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Trial by trial coupling of simultaneous 61-channel EEG and fMRI: The N1-effect revisited
Society Proceedings / Clinical Neurophysiology 118 (2007) e9–e116
activation indicates that structural damage elicits compensatory processes in MS-patients, though cortical atrophy appears to limit the capacity for compensation even at early stages of the disease. doi:10.1016/j.clinph.2006.11.176
Trial by trial coupling of simultaneous 61-channel EEG and fMRI: The N1-effect revisited—C. Mulert 1, L. Ja¨ger 2, C. Seifert 1, S. Karch 1, G. Leicht 1, H.J. Mo¨ller 1, U. Hegerl 1, O. Pogarell 1 (1 Klinik fu¨r Psychiatrie und Psychotherapie der LMU Mu¨ nchen, 2 Institut fu¨ r Klinische Radiologie der LMU Mu¨ nchen) Introduction: Attentional effects in the timeframe of the eventrelated N1 potential have been described and addressed as ‘‘N1effect’’ more than thirty years ago. In the meantime, this effect has been widely used as a tool to investigate attentional processes. While there has been some debate whether about the character of this phenomenon, e.g. in the sense of an overlapping ‘‘processing negativity’’ on the basic and obligatory N1 potential, until recently no doubt has been formulated about the temporal lobe/auditory cortex origin of this effect. In the last years however, some hints exist for an additional contribution of the anterior cingulate cortex (ACC) to the N1 effect: Based on different source localization techniques like dipoles or LORETA, an ACC-generator of the N1 potential has been described. Very recently, an ACC-generator during the N1-timeframe has also been described using intracranial measurements. In the present study we used trial by trial coupling of simultameous EEG and fMRI to investigate the neural generators of the N1-potential in choice reaction tasks. Methods: We investigated ten healthy subjects. The task was a choice reaction paradigm: Two · 30 tones of different pitches (800 and 1300 Hz) were presented by earphones at 85 dB SPL with pseudo-randomized sequence and interstimulus intervals (ISI: 2.5– 7.5 s). The subjects had to press the correct button. FMRI-data: (1.5 T Sonata scanner (Siemens); gradient echo EPI sequence; 12 slices; matrix: 128 · 128; slice thickness: 8 mm; interslice-gap: 0.4 mm; interleaved slice acquisition) were acquired in temporal synchrony to the task. BrainVoyager was used to compare differences in task specific BOLD responses. EEG signals were recorded simultaneously (61 channels; Cz reference; 1000 Hz sampling). After artefact correction, single trial modulations of the N1-potential amplitudes were used for a convolution with a hemodynamic response function to calculate the corresponding BOLD-effects. Results and conclusion: Main fMRI activation patterns using this method were found in the auditory cortex. As expected, additional dorsal anterior cingulate cortex activations were found. These results suggest a contribution of the dorsal ACC to the N1-effect. doi:10.1016/j.clinph.2006.11.177
Increased spinal nociception and reduced pain communication in dementia—V. Mylius 1, M. Kunz 2, S. Scharmann 2, U. Hemmeter 2, S. Lautenbacher 3, K. Schepelmann 1 (1 Klinik fu¨r Neurologie, Universita¨tsklinik Marburg, 2 Klinik fu¨r Psychiatrie, Universita¨tsklinik Marburg, 3 Physiologische Psychologie, Universita¨t Bamberg)
e77
Patients suffering from Alzheimer’s disease (AD) complain less often about acute and chronic pain. The reduce pain report might either be due to a diminished ability to communicate pain or might be due to decreased nociception caused by neuropathological changes in the central pain pathways. Previous studies revealed that the pain threshold is unchanged in patients with AD, whereas the tolerance threshold is markedly increased. In addition to verbal pain ratings we aimed to assessed the nociceptive flexion reflex (NFR). The NFR is a spinal physiological reflex of protection which underlies spinal and supra spinal control. It is known to correlate well with the subjective pain threshold in healthy men. Twenty patients with dementia (Alzheimers’s disease, vascular dementia and mixed dementia) and 51 age matched control participants took part in this study. For recording of the NFR the sural nerve was stimulated electrically. The motor response was recorded from the biceps femoris muscle by surface electrodes. Following the calculation of the reflex threshold (by employing the staircase method), we measured the parameters