cortex to the temporal structure of sounds

  Silke Telkemeyer, Sonja Rossi, S. P. Koch, Till Nierhaus, Jens Steinbrink, David Poeppel, Hellmuth Obrig, Isabell Wartenburger

  Journal of Neuroscience, v.29, 14726-14733 (2009).