of 10 averaged reflexes 5 mA above threshold. In parallel we assessed the verbal pain ratings on a 6-step categorical scale. Complete verbal pain ratings could only be obtained in 45% of the demented patients. The NFR threshold was found to be significantly lower in the group of demented patients compared to the group of healthy subjects (13.9 ± 7.5 mA vs. 21.1 ± 9.6 mA, p < 0.05). No significant group difference in the NFR parameters 5 mA above threshold and in pain ratings were obtained. Finding the NFR threshold to be markedly decreased in dementia indicates an increased nociception on the spinal level. We assume that the degenerative process in both forms of dementia contributes to reduced inhibitory influences. Since there is no significant spinal pathology in dementia, this might be a result of a reduced descending inhibition due to degeneration of cortical neurons. From the present data, we conclude that pain perception is enhanced in dementia while the reduced reliability of verbal pain report might lead to an underestimation of the perceived pain. doi:10.1016/j.clinph.2006.11.178
Auditory orienting to speech and environmental sounds—W. Nager 1, C. Schro¨der 1, J. Mo¨bes 1, R. Dengler 1, T.F. Mu¨nte 2 (1 Medizinische Hochschule Hannover, 2 Otto-VonGuericke Universita¨t Magdeburg) Information selection is mediated by top-down processes whilst bottom-up processes enable the conscious evaluation of potentially important events that are not currently selected by focussed attention. Without a good balance between these two processes, one cannot behave adequately in many situations. Auditory event-related potentials (ERPs) allow for detailed analysis of bottom-up processes. The mismatch negativity (MMN) indicates the preattentive processing of physical differences between a frequently presented standard and a rare deviant sound. The P3a is evoked by unpredictable auditory novel events and is considered to reflect bottom-up processes such as the automatic orienting reaction. Its role in attention shifting was confirmed by the correlation between the P3a amplitude and deterioration of behavioural performance on a primary task. To evaluate the amount of attentional orienting to unexpected environmental sounds and speech sounds, the MMN and the P3a were recorded in 14 healthy subjects. Subjects were instructed to
activation indicates that structural damage elicits compensatory processes in MS-patients, though cortical atrophy appears to limit the capacity for compensation even at early stages of the disease. doi:10.1016/j.clinph.2006.11.176
Trial by trial coupling of simultaneous 61-channel EEG and fMRI: The N1-effect revisited—C. Mulert 1, L. Ja¨ger 2, C. Seifert 1, S. Karch 1, G. Leicht 1, H.J. Mo¨ller 1, U. Hegerl 1, O. Pogarell 1 (1 Klinik fu¨r Psychiatrie und Psychotherapie der LMU Mu¨ nchen, 2 Institut fu¨ r Klinische Radiologie der LMU Mu¨ nchen) Introduction: Attentional effects in the timeframe of the eventrelated N1 potential have been described and addressed as ‘‘N1effect’’ more than thirty years ago. In the meantime, this effect has been widely used as a tool to investigate attentional processes. While there has been some debate whether about the character of this phenomenon, e.g. in the sense of an overlapping ‘‘processing negativity’’ on the basic and obligatory N1 potential, until recently no doubt has been formulated about the temporal lobe/auditory cortex origin of this effect. In the last years however, some hints exist for an additional contribution of the anterior cingulate cortex (ACC) to the N1 effect: Based on different source localization techniques like dipoles or LORETA, an ACC-generator of the N1 potential has been described. Very recently, an ACC-generator during the N1-timeframe has also been described using intracranial measurements. In the present study we used trial by trial coupling of simultameous EEG and fMRI to investigate the neural generators of the N1-potential in choice reaction tasks. Methods: We investigated ten healthy subjects. The task was a choice reaction paradigm: Two · 30 tones of different pitches (800 and 1300 Hz) were presented by earphones at 85 dB SPL with pseudo-randomized sequence and interstimulus intervals (ISI: 2.5– 7.5 s). The subjects had to press the correct button. FMRI-data: (1.5 T Sonata scanner (Siemens); gradient echo EPI sequence; 12 slices; matrix: 128 · 128; slice thickness: 8 mm; interslice-gap: 0.4 mm; interleaved slice acquisition) were acquired in temporal synchrony to the task. BrainVoyager was used to compare differences in task specific BOLD responses. EEG signals were recorded simultaneously (61 channels; Cz reference; 1000 Hz sampling). After artefact correction, single trial modulations of the N1-potential amplitudes were used for a convolution with a hemodynamic response function to calculate the corresponding BOLD-effects. Results and conclusion: Main fMRI activation patterns using this method were found in the auditory cortex. As expected, additional dorsal anterior cingulate cortex activations were found. These results suggest a contribution of the dorsal ACC to the N1-effect. doi:10.1016/j.clinph.2006.11.177
Increased spinal nociception and reduced pain communication in dementia—V. Mylius 1, M. Kunz 2, S. Scharmann 2, U. Hemmeter 2, S. Lautenbacher 3, K. Schepelmann 1 (1 Klinik fu¨r Neurologie, Universita¨tsklinik Marburg, 2 Klinik fu¨r Psychiatrie, Universita¨tsklinik Marburg, 3 Physiologische Psychologie, Universita¨t Bamberg)
e77
Patients suffering from Alzheimer’s disease (AD) complain less often about acute and chronic pain. The reduce pain report might either be due to a diminished ability to communicate pain or might be due to decreased nociception caused by neuropathological changes in the central pain pathways. Previous studies revealed that the pain threshold is unchanged in patients with AD, whereas the tolerance threshold is markedly increased. In addition to verbal pain ratings we aimed to assessed the nociceptive flexion reflex (NFR). The NFR is a spinal physiological reflex of protection which underlies spinal and supra spinal control. It is known to correlate well with the subjective pain threshold in healthy men. Twenty patients with dementia (Alzheimers’s disease, vascular dementia and mixed dementia) and 51 age matched control participants took part in this study. For recording of the NFR the sural nerve was stimulated electrically. The motor response was recorded from the biceps femoris muscle by surface electrodes. Following the calculation of the reflex threshold (by employing the staircase method), we measured the parameters of 10 averaged reflexes 5 mA above threshold. In parallel we assessed the verbal pain ratings on a 6-step categorical scale. Complete verbal pain ratings could only be obtained in 45% of the demented patients. The NFR threshold was found to be significantly lower in the group of demented patients compared to the group of healthy subjects (13.9 ± 7.5 mA vs. 21.1 ± 9.6 mA, p < 0.05). No significant group difference in the NFR parameters 5 mA above threshold and in pain ratings were obtained. Finding the NFR threshold to be markedly decreased in dementia indicates an increased nociception on the spinal level. We assume that the degenerative process in both forms of dementia contributes to reduced inhibitory influences. Since there is no significant spinal pathology in dementia, this might be a result of a reduced descending inhibition due to degeneration of cortical neurons. From the present data, we conclude that pain perception is enhanced in dementia while the reduced reliability of verbal pain report might lead to an underestimation of the perceived pain. doi:10.1016/j.clinph.2006.11.178
Auditory orienting to speech and environmental sounds—W. Nager 1, C. Schro¨der 1, J. Mo¨bes 1, R. Dengler 1, T.F. Mu¨nte 2 (1 Medizinische Hochschule Hannover, 2 Otto-VonGuericke Universita¨t Magdeburg) Information selection is mediated by top-down processes whilst bottom-up processes enable the conscious evaluation of potentially important events that are not currently selected by focussed attention. Without a good balance between these two processes, one cannot behave adequately in many situations. Auditory event-related potentials (ERPs) allow for detailed analysis of bottom-up processes. The mismatch negativity (MMN) indicates the preattentive processing of physical differences between a frequently presented standard and a rare deviant sound. The P3a is evoked by unpredictable auditory novel events and is considered to reflect bottom-up processes such as the automatic orienting reaction. Its role in attention shifting was confirmed by the correlation between the P3a amplitude and deterioration of behavioural performance on a primary task. To evaluate the amount of attentional orienting to unexpected environmental sounds and speech sounds, the MMN and the P3a were recorded in 14 healthy subjects. Subjects were instructed to